JP2005302492A - Electrolyte and battery using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery for improving cycle characteristics, and to provide an electrolyte using the battery. <P>SOLUTION: An electrode WINDER 20 in which a positive electrode 21 and a negative electrode 22 are laminated and wound via a separator is provided inside a battery can. An electrolyte is impregnated to the separator. The electrolyte contains at least one of ethyleneoxide and its dielectric, thus forming a covering having ion conductivity on the surface of the negative electrode 22, restraining an increase in internal resistance, and suppressing the decomposition reaction of a solvent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrolytic solution containing a compound having a specific structure and a battery using the same.

  In recent years, many portable electronic devices such as notebook type portable computers, cellular phones, and camera-integrated VTRs (video tape recorders) have appeared, and their size and weight have been reduced. Accordingly, as a power source for these portable electronic devices, development of a secondary battery that is lightweight and capable of obtaining a high energy density is in progress. As a secondary battery capable of obtaining a high energy density, for example, a lithium ion secondary battery using a material capable of inserting and extracting lithium (Li) such as a carbon material as a negative electrode active material has been put into practical use. ing.

In these lithium ion secondary batteries, it has been conventionally proposed to add various additives to the electrolytic solution in order to improve cycle characteristics. For example, Patent Document 1 describes that a non-conjugated unsaturated cyclic hydrocarbon is added.
JP 09-035746 A

  However, the electrolytic solution to which such an additive is added is not sufficiently effective, and therefore it has been desired to develop an electrolytic solution that can further improve the characteristics.

  The present invention has been made in view of such problems, and an object thereof is to provide a battery capable of improving cycle characteristics and an electrolytic solution used therefor.

  The electrolytic solution according to the present invention contains at least one of ethylene oxide and its derivatives.

  The battery according to the present invention includes an electrolyte solution together with a positive electrode and a negative electrode, and the electrolyte solution includes at least one of ethylene oxide and a derivative thereof.

  According to the electrolytic solution of the present invention, since at least one of ethylene oxide and its derivatives is included, for example, when used in the battery of the present invention, a film having ion conductivity is formed on the surface of the negative electrode. be able to. Therefore, the decomposition reaction of the solvent in the negative electrode can be suppressed while suppressing the increase in internal resistance, and the cycle characteristics can be improved.

  In particular, it is effective if the content of ethylene oxide and its derivative in the electrolytic solution is 0.01% by mass or more and 10% by mass or less.

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

  The electrolyte according to one embodiment of the present invention contains, for example, a liquid so-called electrolytic solution containing a solvent and an electrolyte salt dissolved in the solvent. Examples of the solvent include ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, vinyl ethylene carbonate, vinylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, and 2-methyl. Non-aqueous solvents such as tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate, butyrate or propionate It is done. Any one type of solvent may be used alone, or two or more types may be mixed and used.

Examples of the electrolyte salt include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiCl, or LiBr. Any one electrolyte salt may be used alone, or two or more electrolyte salts may be mixed and used.

  The concentration of the electrolyte salt is preferably in the range of 0.3 mol / l to 3.0 mol / l with respect to the solvent, for example. This is because high ionic conductivity can be obtained within this range.

  This electrolytic solution also contains ethylene oxide or a derivative thereof as an additive. This is because a film having ion conductivity can be formed by the reaction.

  Examples of the ethylene oxide derivative include compounds having the structure shown in Chemical Formula 1.

（式中、Ｘ１〜Ｘ４は水素基，メチル基，エチル基およびエチレン基のうちのいずれかを表す。それらは同一でも異なっていてもよいが、それらのうちの少なくとも１つはメチル基，エチル基あるいはエチレン基である。）

(Wherein X1 to X4 represent any one of a hydrogen group, a methyl group, an ethyl group and an ethylene group. They may be the same or different, but at least one of them is a methyl group, an ethyl group, Group or ethylene group.)

  Specific examples of the compound shown in Chemical Formula 1 include the compounds shown in Chemical Formulas 2 to 6. Any one of these compounds may be used alone, or two or more thereof may be mixed and used.

  The content of these ethylene oxides and ethylene oxide derivatives is preferably in the range of 0.01% by mass or more and 10% by mass or less with respect to the electrolytic solution as a whole. If the amount is too small, the effect of forming a coating is reduced. If the amount is too large, the thickness of the coating formed on the surface of the negative electrode 22 increases, battery resistance increases and lithium ion mobility decreases. is there.

  This electrolytic solution is used for a secondary battery as follows, for example.

  FIG. 1 shows a cross-sectional structure of the secondary battery. This secondary battery is a so-called cylindrical type, and has an electrode winding body 20 inside a substantially hollow cylindrical battery can 11. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the electrode winding body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are interposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the electrode winding body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  FIG. 2 shows a cross-sectional configuration along the line II-II of the electrode winding body 20 shown in FIG. The electrode winding body 20 is formed by laminating a belt-like positive electrode 21 and a belt-like negative electrode 22 with a separator 23 interposed therebetween, and a center pin 24 is inserted in the center. In FIG. 2, the separator 23 is omitted. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the electrode winding body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  The positive electrode 21 includes, for example, a current collector 21A having a pair of opposed surfaces and an active material layer 21B provided on both surfaces or one surface of the current collector 21A. The current collector 21A is made of, for example, aluminum, nickel, stainless steel, or the like.

  The active material layer 21B includes, for example, one or more of positive electrode materials capable of inserting and extracting lithium as a positive electrode active material (hereinafter referred to as positive electrode materials capable of inserting and extracting lithium). In addition, a conductive agent such as a carbon material and a binder such as polyvinylidene fluoride may be included as necessary. 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 the 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, manganese, iron, vanadium, and titanium is still more preferable. Among these, examples of the lithium composite oxide containing manganese include a spinel compound represented by the chemical formula Li _x Mn _{2 -y} M1 _y O ₄ . In the formula, M1 is iron, cobalt, nickel, copper, zinc (Zn), aluminum, tin (Sn), chromium, vanadium, titanium, magnesium (Mg), calcium (Ca), strontium (Sr), boron (B). , Gallium (Ga), indium (In), silicon (Si), and germanium (Ge) represent at least one kind, and the values of x and y are 0.9 ≦ x and 0.01 ≦ y ≦, respectively. 0.5. Examples of the lithium composite oxide containing nickel include those represented by the chemical formula LiNi _1-z M2 _z O ₂ . In the formula, M2 represents at least one selected from the group consisting of iron, cobalt, manganese, copper, zinc, aluminum, tin, chromium, vanadium, titanium, magnesium, calcium, strontium, boron, gallium, indium, silicon, and germanium. , Z is 0.01 ≦ z ≦ 0.5. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiNi _0.5 Co _0.5 O _2, LiNi _0.5 Co _0.3 Mn _0.2 O _{2, and the} like.

Examples of the lithium phosphate compound include LiFePO ₄ or LiFe _0.5 Mn _0.5 PO ₄ .

  Similarly to the positive electrode 21, the negative electrode 22 includes, for example, a current collector 22A having a pair of opposed surfaces, and an active material layer 22B provided on both surfaces or one surface of the current collector 22A. The current collector 22A is made of, for example, copper, nickel, stainless steel, or the like.

  The active material layer 22B includes, for example, one or more negative electrode materials capable of inserting and extracting lithium as a negative electrode active material (hereinafter referred to as negative electrode materials capable of inserting and extracting lithium). Thus, the binder similar to that of the positive electrode 21 may be included as necessary. Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials, metal oxides, and polymer materials. Carbon materials include artificial graphite, natural graphite, graphitizable carbon, cokes, graphites, glassy carbons, organic polymer compound sintered bodies, carbon fibers, activated carbon, carbon blacks, or non-graphitizable carbon Etc. Examples of the cokes include pitch coke, needle coke, and petroleum coke. The organic polymer compound sintered body is a carbonized material obtained by firing a polymer material such as phenols or furans at an appropriate temperature. In addition, examples of the metal oxide include iron oxide, ruthenium oxide, molybdenum oxide, tin oxide, and tungsten oxide, and examples of the polymer material include polyacetylene and polypyrrole.

  Examples of the negative electrode material capable of inserting and extracting lithium include simple elements, alloys, and compounds of metal elements or metalloid elements capable of forming an alloy with lithium. In this case, it is preferable to use it together with a conductive agent such as a carbon material. In addition to the alloy composed of two or more metal elements, the alloy includes an alloy composed of one or more metal elements and one or more metalloid elements. Some of the structures include a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them.

Examples of metal elements or metalloid elements capable of forming an alloy with lithium include magnesium, boron, arsenic (As), aluminum, gallium, indium, silicon, germanium, tin, lead (Pb), antimony (Sb), and bismuth. (Bi), cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), or platinum (Pt). Examples of these alloys or compounds include those represented by the chemical formula D _s E _t Li _u . In this chemical formula, D represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, and E represents at least one of elements other than lithium and D. The values of s, t, and u are s> 0, t ≧ 0, and u ≧ 0, respectively.

  Among them, a simple substance, alloy or compound of a group 14 metal element or metalloid element in the long-period type periodic table is preferable, silicon or tin, or an alloy or compound thereof is more preferable, and silicon or an alloy thereof is particularly preferable. Or it is a compound. These may be crystalline or amorphous.

Specific examples of such alloys or compounds include SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi _2. , Cu ₅ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO, or LiSnO.

  In this secondary battery, the positive electrode 21 includes an exposed region 21C in which the active material layer 21B is not provided, an outer surface active material region 21D in which the active material layer 21B is provided only on the outer surface side of the current collector 21A, The active material layer 21B has a double-sided active material region 21E provided on both sides of the current collector 21A, the negative electrode 22 has an exposed region 22C in which the active material layer 22B is not provided, and an active material layer 22B. It has an outer surface active material region 22D provided only on the outer surface side of the current collector 22A, and a double-sided active material region 22E in which an active material layer 22B is provided on both surfaces of the current collector 22A. The exposed region 21C of the positive electrode 21 is provided at least two turns on the winding center side and at least one turn on the winding outer periphery side, and the exposed region 22C of the negative electrode 22 is provided on each of the winding center side and the winding outer periphery side. One or more rounds are provided. In addition to improving heat dissipation, when pressure is applied from the outside of the battery, a short circuit is selectively generated between the winding center side and the winding outer periphery side of the battery to promote thermal diffusion and improve safety. Because. In particular, the exposed region 21C is provided at least one turn more than the exposed region 22C on the winding center side. If the negative electrode 22 exists inside the positive electrode 21, the weld trace of the positive electrode lead 25 may break through the separator 23 and cause a short circuit. Because there is. Further, the outer surface active material region 21D is provided on the winding center side in almost one turn, and the outer surface active material region 22D is provided on the winding center side.

  As shown in FIG. 3, the positive electrode 21 may have two or less turns as long as the exposed region 21C has one or more turns on the winding center side, and the negative electrode 22 has the exposed region 22C on the winding center side. It is not necessary to have more than one turn. Further, the positive electrode 21 has an inner surface active material region 21 </ b> F provided with an active material layer 21 </ b> B only on the inner surface side of the current collector 21 </ b> A on the winding outer periphery side, and an exposed region provided on the winding outer periphery side of the negative electrode 22. It may be arranged so as to face 22C. Also in this case, heat dissipation is sufficiently improved and safety can be ensured. In FIG. 3, the separator 23 is omitted.

  The separator 23 is made of, for example, a porous film made of a polyolefin-based material such as polypropylene or polyethylene, or a porous film made of an inorganic material such as a ceramic nonwoven fabric, and these two or more kinds of porous films are laminated. It may be made the structure.

  The separator 23 is impregnated with the electrolytic solution according to the present embodiment.

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

  First, for example, a positive electrode material capable of inserting and extracting lithium, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and this positive electrode mixture is mixed with a solvent such as N-methyl-2-pyrrolidone. Disperse to obtain a positive electrode mixture slurry. Next, the positive electrode mixture slurry is applied to the current collector 21A, and the solvent is dried. Then, the positive electrode mixture 21 is formed by compression molding to form the active material layer 21B.

  Further, for example, a negative electrode material capable of inserting and extracting lithium and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to form a negative electrode A mixture slurry is obtained. Next, this negative electrode mixture slurry is applied to the current collector 22A, and the solvent is dried. Then, the negative electrode 22 is produced by compression molding to form the active material layer 22B.

  Subsequently, the positive electrode lead 25 is attached to the current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are laminated and wound via the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15 and the tip of the negative electrode lead 26 is welded to the battery can 11. The wound positive electrode 21 and negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and housed inside the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through a gasket 17. Thereby, the secondary battery shown in FIG. 1 is completed.

  In this secondary battery, when charged, for example, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution. On the other hand, when discharging is performed, for example, lithium ions are separated from the negative electrode 22 and inserted into the positive electrode 21 through the electrolytic solution. Here, since the electrolytic solution contains ethylene oxide or a derivative thereof, a film having ionic conductivity is formed on the surface of the negative electrode 22 to suppress an increase in internal resistance and suppress a decomposition reaction of the solvent. .

  As described above, in the present embodiment, since the electrolytic solution contains at least one of ethylene oxide and its derivative, a film having ion conductivity can be formed on the surface of the negative electrode 22. Therefore, the decomposition reaction of the solvent in the negative electrode 22 can be suppressed while suppressing the increase in internal resistance, and the cycle characteristics can be improved.

  In particular, it is effective if the content of ethylene oxide and its derivative in the electrolytic solution is 0.01% by mass or more and 10% by mass or less.

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

(Examples 1-1 to 1-4, 2-1 to 2-4, 3-1 to 3-4, 4-1 to 4-4, 5-1 to 5-4)
The secondary battery described in the embodiment was manufactured. At that time, the structure of the electrode winding body 20 is the same as that shown in FIG. 3, and the electrolytic solution contains a mixed solvent of ethylene carbonate and dimethyl carbonate in a volume ratio of 2: 8 and chemical additives 2 to 2. A mixture of any one of the compounds shown in ₆ and LiPF _{6 as} an electrolyte salt was used. As shown in Table 1, the addition amount of the additive was changed in the range of 0.01% by mass to 15% by mass, and the addition amount of the electrolyte salt was 1 mol / l. These are concentrations with respect to the electrolyte. As the positive electrode material, LiCoO ₂ as an active material, ketjen black as a conductive agent, and polyvinylidene fluoride as a binder were used in a mass ratio of 93: 3: 4. Further, as the negative electrode material, graphite having an average particle diameter of 15 μm as an active material and polyvinylidene fluoride as a binder were used in a mass ratio of 94: 6. In addition, a microporous polypropylene film having a thickness of 30 μm was used as the separator 23.

  Moreover, as Comparative Example 1 with respect to the present example, except that no additive was used, other examples 1-1 to 1-4, 2-1 to 2-4, 3-1 to 3-4, 4 were used. Secondary batteries were fabricated in the same manner as in -1 to 4-4 and 5-1 to 5-4.

  Secondary of the produced Examples 1-1 to 1-4, 2-1 to 2-4, 3-1 to 3-4, 4-1 to 4-4, 5-1 to 5-4 and Comparative Example 1 The cycle characteristics of the battery were examined.

  The cycle characteristics were determined by determining the capacity retention rate as the ratio of the discharge capacity at the 300th cycle to the discharge capacity obtained in the first charge / discharge (hereinafter referred to as initial capacity). Charging / discharging was performed at 23 ° C. with a battery voltage set to 4.2 V and charged at a constant current of 1 C for 4 hours, and then discharged at a constant current of 1 C until the battery voltage reached 2.5 V. In addition, 1C means a current value at which the initial capacity can be discharged in one hour. The obtained results are shown in Table 1.

  As can be seen from Table 1, Examples 1-1 to 1-4, 2-1 to 2-4, 3-1 to 3-4, 4- in which one of ethylene oxide and its derivatives was added as an additive. According to 1-4-4, 5-1 to 5-4, the cycle characteristics were improved as compared with Comparative Example 1 in which no addition was made. Furthermore, Examples 1-1 to 1-3, 2-1 to 2-3, 3-1 to 3-3, 4-1 to 4 in which the additive amount is 0.01% by mass to 10% by mass. According to −3, 5-1 to 5-3, the cycle characteristics were improved as compared with Examples 1-4, 2-4, 3-4, 4-4 and 5-4, which were 15% by mass.

  That is, it was found that the cycle characteristics can be improved by adding at least one of ethylene oxide and its derivatives as an additive. In particular, it has been found that it is effective if the additive amount is 0.01% by mass or more and 10% by mass or less with respect to the electrolytic solution.

(Examples 6-1 to 6-4)
Except that a mixed solvent having a volume ratio of ethylene carbonate to ethyl methyl carbonate of 2: 8 was used, the other procedures of Examples 6-1 to 6-4 were carried out in the same manner as in Examples 1-1 to 1-4. A secondary battery was produced. The produced secondary battery was also charged and discharged in the same manner as in Examples 1-1 to 1-4, and the capacity retention rate at the 300th cycle was obtained. The obtained results are shown in Table 2.

  As Comparative Example 2 for this example, a secondary battery was fabricated in the same manner as in Examples 6-1 to 6-4, except that no additive was used. The cycle characteristics of this secondary battery were examined in the same manner as in Examples 1-1 to 1-4. The results are shown in Table 2 together with the results of Examples 1-1 to 1-4.

  As can be seen from Table 2, as in Examples 1-1 to 1-4, according to Examples 6-1 to 6-4 in which one of ethylene oxide and its derivatives was added as an additive, The cycle characteristics were improved as compared with Comparative Example 2 which was not. In addition, according to Examples 6-1 to 6-3 in which the additive was added in an amount of 0.01% by mass or more and 10% by mass or less, the cycle characteristics were improved as compared with Example 6-4 being 15% by mass. . That is, it was found that if at least one of ethylene oxide and its derivative was included, cycle characteristics could be improved regardless of the type of solvent. In particular, it has been found that it is effective if the additive amount is 0.01% by mass or more and 10% by mass or less with respect to the electrolytic solution.

(Examples 7-1 to 7-4)
The mass ratio of an alloy powder of tin and copper as the negative electrode active material, graphite (LS-15 manufactured by Lonza), acetylene black, and polyvinylidene fluoride as the binder is 80: 11: 1: 8 using a negative electrode material having a mass ratio of 91: 6: 3 between LiCoO ₂ as a positive electrode active material, graphite (KS-15 manufactured by Lonza) as a conductive agent, and polyvinylidene fluoride as a binder. Example 7- is the same as Example 1-1 to 1-4 except that a certain positive electrode material was used, an aluminum foil was used as the current collector 21A, and a copper foil was used as the current collector 22A. Secondary batteries 1 to 7-4 were produced. The produced secondary battery was also charged and discharged in the same manner as in Examples 1-1 to 1-4, and the capacity retention rate at the 300th cycle was determined. The obtained results are shown in Table 3. The alloy powder was prepared by mixing 90 g of tin powder and 10 g of copper powder, placing the mixture on a quartz boat, heating at 1000 ° C. in an argon atmosphere, and further cooling to room temperature in an argon atmosphere. And pulverized with a ball mill.

  As Comparative Example 3 for this example, a secondary battery was fabricated in the same manner as in Examples 7-1 to 7-4 except that no additive was used. The cycle characteristics of this secondary battery were examined in the same manner as in Examples 1-1 to 1-4. The results are shown in Table 3.

  As can be seen from Table 3, according to Examples 7-1 to 7-4 in which one of ethylene oxide and its derivatives was added as an additive, similar to Examples 1-1 to 1-4, The cycle characteristics were improved as compared with Comparative Example 3 which was not. In addition, according to Examples 7-1 to 7-3 in which the additive amount is 0.01% by mass or more and 10% by mass or less, the cycle characteristics are improved as compared with Example 7-4 which is 15% by mass. .

  That is, even when a single element, alloy, or compound of a metal element or a metalloid element capable of forming an alloy with lithium is used as the negative electrode active material, it is preferable to include at least one of ethylene oxide and an ethylene oxide derivative. It was found that the cycle characteristics can be improved. In particular, it has been found that it is effective if the additive amount is 0.01% by mass or more and 10% by mass with respect to the electrolytic solution.

  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, the case where an electrolytic solution that is a liquid electrolyte is used has been described, but other electrolytes including an electrolytic solution may be used. Other electrolytes include, for example, a gel electrolyte in which an electrolyte is held in a polymer compound, a mixture of a solid electrolyte having ionic conductivity and an electrolyte, or a mixture of a solid electrolyte and a gel electrolyte The thing which was done is mentioned.

  Note that various polymer compounds can be used for the gel electrolyte as long as it absorbs the electrolyte and gels. Examples of such a polymer compound include a fluorine-based polymer compound such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, an ether-based polymer such as polyethylene oxide or a crosslinked product containing polyethylene oxide. A molecular compound, polyacrylonitrile, etc. are mentioned. In particular, a fluorine-based polymer compound is desirable from the viewpoint of redox stability.

  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. At this time, 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, an acrylate polymer compound alone or mixed, Alternatively, it can be used after copolymerization. Further, as the inorganic solid electrolyte, lithium nitride or lithium iodide can be used.

  Moreover, in the said embodiment and Example, although the structure of the electrode winding body 20 was specifically mentioned and demonstrated, this invention is applicable also when it is set as another winding structure. Further, the present invention can be similarly applied to an elliptical or polygonal secondary battery having a winding structure, or a secondary battery having a structure in which a positive electrode and a negative electrode are folded or stacked. Furthermore, the present invention can also be applied to a so-called coin type, button type or card type secondary battery. In addition, the present invention can be applied not only to secondary batteries but also to primary batteries.

Further, in the present embodiment and examples, the case where a lithium composite oxide is used as a positive electrode active material has been described. An oxide containing a metal may be used. Examples of the crystal structure of these compounds include layered compounds and spinel compounds. Examples of the layered compound include a compound represented by the chemical formula A _q M3 _1-r M4 _r O ₂ . In the formula, A represents sodium or potassium, M3 represents at least one selected from the group consisting of iron, cobalt, nickel, manganese, copper, zinc, chromium, vanadium, and titanium, and M4 represents iron, cobalt, manganese. , Copper, zinc, aluminum, tin, boron, gallium, chromium, vanadium, titanium, magnesium, calcium and strontium, and q and r have values of 0.5 ≦ q ≦ 1. 1, 0 <r <1.

It is sectional drawing 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 electrode winding body shown in FIG. It is sectional drawing showing the other structure along the II-II line | wire of the electrode winding body shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulating plate, 14 ... Battery cover, 15 ... Safety valve mechanism, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20 ... Electrode winding body, 21 ... Positive electrode, 21A, 22A ... Current collection Body, 21B, 22B ... active material layer, 21C, 22C ... exposed region, 21D, 22D ... outer surface active material region, 21E, 22E ... double-sided active material region, 21F ... inner surface active material region, 22 ... negative electrode, 23 ... separator, 24 ... Center pin, 25 ... Positive electrode lead, 26 ... Negative electrode lead.

Claims (6)

  An electrolytic solution comprising at least one of ethylene oxide and a derivative thereof. An electrolytic solution comprising at least one member selected from the group consisting of the compounds represented by Chemical Formulas 1 to 5.

  2. The electrolytic solution according to claim 1, wherein the content of ethylene oxide and a derivative thereof is 0.01% by mass or more and 10% by mass or less. A battery comprising an electrolyte solution together with a positive electrode and a negative electrode,
The battery, wherein the electrolytic solution contains at least one of ethylene oxide and a derivative thereof. 5. The battery according to claim 4, wherein the electrolytic solution includes at least one selected from the group consisting of the compounds shown in Chemical Formulas 6 to 10. 5.

5. The battery according to claim 4, wherein the content of ethylene oxide and its derivative in the electrolytic solution is 0.01% by mass or more and 10% by mass or less.

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