JP5098194B2 - battery - Google Patents

Description

  The present invention relates to a battery using an electrolyte containing an electrolytic solution and a polymer compound.

  Industrial batteries occupy an important position as a power source for portable electronic devices. These devices are required to be smaller and lighter, and the batteries are also required to be lighter or to have a shape that can efficiently use the storage space in the device. For example, a lithium ion secondary battery having a large energy density or power density is most suitable as a battery that meets such a requirement.

  Among them, thin and large area sheet type batteries, thin and small area card type batteries or batteries having a high degree of freedom of shape are demanded. When metal cans conventionally used for exterior members are used, for example, Since the liquid electrolyte causes liquid leakage, it is difficult to produce such a battery.

Therefore, it has been proposed to use a gel electrolyte obtained by adding a substance having an adhesive action to a liquid electrolyte, or by mixing a polymer compound with the liquid electrolyte. As a result, an adhesive force is generated between the electrode and the electrolyte.For example, even when a film-like exterior member is used, the electrolyte can be prevented from leaking, so that the battery can be made thin and light. Since it is inexpensive, it has been put into practical use (see, for example, Patent Documents 1 and 2).
JP 2000-243447 A JP 2001-167797 A

  By the way, in order to increase the duration of the battery, that is, the battery capacity, the positive electrode active material or the negative electrode active material that accumulates electrochemical energy is packed at a high density, and the current collector, electrolyte, separator, exterior member, etc. It is preferable to reduce the material as much as possible. However, reducing these materials too much causes various problems and cannot be easily reduced. In particular, since the electrolyte is consumed in the charge / discharge reaction, if it is reduced too much, the charge / discharge characteristics, That is, there is a problem that the cycle characteristics deteriorate.

  In addition, for example, polyethylene used as a separator does not have sufficient oxidation resistance against a strong oxidizing atmosphere created by the positive electrode. If the electrolyte layer between the positive electrode and the separator is thin, for example, float charging (for example, using a personal computer) When trickle charging is performed, or when exposed to a high temperature environment in a fully charged state, there is a problem that an internal short circuit occurs.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a battery capable of improving capacity and battery characteristics such as cycle characteristics or high temperature characteristics.

The battery of the present invention is a battery in which a positive electrode and a negative electrode are laminated via a separator, and includes an electrolyte solution and a polymer compound between the positive electrode and the separator and between the negative electrode and the separator, respectively. layer is interposed, the electrolyte layer is formed by an electrolyte solution and a polymer compound, respectively positive and negative electrodes coated with including solution, electrolyte solution, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, at least one _{solvent, LiPF 6, LiBF 4, LiN} (CF 3 SO 2) 2 and _{LiN (C 2 F 5 SO 2} ) group consisting of _two of the group consisting of diethyl carbonate, ethyl propyl carbonate and dibutyl carbonate At least one electrolyte salt, and the polymer compound is a fluorinated copolymer of hexafluoropropylene in a proportion of 3% by mass to 7.5% by mass. It includes at least one member selected from the group consisting of a copolymer of vinylidene and hexafluoropropylene and a compound obtained by copolymerizing this copolymer with another monomer, and the distance (dC) between the positive electrode and the separator is 0 a larger than 10μm than .5Myuemu, the distance between the negative electrode and the separator (dA) is Ri large 15μm less der than 1 [mu] m, and the distance (dA) is greater than the distance (dC).

According to the battery of the present invention, the distance (dC) between the positive electrode and the separator is less than 10 μm, and the distance (dA) between the negative electrode and the separator is less than 15 μm. The amount can be increased and the capacity can be increased. In addition, since the distance (dC) between the positive electrode and the separator is made larger than 0.5 μm, cycle characteristics or high temperature characteristics can be improved. Furthermore, since the distance (dA) between the negative electrode and the separator is set to be larger than 1 μm, cycle characteristics can be improved. In particular, since the distance (dA) between the negative electrode and the separator is made larger than the distance (dC) between the positive electrode and the separator, a higher effect can be obtained.

Further, the distance between the negative electrode and the separator (dA), if to be larger than 1.1 times the distance between the positive electrode and the separator (dC), it is possible to obtain a higher effect.

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

  FIG. 1 shows an exploded configuration example of a secondary battery according to an embodiment of the present invention. This secondary battery has a configuration in which a wound electrode body 20 to which a positive electrode lead 11 and a negative electrode lead 12 are attached is housed in a film-shaped exterior member 31.

  Each of the positive electrode lead 11 and the negative electrode lead 12 has, for example, a strip shape, and is led out from the inside of the exterior member 31 to the outside, for example, in the same direction. The positive electrode lead 11 and the negative electrode lead 12 are preferably led out in the same direction, but may be led out in any direction as long as a short circuit does not occur and the battery performance does not deteriorate.

  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) or copper (Cu). The positive electrode lead 11 and the negative electrode lead 12 may be, for example, a foil shape, a ribbon shape, or a mesh shape.

  The exterior member 31 is composed of, for example, a moisture-proof and insulating multilayer film in which an aluminum foil is sandwiched between a pair of resin films, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive.

  Between the exterior member 31 and the positive electrode lead 11 and the negative electrode lead 12, adhesion between the positive electrode lead 11 and the negative electrode lead 12 and the exterior member 31 is improved, and the positive electrode lead 11, the negative electrode lead 12, and the exterior member 31 are improved. An adhesion film 32 for preventing a short circuit due to contact with the burr is inserted. The adhesion film 32 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-II of the spirally wound electrode body 20 shown in FIG. The wound electrode body 20 is formed by laminating and winding a positive electrode 21 and a negative electrode 22 with a separator 23 interposed therebetween, and the outermost peripheral portion is protected by a protective tape 25. An electrolyte layer 24 is interposed between the positive electrode 21 and the separator 23 and between the negative electrode 22 and the separator 23.

  The positive electrode 21 includes, for example, a positive electrode current collector 21A and a positive electrode active material layer 21B provided on both surfaces of the positive electrode current collector 21A. In the positive electrode current collector 21A, for example, there is an exposed portion without providing the positive electrode active material layer 21B at one end portion in the longitudinal direction, and the positive electrode lead 11 is attached to this exposed portion. The positive electrode current collector 21A is made of, for example, a metal material such as aluminum.

  The positive electrode active material layer 21B includes, for example, any one or more of positive electrode materials capable of inserting and extracting lithium (Li) as an electrode reactant as a positive electrode active material. . 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 (Fe), vanadium (V), titanium (Ti), chromium (Cr) and copper 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 , LiNi _0.5 Co _0.5 O ₂ , LiNi _0.8 Co _0.2 O _{2, and} LiMn ₂ O ₄ . An example of the lithium phosphate compound is LiFePO ₄ .

  The positive electrode active material layer 21B may also include a conductive material and a binder as necessary. Examples of the conductive material include carbon materials, and one or two or more kinds are used in combination. In addition, examples of the binder include polyvinylidene fluoride and polytetrafluoroethylene, and one kind or a mixture of two or more kinds is used.

  For example, similarly to the positive electrode 21, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B provided on both surfaces of the negative electrode current collector 22A. The negative electrode current collector 22A has, for example, an exposed portion where the negative electrode active material layer 22B is not provided at one end in the longitudinal direction, and the negative electrode lead 12 is attached to the exposed portion. The negative electrode current collector 22A is made of, for example, a metal material such as copper.

  The negative electrode active material layer 22B includes, for example, one or more negative electrode materials capable of occluding and releasing lithium, which is an electrode reactant, as a negative electrode active material. Accordingly, a binder such as polyvinylidene fluoride or styrene butadiene 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. Examples of graphites include artificial graphite such as mesophase carbon microbeads, carbon fiber or coke, or natural graphite.

  Examples of the negative electrode material capable of inserting and extracting lithium and the like include materials capable of inserting and extracting lithium and including at least one of a metal element and a metalloid element as a constituent element. It is done. This is because a high energy density can be obtained by using such a material. The negative electrode material may be a single element, alloy or compound of a metal element or metalloid element, or may have at least a part of one or more of these phases. In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of the metal element or metalloid element constituting the negative electrode material include magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), silicon (Si), which can form an alloy with lithium, Germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), Palladium (Pd) or platinum (Pt) can be mentioned. These may be crystalline or amorphous.

  Among these, as the negative electrode material, a material containing a 4B group metal element or a semimetal element in the short-period type periodic table as a constituent element is preferable, and at least one of silicon and tin is particularly preferable as a constituent element. This is because silicon and tin have a large ability to occlude and release lithium, and a high energy density can be obtained.

  As an alloy of tin (Sn), for example, as a second constituent element other than tin, silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony (Sb), And those containing at least one member selected from the group consisting of chromium. As an alloy of silicon, for example, as a second constituent element other than silicon, among the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing containing at least 1 sort (s) of these is mentioned.

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

Examples of the negative electrode material capable of inserting and extracting lithium further include other metal compounds or polymer materials. Examples of the other metal compounds include oxides such as iron oxide, ruthenium oxide, and molybdenum oxide, and LiN _3. Examples of the polymer material include polyacetylene, polyaniline, and polypyrrole.

  Examples of the separator 23 include non-woven fabrics or porous films such as polyolefin, polytetrafluoroethylene, or polyester, and among them, polyethylene or polypropylene porous films are preferable. It is because it is excellent in the short-circuit prevention effect and can improve the safety of the battery by the shutdown effect.

  The electrolyte layer 24 includes, for example, an electrolyte solution and a polymer compound that holds the electrolyte solution, and is configured by a so-called gel electrolyte. The electrolytic solution contains, for example, a solvent such as a nonaqueous solvent and an electrolyte salt dissolved in the solvent.

  The solvent preferably contains ethylene carbonate, and its content is preferably 15% by mass or more. This is because a stable coating can be formed on the surface of the negative electrode 22 and the decomposition reaction of the electrolytic solution can be suppressed. Further, the dielectric constant is also high, and dissolution and dissociation of the electrolyte salt can be promoted. However, since the melting point is as high as 38 ° C., the use of a large amount deteriorates the low temperature characteristics.

  Preferred examples of the solvent also include chain carbonate esters such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl propyl carbonate, or dibutyl carbonate. This is because the viscosity is low, the movement of ions can be increased, and the battery characteristics can be improved. Moreover, it is because melting | fusing point is low and a low temperature characteristic can also be improved.

  Furthermore, propylene carbonate is also preferred. This is because the dielectric constant is high and the dissociation of the electrolyte salt can be promoted, and the melting point is lower than that of ethylene carbonate, and the low temperature characteristics are not deteriorated as compared with ethylene carbonate. However, since the reactivity with the negative electrode 22 using graphite increases and a film that inhibits the electrode reaction is formed, it is preferably used in combination with ethylene carbonate or vinylene carbonate.

  In addition to these, lactones such as gamma butyrolactone can also be used as the solvent. Any one of the solvents may be used alone, or a plurality of the solvents may be mixed and used.

Examples of the electrolyte salt include lithium salts such as LiPF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) _2, or LiClO ₄ . Among these, LiPF ₆ is preferable from the viewpoint of electrochemical stability, thermal stability, and degree of dissociation. Any one of the electrolyte salts may be used alone, or a plurality of them may be mixed and used.

  The concentration of the electrolyte salt may be a concentration that can be dissolved in the solvent, but the concentration of lithium ions is preferably in the range of 0.4 mol / kg to 2.0 mol / kg with respect to the solvent.

  As the polymer compound, a copolymer of vinylidene fluoride and hexafluoropropylene is preferable. This is because the compatibility with a solvent such as propylene carbonate is high. The proportion of hexafluoropropylene in the copolymer of vinylidene fluoride and hexafluoropropylene is preferably in the range of 3% by mass to 7.5% by mass. When the amount is small, the compatibility with the solvent is lowered. When the amount is large, the viscosity of the electrolyte layer 24 is increased and the handling property is lowered. In addition, the molecular weight of the copolymer of vinylidene fluoride and hexafluoropropylene is such that the number average molecular weight is in the range of 500,000 to 700,000, or the weight average molecular weight is in the range of 210,000 to 310,000. And the intrinsic viscosity is preferably in the range of 1.7 to 2.1.

  As the polymer compound, a copolymer of vinylidene fluoride, hexafluoropropylene and monochlorotrifluoroethylene obtained by further copolymerizing monochlorotrifluoroethylene with the above-mentioned copolymer of vinylidene fluoride and hexafluoropropylene. Coalescence is also preferred. This is because the compatibility with a solvent such as propylene carbonate, dimethyl carbonate or ethyl methyl carbonate is high. The proportion of monochlorotrifluoroethylene in the copolymer of vinylidene fluoride, hexafluoropropylene and monochlorotrifluoroethylene is preferably in the range of 3% by mass to 7.5% by mass. When the amount is small, the compatibility with the solvent is lowered, and when the amount is large, the compatibility with the solvent becomes too high, and it becomes difficult to form a stable gel. Another monomer may be copolymerized with the copolymer of vinylidene fluoride and hexafluoropropylene, or the copolymer of vinylidene fluoride, hexafluoropropylene and monochlorotrifluoroethylene. In addition, any one of the polymer compounds may be used alone, or a plurality of types may be mixed and used.

  In this secondary battery, the distance (dC) between the positive electrode 21 and the separator 23 is less than 10 μm, and the distance (dA) between the negative electrode 22 and the separator 23 is less than 15 μm. This is because the thickness of the electrolyte layer 24 is reduced, the amount of active material that can be filled in the battery can be increased, and the capacity can be increased. Further, the distance (dC) between the positive electrode 21 and the separator 23 is larger than 0.5 μm. Thereby, the occurrence of an internal short circuit due to the oxidation of the separator 23 can be suppressed, and the cycle characteristics or the high temperature characteristics can be improved. Furthermore, the distance (dA) between the negative electrode 22 and the separator 23 is greater than 1 μm. Thereby, the thickness of the electrolyte layer 24 is moderate, and the cycle characteristics can be improved.

  In particular, the distance (dA) between the negative electrode 22 and the separator 23 is preferably larger than the distance (dC) between the positive electrode 21 and the separator 23, and the distance (dC) of the positive electrode 21 and the separator 23 is 1. If it is larger than 1 time, it is more preferable. This is because a higher effect can be obtained.

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

  First, a positive electrode active material, and if necessary, a conductive material and a binder are mixed to prepare a positive electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone to produce a positive electrode mixture slurry. To do. Next, the positive electrode mixture slurry is applied to both surfaces or one surface of the positive electrode current collector 21A by a doctor blade method or the like, dried, and compression-molded to form the positive electrode active material layer 21B, thereby producing the positive electrode 21. Subsequently, for example, the positive electrode lead 11 is joined to the positive electrode current collector 21A by, for example, ultrasonic welding or spot welding. After that, a precursor solution containing an electrolytic solution, a polymer compound, and, if necessary, a diluting solvent is prepared and applied on the positive electrode active material layer 21B, that is, on both surfaces or one surface of the positive electrode 21, and cooled or diluted solvent. Is evaporated to form the electrolyte layer 24.

  Further, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone or methyl ethyl ketone to prepare a negative electrode mixture slurry. Next, this negative electrode mixture slurry is applied to both surfaces or one surface of the negative electrode current collector 22A by a doctor blade method or the like, dried, and compression molded to form the negative electrode active material layer 22B, whereby the negative electrode 22 is fabricated. Subsequently, the negative electrode lead 12 is joined to the negative electrode current collector 22A by, for example, ultrasonic welding or spot welding, and the electrolyte is formed on the negative electrode active material layer 22B, that is, on both sides or one side of the negative electrode 22 in the same manner as the positive electrode 21. Layer 24 is formed. It should be noted that the electrolyte layer 24 formed by coating in this manner can satisfactorily adhere to the interface with the separator 23, and can suppress deterioration in cycle characteristics due to lithium metal precipitation by making it uniform.

  After that, the positive electrode 21 and the negative electrode 22 on which the electrolyte layer 24 is formed are laminated and wound via the separator 23, and the protective tape 25 is adhered to the outermost peripheral portion to form the wound electrode body 20. Finally, for example, the wound electrode body 20 is sandwiched between the exterior members 31, and the outer edges of the exterior members 31 are in close contact with each other by thermal fusion or the like and sealed. At that time, an adhesion film 32 is inserted between the positive electrode lead 11 and the negative electrode lead 12 and the exterior member 31. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and inserted in the negative electrode 22 through the electrolyte layer 24. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolyte layer 24. Here, since the distance (dC) between the positive electrode 21 and the separator 23 and the distance (dA) between the negative electrode 22 and the separator 23 are in the above-described ranges, the amount of the active material that can be filled in the battery is increased. Capacity is improved. Further, the occurrence of internal short circuit due to the oxidation of the separator 23 is suppressed, and the cycle characteristics or the high temperature characteristics are improved. Furthermore, the thickness of the electrolyte layer 24 is moderate, and the cycle characteristics are improved.

  Thus, according to the secondary battery according to the present embodiment, the distance (dC) between positive electrode 21 and separator 23 is less than 10 μm, and the distance (dA) between negative electrode 22 and separator 23 is less than 15 μm. Since it did in this way, the quantity of the active material which can be filled with the inside of a battery can be increased, and a capacity | capacitance can be made high. In addition, since the distance (dC) between the positive electrode 21 and the separator 23 is set to be larger than 0.5 μm, cycle characteristics or high temperature characteristics can be improved. Furthermore, since the distance (dA) between the negative electrode 22 and the separator 23 is set to be larger than 1 μm, the cycle characteristics can be improved.

  In particular, if the distance (dA) between the negative electrode 22 and the separator 23 is made larger than the distance (dC) between the positive electrode 21 and the separator 23, the distance (dA) between the negative electrode 22 and the separator 23 is further increased. If the distance (dC) between the positive electrode 21 and the separator 23 is greater than 1.1 times, a higher effect can be obtained.

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

(Examples 1-1 to 1-12)
First, 92% by mass of lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 5% by mass of powdered graphite as a conductive material, and 3% by mass of powdered polyvinylidene fluoride as a binder were mixed to form a positive electrode. After preparing a mixture, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, and then uniformly applied to both surfaces of the positive electrode current collector 21A made of an aluminum foil, It dried under reduced pressure at 100 degreeC for 24 hours, and compression-molded with the roll press machine, and formed the positive electrode active material layer 21B. Next, the positive electrode current collector 21 </ b> A on which the positive electrode active material layer 21 </ b> B was formed was cut into a 50 mm × 300 mm band to produce the positive electrode 21. After that, the positive electrode lead 11 made of an aluminum ribbon was attached to the positive electrode current collector 21A.

  Further, 91% by mass of artificial graphite as a negative electrode active material and 9% by mass of powdered polyvinylidene fluoride as a binder were prepared to prepare a negative electrode mixture, and this negative electrode mixture was used as N-methyl-2 as a solvent. -After being dispersed in pyrrolidone to form a negative electrode mixture slurry, it is uniformly coated on both surfaces of the negative electrode current collector 22A made of copper foil, dried at 120 ° C for 24 hours, and compression molded with a roll press to negative electrode active material Layer 22B was formed. Next, the negative electrode current collector 22 </ b> A on which the negative electrode active material layer 22 </ b> B was formed was cut into a strip shape of 52 mm × 320 mm to produce the negative electrode 22. After that, the negative electrode lead 12 made of a nickel ribbon was attached to the negative electrode current collector 22A.

Subsequently, LiPF ₆ as an electrolyte salt was dissolved in a solvent in which ethylene carbonate and propylene carbonate were mixed at an equal mass ratio so as to be 1.0 mol / kg to prepare an electrolytic solution. The electrolyte solution, a copolymer of vinylidene fluoride and hexafluoropropylene as a polymer compound, and dimethyl carbonate as a diluent solvent, are in a mass ratio of electrolyte solution: polymer compound: diluent solvent = 6: 1: 12. Were mixed and dissolved to prepare a sol precursor solution. The ratio of hexafluoropropylene in the copolymer was 6.9% by mass.

  The obtained precursor solution was applied to each of the positive electrode 21 and the negative electrode 22 using a bar coater, and heated at 80 ° C. for 2 minutes to volatilize the diluting solvent and form a gel electrolyte layer 24. At that time, the coating amount of the precursor solution was adjusted so that the distance (dC) between the positive electrode 21 and the separator 23 and the distance (dA) between the negative electrode 22 and the separator 23 were 0.5 μm < dC <10 μm, 1 μm <dA <15 μm.

  After that, the positive electrode 21 and the negative electrode 22 respectively formed with the electrolyte layer 24 were laminated via a separator 23 made of a polyethylene film having a thickness of 10 μm and a porosity of 33%, and wound to produce a wound electrode body 20. .

  The obtained wound electrode body 20 is shown in FIG. 1 and FIG. 2 by being sandwiched in an exterior member 31 made of a multilayer film in which an aluminum foil is sandwiched between a pair of resin films, and heat-sealing and sealing under reduced pressure. A secondary battery was prepared. At that time, an adhesive film 32 made of a resin piece was inserted between the positive electrode lead 11 and the negative electrode lead 12 and the exterior member 31. The secondary battery has a width of 37 mm, a height of 60 mm including the sealing portion, and a thickness of 5.0 mm when fully charged and fully expanded.

  As Comparative Examples 1-1 to 1-10 with respect to Examples 1-1 to 1-12, as shown in Table 1, the distance (dC) between the positive electrode 21 and the separator 23 is 0.5 μm or less, or 10 μm or more, or A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-12, except that the distance (dA) between the negative electrode 22 and the separator 23 was 1 μm or less or 15 μm or more.

  Regarding the fabricated secondary batteries of Examples 1-1 to 1-12 and Comparative examples 1-1 to 1-10, the battery capacity, the cycle capacity retention ratio, and the high-temperature storage characteristics were examined. The results are shown in Table 1.

  The battery capacity was examined as follows. First, in a 23 ° C. environment, constant current and constant voltage charging was performed until the total charging time reached 2.5 hours under the conditions of an upper limit voltage of 4.2 V and a current value of 1 C. , Constant current discharge was performed under the conditions of a current value of 0.5 C and a final voltage of 3 V. The capacity was determined based on the discharge capacity at this time. The average voltage is 3.7V. 1C and 0.5C are current values at which the rated capacity can be discharged in 1 hour and 2 hours, respectively.

  The cycle characteristics were examined as follows. First, in a 23 ° C. environment, constant current and constant voltage charging was performed until the total charging time reached 2.5 hours under the conditions of an upper limit voltage of 4.2 V and a current value of 1 C. Then, constant current discharge was performed under the conditions of a current value of 1 C and a final voltage of 3 V. The cycle characteristic is that 500 cycles of this charge / discharge are performed, and the maintenance ratio of the discharge capacity at the 500th cycle relative to the discharge capacity at the first cycle, that is, (discharge capacity at the 500th cycle / discharge capacity at the first cycle) × 100 (% )

  Further, the high temperature characteristics were examined as follows. First, in a 23 ° C. environment, constant current and constant voltage charging was performed until the total charging time reached 2.5 hours under the conditions of an upper limit voltage of 4.2 V and a current value of 1 C. Then, constant current discharge was performed under the conditions of a current value of 0.5 C and a final voltage of 3 V, and the discharge capacity before high-temperature storage was determined. Also, under an environment of 23 ° C., constant current and constant voltage charging was performed until the total charging time reached 2.5 hours under the conditions of an upper limit voltage of 4.2 V and a current value of 1 C, and the battery thickness (before storage at high temperature) Battery thickness) was measured. Subsequently, it was stored for 1 month in an environment of 60 ° C. and 90% humidity. Thereafter, the battery thickness (battery thickness after high-temperature storage) was determined, and the amount of swelling of the battery after high-temperature storage, that is, (battery thickness after high-temperature storage−battery thickness before high-temperature storage) was determined. Next, in a 23 ° C. environment, constant current discharge was performed under the conditions of a current value of 1 C and a final voltage of 3 V, the discharge capacity after high temperature storage was determined, and the remaining capacity was determined. In Table 1, the remaining capacity indicates the ratio of the discharge capacity after high-temperature storage to the discharge capacity before high-temperature storage, that is, (discharge capacity after high-temperature storage / discharge capacity before high-temperature storage) × 100 (%). Subsequently, under the environment of 23 ° C., constant current and constant voltage charging was performed until the total charging time reached 2.5 hours under the conditions of an upper limit voltage of 4.2 V and a current value of 1 C. Under the environment, constant current discharge was performed under the conditions of a current value of 0.5 C and a final voltage of 3 V, and the discharge capacity when charging / discharging was performed again after measuring the remaining capacity was obtained. The recovery capacity is the ratio of the discharge capacity when charge / discharge is performed again after measurement of the remaining capacity relative to the discharge capacity before storage at high temperature, that is, (discharge capacity when charge / discharge is performed again after measurement of remaining capacity / before storage at high temperature. It was calculated from (discharge capacity) × 100 (%).

  As shown in Table 1, according to Examples 1-1 to 1-12 in which 0.5 μm <dC <10 μm and 1 μm <dA <15 μm, the energy density is 410 Wh / L or more, and the cycle characteristic is 70% or more. The swollen amount after high temperature storage was 0.5 mm or less, the remaining capacity was 70% or more, and the recovery capacity was 90% or more.

  That is, if the distance (dC) between the positive electrode 21 and the separator 23 is greater than 0.5 μm and less than 10 μm, and the distance (dA) between the negative electrode 22 and the separator 23 is greater than 1 μm and less than 15 μm, the capacity It has been found that both cycle characteristics and high temperature characteristics can be improved.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above embodiments and examples, a secondary battery having a wound structure has been specifically described, but the present invention is configured by laminating a positive electrode and a negative electrode layer by layer via an electrolyte layer and a separator. Or a secondary battery having a stacked structure in which two or more positive electrodes and negative electrodes are alternately stacked via an electrolyte layer and a separator, or a secondary battery having a structure in which positive electrodes and negative electrodes are stacked and folded The same can be applied.

  Moreover, in the said embodiment and Example, although the case where the film-shaped exterior member 31 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 or a square shape. Further, various sizes such as a thin shape or a large size may be used.

  Furthermore, in the above embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, other group 1 elements in the long-period periodic table such as sodium (Na) or potassium (K), or The present invention can also be applied to the case of using elements of Group 2 in the long-period periodic table such as magnesium or calcium (Ca), other light metals such as aluminum, lithium, or alloys thereof. An effect can be obtained. In addition, lithium metal or a lithium alloy may be used as the negative electrode active material. In that case, the negative electrode 22 is obtained by, for example, applying a lithium metal powder to the negative electrode current collector 21A using a binder. It may be a rolled lithium metal plate. In addition, the present invention can be applied not only to secondary batteries but also to primary batteries.

It is a disassembled perspective view showing the structure of the secondary battery which concerns on one embodiment of this invention. It is sectional drawing showing the structure along the II-II line of the winding electrode body shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Positive electrode lead, 12 ... Negative electrode lead, 20 ... Winding electrode body, 21 ... Positive electrode, 21A ... Positive electrode collector, 21B ... Positive electrode active material layer, 22 ... Negative electrode, 22A ... Negative electrode collector, 22B ... Negative electrode active Material layer, 23 ... separator, 24 ... electrolyte layer, 25 ... protective tape, 31 ... exterior member, 32 ... adhesion film.

Claims (5)

A positive electrode and a negative electrode are laminated via a separator ,
Wherein between the positive electrode and the separator, and between the negative electrode and the separator is the electrolyte layer is interposed including each electrolytic solution and the polymer compound,
The electrolyte layer, the positive electrode and the electrolyte to the negative electrode, respectively the polymer compound is formed by applying the including solution,
The electrolyte includes at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl propyl carbonate, and dibutyl carbonate, and LiPF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ and LiN (C ₂ F ₅ SO ₂ ) ₂ and at least one electrolyte salt of the group consisting of
The polymer compound includes a copolymer of vinylidene fluoride and hexafluoropropylene obtained by copolymerizing hexafluoropropylene at a ratio of 3% by mass to 7.5% by mass, and other monomers added to the copolymer. Comprising at least one member of the group consisting of copolymerized compounds,
The distance between the positive electrode and the separator (dC) is greater than 10μm than 0.5 [mu] m, the negative electrode and the distance between the separator (dA) is Ri large 15μm less der than 1 [mu] m, and the distance (DA) is a battery larger than the distance (dC) . The distance between the negative electrode and the separator (dA), the greater than 1.1 times the distance between the positive electrode and the separator (dC), battery of claim 1, wherein. In the polymer compound, hexafluoropropylene was copolymerized in a proportion of 3% by mass to 7.5% by mass, and monochlorotrifluoroethylene was copolymerized in a proportion of 3% by mass to 7.5% by mass. a copolymer of vinylidene fluoride and hexafluoropropylene and monochlorotrifluoroethylene trifluoroethylene, and others to the copolymer includes at least one of the group consisting of compounds obtained by copolymerizing a monomer according to claim 1, wherein battery. The negative electrode comprises a carbon material, a battery of claim 1, wherein. The positive electrode contains a lithium transition metal oxide containing lithium capable of occluding and releasing lithium and a transition metal, batteries of claim 1, wherein.

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