JP2008059766A - Nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery excellent in safety and productivity. <P>SOLUTION: The nonaqueous secondary battery is provided with a laminated electrode body with a cathode sheet made of a layer containing a cathode active material formed on a cathode collector and an anode sheet made of a layer containing an anode active material formed on an anode collector laminated through a separator. The separator includes a rectangular nonwoven fabric made of a material with a melting point of 200°C or more, and a rectangular porous film made of a material with a melting point of 140°C or less. The rectangular nonwoven fabric is arranged on both sides of the cathode sheet in the separator. The nonwoven fabric of a lower side of the cathode sheet and that of an upper side are fixed at least at three sides, and the rectangular porous film in the separator is fixed at its one side on at least one side of the rectangular nonwoven fabric arranged on both sides of the cathode sheet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-aqueous secondary battery, and more particularly to a 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. is there.

  A lithium ion secondary battery, which is a type of non-aqueous secondary 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 source of small portable devices such as mobile phones, the power source of these medium-sized and large-sized devices requires a high-power secondary battery having a large capacity.

  However, as batteries have higher capacities and higher energies, it has become difficult to ensure safety.For example, in abnormal situations during overheating or overcharging, the batteries can run out of heat, causing ignition or rupture. There is also a concern that causes it.

  Under such circumstances, various technologies for preventing thermal runaway of the battery and improving safety have been proposed. For example, Patent Document 1 discloses that two types of separators such as a porous polyimide film and a porous polyolefin film are provided between electrodes in order to prevent a battery from undergoing thermal runaway due to a short circuit due to a nail penetration or the like. A technique for configuring a battery by disposing the battery is disclosed.

JP 10-302749 A

  In a normal battery, for example, a plurality of positive electrodes and a plurality of negative electrodes may be used as a laminated electrode body in which separators are stacked. However, when two types of separators are used, There is a possibility that the two separators are displaced and their functions are not sufficiently exhibited. Therefore, it is necessary to laminate the positive and negative electrodes while preventing the separators from shifting, and this may impair battery productivity.

  This invention is made | formed in view of the said situation, and it is providing the non-aqueous secondary battery excellent in safety | security and favorable productivity.

  The non-aqueous secondary battery of the present invention that has achieved the above-described object includes a positive electrode sheet in which a positive electrode active material-containing layer is formed on a positive electrode current collector, and a negative electrode active material-containing layer formed on the negative electrode current collector The negative electrode sheet is provided with a laminated electrode body laminated via a separator, and the separator is a rectangular nonwoven fabric made of a material having a melting point of 200 ° C. or higher, and a melting point of 140 ° C. A rectangular porous film composed of the following materials, a rectangular nonwoven fabric in the separator is disposed on both sides of the positive electrode sheet, and a lower nonwoven fabric and an upper nonwoven fabric of the positive electrode sheet, Is fixed on at least three sides, and the rectangular porous film in the separator is fixed on one side of at least one of the square nonwoven fabrics arranged on both sides of the positive electrode sheet. It is a non-aqueous secondary battery according to symptoms.

  In the non-aqueous secondary battery of the present invention, for example, even in a high temperature environment of about 150 ° C., the non-woven fabric present so as to enclose the positive electrode sheet is made of a material having a high melting point. Does not heat 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. In the nonaqueous secondary battery of the present invention, the safety is ensured by these actions.

  Moreover, in the nonaqueous secondary battery of the present invention, 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 of the present invention is manufactured, when the positive electrode, the negative electrode, and the separator are laminated to form a laminated electrode body (hereinafter sometimes referred to as “stack”), the positive electrode may be displaced in the separator. Therefore, the battery can be manufactured with high yield, and the productivity of the battery can be increased.

  According to the present invention, it is possible to provide a non-aqueous secondary battery having excellent safety and good productivity.

  The nonaqueous secondary battery of the present invention includes a stack in which a positive electrode sheet and a negative electrode sheet are laminated via a separator, and the separator is composed of a nonwoven fabric and a porous film.

  The nonwoven fabric according to the separator is 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 according to JIS K 7121. It is arranged on the upper and lower surfaces. 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.

  The porous film according to the separator is composed of a material having a melting point, that is, a melting temperature measured using a differential scanning calorimeter (DSC) of 140 ° C. or higher in accordance with JIS K 7121. It arrange | positions and fixes on the at least one of the nonwoven fabric arrange | positioned at the upper and lower surfaces of a positive electrode. 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, the configuration of the non-aqueous secondary battery of the present invention will be described with reference to the drawings. FIG. 1 is a schematic plan view illustrating a situation where a positive electrode sheet is accommodated in a separator. Reference numeral 1 denotes a rectangular nonwoven fabric related to the separator, which is disposed on the upper surface side of the positive electrode sheet, and is fixed to the rectangular nonwoven fabric (not shown) disposed on the lower surface side of the positive electrode sheet at the fixing portion 4. And the rectangular porous film 2 is arrange | positioned on the nonwoven fabric 1, and the porous film 2 and the nonwoven fabric 1 are being fixed by the fixing | fixed part 5 in the edge | side facing the edge | side at the side of the positive electrode tab 3. FIG. In FIG. 1, the porous film 2 is shown as being transparent in order to facilitate understanding of each component. 6 is a heat-resistant tape (for example, polyimide tape) for fixing the nonwoven fabric 1 to the positive electrode sheet.

  The fixing portion 4 is provided on three sides of the rectangular nonwoven fabric 1 (two sides on the vertical side and one side on the positive electrode tab 3 side). Here, the upper nonwoven fabric 1 and the lower side of the positive electrode sheet are formed by intermittent welding. The non-woven fabric is fixed. The fixing of the upper nonwoven fabric and the lower nonwoven fabric of the positive electrode sheet may be performed by intermittent welding as shown in FIG. 1, for example, by whole surface welding that welds from one end of the side to the other end. In FIG. 1, as described above, the nonwoven fabric 1 and the porous film 2 are fixed by welding on the side facing the side on the positive electrode tab 3 side. The lower nonwoven fabric is also welded at this location. That is, the configuration shown in FIG. 1 corresponds to an example in which the upper nonwoven fabric 1 and the lower nonwoven fabric of the positive electrode sheet are fixed on four sides. The upper nonwoven fabric 1 and the lower nonwoven fabric of the positive electrode sheet may be fixed on three 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 4 may be a portion obtained by folding the single nonwoven fabric. 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.

  For example, as shown in FIG. 1, the nonwoven fabric 1 and the porous film 2 may be fixed by whole surface welding from one end to the other end of the side or by intermittent welding.

  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 stack increases and the energy density per volume of the battery may decrease. Moreover, when fixing the nonwoven fabric 1 and the lower nonwoven fabric of a positive electrode sheet by intermittent welding, or fixing the nonwoven fabric 1 and the porous film 2 by intermittent welding, the space | interval of welding is 2-5 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 in the present invention 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. 1, the upper nonwoven fabric 1 and the lower nonwoven fabric of the positive electrode sheet are fixed on at least three sides, and the upper nonwoven fabric 1 or the lower nonwoven fabric and the porous film 2 are fixed on one side. Then, as shown in FIG. 2, it is preferable to fix the free end of the porous film 2 to the positive electrode (positive electrode tab 3) with a heat-resistant tape (polyimide tape or the like) 6 or the like.

  The positive electrode sheet and separator integrated product thus obtained and the negative electrode sheet are alternately laminated to form a stack as shown in FIG. In FIG. 3, in order to facilitate understanding of the arrangement of each component, some components are shown to be transparent. In FIG. 3, 7 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 tape (polyimide tape etc.) 6. If the number of fixing points on the heat-resistant tape 6 is four or more per side, the permeability of the electrolytic solution into the electrode is lowered, the time for injecting the electrolytic solution is increased, and workability may be lowered. On the other hand, if the fixing with the heat-resistant tape 6 is not performed, the stacked electrodes are likely to be displaced, and the probability of occurrence of a short circuit may increase.

  Terminals are welded to the stack thus obtained as shown in FIG. As the positive electrode terminal 8, for example, an aluminum terminal is preferably used, and as the negative electrode terminal 9, for example, a nickel-plated copper terminal is preferably used. The positive electrode terminal 8 can be welded to the positive electrode tab, and the negative electrode terminal 9 can be welded to the negative electrode tab by ultrasonic welding or the like. Further, the welded portion (both surfaces) of the positive electrode terminal 8 and the welded portion (both surfaces) of the negative electrode terminal 9 are protected with a heat-resistant tape (polyimide tape or the like) 6. In FIG. 4, the heat-resistant tape 6 is hatched and represented as transparent, but this is for the purpose of facilitating understanding of the presence of the heat-resistant tape 6 and the structure below the heat-resistant tape 6. The cross section of the heat-resistant tape 6 is not shown.

  The stack in which the positive electrode terminal and the negative electrode terminal are welded is accommodated in a battery container together with an electrolyte (nonaqueous electrolyte), and the container is sealed to obtain a nonaqueous secondary battery. FIG. 5 shows an example of the non-aqueous secondary battery of the present invention. In FIG. 5, (a) is a plan view of the non-aqueous secondary battery, and (b) is a side view. The non-aqueous secondary battery of FIG. 5 is a laminate type battery using a laminate outer packaging material 10 in which a metal foil such as aluminum is laminated with a resin sheet of nylon, polyethylene, polypropylene, etc. as a container, as shown in FIG. The portion indicated by hatching is the welded portion 11 of the laminate exterior material.

  The container (exterior material) according to the non-aqueous secondary battery of the present invention is not limited to the above-described laminated external material, and includes, for example, a rectangular (in particular, a thin rectangular with a small thickness to width ratio) external material ( Various storage containers to which a laminated electrode body is applied, such as a battery can), can also be used.

  In the case of a laminate type battery using a laminate outer packaging material, it is difficult to provide safety devices such as safety valves, shut-off vents, and cleavage vents used in ordinary cylindrical batteries in the battery container. . However, the non-aqueous secondary battery of the present invention can ensure the safety of the battery by preventing thermal runaway of the battery without providing a safety device in the battery container. Therefore, when the battery of the present invention is a laminated battery in which it is difficult to install a safety device, the effect is more remarkable.

  In addition, although the structure of the non-aqueous secondary battery of this invention was demonstrated so far using FIGS. 1-5, the structure and structure of the non-aqueous secondary battery of this invention are illustrated in these FIGS. It is not limited to what was done. 1 to 5 are shown for the purpose of facilitating understanding of the configuration of the nonaqueous secondary battery of the present invention, and the size of each component is not necessarily accurate.

The positive electrode according to the nonaqueous secondary battery of the present invention has a positive electrode active material-containing layer containing a positive electrode active material, a conductive additive, a binder, and the like formed on a current collector (one side or both sides of the current collector). Is. 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 according to the non-aqueous secondary battery of the present invention has a negative electrode active material and a binder, and further, a negative electrode active material-containing layer containing a conductive auxiliary agent as necessary on the current collector (one side or both sides of the current collector). ). 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 preparing 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 aid 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.

As an electrolytic solution (nonaqueous electrolytic solution) used for the nonaqueous secondary battery of the present invention, LiPF ₆ , LiBF ₄ , LiAsF ₆ may be used in an organic solvent such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, ethylene carbonate, or the like. A solution in which a solute such as LiCF ₃ SO ₃ is dissolved can be used.

  Moreover, said electrolyte solution can also be used by mixing resin, a crosslinking agent, etc., and making it gelatinize or solidify. By gelling the electrolyte, the components of the electrolyte are decomposed when the battery is overcharged, and gas is generated. This gas causes separation between the separator layers and between the separator and the negative electrode. Since a gap is formed, the safety of the battery can be further improved.

  Furthermore, at least one additive selected from an aromatic compound having a benzene ring and a phosphazene derivative may be added to the electrolytic solution. 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 electrolytic solution, either a cyclic type or a chain type can be used. In consideration of battery characteristics such as load characteristics, the phosphazene derivative is particularly represented by the following general formula (1). An annular structure 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.

  When the above additives are used, the addition amount in the electrolytic solution is preferably 3 to 15% by mass in the total amount of the electrolytic solution for aromatic compounds, and 1 to 15% by mass in the total amount of the electrolytic solution for phosphazene derivatives. It is good to do. One of these additives may be used alone, or two or more different additives may be used in combination.

  The non-aqueous secondary battery of the present invention can improve the productivity while improving the safety, which is a problem particularly in a large-capacity non-aqueous secondary battery. Therefore, the battery of the present invention is required to have a large capacity battery such as a hybrid vehicle, an electrically assisted bicycle, an electric vehicle, an electric motorcycle, an electric chair, a household or commercial power storage system, taking advantage of such characteristics. It can be used for various applications in which a non-aqueous secondary battery is used, such as a power source for portable devices such as mobile phones and notebook personal computers.

  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.

Example 1
<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 three sides excluding the side facing the side on the positive electrode tab 3 side were intermittently welded at intervals of 2 mm. The welding allowance at that time was 1 mm. Thereafter, the nonwoven fabric 1 and the positive electrode tab 3 portion were fixed with a polyimide tape 6. 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 disposed on the nonwoven fabric 1 and shown in FIG. In this way, the porous film 2 and the nonwoven fabric 1 were entirely welded with a welding allowance of 1 mm on the side facing the side on the positive electrode tab 3 side. At this time, simultaneously with the welding of the porous film 2 and the nonwoven fabric 1, the nonwoven fabric 1 and the nonwoven fabric under the positive electrode sheet were also welded. That is, the upper nonwoven fabric 1 and the lower nonwoven fabric of the positive electrode sheet are welded on four sides. Then, as shown in FIG. 2, the free end of the porous film 2 was fixed to the positive electrode tab 3 part using the polyimide tape 6 (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. 1 and 2.

  Fourteen integrated products of the above positive electrode sheet and separator were prepared, and alternately stacked with 15 negative electrode sheets to produce a stack as shown in FIG. For fixing the positive electrode sheet and separator constituting the stack and the negative electrode sheet, a polyimide tape 6 of 10 mm × 10 mm was used, and as shown in FIG. One side was fixed on each side. In the obtained stack, c: 10 mm, d: 5 mm, e: 67 mm, f: 30 mm, g: 30 mm, h: 60 ± 2 mm, and i: 121 mm in FIG. 3.

  Next, as shown in FIG. 4, a positive electrode terminal 8 made of aluminum having a width of 15 mm and a thickness of 0.2 mm is formed on the positive electrode tab of the above stack, and a nickel-plated copper made of nickel having a width of 15 mm and a thickness of 0.2 mm is formed on the negative electrode tab. Each of the negative electrode terminals 9 was welded by ultrasonic welding, and a 15 mm × 25 mm polyimide tape 6 was attached to each welded portion for protection. In the stack after the positive electrode terminal 8 and the negative electrode terminal 9 are attached, j is 143 ± 0.5 mm in FIG.

The stack after the attachment of the positive electrode terminal and the negative electrode terminal was accommodated in an aluminum laminate container together with the electrolyte, and the container was sealed to obtain a laminated nonaqueous secondary battery having the structure shown in FIG. . In FIG. 5, k: 90 ± 1 mm, l: 15 mm, m: 25 mm, n: 10 mm, o: 143 ± 1 mm, p: 158 mm, q: 10 mm, r: 5 ± 0.1 mm. In the electrolytic solution, LiPF ₆ was dissolved at a concentration of 1 mol / l in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a ratio (mass ratio) of 50:50, and 2% by mass of biphenyl as an aromatic compound, What added 0.5 mass% of vinylene carbonate, 5 mass% of phoslites which are phosphazene type compounds, and also added 2 mass% of alicyclic epoxy acryl which is a gelling agent was 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.

Example 2
Using the same positive electrode sheet and polyarylate non-woven fabric as used in Example 1, as shown in FIG. 6, the upper non-woven fabric 1 and the lower non-woven fabric of the positive electrode sheet are shown in two vertical sides in FIG. Intermittent welding was performed at an interval of 2 mm and a welding allowance of 1 mm. Thereafter, the nonwoven fabric 1 and the positive electrode tab 3 portion were fixed with a polyimide tape 6. Next, the same porous film 2 as used in Example 1 is placed on the nonwoven fabric 1, and the porous film 2 and the nonwoven fabric 1 are welded on the side facing the side on the positive electrode tab 3 side. Was welded to the entire surface. At this time, simultaneously with the welding of the porous film 2 and the nonwoven fabric 1, the nonwoven fabric 1 and the nonwoven fabric under the positive electrode sheet were also welded. That is, the upper nonwoven fabric 1 and the lower nonwoven fabric of the positive electrode sheet are welded on three sides. Thereafter, the free end of the porous film 2 was fixed to the positive electrode tab 3 portion using a polyimide tape (2 mm × 3 mm) to obtain an integrated product of the positive electrode sheet and the separator.

  A laminate type nonaqueous secondary battery was produced in the same manner as in Example 1 except that this positive electrode sheet and separator were integrated.

Example 3
As shown in FIG. 7, in the non-woven fabric on the upper side and the lower side of the positive electrode sheet, the welding on the three sides excluding the side facing the side on the positive electrode tab side is the entire surface welding with a welding margin of 1 mm. In the same manner as in Example 1, an integrated product of the positive electrode sheet and the separator was obtained.

  A laminate type nonaqueous secondary battery was produced in the same manner as in Example 1 except that this positive electrode sheet and separator were integrated.

Example 4
As shown in FIG. 8, in the upper nonwoven fabric and the lower nonwoven fabric of the positive electrode sheet, the welding on the two vertical sides in FIG. Thus, an integrated product of the positive electrode sheet and the separator was obtained.

  A laminate type nonaqueous secondary battery was produced in the same manner as in Example 1 except that this positive electrode sheet and separator were integrated.

Comparative Example 1
On the porous film made of the same material as that used in Example 1, a polyarylate non-woven fabric made of the same material as that used in Example 1 was placed, and the same as that produced in Example 1 was further formed thereon. A positive electrode sheet was provided. Thereafter, the laminate of the porous film and the nonwoven fabric is folded back to be larger than the positive electrode active material-containing layer of the positive electrode sheet, and the positive electrode active material-containing layer portion of the positive electrode sheet is wrapped with the laminate, as shown in FIG. The four sides of the laminate were intermittently welded at intervals of 2 mm with a welding margin of 1 mm, and the laminate and the positive electrode tab 3 portion were fixed with a polyimide tape 6 to obtain an integrated product of the positive electrode sheet and the separator.

  A laminate type nonaqueous secondary battery was produced in the same manner as in Example 1 except that this positive electrode sheet and separator were integrated.

Comparative Example 2
As shown in FIG. 10, the positive electrode sheet and the separator were integrated in the same manner as in Comparative Example 1 except that the welded portion of the laminate composed of the porous film and the nonwoven fabric was changed to three sides excluding the side on the positive electrode tab 3 side. The compound was obtained.

  A laminate type nonaqueous secondary battery was produced in the same manner as in Example 1 except that this positive electrode sheet and separator were integrated.

  The following three types of safety tests were performed on the laminated nonaqueous secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2. The results are shown in Table 1.

<150 ° C heating test>
About each of five batteries of Examples 1 to 4 and Comparative Examples 1 and 2, after being fully charged at a constant current of 0.8 A (0.2 C) and a constant voltage of 4.2 V at room temperature, The sample was heated up to 150 ° C. at 10 ° C./min and then kept at 150 ° C. for 1 hour, and the number of batteries whose temperature was raised to 180 ° C. or higher was examined.

<Nail penetration test>
For each of the five batteries of Examples 1 to 4 and Comparative Examples 1 and 2 (batteries not subjected to the high-temperature safety test), a constant current of 0.8 A (0.2 C) and a constant voltage of 4.2 V were obtained at room temperature. After the battery was fully charged, a nail having a diameter of 3 mm was passed through the battery at a speed of 1 mm / s at room temperature, and then the number of batteries whose temperature was raised to 180 ° C. or higher was examined.

<Overcharge test>
For each of the five batteries of Examples 1 to 4 and Comparative Examples 1 and 2 (batteries not subjected to the high-temperature safety test and the nail penetration test), the battery was charged to 12 V at a constant current of 4 A (1 C) at room temperature. Holding at a constant voltage for 1 hour, the number of batteries whose temperature was raised to 180 ° C. or higher was examined.

  As apparent from Table 1, in the batteries of Examples 1 to 4, thermal runaway such as heating to 180 ° C. or higher did not occur in any of heating at 150 ° C., nail penetration, and overcharging, and Comparative Example 1 The safety is improved as compared with the second battery. In addition, the batteries of Examples 1 to 4 did not cause a separator shift during the production of the stack and had good productivity.

3 is a schematic plan view illustrating a state in which a positive electrode sheet according to the nonaqueous secondary battery of Example 1 is accommodated in a separator. FIG. 3 is a schematic plan view illustrating a state in which a positive electrode sheet according to the nonaqueous secondary battery of Example 1 is accommodated in a separator. FIG. 3 is a schematic plan view illustrating a configuration of a laminated electrode body (stack) according to the nonaqueous secondary battery of Example 1. FIG. 3 is a schematic plan view illustrating a configuration of a laminated electrode body (stack) according to the nonaqueous secondary battery of Example 1. FIG. It is a schematic diagram which shows the structure of the non-aqueous secondary battery of an Example, (a) Top view, (b) Side view. It is a plane schematic diagram which shows the condition which accommodated the positive electrode sheet which concerns on the nonaqueous secondary battery of Example 2 in the separator. 6 is a schematic plan view illustrating a state in which a positive electrode sheet according to a nonaqueous secondary battery of Example 3 is accommodated in a separator. FIG. It is a plane schematic diagram which shows the condition which accommodated the positive electrode sheet which concerns on the nonaqueous secondary battery of Example 4 in the separator. It is a plane schematic diagram which shows the condition which accommodated the positive electrode sheet which concerns on the nonaqueous secondary battery of the comparative example 1 in the separator. It is a plane schematic diagram which shows the condition which accommodated the positive electrode sheet which concerns on the nonaqueous secondary battery of the comparative example 2 in the separator.

Explanation of symbols

1 Nonwoven fabric 2 Porous film 3 Positive electrode tab

Claims (6)

A laminate in which a positive electrode sheet in which a positive electrode active material-containing layer is formed on a positive electrode current collector and a negative electrode sheet in which a negative electrode active material-containing layer is formed on a negative electrode current collector are laminated via a separator. A non-aqueous secondary battery provided with an electrode body,
The separator has 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,
A rectangular nonwoven fabric in the separator is disposed on both surfaces of the positive electrode sheet, and the lower nonwoven fabric and the upper nonwoven fabric of the positive electrode sheet are fixed on at least three sides,
A non-aqueous secondary battery, wherein a rectangular porous film in the separator is fixed on one side of at least one of the rectangular nonwoven fabrics arranged on both surfaces of the positive electrode sheet.   The nonaqueous secondary battery according to claim 1, wherein the lower nonwoven fabric and the upper nonwoven fabric of the positive electrode sheet are fixed by intermittent welding or whole surface welding.   The nonaqueous secondary battery according to claim 1 or 2, wherein the nonwoven fabric and the porous film in the separator are fixed by intermittent welding or whole surface welding.   The nonaqueous secondary battery according to any one of claims 1 to 3, wherein the nonwoven fabric in the separator is composed of at least one material selected from the group consisting of polyarylate, polyethylene terephthalate, and polybutylene terephthalate.   The non-aqueous secondary battery according to claim 1, wherein the nonwoven fabric in the separator has an air permeability of 300 s / 100 ml or less, a porosity of 30 to 80%, and a thickness of 5 to 50 μm. The nonaqueous secondary battery according to claim 1, wherein the porous film in the separator has an air permeability of 600 s / 100 ml or less, a porosity of 30 to 80%, and a thickness of 5 to 50 μm.

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