JP2005108459A - Electrolyte and battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte and a battery capable of suppressing deterioration discharge capacity. <P>SOLUTION: A positive electrode 21 and a negative electrode 22 are wound through a separator 23 impregnated with the electrolyte. The electrolyte includes a carbonate and a lithium salt, and a benzene derivative having three or more oxygen atoms bonded to a benzene ring or a carbon 6-member ring compound having 6π electrons in which four or more oxygen atoms bonded to a carbon 6-member ring by double bond is added thereto as an additive. Examples of the benzene derivative include 1,2,4-triacetoxybenzene or 1,2,4,5-tetraacetoxybenzene, and examples of the carbon 6-member ring compound include sodium rhodizonate. According to this, the cycle characteristic can be improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a battery including an electrolyte together with a positive electrode and a negative electrode, and particularly to a battery using lithium (Li) or the like as an electrode reactive species, and an electrolyte used therefor.

  In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a digital still camera, a mobile phone, a portable information terminal, or a notebook computer have appeared, and their size and weight have been reduced. Accordingly, as a portable power source for electronic devices, research and development for improving the energy density of batteries, particularly secondary batteries, are being actively promoted. Above all, lithium ion secondary batteries that use carbon materials as the negative electrode active material and a mixture of carbonates in the electrolyte solution are widely put into practical use because they have a higher energy density than conventional lead batteries and nickel cadmium batteries. Has been.

  However, since the carbonic acid ester is gradually decomposed at the electrode, the lithium ion secondary battery using the carbonic acid ester as the electrolytic solution has a problem in that the discharge capacity decreases when charging and discharging are repeated.

Thus, as a method for solving this problem, for example, it has been proposed to add hydroquinone to the electrolytic solution (see, for example, Patent Document 1). For example, it has also been proposed to add quinones to the electrolytic solution (see, for example, Patent Document 2).
JP 2000-77095 A JP 2000-21444 A

  However, hydroquinone has a problem that even if the cycle characteristics are improved, its degree is small and it cannot be said that it is sufficient. In addition, quinones have a problem that the self-discharge of the battery in a charged state is increased by an oxidation-reduction reaction. Therefore, development of a new additive to replace these has been demanded.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an electrolyte and a battery that can suppress deterioration of discharge capacity.

  The first electrolyte according to the present invention includes a benzene derivative in which three or more oxygen atoms are bonded to a benzene ring.

  The second electrolyte according to the present invention includes a carbon 6-membered ring compound having 6π electrons in which 4 or more oxygen atoms are bonded to the carbon 6-membered ring by double bonds.

  A first battery according to the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the electrolyte includes a benzene derivative in which three or more oxygen atoms are bonded to a benzene ring.

  A second battery according to the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the electrolyte is a carbon 6-membered ring having 6π electrons in which four or more oxygen atoms are bonded to the carbon 6-membered ring by double bonds. Contains compounds.

  According to the first electrolyte and the first battery according to the present invention, since the benzene derivative having three or more oxygen atoms bonded to the benzene ring is included, the second electrolyte and the second battery according to the present invention are also included. Since the carbon 6-membered ring compound having 6π electrons in which four or more oxygen atoms are bonded to the carbon 6-membered ring by double bonds is included, the stability of the electrolyte can be improved, and the discharge capacity can be improved. Can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, a so-called lithium ion secondary battery will be described.

  FIG. 1 shows a cross-sectional structure of a secondary battery according to an embodiment of the present invention. This secondary battery is a so-called cylindrical type, and is a wound electrode in which a strip-like positive electrode 21 and a strip-like negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. It has a body 20. 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, an electrolytic solution which is a liquid electrolyte is injected and impregnated in the separator 23. In addition, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode 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 wound electrode 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.

  The wound electrode body 20 is wound around a center pin 24, for example. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the spirally wound electrode 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 has, for example, a structure in which a positive electrode mixture layer is provided on both surfaces or one surface of a positive electrode current collector having a pair of opposed surfaces, although not shown. The positive electrode current collector is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode mixture layer includes, for example, a positive electrode active material, and may include a conductive agent such as a carbon material and a binder such as polyvinylidene fluoride as necessary.

Examples of the positive electrode active material include lithium such as lithium cobaltate, lithium nickelate, solid solutions containing these, manganese spinel (LiMn ₂ O ₄ ), or olivine structure oxides such as lithium iron phosphate (LiFePO ₄ ). Containing compounds are preferred. This is because a high energy density can be obtained. Other examples of the positive electrode active material include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as titanium sulfide and molybdenum sulfide, and conductive polymers such as polyaniline and polythiophene. . The positive electrode active material may be used alone or in combination of two or more.

  Although not shown, the negative electrode 22 has, for example, a structure in which a negative electrode mixture layer is provided on both surfaces or one surface of a negative electrode current collector having a pair of opposed surfaces, similarly to the positive electrode 21. The negative electrode current collector is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The negative electrode mixture layer includes, for example, a negative electrode active material, and may include a binder such as polyvinylidene fluoride as necessary. The negative electrode active material may be used alone or in combination of two or more.

  Examples of the negative electrode active material include carbon materials, metal oxides, and polymer materials. Examples of the carbon material include non-graphitizable carbon, artificial graphite, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, activated carbon, and carbon blacks. Of these, coke includes pitch coke, needle coke, and petroleum coke. Organic polymer compound fired bodies are carbonized by firing polymer materials such as phenols and furans at an appropriate temperature. What you did. In addition, examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide, and examples of the polymer material include polyacetylene and polypyrrole.

  As the negative electrode active material, a simple substance, an alloy or a compound of a metal element or a metalloid element capable of forming an alloy with lithium can be given. 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. 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 capable of forming an alloy with lithium include magnesium (Mg), boron (B), arsenic (As), aluminum, gallium (Ga), indium (In), silicon (Si), Germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), Examples thereof include yttrium (Y), palladium (Pd), and platinum (Pt). These alloys or compounds, for example, those represented by the chemical formula Ma _s Mb _t Li _u or a chemical formula Ma _p Mc _q Md _r,. In these chemical formulas, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, Mb represents at least one of a metal element and a metalloid element other than lithium and Ma, Mc represents at least one of nonmetallic elements, and Md represents at least one of metallic elements and metalloid elements other than Ma. The values of s, t, u, p, q, and r are s> 0, t ≧ 0, u ≧ 0, p> 0, q> 0, and r ≧ 0, respectively.

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

Specific examples of such alloys or compounds include LiAl, AlSb, CuMgSb, 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), there is such SnSiO _3, LiSiO or LiSnO.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. 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. It may be said.

  The electrolytic solution impregnated in the separator 23 includes a solvent and a lithium salt that is an electrolyte salt dissolved in the solvent. Examples of the solvent include ethylene carbonate shown in Chemical formula 1, propylene carbonate shown in Chemical formula 2, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, butylene carbonate shown in Chemical formula 3, fluoroethylene carbonate shown in Chemical formula 4 or Chemical formula 5. Carbonate such as trifluoropropylene carbonate shown, or chain such as methyl formate, ethyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, methyl isobutyrate or ethyl isobutyrate A carboxylic acid ester or a cyclic carboxylic acid ester such as γ-butyrolactone shown in Chemical formula 6 or γ-valerolactone shown in Chemical formula 7 can be used. Also, cyclic ethers such as tetrahydropyran or 1,3-dioxane, amide compounds such as N, N′-dimethylformamide, N-methylpyrrolidone shown in Chemical formula 8 or N-methyloxazolidinone shown in Chemical formula 9, or Room temperature melting of sulfur compounds such as sulfolane shown in Chemical formula 10, or 1-ethyl-3-methylimidazolium tetrafluoroborate shown in Chemical formula 11 or 1-butylpyridinium tetrafluoroborate shown in Chemical formula 12 Salts can also be used. The solvent may be used alone or in combination of two or more.

  Among these, as the main solvent, it is preferable to use a carbonate ester. This is because the carbonate ester is stable against oxidation and reduction and can obtain a high voltage. In particular, it is preferable to use a mixture of a cyclic carbonate such as ethylene carbonate or propylene carbonate and a chain carbonate such as dimethyl carbonate or diethyl carbonate. This is because cyclic carbonates have a high dielectric constant but a high viscosity, and chain carbonates have a low viscosity but a low dielectric constant, so that higher conductivity can be obtained by mixing them than either one. As the cyclic ester carbonate, ethylene carbonate or propylene carbonate is preferable, and it is more preferable to use these together. Ethylene carbonate has a high dielectric constant, but its melting point is as high as 37 ° C, so the low temperature characteristics are poor. Propylene carbonate has a dielectric constant lower than that of ethylene carbonate, but its melting point is -49 ° C, so it is better to mix it than either one. This is because high battery characteristics can be obtained. As the chain carbonate, dimethyl carbonate is preferred. This is because the viscosity is smaller than that of ethyl carbonate, so that high conductivity can be obtained.

  As the solvent, a carboxylic acid ester is also preferable because it has a low melting point and a low viscosity, so that low temperature characteristics can be improved, and electrical conductivity is high and load characteristics can be improved. However, since the carboxylate ester has low reduction resistance, it may be decomposed at the negative electrode 22 to deteriorate the cycle characteristics, so that it is preferable to use it in combination with a carbonate ester.

Examples of the lithium salt include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), and trifluoromethanesulfonic acid. Lithium (CF ₃ SO ₃ Li), bis [trifluoromethanesulfonyl] imido lithium ((CF ₃ SO ₂ ) ₂ NLi), tris (trifluoromethanesulfonyl) methyl lithium ((CF ₃ SO ₂ ) ₃ CLi)) or bis [ Pentafluoroethanesulfonyl] imidolithium ((C ₂ F ₅ SO ₂ ) ₂ NLi) and the like. One lithium salt may be used alone, or two or more lithium salts may be mixed and used.

  This electrolyte also has, as an additive, a benzene derivative in which three or more oxygen atoms are bonded to the benzene ring, or a six-membered carbon having 6π electrons in which four or more oxygen atoms are bonded to the carbon six-membered ring by double bonds. A ring compound is contained, and these may be contained together. These benzene derivatives or carbon 6-membered ring compounds may be used alone or in combination of two or more. These compounds are for suppressing, for example, a decrease in discharge capacity due to repeated charge and discharge, and have stable characteristics against oxidation and reduction. For example, quinones in which two oxygen atoms are bonded to a carbon 6-membered ring are easily oxidized and reduced, whereas carbon 6-membered compounds in which four or more oxygen atoms are bonded to each other are double-conjugated. It is thought that stability will increase. In this embodiment, attention is paid to the functions of these benzene derivatives and carbon 6-membered ring compounds, and these are described as additives, but they may also function as solvents.

  Examples of such benzene derivatives include polyphenols having 3 or more hydroxy groups bonded to the benzene ring, esters having 3 or more —C (═O) O— groups bonded to the benzene ring with oxygen atoms, or benzene rings. Examples include ethers having three or more —O— groups bonded thereto.

  Specifically, examples of three oxygen atoms bonded to the benzene ring include 1,2,3-trihydroxybenzene (pyrogallol) shown in Chemical formula 13, and 1,2,4- shown in Chemical formula 14. Examples thereof include trihydroxybenzene (hydroxyhydroquinone), 1,3,5-trihydroxybenzene (phloroglucinol) shown in Chemical formula 15, and 1,2,4-triacetoxybenzene shown in Chemical formula 16. Examples of those in which four oxygen atoms are bonded to the benzene ring include 1,2,4,5-tetrahydroxybenzene shown in Chemical Formula 17, 1,2,3,5-tetrahydroxybenzene shown in Chemical Formula 18, 1,2,3,4-tetrahydroxybenzene shown in Chemical formula 19 or 1,2,4,5-tetraacetoxybenzene shown in Chemical formula 20 can be mentioned. Examples of those in which five oxygen atoms are bonded to the benzene ring include pentahydroxybenzene shown in Chemical formula 21 below. Examples of those in which six oxygen atoms are bonded to the benzene ring include hexahydroxybenzene shown in Chemical Formula 22.

  Among them, those having an acyl group, for example, esters are preferable because higher effects can be obtained. Among the above-mentioned compounds, 1,2,4-triacetoxybenzene shown in Chemical formula 16 and 1,2,4,5-tetraacetoxybenzene shown in Chemical formula 20 are preferable.

  Examples of the carbon 6-membered ring compound having 6π electrons in which four or more oxygen atoms are bonded to the carbon 6-membered ring by a double bond include sodium rhodizonate shown in Chemical formula 23, rhodizone acid shown in Chemical formula 24, or chemical formula The triquinoyl shown in 25 is mentioned.

  The content of these benzene derivatives or carbon 6-membered ring compounds in the electrolytic solution is preferably 0.5% by mass or more and 3% by mass or less. This is because a higher effect can be obtained within this range.

  Note that a gel electrolyte may be used instead of the electrolytic solution. The gel electrolyte is obtained by holding an electrolytic solution in a holding body. The holding body is made of, for example, a polymer compound or an inorganic compound. Examples of the polymer compound include, 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 an acrylate polymer compound, or polyvinylidene fluoride or vinylidene fluoride. Fluorine polymer compounds such as a copolymer with hexafluoropropylene can be mentioned, and any one or two or more of these can be used in combination. In particular, it is desirable to use a fluorine-based polymer compound from the viewpoint of redox stability. Examples of the inorganic compound include lithium nitride and lithium phosphate.

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

  First, for example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture, and this positive electrode mixture is dispersed in a solvent such as N-methylpyrrolidone to obtain a positive electrode mixture coating solution. Next, the positive electrode mixture coating solution is applied to a positive electrode current collector and dried, and then compression molded to form a positive electrode mixture layer, whereby the positive electrode 21 is produced.

  Further, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methylpyrrolidone to obtain a negative electrode mixture coating solution. Next, the negative electrode mixture coating solution is applied to a negative electrode current collector and dried, and then compression molded to form a negative electrode mixture layer, whereby the negative electrode 22 is manufactured.

  Subsequently, the positive electrode lead 25 is attached to the positive electrode current collector by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound through 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 positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. Next, the electrolytic solution is injected into the battery can 11. 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 the secondary battery, when charged, for example, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolyte. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and are inserted in the positive electrode 21 through the electrolyte. Here, since the above-described benzene derivative or carbon 6-membered ring compound is contained in the electrolytic solution, the decomposition of the solvent is suppressed and the cycle characteristics are improved. Further, the electrolyte solution is stable even in a charged state, self-discharge is suppressed, and high storage characteristics can be obtained.

  As described above, in the present embodiment, since the electrolytic solution contains the benzene derivative or the carbon 6-membered ring compound described above, cycle characteristics can be improved. Further, since these compounds are stable against oxidation and reduction, high storage characteristics can be obtained.

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

(Examples 1-1 to 1-12)
The secondary battery described in the embodiment was manufactured. First, 94 parts by mass of lithium cobaltate (LiCoO ₂ ) as a positive electrode active material, 3 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed uniformly. N-methylpyrrolidone was added to obtain a positive electrode mixture coating solution. Next, the obtained positive electrode mixture coating liquid was uniformly applied to a positive electrode current collector made of an aluminum foil having a width of 56 mm, a length of 550 mm, and a thickness of 20 μm and dried to form a positive electrode mixture layer having a thickness of 70 μm. Similarly, a positive electrode mixture layer having a thickness of 70 μm was also formed on the back surface of the positive electrode current collector. After that, a positive electrode lead 25 made of aluminum was attached to one end of the positive electrode current collector.

  Further, 94 parts by mass of graphite as a negative electrode active material and 6 parts by mass of polyvinylidene fluoride as a binder were uniformly mixed, and then N-methylpyrrolidone was added to obtain a negative electrode mixture coating solution. Next, the obtained negative electrode mixture coating liquid was uniformly applied to a negative electrode current collector made of a copper foil having a width of 58 mm, a length of 600 mm, and a thickness of 15 μm, and dried to form a negative electrode mixture layer having a thickness of 70 μm. Similarly, a negative electrode mixture layer having a thickness of 70 μm was also formed on the back surface of the negative electrode current collector. After that, a nickel negative electrode lead 26 was attached to one end of the negative electrode current collector.

  Next, after laminating the positive electrode 21 and the negative electrode 22 with a separator 23 made of a microporous polypropylene film having a thickness of 25 μm, the wound electrode body 20 is formed by winding with a winder. The battery can 11 was housed in a stainless steel can 11 having a diameter of 18 mm and a length of 65 mm. The capacity of this battery is 2000 mAh.

  Subsequently, ethylene carbonate, propylene carbonate, and dimethyl carbonate were prepared as solvents, and an electrolyte was prepared by adding lithium hexafluorophosphate as an electrolyte salt and an additive thereto. At that time, the ratio of ethylene carbonate, propylene carbonate, dimethyl carbonate and lithium hexafluorophosphate was ethylene carbonate: propylene carbonate: dimethyl carbonate: lithium hexafluorophosphate = 15: 10: 55: 20 by weight ratio. . As the additive, 1,2-1,4-triacetoxybenzene shown in Chemical formula 16 was used in Examples 1-1 to 1-4, and 1 shown in Chemical formula 20 in Examples 1-5 to 1-8. , 2,4,5-tetraacetoxybenzene was used, and sodium rhodizonate shown in Chemical formula 23 was used in Examples 1-9 to 1-12. The content of the additive in the electrolytic solution was changed as shown in Table 1 in Examples 1-1 to 1-12.

  After that, 4.5 g of the produced electrolyte solution is injected into the battery can 11 and the battery lid 14 is caulked to the battery can 11 via the gasket 17, whereby Examples 1-1 to 1-12 are shown in FIG. The cylindrical secondary battery shown in 1 was obtained.

  As Comparative Example 1-1 with respect to Examples 1-1 to 1-12, a secondary battery was fabricated in the same manner as in Examples 1-1 to 1-12, except that no additive was added to the electrolytic solution. . Moreover, as Comparative Example 1-2 with respect to Examples 1-1 to 1-12, except that 1% by mass of hydroquinone shown in Chemical Formula 26 was added as an additive to the electrolyte, the other examples were 1-1-1 A secondary battery was fabricated in the same manner as in -12. As shown in Chemical formula 26, hydroquinone has two oxygen atoms bonded to the benzene ring.

  For the obtained secondary batteries of Examples 1-1 to 1-12 and Comparative examples 1-1 and 1-2, at 23 ° C., 2 A was charged for 2 hours up to 4.2 V, and then rested for 30 minutes. Then, charging / discharging of discharging until reaching 3V at 2A was repeated, and the discharge capacity maintenance rate at the 300th cycle was determined. The discharge capacity retention rate at the 300th cycle was calculated as (discharge capacity at the 300th cycle / initial discharge capacity) × 100. The results are shown in Table 1 and FIG.

  As shown in Table 1 and FIG. 2, according to Examples 1-1 to 1-12, a higher cycle discharge capacity was maintained than Comparative Example 1 in which no additive was added and Comparative Example 2 in which hydroquinone was added. The rate was obtained. That is, if a benzene derivative in which 3 or more oxygen atoms are bonded to the benzene ring or a carbon 6-membered ring compound having 6π electrons in which 4 or more oxygen atoms are bonded to the carbon 6-membered ring by a double bond is included, It was found that cycle characteristics can be improved.

  Moreover, when Examples 1-1 to 1-4, Examples 1-5 to 1-8, and Examples 1-9 to 1-12 are respectively compared, the discharge capacity retention ratio increases as the content of the additive is increased. There was a tendency to increase and then decrease after showing a local maximum. That is, it was found that a higher effect can be obtained if the content of the benzene derivative or the carbon 6-membered ring compound described above is 0.5% by mass or more and 3% by mass of the electrolytic solution.

(Examples 2-1 and 2-2)
As Example 2-1, a secondary battery was fabricated in the same manner as Example 1-6. Further, as Example 2-2, a secondary battery was fabricated in the same manner as Example 1-10. As Comparative Example 2-1 with respect to Examples 2-1 and 2-2, except that 1% by mass of 2,5-dihydroxybenzoquinone shown in Chemical Formula 27 was added as an additive to the electrolytic solution, the rest was the same as in Example 2- Secondary batteries were fabricated in the same manner as in 1 and 2-2. 2,5-dihydroxybenzoquinone is one in which two oxygen atoms are bonded to a carbon 6-membered ring by a double bond, as shown in Chemical Formula 27.

  For the obtained secondary batteries of Examples 2-1 and 2-2 and Comparative Example 2-1, at 23 ° C., 2 A was charged for 2 hours up to 4.2 V, then rested for 30 minutes, and then 2 V for 3 V The battery was discharged until the initial discharge capacity was reached. Next, the battery was charged at 23 ° C. with 2 A at 4.2 V as the upper limit for 2 hours, then stored at 60 ° C. for 100 hours, discharged again at 2 A at 2 A until reaching 3 V, and the discharge capacity after storage was determined. From these results, the discharge capacity retention rate after storage was determined as (discharge capacity after storage / initial discharge capacity) × 100. Table 2 shows the obtained discharge capacity retention ratio after storage.

  As shown in Table 2, according to Examples 2-1 and 2-2, the discharge capacity retention rate after storage was higher than that of Comparative Example 2 in which 2,5-dihydroxybenzoquinone was added. That is, if a benzene derivative in which 3 or more oxygen atoms are bonded to the benzene ring or a carbon 6-membered ring compound having 6π electrons in which 4 or more oxygen atoms are bonded to the carbon 6-membered ring by a double bond is included, It was found that high storage characteristics can be obtained.

  In the above embodiment, the case where 1,2,4-triacetoxybenzene, 1,2,4,5-tetraacetoxybenzene or sodium rhodizonate is used as an additive has been described, but oxygen atoms are present in the benzene ring. Similar results can be obtained by using other benzene derivatives having three or more bonds, or other carbon six-membered compounds having 6π electrons in which four or more oxygen atoms are bonded to the carbon six-membered ring by double bonds. be able to. Moreover, although the case where the electrolytic solution is used has been described in the above embodiment, the same result can be obtained even when a gel electrolyte is used.

  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 composition of the electrolyte has been specifically described, but those having other compositions can also be used. In addition, other additives may be further added according to the intended characteristics.

  Furthermore, the present invention is not limited to a cylindrical secondary battery having a winding structure, but has an elliptical or polygonal secondary battery having a winding structure, or a structure in which a positive electrode and a negative electrode are folded or stacked. The present invention can also be applied to a secondary battery. In addition, the present invention can also be applied to a so-called coin type, button type, or card type secondary battery.

  In addition, in the above-described embodiments and examples, the lithium ion secondary battery has been described. However, the present invention can be applied to other secondary batteries, and similar effects can be obtained. Examples of the other secondary battery include a so-called metal lithium secondary battery using metal lithium as a negative electrode active material, and a magnesium secondary battery or an aluminum secondary battery that is being studied for practical use. Furthermore, the present invention can be applied not only to secondary batteries but also to other batteries such as primary batteries. In addition, the present invention can be applied not only to a battery with a chemical reaction but also to an electric double layer capacitor using an electrolytic solution.

It is sectional drawing showing the structure of the secondary battery which concerns on one embodiment of this invention. It is a characteristic view showing the relationship between the additive and the discharge capacity maintenance factor in the Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20 ... Winding electrode body, 21 ... Positive electrode, 22 ... negative electrode, 23 ... separator, 24 ... center pin, 25 ... positive electrode lead, 26 ... negative electrode lead.

Claims (22)

  An electrolyte comprising a benzene derivative having three or more oxygen atoms bonded to a benzene ring.   The electrolyte according to claim 1, wherein the benzene derivative has an acyl group.   2. The electrolyte according to claim 1, wherein the benzene derivative contains at least one of 1,2,4-triacetoxybenzene and 1,2,4,5-tetraacetoxybenzene.   2. The electrolyte according to claim 1, comprising an electrolytic solution containing the benzene derivative, a carbonate, and an electrolyte salt.   The electrolyte according to claim 4, wherein the electrolytic solution contains ethylene carbonate, propylene carbonate, and dimethyl carbonate.   5. The electrolyte according to claim 4, wherein a content of the benzene derivative in the electrolytic solution is in a range of 0.5 mass% to 3 mass%.   An electrolyte comprising a carbon 6-membered ring compound having 6π electrons in which four or more oxygen atoms are bonded to the carbon 6-membered ring by a double bond.   The electrolyte according to claim 7, wherein the carbon 6-membered ring compound includes sodium rhodizonate.   The electrolyte according to claim 7, comprising an electrolytic solution containing the carbon 6-membered ring compound, a carbonate ester, and an electrolyte salt.   The electrolyte according to claim 9, wherein the electrolytic solution contains ethylene carbonate, propylene carbonate, and dimethyl carbonate.   10. The electrolyte according to claim 9, wherein a content of the carbon 6-membered ring compound in the electrolytic solution is in a range of 0.5 mass% to 3 mass%. A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The battery, wherein the electrolyte includes a benzene derivative having three or more oxygen atoms bonded to a benzene ring.   The battery according to claim 12, wherein the benzene derivative has an acyl group.   The battery according to claim 12, wherein the benzene derivative includes at least one of 1,2,4-triacetoxybenzene and 1,2,4,5-tetraacetoxybenzene.   The battery according to claim 12, wherein the electrolyte contains an electrolytic solution containing the benzene derivative, a carbonate, and an electrolyte salt.   The battery according to claim 15, wherein the electrolytic solution contains ethylene carbonate, propylene carbonate, and dimethyl carbonate.   The battery according to claim 15, wherein a content of the benzene derivative in the electrolytic solution is in a range of 0.5 mass% to 3 mass%. A battery comprising an electrolyte together with a positive electrode and a negative electrode,
The battery includes a carbon 6-membered ring compound having 6π electrons in which four or more oxygen atoms are bonded to a carbon 6-membered ring by a double bond.   The battery according to claim 18, wherein the carbon 6-membered ring compound includes sodium rhodizonate.   19. The battery according to claim 18, wherein the electrolyte contains an electrolytic solution containing the carbon 6-membered ring compound, a carbonate, and an electrolyte salt.   21. The battery according to claim 20, wherein the electrolytic solution contains ethylene carbonate, propylene carbonate, and dimethyl carbonate. 21. The battery according to claim 20, wherein the content of the carbon 6-membered ring compound in the electrolytic solution is in the range of 0.5 mass% to 3 mass%.

Images