JP2007157499A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of improving cycle property or the like while restraining increase of its cubic volume. <P>SOLUTION: The battery element 10 is formed by laminating and winding a cathode 13 and an anode 14 through an electrode layer 15 and a separator 16. The electrolyte layer 15 is interposed between the anode 14 and the separator 16, and the cathode 13 is made to contact the separator 16. The electrolyte layer 15 contains electrolyte liquid and polymer compound, and gelled. The thickness of the electrolyte layer 15 is 3μm or thicker and 10μm or thinner. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery in which a positive electrode and a negative electrode are arranged to face each other via a separator.

  In recent years, many portable electronic devices such as a camera-integrated VTR, a mobile phone, or a notebook personal computer have appeared, and their size has been reduced. Thus, research and development for improving the energy density of batteries used as power sources for these electronic devices, particularly secondary batteries, are being actively promoted. Among these, lithium ion secondary batteries are widely used because they can obtain a higher energy density than conventional aqueous electrolyte secondary batteries such as lead batteries or nickel cadmium batteries.

As this lithium ion secondary battery, for example, there is a battery in which a positive electrode and a negative electrode are arranged to face each other with a separator interposed therebetween, and the separator is impregnated with an electrolytic solution (see, for example, Patent Document 1). In addition, there is also one using an electrolyte that is gelled by holding an electrolytic solution in a polymer compound (see, for example, Patent Document 2).
JP-A-10-189044 JP 2001-167797 A

However, in a battery using an electrolyte solution as it is, if the adhesion between the electrode and the separator is poor, the electrolyte solution is locally depleted, and in particular, lithium is partially deposited in the negative electrode, resulting in poor cycle characteristics. There was a problem that. In addition, in a battery using an electrolyte in which an electrolytic solution is held in a polymer compound, the adhesion between the electrode and the electrolyte is improved, but there is a problem that the volume increases by the amount of the polymer compound.

  The present invention has been made in view of such problems, and an object thereof is to provide a battery capable of improving characteristics while suppressing an increase in volume.

  In the battery of the present invention, a positive electrode and a negative electrode are arranged to face each other with a separator interposed therebetween, and the positive electrode is in contact with the separator, and an electrolytic solution and a polymer compound are placed between the negative electrode and the separator. An electrolyte layer is disposed, and the thickness of the electrolyte layer is 3 μm or more and 10 μm or less.

  According to the battery of the present invention, since the electrolyte layer is arranged between the negative electrode and the separator, the electrolyte layer can be adhered to the negative electrode, and lithium can be prevented from being deposited on the negative electrode. Moreover, since the separator is brought into contact with the positive electrode, an increase in volume can be suppressed. Therefore, characteristics can be improved while suppressing an increase in volume.

  In particular, if at least a part of the separator in contact with the positive electrode is made of polypropylene, oxidation of the separator can be suppressed and the characteristics can be further improved.

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

  FIG. 1 shows a configuration of a secondary battery according to an embodiment of the present invention. This secondary battery has a configuration in which a battery element 10 to which a positive electrode lead 11 and a negative electrode lead 12 are attached is housed inside a film-shaped exterior member 21.

  Each of the positive electrode lead 11 and the negative electrode lead 12 has a strip shape, for example, and is led out from the inside of the exterior member 21 to the outside, for example, in the same direction. The positive electrode lead 11 is made of a metal material such as aluminum (Al), and the negative electrode lead 12 is made of a metal material such as nickel (Ni).

  The exterior member 21 has a structure in which, for example, an insulating layer, a metal layer, and an outermost layer are laminated in this order and bonded together by laminating or the like. The exterior member 21 is, for example, in contact with each other by fusion bonding or an adhesive, with the insulating layer side being the inside.

  The insulating layer is made of, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, modified polypropylene, or a copolymer thereof. This is because moisture permeability can be lowered and airtightness is excellent. The metal layer is made of foil-like or plate-like aluminum, stainless steel, nickel, iron (Fe), or the like. The outermost layer may be made of, for example, the same resin as the insulating layer, or may be made of nylon or the like. This is because the strength against tearing and piercing can be increased. The exterior member 21 may include a layer other than the insulating layer, the metal layer, and the outermost layer.

  An adhesion film 22 between the exterior member 21 and the positive electrode lead 11 and the negative electrode lead 12 for improving the adhesion between the positive electrode lead 11 and the negative electrode lead 12 and the inside of the exterior member 21 and preventing the intrusion of outside air. Has been inserted. The adhesion film 22 is made of a material having adhesion to the positive electrode lead 11 and the negative electrode lead 12. For example, when the positive electrode lead 11 and the negative electrode lead 12 are made of the metal materials described above, polyethylene, polypropylene, It is preferably composed of a polyolefin resin such as modified polyethylene or modified polypropylene.

  FIG. 2 shows a cross-sectional structure taken along line II of the battery element 10 shown in FIG. The battery element 10 is formed by winding a positive electrode 13 and a negative electrode 14 facing each other with an electrolyte layer 15 and a separator 16 therebetween, and the outermost peripheral portion is protected by a protective tape 17. The electrolyte layer 15 is disposed between the negative electrode 14 and the separator 16, and the positive electrode 13 is in contact with the separator 15.

  The positive electrode 13 includes, for example, a positive electrode current collector 13A and a positive electrode active material layer 13B provided on both surfaces of the positive electrode current collector 13A. The positive electrode current collector 13A is made of, for example, a metal foil such as an aluminum foil, and the positive electrode lead 11 is attached to one end thereof.

  The positive electrode active material layer 13B includes, for example, any one or more of positive electrode materials capable of inserting and extracting lithium (Li) as a positive electrode active material, and a carbon material or the like as necessary. And a binder such as polyvinylidene fluoride or polytetrafluoroethylene. As the positive electrode material capable of inserting and extracting lithium, for example, a lithium composite oxide containing lithium and a transition metal or a lithium phosphate compound is preferable. This is because they can generate a high voltage and have a high density, so that the capacity can be increased.

As a lithium composite oxide, as a transition metal, cobalt (Co), nickel, manganese (Mn), iron, vanadium (V), titanium (Ti), chromium (Cr) and copper (Cu) What contains at least 1 type is preferable, and what contains at least 1 type in the group which consists of cobalt, nickel, and manganese is especially more preferable. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _{4, and} LiNi _0.5 Co _0.5 O ₂ . Examples of the lithium phosphate compound include LiFePO ₄ or LiFe _0.5 Mn _0.5 PO ₄ .

  For example, similarly to the positive electrode 13, the negative electrode 14 includes a negative electrode current collector 14 </ b> A and a negative electrode active material layer 14 </ b> B provided on both surfaces of the negative electrode current collector 14 </ b> A. The negative electrode current collector 14 </ b> A is made of, for example, a metal foil such as a copper foil, and the negative electrode lead 12 is attached to one end thereof.

  The negative electrode active material layer 14B includes, for example, any one or more of negative electrode materials capable of inserting and extracting lithium as a negative electrode active material, and if necessary, polyvinylidene fluoride or styrene butadiene A binder such as rubber may be included.

  Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon. Any one of these carbon materials may be used alone, or two or more of them may be mixed and used, or two or more of them having different average particle diameters may be mixed and used.

  Examples of the negative electrode material capable of inserting and extracting lithium include a material containing a metal element or a metalloid element capable of forming an alloy with lithium as a constituent element. Specifically, a single element, alloy, or compound of a metal element capable of forming an alloy with lithium, or a single element, alloy, or compound of a metalloid element capable of forming an alloy with lithium, or one or more of these. The material which has these phases in at least one part is mentioned.

  Examples of such metal elements or metalloid elements include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), and bismuth (Bi). , Cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (Hf) Is mentioned. Among them, a group 14 metal element or metalloid element in the long-period type periodic table is preferable, and silicon or tin is particularly preferable. This is because silicon and tin have a large ability to occlude and release lithium, and a high energy density can be obtained.

The electrolyte layer 15 includes an electrolytic solution and a polymer compound that holds the electrolytic solution, and has a so-called gel shape. The electrolytic solution includes an electrolyte salt and a solvent that dissolves the electrolyte salt. Examples of the electrolyte salt include lithium salts such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or LiAsF ₆ . Any one of the electrolyte salts may be used, or two or more of them may be mixed and used.

  Examples of the solvent include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, carbonic acid ester such as ethyl methyl carbonate and diethyl carbonate, 1,2-dimethoxyethane, 1-ethoxy-2-methoxyethane, 1,2 -Ethers such as diethoxyethane, tetrahydrofuran or 2-methyltetrahydrofuran, γ-butyrolactone, γ-valerolactone, cyclic carboxylic acid esters such as δ-valerolactone or ε-caprolactone, nitriles such as acetonitrile, sulfolane, phosphorus Nonaqueous solvents such as acids, phosphate esters, or pyrrolidones are mentioned. Any one kind of solvent may be used, but two or more kinds may be mixed and used.

  In particular, it is preferable to use ethylene carbonate as the solvent, and it is more preferable to include ethylene carbonate and at least one member selected from the group consisting of propylene carbonate, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate. This is because higher ionic conductivity can be obtained.

  The polymer compound only needs to absorb the solvent and gel, and examples thereof include a polymer using vinylidene fluoride, ethylene oxide, propylene oxide, acrylonitrile, or methacrylonitrile as at least one monomer. . Any one of these polymer compounds may be used alone, or two or more thereof may be mixed and used. Among them, a polymer using vinylidene fluoride as a monomer is preferable because high redox stability can be obtained. Examples of such a polymer compound include polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride, hexafluoropropylene, and monochlorotrifluoroethylene, or vinylidene fluoride. And a copolymer of hexafluoropropylene and monomethylmaleic acid ester. The copolymerization amount of the monomer copolymerized with vinylidene fluoride is preferably 3% by mass or more and 20% by mass or less with respect to the entire copolymer. If the amount is less than this, it is difficult to synthesize the copolymer. If the amount is more than this, the electrochemical stability of the copolymer is lowered, and the battery characteristics are lowered.

  The thickness of the electrolyte layer 15 is 3 μm or more and 10 μm or less. If it is thinner than 3 μm, the negative electrode 14, the electrolyte layer 15 and the separator 16 cannot be sufficiently adhered, and if it is thicker than 10 μm, the volume increases and the energy density per unit volume decreases. This is because the load characteristics are degraded.

  Any separator 16 may be used as long as it is electrically and chemically stable and does not have electrical conductivity. For example, non-woven fabric or porous film such as polymer, glass or ceramic can be used, and a plurality of these may be laminated. Among them, it is preferable to use a porous polyolefin film, and examples thereof include those made of polyethylene or polypropylene. In particular, at least a part of the side in contact with the positive electrode 13 is preferably made of polypropylene. This is because oxidation on the positive electrode 13 side can be suppressed. For example, the separator 16 may have a single layer structure of polypropylene, a two layer structure of a polypropylene layer and a polyethylene layer, or a three layer structure in which a polyethylene layer is sandwiched between polypropylene layers.

  The separator 16 is impregnated with an electrolytic solution, and the polymer compound of the electrolyte layer 15 may be impregnated with the electrolytic solution. The electrolytic solution impregnated in the separator 16 may have the same composition as the electrolytic solution contained in the electrolyte layer 15 or may have a different composition.

  The secondary battery having such a configuration can be manufactured, for example, as follows.

  First, for example, the positive electrode active material layer 13B is formed on the positive electrode current collector 13A to produce the positive electrode 13. The positive electrode active material layer 13B is prepared by, for example, mixing a powder of a positive electrode active material, a conductive material, and a binder, dispersing it in a dispersion medium to form a paste, and applying and drying the positive electrode current collector 13A. It is formed by molding. Further, for example, in the same manner as the positive electrode 13, the negative electrode active material layer 14 </ b> B is formed on the negative electrode current collector 14 </ b> A to produce the negative electrode 14. Next, the positive electrode terminal 11 is attached to the positive electrode current collector 13A, and the negative electrode terminal 12 is attached to the negative electrode current collector 14A.

  Subsequently, the electrolytic solution and the polymer compound are mixed using a mixed solvent, the mixed solution is applied onto the negative electrode active material layer 14B, and the mixed solvent is volatilized to form the electrolyte layer 15. Subsequently, the positive electrode 13, the separator 16, the negative electrode 14, and the separator 16 are sequentially stacked and wound, and the protective tape 17 is adhered to the outermost peripheral portion to form the battery element 10. The outer peripheral edge of the member 21 is heat-sealed. At that time, the adhesion film 22 is inserted between the positive electrode lead 11 and the negative electrode lead 12 and the exterior member 21. As a result, the secondary battery shown in FIGS.

  The electrolyte layer 15 may be formed on the separator 16 instead of being formed on the negative electrode 14. Further, before sealing the exterior member 21, if necessary, a solvent or an electrolytic solution may be injected into the exterior member 21 and impregnated in the separator 16. In that case, the composition of the solvent or the electrolytic solution may be the same as or different from the composition of the solvent or the electrolytic solution used when forming the electrolyte layer 15.

  In this secondary battery, when charged, lithium ions are released from the positive electrode 13 and inserted in the negative electrode 14 through the separator 16 and the electrolyte layer 15. When the discharge is performed, for example, lithium ions are released from the negative electrode 14 and inserted into the positive electrode 13 through the electrolyte layer 15 and the separator 16. At that time, since the electrolyte layer 15 is disposed between the negative electrode 14 and the separator 16 and the negative electrode 14 and the electrolyte layer 15 are in close contact with each other, local depletion of the electrolytic solution is suppressed, and lithium deposition is suppressed. Is suppressed.

  As described above, according to the present embodiment, since the electrolyte layer 15 having a thickness of 3 μm or more is disposed between the negative electrode 14 and the separator 16, the adhesion between the negative electrode 14, the electrolyte layer 15, and the separator 16 is improved. It can improve, and it can suppress that lithium precipitates on the negative electrode 14. FIG. Further, since the thickness of the electrolyte layer 15 is set to 10 μm or less and the separator 16 is brought into contact with the positive electrode 13, an increase in volume can be suppressed and load characteristics can be improved. Therefore, the energy density per unit volume can be improved, and battery characteristics such as cycle characteristics and load characteristics can be improved.

  In particular, if at least a part of the separator 16 in contact with the positive electrode 13 is made of polypropylene, the oxidation of the separator 16 can be suppressed, and the characteristics can be further improved.

  Further, specific embodiments of the present invention will be described in detail with reference to the drawings.

(Examples 1-1 to 1-9)
First, 90% by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 4% by mass of carbon black as a conductive material, and 6% by mass of polyvinylidene fluoride as a binder, N-methyl-2 as a dispersion medium -Pyrrolidone was used for kneading, coating on both surfaces of the positive electrode current collector 13A made of aluminum foil and drying, followed by compression molding to form the positive electrode active material layer 13B. After that, the positive electrode lead 11 made of aluminum was welded to the end of the positive electrode 13.

  Also, 90% by mass of artificial graphite as a negative electrode active material and 10% by mass of polyvinylidene fluoride as a binder are kneaded using N-methyl-2-pyrrolidone as a dispersion medium, and a negative electrode current collector made of copper foil After apply | coating to both surfaces of the body 14A and making it dry, it compression-molded, the negative electrode active material layer 14B was formed, and the negative electrode 14 was produced. After that, the negative electrode lead 12 made of nickel was welded to the end of the negative electrode 14. The ratio between the amount of the positive electrode active material and the amount of the negative electrode active material charged into the battery was designed so that lithium does not precipitate on the negative electrode 14 when charged to 4.2V.

Next, LiPF ₆ as an electrolyte salt was dissolved at a concentration of 1 mol / l in a solvent obtained by mixing 40% by mass of ethylene carbonate and 60% by mass of propylene carbonate to prepare an electrolytic solution. Subsequently, a copolymer of vinylidene fluoride and hexafluoropropylene is used as the polymer compound, the polymer compound and the electrolytic solution are mixed using a mixed solvent, and then applied to the surface of the negative electrode 14. The gelled electrolyte layer 15 was formed by volatilization. The copolymerization amount of hexafluoropropylene in the polymer compound was 7% by mass, and the thickness of the electrolyte layer 15 was changed as shown in Table 1 in Examples 1-1 to 1-9. Specifically, it was 3 μm in Examples 1-1 to 1-3, 5 μm in Examples 1-4 to 1-6, and 10 μm in Examples 1-7 to 1-9.

  After that, the positive electrode 13 and the negative electrode 14 on which the electrolyte layer 15 is formed are stacked via the separator 16, and flatly wound to form the battery element 10, which is housed in the exterior member 21 made of an aluminum laminate film. . As a result, the secondary battery shown in FIGS. Note that a single-layer porous polypropylene film or a single-layer porous polyethylene film was used as the separator 16, and two types of secondary batteries having different types of the separator 16 were produced for each example.

  As Comparative Examples 1-1 to 1-12 with respect to Examples 1-1 to 1-9, except that the thickness of the electrolyte layer was changed as shown in Table 1, other examples 1-1 to 1-9 were used. A secondary battery was fabricated in the same manner as described above. Specifically, the thickness of the electrolyte layer is 1 μm in Comparative Examples 1-1 to 1-3, 2 μm in Comparative Examples 1-4 to 1-6, and 20 μm in Comparative Examples 1-7 to 1-9. In Comparative Examples 1-10 to 1-12, the thickness was 30 μm.

  For the fabricated secondary batteries of Examples 1-1 to 1-9 and Comparative examples 1-1 to 1-12, cycle characteristics, lithium deposition in the negative electrode 14, load characteristics, and high-temperature storage characteristics were evaluated. The obtained results are shown in Table 1.

At that time, the cycle characteristics were as follows: constant current and constant voltage charging at 23 ° C. until the total charging time reached 2.5 hours at an upper limit voltage of 4.2 V and a current of 0.5 A, and then a current of 0.5 A at 23 ° C. Then, constant current discharge was performed at a final voltage of 2.5 V, and the discharge capacity at the first cycle and the discharge capacity at the 400th cycle were obtained by Equation 1. When the obtained cycle characteristics were 80% or more, it was judged good, and when it was less than 80%, it was judged as bad. The cycle characteristics are shown in one column because the same results were obtained when a porous polypropylene film was used as the separator 16 and when a porous polyethylene film was used.
(Formula 1)
Cycle characteristics (%)
= (Discharge capacity at 400th cycle / Discharge capacity at 1st cycle) × 100

  For lithium deposition, the battery charged at 4.2 V was disassembled, the negative electrode 14 was taken out, and it was judged by visual observation whether lithium was deposited on the negative electrode 14 or not. The lithium deposition state was also shown in one column because the same result was obtained regardless of the type of separator 16.

The load characteristics are as follows: the discharge capacity when performing a constant current discharge at 23 ° C. with a current of 0.5 A and a final voltage of 2.5 V; It calculated | required by Formula 2 from discharge capacity. At that time, charging was performed at a constant current and a constant voltage at 23 ° C. with an upper limit voltage of 4.2 V and a current of 0.5 A until the total charging time reached 2.5 hours. When the load characteristics obtained by this were 80% or more, it was judged as good, and when it was less than 80%, it was judged as bad. In addition, since the same result was obtained also about the load characteristic irrespective of the kind of separator 16, it showed according to one column.
(Formula 2)
Load characteristics (%) = (discharge capacity at current 2 A / discharge capacity at current 0.5 A) × 100

  The high-temperature storage characteristics were determined by storing the battery charged to 4.30 V in a thermostatic bath at 60 ° C. for one month and then examining the open circuit voltage of the battery. When the open circuit voltage after high-temperature storage is 4.00 V or higher, it is judged as good when it is below 4.00 V, and in Table 1, good is indicated with ◯, and bad is indicated with x. The high temperature storage characteristics are shown by type because different results were obtained depending on the type of the separator 16.

  As shown in Table 1, according to Examples 1-1 to 1-9 in which the electrolyte layer 15 having a thickness of 3 μm or more and 10 μm or less was provided between the negative electrode 14 and the separator 16, no lithium deposition was observed. Good cycle characteristics and load characteristics were obtained. On the other hand, in Comparative Examples 1-1 to 1-6 in which the thickness of the electrolyte layer 15 was reduced, precipitation of lithium was observed, and a decrease in cycle characteristics was observed. Further, in Comparative Examples 1-7 to 1-12 in which the thickness of the electrolyte layer 15 was increased, lithium deposition was not observed, but a decrease in load characteristics was observed. That is, it was found that cycle characteristics and load characteristics can be improved by providing an electrolyte layer 15 having a thickness of 3 μm or more and 10 μm or less between the negative electrode 14 and the separator 16.

  Further, when the porous polypropylene film was used as the separator 16, the decrease in the open circuit voltage after high temperature storage was smaller than when the porous polyethylene film was used. That is, it was found that if at least a part of the side of the palator 16 in contact with the positive electrode 13 is made of polypropylene, oxidation of the separator 16 can be suppressed and high temperature characteristics can be improved.

(Examples 2-1 to 2-21)
By adjusting the ratio between the amount of the positive electrode active material and the amount of the negative electrode active material charged into the battery, the full charge voltage by standard charging is 4.20V, 4.25V, 4.30V, 4.35V, 4. Except that the voltage is set to 40 V, 4.45 V, or 4.50 V and that the lithium is not deposited on the negative electrode 14 at the full charge voltage, the rest is the same as in Examples 1-4 to 1-6. A secondary battery was produced. That is, the thickness of the electrolyte layer 15 was 5 μm, and a separator 16 using a porous polypropylene film and a separator using a porous polyethylene film were prepared. The full charge voltage by standard charging is 4.20V in Examples 2-1 to 2-3, 4.25V in Examples 2-4 to 2-6, and 4 in Examples 2-7 to 2-9. .30V, Examples 2-10 to 2-12 are 4.35V, Examples 2-13 to 2-15 are 4.40V, Examples 2-16 to 2-18 are 4.45V, and Example 2-19 ~ 2-21 is 4.50V. In addition, standard charging means that constant current charging is performed at 23 ° C. with a constant current of 0.5 A until a predetermined voltage is reached, and then the total charging time reaches 2.5 hours at that predetermined voltage. Constant voltage charging shall be performed.

  About the produced secondary battery of Examples 2-1 to 2-21, the high temperature storage characteristic and the high temperature float characteristic were evaluated. The obtained results are shown in Table 2.

  At that time, the high temperature storage characteristics were determined by storing the battery fully charged by standard charging in a constant temperature bath at 60 ° C. for one month, and then examining the open circuit voltage of the battery. In Examples 2-1 to 2-3, the case where the open circuit voltage after high temperature storage is 4.00 V or more is good, and in Examples 2-4 to 2-6, the open circuit voltage after high temperature storage is 4.04 V or more. The case is good, in Examples 2-7 to 2-9, the case where the open circuit voltage after high temperature storage is 4.10 V or more is good, and in Examples 2-10 to 2-12, the open circuit voltage after high temperature storage is 4 Good when 14V or higher, Examples 2-13 to 2-15 are good when the open circuit voltage after high temperature storage is 4.18V or higher, and Examples 2-16 to 2-18 are open after high temperature storage. The case where the circuit voltage was 4.23V or more was good, and in Examples 2-19 to 2-21, the case where the open circuit voltage after high temperature storage was 4.30V or more was good, and the others were bad. In Table 2, the case of good is indicated by ○ and the case of failure is indicated by ×.

  The high-temperature float characteristics are as follows: constant current charging to a full charge voltage at a constant current of 0.5 A at 60 ° C., then constant voltage charging is continuously performed at that voltage, and after the current settles to 5 mA or less, 5 mA is again applied. It was judged good when the period until exceeding 1 month or more, and bad when shorter than 1 month. In Table 2, the case of good is indicated by ○ and the case of failure is indicated by ×.

  As shown in Table 2, when a porous polypropylene film was used for the separator 16, good results were obtained for both high temperature storage characteristics and high temperature float characteristics, but when a porous polyethylene film was used, Sufficient results were not obtained. That is, it was found that if at least a part of the side of the palator 16 in contact with the positive electrode 13 is made of polypropylene, the oxidation of the separator 16 can be suppressed even when the full charge voltage is increased.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the case where the battery element 10 is wound has been described. However, the battery element 10 includes a card-type battery element in which a positive electrode and a negative electrode are stacked one layer at a time via an electrolyte and a separator. Or a battery element in which two or more positive and negative electrodes are alternately laminated via an electrolyte and a separator, or a battery element in which a positive electrode and a negative electrode are laminated via an electrolyte and a separator The present invention can be similarly applied to the case of including

  Moreover, in the said embodiment and Example, although the case where the film-shaped exterior member 21 was used was demonstrated, you may use the exterior member of a can. In that case, the shape may be any shape such as a cylindrical shape, a square shape, a coin shape, or a button shape.

  Further, in the above embodiments and examples, the case where lithium is used for the electrode reaction has been described, but other alkali metals such as sodium (Na) or potassium (K), or alkaline earth such as magnesium or calcium (Ca). The present invention can also be applied to the case where a similar metal, other light metal such as aluminum, lithium, or an alloy thereof is used, and similar effects can be obtained.

  In addition, the present invention can be applied not only to secondary batteries but also to primary batteries.

It is a partial section perspective view showing composition of a rechargeable battery concerning one embodiment of the present invention. It is sectional drawing showing the structure along the II line of the battery element shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Battery element, 11 ... Positive electrode lead, 12 ... Negative electrode lead, 13 ... Positive electrode, 13A ... Positive electrode collector, 13B ... Positive electrode active material layer, 14 ... Negative electrode, 14A ... Negative electrode collector, 14B ... Negative electrode active material layer , 15 ... electrolyte layer, 16 ... separator, 17 ... protective tape, 21 ... exterior member, 22 ... adhesion film

Claims (6)

A battery in which a positive electrode and a negative electrode are arranged to face each other with a separator interposed therebetween,
The positive electrode is in contact with the separator;
Between the negative electrode and the separator, an electrolyte layer containing an electrolytic solution and a polymer compound is disposed,
The electrolyte layer has a thickness of 3 μm or more and 10 μm or less. The battery according to claim 1, wherein the electrolytic solution contains at least ethylene carbonate, and further contains at least one member selected from the group consisting of propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. 2. The battery according to claim 1, wherein the polymer compound contains a polymer using vinylidene fluoride, ethylene oxide, propylene oxide, acrylonitrile, or methacrylonitrile as at least one monomer. 3. The polymer compound includes polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride, hexafluoropropylene, and monochlorotrifluoroethylene, and vinylidene fluoride and hexafluoropropylene. The battery according to claim 3, comprising at least one member selected from the group consisting of copolymers with monomethylmaleic acid esters. The battery according to claim 1, wherein at least a part of the separator in contact with the positive electrode is made of polypropylene. The battery according to claim 5, wherein the separator has a single-layer structure of polypropylene, a two-layer structure of a polypropylene layer and a polyethylene layer, or a three-layer structure in which a polyethylene layer is sandwiched between polypropylene layers.

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