JP2008084666A - Laminated nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated nonaqueous secondary battery retaining high reliability over a long period of time even under a special environment such as a high temperature environment. <P>SOLUTION: The laminated type nonaqueous secondary battery has a group of electrodes which are composed by laminating a positive electrode sheet and a negative electrode sheet with a separator therebetween stored in a rectangular laminate sheet battery package and is weld shielded in three sides or four sides of the laminate sheet battery package in a state with a positive electrode terminal connected to the positive sheet and a negative electrode terminal connected to the negative sheet projecting outside. The problem is solved by the laminated nonaqueous secondary battery in which heat resistant material is arranged in a boundary portion between a welded part and a non-welded part in at least one part of a corner part where weld shielded sides intersect in an inner side of the battery of the laminate sheet on a top side of the electrode group and/or the laminate sheet below the electrode group. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laminated non-aqueous secondary battery, and more particularly, a laminated non-aqueous secondary battery suitable for use as a power source for portable electronic devices, electric vehicles, electric assist bicycles, electric motorcycles, road leveling and the like. It relates to batteries.

  A lithium ion secondary battery, which is a type of nonaqueous electrolyte battery, is widely used as a power source for portable devices such as mobile phones and notebook personal computers because of its high energy density. In addition, the importance of secondary batteries that can be repeatedly charged is increasing due to considerations for environmental issues. In addition to portable devices, application to automobiles, electric chairs, household and commercial power storage systems is being considered. Yes.

  2. Description of the Related Art In recent years, hybrid vehicles (HEV) that use both battery and gasoline due to environmental problems, assist bicycles that support power with batteries, electric vehicles and motorcycles that use batteries for all power, have become widespread. Compared to the power sources of small portable devices such as mobile phones, these medium and large power sources require high-power secondary batteries with a large capacity.

  Lithium ion secondary batteries include cylindrical batteries and laminated batteries. A laminated nonaqueous secondary battery is formed by laminating a heat-fusible resin layer (for example, a polyethylene layer) on one side of a metal sheet and a resin layer (for example, a polyethylene terephthalate layer) having excellent mechanical strength on the other side. Using a laminate sheet, a laminate electrode body in which a sheet-like positive electrode and a sheet-like negative electrode are overlapped with a separator inside a laminate sheet outer package configured such that the heat-fusible resin layer side is inside An electrode group is enclosed (for example, Patent Document 1). The sealing of the laminate sheet outer package is performed by bringing the heat-fusible resin layers into close contact with each other at the peripheral portion of the laminate sheet on the upper side of the electrode group and the peripheral portion of the laminate sheet on the lower side of the electrode group. This is performed by heating and thermally fusing the heat-fusible resin layers. Such a laminated battery has a higher energy density per weight than a cylindrical battery, and has a large degree of freedom in size and thickness, so that various shapes are manufactured.

  Batteries used as power sources for equipment used outdoors, especially batteries for vehicles, power tools, and bicycles, are used for a long time in a wide temperature range and environment. When applying a secondary battery, sealing of the laminate sheet outer package is particularly important. If the sealing of the laminate sheet exterior is insufficient, the non-aqueous electrolyte (non-aqueous electrolyte) leaks out of the battery, causing corrosion of the equipment used, accidents, and deterioration of battery characteristics.

  When sealing a rectangular laminate sheet outer package in plan view, first, one side is left for non-aqueous electrolyte injection, the other side is welded, and the remaining non-aqueous electrolyte is injected into the inner side. To weld. Therefore, the end portion of one side to be welded last is once welded as the end portion of the side to be welded first, so that it is double-welded. Of the heat-fusible resin placed inside the laminate sheet outer package, the area around the welded part may melt partially due to the heat of welding, but the area around the double-welded part The part is particularly susceptible to the effects of heat during welding.

  Due to the influence of heat at the time of welding as described above, when the heat-fusible resin around the welded portion melts and the metal sheet is exposed, the metal sheet corrodes due to long-term contact with the nonaqueous electrolyte. There is a risk of leakage of the non-aqueous electrolyte.

  Conventionally, leakage due to the effects of heat described above has not been a problem in relation to the period of use of laminated non-aqueous secondary batteries, but in recent applications of laminated non-aqueous secondary batteries, The usage period is very long. Therefore, in the laminate type non-aqueous secondary battery, the influence of heat generated in the process of welding the laminate sheet outer package is mitigated to suppress the occurrence of liquid leakage and to maintain good reliability over a long period of time. Is required.

JP 2000-268789 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a laminated nonaqueous secondary battery that can maintain good reliability over a long period of time even in a special environment such as a high temperature environment. It is in.

  The laminated non-aqueous secondary battery of the present invention that has achieved the above-mentioned object has an electrode group in which a positive electrode sheet and a negative electrode sheet are laminated via a separator accommodated in a rectangular laminate sheet outer package, and the positive electrode A battery in which the positive electrode terminal connected to the sheet and the negative electrode terminal connected to the negative electrode sheet protrude to the outside and are welded and sealed on three or four sides of the laminate sheet outer package, At least one of the boundary portion between the welded portion and the non-welded portion at the corner portion where the welded and sealed sides intersect each other inside the battery of the laminate sheet on the upper side of the electrode group and / or the laminate sheet on the lower side of the electrode group. A heat-resistant material is arranged in the part.

  In the present invention, when the laminate sheet outer package is welded and sealed, the laminate sheet is formed at a position where the double-welded portion is particularly easily affected by the heat, that is, at the corner where the welded and sealed sides intersect. By disposing the heat-resistant material at the boundary between the welded portion and the non-welded portion inside the battery, the non-welded portion at the corner portion prevents exposure of the metal sheet due to melting of the heat-fusible resin, The occurrence of corrosion due to contact between the metal sheet and the nonaqueous electrolyte is suppressed.

  Due to the above-described action of the heat-resistant material, the present invention maintains high reliability over a long period of time not only in an environment where a laminated nonaqueous secondary battery is usually used but also in a special environment such as a high temperature environment. It is possible to provide a laminated non-aqueous secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, the lamination type non-aqueous secondary battery which can hold | maintain favorable reliability over a long period of time also in special environments, such as a high temperature environment, can be provided.

  The laminated nonaqueous secondary battery of the present invention is formed by enclosing a laminated electrode group in which a positive electrode sheet and a negative electrode sheet are laminated via a separator in a rectangular laminate sheet outer package in a plan view. The laminate sheet exterior body is composed of a laminate sheet having a structure in which at least one layer of an insulating heat-fusible resin film (heat-fusible resin layer) is laminated on one side or both sides of a metal sheet having air-blocking properties. Can be mentioned.

  The metal sheet constituting the laminate sheet may be any material that can prevent moisture and oxygen outside the battery from entering the battery and transpiration of the nonaqueous electrolyte (nonaqueous electrolyte) inside the battery to the outside of the battery. There is no restriction | limiting in particular, The sheet | seat which consists of a well-known metal material can be used. Specifically, the sheet | seat comprised by metal materials, such as aluminum, stainless steel, nickel, copper, is mentioned.

  From the viewpoint of better preventing the movement of substances (moisture and oxygen outside the battery and nonaqueous electrolyte inside the battery) between inside and outside the battery, the thickness of the metal sheet related to the laminate sheet is 10 μm or more, more preferably 30 μm. The above is preferable. However, if the metal sheet is too thick, when the laminate sheet outer package is welded and sealed, heat cannot be sufficiently transferred to the heat-fusible resin layer, and the hermetic reliability after the welding and sealing is lowered. In some cases, the laminate sheet outer package itself becomes thick and the energy density of the battery tends to decrease. Therefore, the thickness of the metal sheet is preferably 150 μm or less, and more preferably 100 μm or less.

  The insulating heat-fusible resin for forming the heat-fusible resin layer is not particularly limited as long as it can seal the laminate sheet outer package by heat-sealing (welding). Can be used. Specifically, polyolefins such as polyethylene, maleic acid modified polyethylene, polypropylene, maleic acid modified polypropylene; polyesters such as polyethylene terephthalate and heat fusible polyethylene terephthalate; heat fusible polyimides; polymethyl methacrylate; ionomer resin; And a copolymer (such as an ethylene-propylene copolymer) composed of two or more monomers for forming these resins.

  The thickness of the heat-fusible resin layer according to the laminate sheet is preferably 20 μm or more, and more preferably 30 μm or more, from the viewpoint of further increasing the mechanical strength after welding. However, if the heat-sealable resin layer is too thick, the area of the heat-sealable resin exposed to the outside of the battery after welding becomes large, and the airtight reliability may be lowered. Therefore, the thickness of the heat-fusible resin layer is preferably 100 μm or less, and more preferably 80 μm or less.

  The laminate sheet outer package having the above-described configuration has good gas barrier properties and light blocking properties due to the metal sheet, and can be easily welded and sealed with the heat-fusible resin layer.

  In addition, the laminate sheet constituting the laminate sheet exterior body has the above-mentioned heat-fusible resin layer on one side (the surface that becomes the inside of the battery) of the metal sheet, and the other side (the surface that becomes the outside of the battery) It is preferable to have a layer (outer layer) composed of a resin excellent in mechanical strength. By using a laminate sheet outer package having such an outer layer, the durability of the battery can be enhanced. Examples of the resin that can form the outer layer in this case include polyesters such as polyethylene terephthalate, nylons such as nylon 66, and the like.

  The thickness of the outer layer is preferably 20 μm or more, and more preferably 30 μm or more, from the viewpoint of more effectively exerting the effect of providing the outer layer. However, if the outer layer is too thick, the energy density of the battery tends to decrease. Therefore, the thickness is preferably 100 μm or less, and more preferably 80 μm or less.

  In the laminate type nonaqueous secondary battery of the present invention, a rectangular laminate sheet outer package is used in a plan view. This “square” includes squares and rectangles, for example, one or more of four corners. And a shape in which one or more of the four corners are cut off.

  FIG. 1 schematically shows a state in which a laminated electrode group 20 in which a positive electrode sheet and a negative electrode sheet are laminated via a separator is housed in a laminated sheet outer package 10. In the laminated electrode group 20, 30 is a positive terminal and 40 is a negative terminal. In FIG. 1, a part of the laminated electrode group 20 is shown to be transparent, and a hatched portion in the laminated electrode group 20 represents a heat-resistant tape (for details, see FIG. 6 described later). However, it is not a cross section.

  The laminate sheet outer package 10 shown in FIG. 1 is folded back so as to sandwich the laminated electrode group 20, and the laminated sheet 11 on the upper side of the laminated electrode group 20 and the laminated sheet on the lower side of the laminated electrode group 20 are This is an exterior body of a type that is sealed by welding at the three sides of the side and the terminals 30 and 40 side. The laminated electrode group 20 is arranged so that the terminals 30 and 40 protrude out of the exterior body 10 after sealing the laminate sheet exterior body 10.

  And in the laminate sheet exterior body 10 of FIG. 1, the welding part and the non-welding part in the corner | angular part where the sides by which welding sealing is carried out of the surface which becomes the battery inner side of the laminated sheet 11 of the upper side of the laminated electrode group 20 are carried out. The heat-resistant materials 50 and 50 are arranged at the locations (two locations) that are planned to be the boundary portions of the.

  After arranging the laminated electrode group 20 and the heat-resistant materials 50 and 50 as shown in FIG. 1, the laminate sheet 11 and the laminate sheet 12 are overlapped and welded. In the case of the laminate sheet exterior body 10 shown in FIG. 1, the three sides are welded, but two sides (for example, the left side in the figure and the side on the terminals 30 and 40 side) are welded first. Then, a predetermined amount of non-aqueous electrolyte is injected into the laminate sheet exterior body from the unwelded side, and then the unwelded side portion is welded under reduced pressure, and a laminated non-aqueous secondary as shown in FIG. Use batteries. 2A and 2B are schematic views of the laminated nonaqueous secondary battery of the present invention, where FIG. 2A is a plan view and FIG. 2B is a side view. In FIG. is there. In FIG. 2, the heat-resistant materials 50 and 50 are illustrated, but this is for facilitating understanding of the arrangement of the heat-resistant materials, and the heat-resistant materials 50 and 50 are arranged inside the battery (laminated sheet outer package 10). Inside).

  When the laminate sheet outer package is welded by the procedure as described above, the welded portion at the corner portion where the vertical side on the right side and the side on the terminals 30 and 40 side in FIG. Therefore, particularly in the vicinity of the welded portion, a part of the heat-sealable resin related to the laminate sheet is melted and the metal sheet is easily exposed. However, as shown in FIG. By disposing a heat-resistant material (the heat-resistant material 50 on the right side in FIG. 1) at the boundary with the part, the metal sheet and the non-aqueous electrolyte are prevented from being exposed by melting the heat-fusible resin. Can be prevented, and leakage of the non-aqueous electrolyte can be suppressed.

  As described above, the heat-resistant material may be disposed at the boundary portion between the welded portion and the non-welded portion at the location where the laminate sheet exterior is subjected to double welding as described above. Of the corners where the sides to be welded and sealed intersect with each other, the welded portion is also welded in a single welding operation (the corner where the left heat-resistant material 50 is disposed in FIG. 1). It is preferable to dispose a heat-resistant material at the boundary portion with the non-welded portion, and in this case, it is possible to better prevent the occurrence of liquid leakage based on the exposure of the metal sheet that may occur due to melting of the hot-melt resin.

  Further, as shown in FIG. 1, the heat-resistant material may be disposed on the battery inner surface of the laminate sheet on the upper side of the laminated electrode group, or on the surface of the lower laminated sheet on the battery inner side of the laminated electrode group. You may arrange | position and may arrange | position to the surface used as the battery inner side of both laminate sheets.

  The heat-resistant material is preferably a sheet composed of a material having a melting point, that is, a melting temperature measured using a differential scanning calorimeter (DSC) of 200 ° C. or higher, in accordance with JIS K 7121. Specific examples of the material constituting the heat-resistant material include polyimide, polyphenylene sulfide, and the like. The heat-resistant material may be composed of one of these alone, or the heat-resistant material may be composed of two or more kinds in combination. Good.

  The shape (planar shape) of the heat-resistant material may be any shape such as a rectangle as shown in FIG. 1, a square such as a square, a circle (true circle or ellipse), or a triangle.

  When arranging the heat-resistant material on the laminate sheet, the thickness of the heat-resistant material is preferably 50 μm or more, and more preferably 60 μm or more, from the viewpoint of improving workability by preventing wrinkles and the like from entering. However, if the heat-resistant material is too thick, there is a risk that a relatively large step will occur between the part where the heat-resistant material is placed and the other laminated sheet part, and wrinkles may occur in the laminated sheet itself. The thickness of is preferably 100 μm or less, and more preferably 80 μm or less. Therefore, when the heat-resistant material is arranged on both the upper laminate sheet and the lower laminate sheet of the laminated electrode group and the two heat-resistant materials are overlapped after becoming a battery, the total thickness of both heat-resistant materials is It is preferable to satisfy the above preferable upper limit value.

  Moreover, the thing of the aspect which has an adhesive material layer in the single side | surface is preferable for a heat-resistant material. Such a heat-resistant material can be adhered to the laminate sheet by the pressure-sensitive adhesive material related to the pressure-sensitive adhesive layer. As the adhesive material for forming the adhesive material layer, an adhesive material excellent in heat resistance such as a silicone-based adhesive material and an acrylic resin-based adhesive material is preferable. The thickness of the pressure-sensitive adhesive layer is preferably 5 to 20 μm.

  The configuration of the laminated non-aqueous secondary battery of the present invention has been described so far with reference to FIGS. 1 and 2, and the configuration and structure of the laminated non-aqueous secondary battery of the present invention are shown in FIG. It is not necessarily limited to that shown in FIG. For example, as a laminate sheet outer package, a side facing the positive electrode terminal and negative electrode terminal side is not a folded portion of the laminate sheet, but a laminate sheet outer package of a type that is welded and sealed (that is, all four sides are welded and sealed) The battery may be formed using a laminate sheet outer package of the type to be used. In addition, even when using a laminate sheet outer package of the type in which all four sides are welded and sealed, the heat-resistant material is welded in duplicate at the corners where the sides to be welded and sealed in the laminate sheet outer package intersect. It is only necessary to be located at the boundary between the welded part and the non-welded part at the place where the heat is received, but it is better to prevent the occurrence of liquid leakage due to the exposure of the metal sheet that can occur due to melting of the hot-melt resin. From the viewpoint of performing, a heat-resistant material is disposed at a boundary portion between the welded portion and the non-welded portion even at a portion where the welded and sealed edges intersect at a portion welded by one welding operation. Is preferred.

  FIG. 1 shows a laminate sheet outer package slightly larger than the size of the final laminated nonaqueous secondary battery (FIG. 2). When using such a laminate sheet outer package, What is necessary is just to adjust a size, such as cutting an exterior body, when carrying out welding sealing and setting it as a laminate type non-aqueous secondary battery. On the other hand, a laminate sheet outer package that does not require size adjustment such as cutting just by welding and sealing may be used.

  Furthermore, in FIG. 1 and FIG. 2, it is illustrated for the purpose of facilitating understanding of the configuration of the laminated nonaqueous secondary battery of the present invention, and the size of each component is not necessarily accurate.

In the positive electrode (positive electrode sheet) according to the laminated nonaqueous secondary battery of the present invention, the positive electrode active material-containing layer containing a positive electrode active material, a conductive additive, a binder and the like is on the current collector (one or both surfaces of the current collector). ). As the positive electrode active material, for example, lithium cobalt oxide such as LiCoO ₂ , lithium manganese oxide such as LiMn ₂ O _4, and lithium composite oxide exemplified by lithium nickel oxide such as LiNiO ₂ are preferably used. Co, Mn, or Ni of these active materials may be substituted with other elements, respectively. Moreover, these active materials may be used individually by 1 type, and may use 2 or more types together.

  As the positive electrode current collector, an aluminum foil having a thickness of 5 to 60 μm is suitable. The positive electrode tab may leave an exposed portion of the current collector without forming a positive electrode active material-containing layer in a part of the positive electrode current collector, and may be used as a positive electrode tab. You may connect and provide.

  In producing the positive electrode, the positive electrode active material, a conductive additive such as graphite, acetylene black, and carbon black, and a positive electrode mixture containing a binder such as polyvinylidene fluoride and polytetrafluoroethylene are mixed with N-methyl. A paste-like or slurry-like composition uniformly dispersed using a solvent such as -2-pyrrolidone (NMP) is prepared (the binder may be dissolved in the solvent), and this composition is collected into the positive electrode current collector. The method of apply | coating on a body, drying, and adjusting the thickness and density of a positive electrode active material content layer by press processing as needed can be employ | adopted. However, the manufacturing method of the positive electrode according to the present invention is not limited to the above method, and other methods may be adopted.

  The thickness of the positive electrode active material-containing layer in the positive electrode is preferably 30 to 300 μm per side. Moreover, it is preferable that content of each structural component in a positive electrode active material content layer shall be 85-95 mass% of positive electrode active materials, 1-5 mass% of conductive support agents, and 2-5 mass% of binders.

  The negative electrode (negative electrode sheet) according to the laminated nonaqueous secondary battery of the present invention has a negative electrode active material-containing layer containing a negative electrode active material, a binder, and a conductive auxiliary agent as necessary. It is formed on one side or both sides of the electric body. Although it does not specifically limit as a negative electrode active material, It is preferable to use carbon materials, such as graphites which can dope and dedope lithium ion, pyrolytic carbons, cokes, and glassy carbons.

  It is preferable to use a copper foil having a thickness of 5 to 60 μm for the negative electrode current collector. The negative electrode tab may leave an exposed portion of the current collector without forming a negative electrode active material-containing layer in a part of the negative electrode current collector, and may be used as a negative electrode tab. You may connect and provide.

  In producing the negative electrode, a negative electrode mixture containing the above negative electrode active material, a binder such as polyvinylidene fluoride and polytetrafluoroethylene, and a conductive auxiliary agent such as graphite, acetylene black, and carbon black as necessary. A paste-like or slurry-like composition uniformly dispersed using a solvent such as NMP is prepared (the binder may be dissolved in the solvent), and this composition is applied onto the negative electrode current collector. Then, a method of adjusting the thickness and density of the negative electrode active material-containing layer by pressing may be employed as necessary. However, the manufacturing method of the negative electrode according to the present invention is not limited to the above method, and other methods may be adopted.

  The thickness of the negative electrode active material-containing layer in the negative electrode is preferably 30 to 300 μm per side. Moreover, it is preferable that content of each structural component in a negative electrode active material content layer shall be negative electrode active material: 85-95 mass%, binder: 2-5 mass%, and when using a conductive support agent, it is a negative electrode The content of the conductive additive in the active material-containing layer is preferably 1 to 5% by mass.

Examples of the nonaqueous electrolyte used in the laminated nonaqueous secondary battery of the present invention include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF _{3 in} organic solvents such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, and ethylene carbonate. it can be used a material obtained by dissolving a solute such as SO _3.

  The non-aqueous electrolyte can also be used by mixing a resin, a cross-linking agent, etc., and gelling or solidifying. By making the electrolyte into a gel, the components of the electrolyte decompose when the battery is overcharged, and gas is generated. This gas causes separation between the separator layers (for example, a nonwoven fabric and a porous material described later). In the case of a separator composed of a quality film), a gap is formed between the separator and the negative electrode, and thus the safety of the battery can be further improved.

  Further, at least one additive selected from an aromatic compound having a benzene ring and a phosphazene derivative may be added to the non-aqueous electrolyte. The aromatic compound having a benzene ring is not particularly limited as long as it decomposes in the vicinity of 4.2 to 4.7 V to generate gas and polymerizes on the positive electrode surface to form a film. Examples thereof include alkylbenzenes such as xylene and cyclohexylbenzene, aromatic halogens, aromatic amines, aromatic carboxylic acids, and biphenyl. Among the above aromatic compounds, biphenyl, cyclohexylbenzene, or derivatives thereof (fluorine-substituted products and the like) are preferably used from the viewpoint of film forming ability. As the aromatic compound having a benzene ring, those exemplified above may be used alone or in combination of two or more.

  As the phosphazene derivative that can be added to the nonaqueous electrolyte, either a cyclic type or a chain type can be used. However, when battery characteristics such as load characteristics are taken into consideration, the phosphazene derivative is represented by the following general formula (1). A ring structure having a ring shape is preferably used.

In the general formula (1), the side chains R _{1 to} R ₆ are
₍₁₎ -CH 3, alkyl group having 1 to 10 carbon atoms, such as _-CH 2 CH ₃ (although some hydrogen or all may be substituted with a halogen element such as fluorine);
(2) Alkoxy groups having 1 to 10 carbon atoms such as —OCH ₃ , —OCH ₂ CH ₃ , —OC ₆ H ₅ , —OCH ₂ OCH ₂ CH ₃ (however, part or all of hydrogen is halogen such as fluorine) May be substituted with an element);
_{(3) -COOCH 3, -COOCH 2} CH 3, -COOC 6 H 5 carboxyl group having 1 to 10 carbon atoms such as (although some hydrogen or all may be substituted with a halogen element such as fluorine );
(4) Carbonyl group having 1 to 10 carbon atoms such as —COCH ₃ , —COCH ₂ CH ₃ , —COC ₆ H ₅ (however, part or all of hydrogen may be substituted with a halogen element such as fluorine) );
(5) an aryl group having 1 to 12 carbon atoms such as —C ₆ H ₅ , —C ₆ H ₄ CH ₃ , —C ₆ H ₅ (CH ₃ ) ₂ (provided that part or all of hydrogen is fluorine or the like) Optionally substituted with a halogen element);
(6) A vinyl group having 1 to 10 carbon atoms such as —CH═CH ₂ , —CH═CH ₂ C ₂ H ₅ , —CH═CH ₂ C ₆ H ₅ (however, part or all of hydrogen is fluorine, etc.) May be substituted with a halogen element);
(7) Hydrogen or halogen elements such as fluorine and chlorine;
Which may be the same as or different from each other.

  In the case of using the above additives, the addition amount in the non-aqueous electrolyte is preferably 3 to 15% by mass in the total amount of the non-aqueous electrolyte in the case of aromatic compounds, and 1 to 15 in the total amount of the non-aqueous electrolyte in the case of the phosphazene derivative. It is good to set it as the mass%. One of these additives may be used alone, or two or more different additives may be used in combination.

  As the separator according to the battery of the present invention, a known separator, for example, a separator made of a porous film or a nonwoven fabric made of polyolefin such as polyethylene, polypropylene, or a fusion product of polyethylene and polypropylene can be used.

  In the battery of the present invention, the separator has a rectangular non-woven fabric made of a material having a melting point of 200 ° C. or higher and a rectangular porous film made of a material having a melting point of 140 ° C. or lower, A square non-woven fabric in the separator is disposed on both sides of the positive electrode sheet, and the non-woven fabric on the lower side of the positive electrode sheet and the non-woven fabric on the upper side are fixed on at least three sides. It is preferable that a rectangular porous film in the separator is fixed to at least one of the sides.

  When a separator having a rectangular non-woven fabric composed of a material having a melting point of 200 ° C. or higher and a rectangular porous film composed of a material having a melting point of 140 ° C. or lower is disposed and used as described above, For example, even in a high temperature environment of about 150 ° C., the non-woven fabric present so as to wrap around the positive electrode sheet in the separator is made of a material having a high melting point and does not thermally shrink. Therefore, even in a high temperature environment as described above, the occurrence of a short circuit due to the positive electrode being exposed and in contact with the negative electrode is suppressed, and thermal runaway of the battery is suppressed. Also, in a high temperature environment as described above, the so-called shutdown function that the porous film constituting the separator melts, fills the pores of the porous film and the voids of the nonwoven fabric, and blocks the movement of lithium ions in the separator. Is demonstrated. Moreover, since the porous film is fixed only by the nonwoven fabric and its one side, even if the porous film shrinks before melting, the nonwoven fabric in contact with the positive electrode shrinks following the shrinkage of the porous film. The shape is maintained without being deformed. Therefore, in the battery using the separator, the safety can be further enhanced by these actions.

  Moreover, in the above separator, the lower nonwoven fabric and the upper nonwoven fabric of the positive electrode are fixed on at least three sides, and at least one of these nonwoven fabrics and the porous film are fixed. Therefore, when the battery is manufactured, when the positive electrode, the negative electrode, and the separator are laminated to form a laminated electrode group, the positive electrode is not displaced in the separator, and thus the battery can be manufactured with high yield. Battery productivity can also be increased.

  In a separator having a rectangular non-woven fabric made of a material having a melting point of 200 ° C. or higher and a rectangular porous film made of a material having a melting point of 140 ° C. or lower, the non-woven fabric has a melting point, that is, JIS K 7121 The melting temperature measured using a differential scanning calorimeter (DSC) is made of a material having a melting point of 200 ° C. or higher, and is disposed on the upper and lower surfaces of the positive electrode sheet. Specifically, the material constituting the nonwoven fabric is preferably polyarylate, polyethylene terephthalate, polybutylene terephthalate, etc., and the nonwoven fabric may be composed of only one of these, or the nonwoven fabric may be used in combination of two or more. May be configured.

  The thickness of the nonwoven fabric is preferably 5 μm or more from the viewpoint of more effectively preventing the occurrence of a short circuit. On the other hand, if the nonwoven fabric is too thick, the battery becomes thick and the energy density per volume may decrease or the high rate discharge characteristics may decrease, so the thickness of the nonwoven fabric is preferably 50 μm or less, More preferably, it is 25 μm or less.

  Further, the air permeability of the nonwoven fabric is a Gurley value measured by a method defined in JIS P 8117, preferably 300 s / 100 ml or less, and more preferably 250 s / 100 ml or less. If the air permeability of the nonwoven fabric is too large, the ion permeability may be reduced. On the other hand, if the air permeability is too small, the strength of the nonwoven fabric is reduced. Therefore, the air permeability of the nonwoven fabric is preferably 100 s / 100 ml or more. The air permeability of the nonwoven fabric can be controlled by adjusting the thickness and porosity of the nonwoven fabric.

  Furthermore, the porosity of the nonwoven fabric is preferably 30% or more, and more preferably 45% or more, from the viewpoint of ensuring good ion permeability. On the other hand, if the porosity is too large, the strength of the nonwoven fabric may be insufficient. Therefore, the porosity of the nonwoven fabric is preferably 80% or less, and more preferably 70% or less.

  In addition, the porosity of the nonwoven fabric referred to in the present specification and the porosity of the porous film described later are obtained by cutting out a sample of a certain area, measuring its weight and thickness, and calculating from these measured values. Value.

  In a separator having a rectangular nonwoven fabric made of a material having a melting point of 200 ° C. or higher and a rectangular porous film made of a material having a melting point of 140 ° C. or lower, the porous film has a melting point, that is, JIS K In accordance with the provisions of 7121, the melting temperature measured using a differential scanning calorimeter (DSC) is made of a material having a melting point of 140 ° C. or higher, and is formed on at least one of the nonwoven fabrics arranged on the upper and lower surfaces of the positive electrode. Arranged and fixed. Note that if the melting point of the constituent material of the porous film is too low, a shutdown phenomenon may occur in the operating temperature range of the battery.

  Specific examples of the material constituting the porous film include polyolefin such as polyethylene and copolymer polypropylene (ethylene-propylene copolymer, etc.), and the porous film is composed of only one of these materials. It may be composed of two or more.

  The thickness of the porous film is preferably 5 μm or more from the viewpoint of more effectively preventing the occurrence of a short circuit. On the other hand, if the porous thickness is too thick, the battery becomes thick and the energy density per volume may decrease or the high rate discharge characteristics may decrease, so the porous thickness may be 50 μm or less. Preferably, it is more preferably 25 μm or less.

  Further, the air permeability of the nonwoven fabric is a Gurley value measured by a method prescribed in JIS P 8117, preferably 600 s / 100 ml or less, and more preferably 500 s / 100 ml or less. If the air permeability of the porous film is too large, the ion permeability may be reduced. On the other hand, if the air permeability is too small, the strength of the porous film becomes small. Therefore, the air permeability of the porous film is preferably 300 s / 100 ml or more. The air permeability of the porous film can be controlled by adjusting the thickness and porosity of the porous film.

  Furthermore, the porosity of the porous film is preferably 30% or more, and more preferably 45% or more, from the viewpoint of ensuring good ion permeability. On the other hand, if the porosity is too large, the strength of the porous film may be insufficient. Therefore, the porosity of the porous film is preferably 80% or less, and more preferably 70% or less. .

  Only one porous film may be fixed on the nonwoven fabric, but two or more porous films may be laminated and fixed on the nonwoven fabric. When laminating a plurality of porous films, the number is preferably 5 or less from the viewpoint of improving the workability. Moreover, it is preferable that the total number of laminated sheets in the separator (total number of nonwoven fabrics and porous films constituting the separator) is 2 to 5.

  Next, a method for manufacturing a laminated nonaqueous secondary battery according to the present invention includes a rectangular non-woven fabric made of a material having a melting point of 200 ° C. or higher and a rectangular porous film made of a material having a melting point of 140 ° C. or lower. An example of using a separator having the following will be described with reference to the drawings. FIG. 3 is a schematic plan view illustrating a situation where the positive electrode sheet is accommodated in the separator. Reference numeral 70 denotes a rectangular non-woven fabric related to the separator, which is arranged on the upper surface side of the positive electrode sheet, and is fixed to the rectangular non-woven fabric (not shown) arranged on the lower surface side of the positive electrode sheet at the fixing portion 90. And the rectangular porous film 80 is arrange | positioned on the nonwoven fabric 70, and the porous film 80 and the nonwoven fabric 70 are being fixed by the fixing | fixed part 91 in the edge | side facing the edge | side at the side of the positive electrode tab 31 side. In FIG. 3, the porous film 80 is shown to be transparent in order to facilitate understanding of each component. Reference numeral 100 denotes a heat-resistant tape (for example, a polyimide tape) for fixing the nonwoven fabric 70 to the positive electrode sheet.

  The fixing portion 90 is provided on two sides of the rectangular nonwoven fabric 70 (vertical two sides in the figure). Here, the upper nonwoven fabric 70 and the lower nonwoven fabric of the positive electrode sheet are fixed by intermittent welding. . The upper nonwoven fabric and the lower nonwoven fabric of the positive electrode sheet may be fixed by intermittent welding as shown in FIG. 3, for example, by whole-surface welding that is welded from one end of the side to the other end. In FIG. 3, as described above, the nonwoven fabric 70 and the porous film 80 are fixed by welding on the side facing the side on the positive electrode tab 31 side. The lower nonwoven fabric is also welded at this location. That is, the configuration shown in FIG. 3 corresponds to an example in which the upper nonwoven fabric 70 and the lower nonwoven fabric of the positive electrode sheet are fixed on three sides. The upper nonwoven fabric 70 and the lower nonwoven fabric of the positive electrode sheet may be fixed on four sides.

  Alternatively, the upper nonwoven fabric and the lower nonwoven fabric of the positive electrode sheet may be a single nonwoven fabric, and one side of the fixing portion 90 may be a portion where the single nonwoven fabric is folded. That is, using a non-woven fabric having an area twice or more that of the positive electrode sheet, placing the positive electrode sheet thereon, folding the non-woven fabric so as to wrap the positive electrode sheet, and then removing two or more of the three unfixed sides It may be fixed by welding or the like.

  The nonwoven fabric 70 and the porous film 80 may be fixed by, for example, intermittent welding as shown in FIG. 3 or by whole surface welding that welds from one end of the side to the other end.

  In addition, it is preferable that the welding allowance (width | variety of a welding part) shall be 0.5-2 mm. If the welding allowance is too small, workability and reliability may be reduced. On the other hand, if the welding allowance is too large, the size of the laminated electrode group increases and the energy density per volume of the battery tends to decrease. In addition, when the upper nonwoven fabric 70 and the lower nonwoven fabric of the positive electrode sheet are fixed by intermittent welding, or when the nonwoven fabric 70 and the porous film 80 are fixed by intermittent welding, the welding interval is 2 to 5 mm. It is preferable to do.

  The nonwoven fabric and the porous film constituting the separator are rectangular and include a rectangle (rectangle) and a square, and a suitable shape may be selected according to the shape of the positive electrode sheet and the negative electrode sheet. In addition, the “square” of the nonwoven fabric and the porous film referred to in the present specification includes, for example, a shape in which one or more of the four corners are curved and a shape in which one or more of the four corners are cut off.

  As shown in FIG. 3, the upper nonwoven fabric 70 and the lower nonwoven fabric of the positive electrode sheet are fixed on at least three sides, and the upper nonwoven fabric 70 or the lower nonwoven fabric and the porous film 80 are fixed on one side. After that, as shown in FIG. 4, it is preferable to fix the free end of the porous film 80 to the positive electrode (positive electrode tab 31) with a heat-resistant tape (polyimide tape or the like) 100 or the like.

  The positive electrode sheet and separator integrated product thus obtained and the negative electrode sheet are alternately laminated to form a laminated electrode group 20 as shown in FIG. In FIG. 5, some components are shown as being transparent in order to facilitate understanding of the arrangement of the components. In FIG. 5, 41 is a negative electrode tab. In addition, the laminated | stacked positive electrode sheet, the integrated product of a separator, and the negative electrode sheet fix 1 to 3 places of each side with heat-resistant tapes (polyimide tape etc.) 100. If the number of fixing points on the heat-resistant tape 100 is four or more per side, the permeability of the non-aqueous electrolyte into the electrode is reduced, the time for injecting the non-aqueous electrolyte is increased, and workability may be reduced. is there. On the other hand, if fixing with the heat-resistant tape 100 is not performed, the stacked electrodes are likely to be displaced, and the probability of occurrence of a short circuit may increase.

  A terminal is welded to the multilayer electrode group thus obtained as shown in FIG. As the positive electrode terminal 30, for example, an aluminum terminal is preferably used, and as the negative electrode terminal 40, for example, a nickel-plated copper terminal is preferably used. The positive electrode terminal 30 can be welded to the positive electrode tab, and the negative electrode terminal 40 can be welded to the negative electrode tab by ultrasonic welding or the like. Moreover, the welding location (both surfaces) of the positive electrode terminal 30 and the welding location (both surfaces) of the negative electrode terminal 40 are protected by a heat resistant tape (polyimide tape or the like) 100. In FIG. 6, the heat-resistant tape 100 is represented by being shaded and transparent, but this is similar to the presence of the heat-resistant tape 100, as in the laminated electrode group 20 shown in FIG. 1. This is to facilitate understanding of the structure of the lower part, and does not show a cross section of the heat-resistant tape 100.

  The laminated electrode group in which the positive electrode terminal and the negative electrode terminal are welded is accommodated in, for example, a laminate sheet exterior body as shown in FIG. 1, and the laminate sheet exterior body is welded leaving one side for injecting the nonaqueous electrolyte, After injecting the nonaqueous electrolyte into the laminate outer package, the remaining sides are welded under reduced pressure to obtain a laminate type nonaqueous secondary battery.

  In the case of a laminated battery using a laminate sheet exterior material, such as the battery of the present invention, a safety device such as a safety valve, a shut-off vent, or a cleavage vent that is employed in a normal cylindrical battery is used as a battery container. It is difficult to provide. However, a laminate type in which a separator having a rectangular non-woven fabric composed of a material having a melting point of 200 ° C. or higher and a rectangular porous film composed of a material having a melting point of 140 ° C. or lower is arranged and used as described above. If it is a non-aqueous secondary battery, even if it does not provide a safety device in the battery container, thermal runaway of the battery can be suppressed and its safety can be ensured.

  The laminated non-aqueous secondary battery shown in FIGS. 3 to 6 is merely a preferred example of the present invention. For example, as described above, the laminated non-aqueous secondary battery of the present invention is A conventionally known separator can also be used. 3 to 6 are only shown for the purpose of facilitating understanding of the configuration of the laminated nonaqueous secondary battery, and the size of each component is not necessarily accurate.

  The laminated non-aqueous secondary battery of the present invention has good reliability over a long period of time not only in a normal environment where a conventional laminated non-aqueous secondary battery is used, but also in a special environment such as a high temperature environment. Therefore, taking advantage of this characteristic, high capacity batteries such as hybrid cars, electric assist bicycles, electric cars, electric bikes, electric chairs, home and commercial power storage systems, and road leveling are required. It can be used for various applications where a non-aqueous secondary battery is used, such as a power source for portable electronic devices such as a mobile phone and a notebook personal computer.

  Hereinafter, the present invention will be described in detail based on examples. However, the following examples are not intended to limit the present invention, and all modifications made without departing from the spirit of the preceding and following descriptions are included in the technical scope of the present invention.

<Preparation of positive electrode sheet>
92 parts by mass of LiCoO _{2 as a} positive electrode active material, 4 parts by mass of acetylene black as a conductive auxiliary agent, and 4 parts by mass of polyvinylidene fluoride as a binder are uniformly dispersed in NMP to obtain a positive electrode mixture-containing paste. Prepared. A positive electrode mixture-containing paste was applied to both surfaces of an aluminum foil with a thickness of 20 μm serving as a positive electrode current collector, leaving portions to be positive electrode tabs, dried, and then pressed to a thickness of 120 μm. A sheet was produced.

<Preparation of negative electrode sheet>
A negative electrode mixture-containing paste was prepared by uniformly dispersing 94 parts by mass of mesocarbon microbeads as a negative electrode active material and 6 parts by mass of polyvinylidene fluoride as a binder in NMP. A negative electrode mixture-containing paste was applied to both sides of a copper foil having a thickness of 10 μm to be a negative electrode current collector, leaving portions to be negative electrode tabs, dried, and then pressed to a thickness of 110 μm. A sheet was produced.

<Battery assembly>
A rectangular nonwoven fabric made of polyarylate (melting point: 250 ° C.) having an air permeability of 7 s / 100 ml, a thickness of 25 μm, and a porosity of 70% is arranged above and below the positive electrode sheet, as shown in FIG. The two vertical sides in the figure were intermittently welded at intervals of 2 mm. The welding allowance at that time was 1 mm. Thereafter, the nonwoven fabric 70 and the positive electrode tab 31 portion were fixed with the polyimide tape 100. A rectangular copolymer polypropylene (melting point: 140 ° C.) porous film having an air permeability of 500 s / 100 ml, a thickness of 25 μm, and a porosity of 54% is arranged on the non-woven fabric 70, as shown in FIG. Thus, the porous film 80 and the nonwoven fabric 70 were intermittently welded at intervals of 2 mm with a welding margin of 1 mm on the side facing the side on the positive electrode tab 31 side. At this time, simultaneously with the welding of the porous film 80 and the nonwoven fabric 70, the nonwoven fabric 70 and the nonwoven fabric under the positive electrode sheet were also welded. That is, the upper nonwoven fabric 70 and the lower nonwoven fabric of the positive electrode sheet are welded on three sides. Then, as shown in FIG. 4, the free end of the porous film 80 was fixed to the positive electrode tab 31 part using the polyimide tape 100 (2 mm x 3 mm). In the integrated product of the positive electrode sheet and the separator thus obtained, a: 3 mm and b: 1 mm in FIGS. 3 and 4.

  Fourteen integrated sheets of the above positive electrode sheet and separator were prepared, and alternately stacked with 15 negative electrode sheets to produce a laminated electrode group as shown in FIG. For the fixation of the positive electrode sheet and separator constituting the laminated electrode group and the negative electrode sheet, a polyimide tape 100 of 10 mm × 10 mm was used, and as shown in FIG. One side was fixed on each side. In the obtained laminated electrode group, o: 10 mm, p: 5 mm, q: 30 mm, r: 30 mm, s: 67 mm, t: 60 ± 2 mm, u: 121 mm in FIG. 3.

  Next, as shown in FIG. 6, the positive electrode tab 30 of the laminated electrode group 20 was plated with a positive electrode terminal 30 made of aluminum having a width of 15 mm and a thickness of 0.2 mm, and the negative electrode tab was nickel-plated with a width of 15 mm and a thickness of 0.2 mm. The copper negative electrode terminals 40 were each welded by ultrasonic welding, and a 15 mm × 25 mm polyimide tape 100 was attached to each welded portion for protection. In the laminated electrode group after the positive electrode terminal 30 and the negative electrode terminal 40 are attached, v is 143 ± 0.5 mm in FIG.

  A laminate sheet exterior body of a three-layer structure of nylon / aluminum / polypropylene is prepared, and the sides to be welded and sealed on the inner side (polypropylene layer side) of the laminate sheet 11 that becomes the upper side of the laminated electrode group 20 as shown in FIG. A polyimide tape having a rectangular shape of 5 mm × 10 mm and a thickness of 50 μm is pasted as a heat-resistant material 50 at locations (two locations) that are planned to be the boundary between the welded portion and the non-welded portion at the corner where I attached.

Then, as shown in FIG. 1, the laminated electrode group 20 is disposed on the laminated sheet outer package 10, and the laminated sheet outer package 10 is folded back so as to sandwich the laminated electrode group 20, and the left side of the laminated sheet outer package 10 in FIG. Two sides of the vertical side (side on the positive electrode terminal 30 side) and the side on the terminal 30 and 40 side were welded using a heat sealer at 210 ° C. for 4 seconds with a welding margin of 10 mm (see FIG. 1). The laminated electrode group 20 shown in FIG. 4 and the laminated electrode group 20 produced in Example 1 are different in the fixing part of the heat-resistant tape). Next, a non-aqueous electrolyte is injected into the laminate sheet outer package 10 from the non-welded side (vertical side on the negative electrode terminal 40 side in FIG. 1), and then the non-welded side is removed with a heat sealer. A laminate type non-aqueous secondary battery having a configuration shown in FIG. 2 is prepared by using a welding margin of 10 mm under conditions of 210 ° C. for 4 seconds and adjusting the size by cutting unnecessary portions of the outer package. Obtained. In FIG. 2, d: 90 ± 1 mm, e: 15 mm, f: 25 mm, g: 10 mm, h: 143 ± 1 mm, i: 158 mm, j: 10 mm, k: 5 ± 0.1 mm. For the non-aqueous electrolyte, LiPF ₆ is dissolved at a concentration of 1 mol / l in a mixed solvent in which ethylene carbonate and diethyl carbonate are mixed at a ratio (mass ratio) of 50:50, and biphenyl which is an aromatic compound is dissolved in 2 parts. Mass%, 0.5% by mass of vinylene carbonate, 5% by mass of phoslite, which is a phosphazene compound, and 2% by mass of alicyclic epoxy acryl, which is a gelling agent, were used.

  The laminated non-aqueous secondary battery was stored at 70 ° C. for 15 hours, and the gelling agent was polymerized to make the electrolyte into a gel. Then, after cooling to room temperature and fully charged with a constant current of 0.8A (0.2C) and a constant voltage of 4.2V, chemical conversion inspection is performed by discharging to 3V with a constant current of 0.8A It was. The capacity of the obtained laminated nonaqueous secondary battery is 4 Ah.

Comparative Example 1
A laminated nonaqueous secondary battery was produced in the same manner as in Example 1 except that the heat-resistant materials 50 and 50 were not arranged inside the laminate sheet 11 on the upper side of the laminated electrode group 20.

  The batteries of Example 1 and Comparative Example 1 were subjected to the following hot and humid test and heat shock cycle test. The results are shown in Table 1.

<High temperature and humidity test>
Each of the five batteries of Example 1 and Comparative Example 1 was fully charged with a constant current of 0.8 A (0.2 C) and a constant voltage of 4.2 V, and then an environment with a temperature of 60 ° C. and a relative humidity of 90%. The sample was stored for 30 days, and then the environment was returned to room temperature to observe the presence or absence of battery leakage.

<Heat shock cycle test>
Each of the five batteries of Example 1 and Comparative Example 1 (batteries different from those used in the high temperature and humidity test) were fully charged at a constant current of 0.8 A (0.2 C) and a constant voltage of 4.2 V. I made it. Next, for these batteries, a series of operations of holding at a temperature of 60 ° C. for 1 hour, setting to −10 ° C. in 1 minute, holding at −10 ° C. for 1 hour, and returning to 60 ° C. in 1 minute is performed for 240 cycles (20 Sun) went. Then, each battery was returned to room temperature and the presence or absence of liquid leakage was observed.

  As is clear from Table 1, the laminate-type hiss secondary battery of Example 1 in which a heat-resistant material is arranged at a predetermined position is different from the battery of Comparative Example 1 in which no heat-resistant material is arranged. It can be seen that there is no leakage in the cycle test, and excellent reliability can be maintained for a long time even in a special environment.

It is a schematic diagram which shows a mode that the laminated electrode group which concerns on the laminated nonaqueous secondary battery of this invention is accommodated in a laminated sheet exterior body. It is a schematic diagram which shows an example of the lamination type non-aqueous secondary battery of this invention. It is a plane schematic diagram which shows the condition which accommodated the positive electrode sheet in the suitable example of the laminate-type non-aqueous secondary battery of this invention in the separator. It is a plane schematic diagram which shows the condition which accommodated the positive electrode sheet in the suitable example of the laminate-type non-aqueous secondary battery of this invention in the separator. It is a plane schematic diagram which shows the structure of the laminated electrode group in the suitable example of the laminate type non-aqueous secondary battery of this invention. It is a plane schematic diagram which shows the structure of the laminated electrode group in the suitable example of the laminate type non-aqueous secondary battery of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Laminate sheet exterior body 20 Laminated electrode group 30 Positive electrode terminal 40 Negative electrode terminal 50 Heat-resistant material

Claims (4)

An electrode group in which a positive electrode sheet and a negative electrode sheet are laminated via a separator is accommodated in a rectangular laminate sheet outer package, and a positive electrode terminal connected to the positive electrode sheet and a negative electrode terminal connected to the negative electrode sheet are external A laminate type non-aqueous secondary battery that is welded and sealed on three or four sides of the laminate sheet outer package in a state protruding to
Between the welded portion and the non-welded portion at at least a part of the corner where the welded and sealed sides intersect each other inside the battery of the laminate sheet on the upper side of the electrode group and / or the laminate sheet on the lower side of the electrode group A laminated non-aqueous secondary battery, characterized in that a heat-resistant material is disposed at the boundary portion.   2. The laminated nonaqueous secondary battery according to claim 1, wherein the heat-resistant material is a sheet having a thickness of 50 to 100 μm made of a material having a melting point of 200 ° C. or higher.   The laminated nonaqueous secondary battery according to claim 2, wherein the constituent material of the heat-resistant material is polyimide and / or polyphenylene sulfide.   The laminated heat-resistant secondary battery according to claim 2 or 3, wherein the heat-resistant material has an adhesive layer on one side thereof.

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