JP2007172968A - Electrolyte and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte capable of enhancing battery characteristics such as charge discharge characteristics such as charge discharge efficiency and thermal stability in overcharge; and to provide a battery using the electrolyte. <P>SOLUTION: An electrolyte layer 24 contains the electrolyte and a polymer compound, and becomes in a gel state. The electrolyte contains a solvent containing trans-stilbenzene. The contents of trans-stilbenzene in the solvent is 0.05-9 mass%. The battery characteristics such as charge discharge efficiency and thermal stability in overcharge are enhanced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrolyte containing an additive and a battery using the same.

  Batteries occupy an important position as a power source for portable electronic devices such as cellular phones and portable information terminals. These electronic devices are required to be further reduced in size and weight, the batteries are also required to be lighter, and the storage space in the devices is required to be shaped efficiently. 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.

  In this lithium ion secondary battery, further improvement in battery characteristics is required as electronic devices have higher performance. The problem at this time is that the electrolyte is decomposed in the negative electrode and battery characteristics such as cycle characteristics are deteriorated. This is because the periphery of the negative electrode is exposed to a strong reducing atmosphere in a charged state and is very easy to react with the electrolyte.

  In a conventional lithium ion secondary battery, a passive film is formed on the surface of the negative electrode due to decomposition of the electrolyte, and is in a metastable state. However, since this passive film is formed mainly at the time of the first charge, a certain amount of charge is required, which causes a reduction in battery capacity. For example, when the lithium occlusion / release capacity of a carbon material normally used as a negative electrode active material is examined, in the case of a test electrode using lithium metal as a counter electrode, the initial discharge capacity relative to the initial charge capacity is low, and the initial charge / discharge efficiency [(initial Discharge capacity / initial charge capacity) × 100 (%)] was 80% to 95%. That is, the capacity that can be used with respect to the filling amount of the negative electrode active material is low, and waste is increased.

  Therefore, conventionally, one or more non-aqueous solvents having a reduction potential more noble than the main solvent, such as vinylene carbonate, 4-vinyl-1,3-dioxolan-2-one, succinic anhydride, ethylene sulfite, It has been proposed to form a passive film on the negative electrode and suppress reductive decomposition of the main solvent by adding and charging fluoroethylene carbonate or its derivative as an additive (see, for example, Patent Document 1).

  By the way, in such a lithium ion secondary battery, when it is overcharged, lithium is excessively extracted from the positive electrode, and excessive lithium is inserted into the negative electrode, so that the thermal stability of both electrodes is lowered. . As a result, the nonaqueous solvent is decomposed, the battery temperature rises, and a short circuit occurs.

Thus, it has been proposed to add a small amount of an aromatic compound such as an anisole derivative, terphenyl derivative, carbonic acid diphenyl derivative, biphenyl derivative or aromatic ether compound to the electrolytic solution (see, for example, Patent Documents 2 to 5). This is because these aromatic compounds can be oxidatively decomposed at a potential of about 4.5 V to form a polymer and form a film on the positive electrode, thereby consuming overcharge.
JP 2001-325988 A US Pat. No. 5,709,968 JP-A-2005-135906 JP 2005-322610 A JP-A-7-302614

  However, when these additives are used together for the purpose of improving the charge / discharge efficiency such as the initial charge / discharge efficiency or the cycle characteristics and the thermal stability during overcharge, for example, vinylene carbonate is decomposed at the positive electrode, There is a problem that a group compound or the like is decomposed in the negative electrode, and further, a side reaction occurs in which they react with each other. In addition, since two or more additives are used in combination, there is a problem that the cost increases. Therefore, development of an additive capable of achieving both of these purposes has been desired.

  The present invention has been made in view of such problems, and an object thereof is to provide an electrolyte capable of improving battery characteristics such as charge / discharge efficiency and thermal stability during overcharge, and a battery using the electrolyte. There is.

  The electrolyte of the present invention contains a solvent containing transstilbene in a range of 0.05% by mass to 9% by mass.

  The battery of the present invention is provided with an electrolyte together with a positive electrode and a negative electrode, and the electrolyte contains a solvent containing transstilbenzene in a range of 0.05 mass% to 9 mass%.

  According to the electrolyte and battery of the present invention, since the solvent containing transstilbenzene in the range of 0.05% by mass or more and 9% by mass or less is contained, the charge / discharge efficiency and the thermal stability during overcharge are included. The battery characteristics such as can be improved.

  In particular, if the content of transstilbenzene in the solvent is 0.1% by mass or more, the charge / discharge efficiency can be further improved.

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

  FIG. 1 shows an exploded structural 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 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 31 is made of, for example, a rectangular laminate film in which a nylon film, an aluminum foil, and a polypropylene film are bonded together in this order. The exterior member 31 is disposed, for example, so that the polypropylene film side and the wound electrode body 20 face each other, and the outer edge portions are in close contact with each other by fusion or an adhesive.

  An adhesion film 32 between the exterior member 31 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 31 and preventing the intrusion of outside air. Has been 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 obtained by stacking and winding a positive electrode 21 and a negative electrode 22 with a separator 23 and an electrolyte layer 24 interposed therebetween, and the outermost peripheral portion is protected by a protective tape 25.

  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 or one surface 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, one or more positive electrode materials capable of inserting and extracting lithium (Li), which is an electrode reactant, as a positive electrode active material. A conductive material such as graphite and a binding material such as polyvinylidene fluoride are included.

As a positive electrode material capable of inserting and extracting lithium, for example, a lithium-containing compound such as lithium oxide, lithium phosphorus oxide, lithium sulfide, or an intercalation compound containing lithium is suitable, and two or more kinds are mixed. May be used. In particular, in order to increase the energy density, a lithium composite oxide represented by the general formula Li _x MIO ₂ or a lithium phosphorus oxide represented by Li _y MIIPO ₄ is preferable. In the formula, MI and MII contain one or more transition metals, for example, cobalt (Co), nickel, manganese (Mn), iron (Fe), aluminum, vanadium (V), and titanium (Ti). It is preferable that at least one of them is included. The values of x and y vary depending on the charge / discharge state of the battery, and are usually values in the range of 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10. Specific examples of the lithium composite oxide represented by Li _x MIO ₂ include LiCoO ₂ , LiNiO ₂ , LiNi _0.5 Co _0.5 O ₂ , LiNi _0.5 Co _0.3 Mn _0.2 O ₂ , or LiMn ₂ O having a spinel crystal structure. ₄ and so on. Specific examples of the lithium phosphorus oxide represented by Li _y MIIPO ₄ include LiFePO ₄ and LiFe _0.5 Mn _0.5 PO ₄ .

  The negative electrode 22 includes, for example, a negative electrode current collector 22A and a negative electrode active material layer 22B provided on both surfaces or one surface of the negative electrode current collector 22A, as with the positive electrode 21. 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 anode current collector 22A is made of a metal material such as copper (Cu), for example.

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of occluding and releasing lithium, which is an electrode reactant, as a negative electrode active material. It is configured to include the same binder as the positive electrode active material layer 21B.

  Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials, metal oxides, and polymer materials. As the carbon material, any one of carbon materials such as non-graphitizable carbon, graphitizable carbon, graphites, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, activated carbon, and carbon black. Species or two or more can be used. Among these, cokes include pitch coke, needle coke, and petroleum coke. Organic polymer compound fired bodies are carbonized by firing polymer compounds such as phenol resin and furan resin at an appropriate temperature. What you did. Examples of the metal oxide include tin oxide, and examples of the polymer material include polyacetylene or polypyrrole.

  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 metal elements or metalloid elements constituting the negative electrode material include magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), and silicon (Si) that 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). 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.

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

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

  The separator 23 is made of, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and has a structure in which two or more kinds of porous films are laminated. May be. Among these, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve the safety of the battery due to the shutdown effect.

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

  Examples of the solvent include ethylene carbonate, propylene carbonate, vinylene carbonate, γ-butyrolactone, sulfolane, methyl sulfolane, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. A solvent may be used individually by 1 type and may be used in mixture of multiple types.

  The solvent also contains transstilbenzene shown in Chemical formula 1. This is because transstilbene has a double bond in the molecule and can be reduced at the negative electrode 22 to form a polymer to form a film and suppress the decomposition reaction of the solvent. In addition, when it has two benzene rings and becomes overcharged, π electrons are oxidized and polymerized to form a film on the positive electrode 21, thereby suppressing excessive lithium extraction. Because you can.

  The content of transstilbenzene in the solvent is in the range of 0.05% by mass or more and 9% by mass or less, and more preferably 0.1% by mass or more. This is because if the amount is small, the effect is low, and if the amount is large, the charge / discharge efficiency decreases due to an increase in internal resistance.

For example, LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiCl, or LiBr is used as the electrolyte salt. Any one electrolyte salt may be used alone, or a plurality of electrolyte salts may be mixed and used.

  The polymer compound may be any one that gels upon absorption of a solvent. For example, a fluorine polymer compound such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, polyethylene oxide or polyethylene oxide. And ether-based polymer compounds such as crosslinked products containing polyacrylonitrile, polypropylene oxide, or polymethacrylonitrile as repeating units. In particular, a fluorine-based polymer compound is desirable from the viewpoint of redox stability. Any one of these polymer compounds may be used alone, or two or more thereof may be mixed and used.

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

  First, for example, a positive electrode active material, a binder, and a conductive material are mixed to prepare a positive electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. Next, this positive electrode mixture slurry is applied to both surfaces or one surface of the positive electrode current collector 21A, 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 a mixed solvent is prepared and applied on the positive electrode active material layer 21B, that is, on both sides or one side of the positive electrode 21, and the mixed solvent is volatilized to obtain an electrolyte. Layer 24 is formed.

  Further, for example, a negative electrode mixture slurry is prepared by mixing a negative electrode active material and a binder to prepare a negative electrode mixture and dispersing it in a solvent such as N-methyl-2-pyrrolidone. Next, the negative electrode mixture slurry is applied to both surfaces or one surface of the negative electrode current collector 22A, 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.

  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.

  Moreover, you may produce the above-mentioned secondary battery as follows. First, the positive electrode 21 and the negative electrode 22 are prepared as described above, and after the positive electrode lead 11 and the negative electrode lead 12 are attached to the positive electrode 21 and the negative electrode 22, the positive electrode 21 and the negative electrode 22 are stacked via the separator 23 and wound. Then, the protective tape 25 is bonded to the outermost peripheral portion to form a wound body that is a precursor of the wound electrode body 20. Next, the wound body is sandwiched between the exterior members 31, and the outer peripheral edge portion excluding one side is heat-sealed to form a bag shape, and is stored inside the exterior member 31. Subsequently, an electrolyte composition including an electrolytic solution, a monomer that is a raw material of the polymer compound, and other materials such as a polymerization initiator or a polymerization inhibitor as necessary is prepared, and the interior of the exterior member 31 is prepared. inject.

  After injecting the electrolyte composition, the opening of the exterior member 31 is heat-sealed in a vacuum atmosphere and sealed. Then, if necessary, heat is applied to polymerize the monomer to form a polymer compound, thereby forming the gel electrolyte layer 24, and assembling the secondary battery shown in FIGS.

  In the secondary battery, when charged, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolyte layer 24. Next, when discharging is performed, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolyte layer 24. At that time, since the electrolyte layer 24 contains transstilbenzene at the above-described ratio, a film is formed on the negative electrode 22 and the decomposition reaction of the solvent is suppressed. Further, when the battery is overcharged, a film is formed on the positive electrode 21, and excessive lithium extraction is suppressed.

  As described above, in the present embodiment, the electrolyte layer 24 contains a solvent containing transstilbenzene in the range of 0.05% by mass or more and 9% by mass or less. Battery characteristics such as thermal stability can be improved.

  In particular, if the content of transstilbenzene in the solvent is 0.1% by mass or more, the initial charge / discharge efficiency can be further improved.

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

(Examples 1 to 10)
First, LiCoO ₂ as a positive electrode active material, graphite as a conductive material, polyvinylidene fluoride as a binder, and dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a positive electrode mixture slurry, This positive electrode mixture slurry was uniformly applied to a positive electrode current collector 21A made of an aluminum foil, dried, and compression molded to form a positive electrode active material layer 21B, whereby a positive electrode 21 was produced. After that, the positive electrode lead 11 made of aluminum was attached to one end of the positive electrode current collector 21A.

  In addition, artificial graphite as a negative electrode active material and polyvinylidene fluoride as a binder are mixed and dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry. The negative electrode 22 was manufactured by uniformly applying the electric body 22A, drying it, and compression-molding it with a roll press to form the negative electrode active material layer 22B. After that, the negative electrode lead 12 made of nickel was attached to one end of the negative electrode current collector 21A.

Subsequently, ethylene carbonate, propylene carbonate, and transstilbenzene were mixed as a solvent, and LiPF ₆ was dissolved as an electrolyte salt to prepare an electrolytic solution. At that time, the mixing ratio (mass ratio) of ethylene carbonate and propylene carbonate was ethylene carbonate: propylene carbonate = 6: 4. Moreover, as shown in Table 1, the content of transstilbenzene in the solvent was 0.05% by mass to 9% by mass. Furthermore, the concentration of LiPF ₆ in the electrolytic solution was set to 0.7 mol / kg.

  This electrolytic solution, a copolymer of vinylidene fluoride and hexafluoropropylene as a polymer compound, and dimethyl carbonate as a mixed solvent were mixed and dissolved to prepare a sol-like 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 the mixed solvent was volatilized to form a gel electrolyte layer 24.

  After that, the positive electrode 21 and the negative electrode 22 each formed with the electrolyte layer 24 were laminated via a separator 23 made of a polyethylene film, and wound to produce a wound electrode body 20.

  The obtained wound electrode body 20 was sandwiched between exterior members 31 made of a laminate film, and sealed under reduced pressure to produce the secondary battery shown in FIGS.

  As Comparative Example 1 with respect to Examples 1 to 10, a secondary battery was fabricated in the same manner as in Examples 1 to 10 except that transstilbenzene was not used. Further, as Comparative Examples 2 to 5, except that the content of transstilbene in the solvent was 0.01% by mass, 0.03% by mass, 10% by mass, or 12% by mass, other examples 1 to 10 were used. A secondary battery was fabricated in the same manner as described above.

  About the secondary battery of Examples 1-10 and Comparative Examples 1-5, the charging / discharging test was done and initial stage charging / discharging efficiency and cycling characteristics were investigated. At that time, after charging at a constant current of 0.5 C at 23 ° C. up to an upper limit of 4.2 V, constant voltage charging was performed at 4.2 V for 2 hours, and discharging was performed at a constant current of 0.2 C. The final voltage was 2.5V. The initial charge / discharge efficiency is obtained from the ratio of the initial discharge capacity (discharge capacity at the first cycle) to the initial charge capacity (charge capacity at the first cycle), that is, (initial discharge capacity / initial charge capacity) × 100 (%). It was. In addition, the cycle characteristic is that 500 cycles of charge and discharge are performed under the above-described conditions, and the discharge capacity maintenance rate of the 500th cycle with respect to the discharge capacity of the first cycle, that is, (discharge capacity of 500th cycle / discharge capacity of 1st cycle) It calculated | required from x100 (%). The results are shown in Table 1. Note that 0.2C and 0.5C are current values at which the theoretical capacity can be discharged in 5 hours and 2 hours, respectively.

  Moreover, the overcharge test was done about the secondary battery of Examples 1-10 and Comparative Examples 1-5. Specifically, a constant current charge of 1 C was performed from 3.6 V to 12 V for 2.5 hours to obtain an overcharged state, and the occurrence of an internal short circuit due to a rise in battery temperature was examined. The results are shown in Table 1. In Table 1, those that could not be used due to an internal short circuit due to a rise in the temperature of the battery were marked as x, and those that could be used were marked as ◯.

  As shown in Table 1, according to Examples 1 to 10 in which the content of transstilbenzene in the solvent was 0.05% by mass or more and 9% by mass or less, the content of transstilbenzene was 0.05% by mass. As compared with Comparative Examples 1 to 3, the initial charge / discharge efficiency and cycle characteristics were improved, and the results in the overcharge test were better. Further, the cycle characteristics were improved as compared with Comparative Examples 4 and 5 in which the content of transstilbenzene was more than 9% by mass. Furthermore, in Examples 3 to 10 in which the content of transstilbenzene in the solvent was 0.1% by mass or more, a high value was obtained for the initial charge / discharge efficiency.

  That is, if the electrolyte layer 24 contains a solvent containing transstilbenzene in the range of 0.05% by mass or more and 9% by mass or less, a battery such as charge / discharge efficiency and thermal stability during overcharge is obtained. It was found that the characteristics can be improved, and it is preferable that the content of transstilbenzene in the solvent is 0.1% by mass or more.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, a secondary battery having a winding structure using a film-like exterior member has been specifically described, but the present invention is a cylindrical type, a coin type, a sheet type, The present invention can be similarly applied to a secondary battery having another shape such as a button type or a square type, or a secondary battery having another stacked structure in which the positive electrode and the negative electrode are folded or the positive electrode and the negative electrode are stacked. Furthermore, the present invention can be applied not only to secondary batteries but also to primary batteries.

  In the above embodiments and examples, the case where lithium is used as the electrode reactant has been described, but other group 1 elements in the long-period periodic table such as sodium (Na) or potassium (K), or magnesium Alternatively, the present invention can be applied to the case where a Group 2 element in a long-period periodic table such as calcium (Ca), another light metal such as aluminum, lithium, or an alloy thereof is used, and similar effects are obtained. Can be obtained. At that time, a positive electrode active material or a solvent that can occlude and release the electrode reactant is selected according to the electrode reactant.

  Further, although cases have been described with the above embodiment and examples where a gel electrolyte in which an electrolytic solution is held in a polymer compound is used, other electrolytes may be used instead of these electrolytes. . Examples of other electrolytes include a liquid electrolyte only, a mixture of an ion conductive solid electrolyte and an electrolyte, or a mixture of a solid electrolyte and a gel electrolyte.

  As the solid electrolyte, for example, a polymer solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity, or an inorganic solid electrolyte made of ion conductive glass or ionic crystals can be used. In this case, as the polymer compound, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate or polyacrylate, or a mixture thereof, or in the molecule It can be used after being copolymerized. As the inorganic solid electrolyte, lithium nitride, lithium iodide, or the like can be used.

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 (6)

  An electrolyte comprising a solvent containing transstilbenzene in a range of 0.05% by mass to 9% by mass.   2. The electrolyte according to claim 1, wherein the content of transstilbenzene in the solvent is 0.1% by mass or more.   The electrolyte according to claim 1, further comprising a polymer compound. A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The battery contains a solvent containing transstilbene in a range of 0.05% by mass to 9% by mass.   The battery according to claim 4, wherein the content of transstilbene in the solvent is 0.1% by mass or more.   The battery according to claim 4, wherein the electrolyte further contains a polymer compound.

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