JP2006221936A - Electrolyte and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte capable of enhancing charge discharge efficiency and to provide a battery using it. <P>SOLUTION: A positive electrode 21 and a negative electrode 22 are laminated through a separator 23. The separator 23 is impregnated with an electrolyte. The electrolyte contains an acetophenone derivative having a polyfluoroalkoxy group. As the acetophenone derivative, 3'-(trifluoromethyl)acetophenone, 2'-(trifluoromethoxy)acetophenone, 3'-(2,2,2-trifluoroethyl)acetophenone, 7'-(trifluoromethoxy)acetonaphthone, or the like is listed. Thereby, an excellent film can be formed on the negative electrode 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In recent years, mobile electronic devices such as mobile phones, PDAs (personal digital assistants) or notebook computers have been energetically reduced in size and weight, and as part of these efforts, Improvement of the energy density of a battery as a driving power source, particularly a secondary battery is strongly desired.

  As a secondary battery capable of obtaining a high energy density, for example, a secondary battery using lithium (Li) as an electrode reactant is known. Among these, lithium ion secondary batteries using a material capable of inserting and extracting lithium such as a carbon material in the negative electrode are widely put into practical use. In order to further increase the capacity, the use of a material capable of forming an alloy with lithium for the negative electrode has been studied, and further, a material capable of inserting and extracting lithium is used for the negative electrode. Secondary batteries have also been developed in which lithium is deposited on the negative electrode during charging by making the charge capacity smaller than the charge capacity of the positive electrode (see, for example, Patent Document 1).

By the way, in these secondary batteries, in order to improve battery characteristics, adding various additives to electrolyte solution is examined. For example, Patent Document 2 describes that a ketone is added to suppress the generation of gas.
International Publication No. WO 01/22519 A1 Pamphlet JP 2003-197259 A

  However, these ketones have a problem that the charge / discharge efficiency, and thus the cycle characteristics, cannot be sufficiently improved.

  This invention is made | formed in view of this problem, The objective is to provide the electrolyte which can improve charging / discharging efficiency, and a battery using the same.

  The electrolyte according to the present invention contains a solvent containing an acetophenone derivative having a polyfluoroalkyl group.

  The battery according to the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the electrolyte contains a solvent containing an acetophenone derivative having a polyfluoroalkyl group.

  According to the electrolyte of the present invention, since an acetophenone derivative having a polyfluoroalkyl group is included, for example, when used in a battery, a good film can be formed on the surface of the negative electrode. Therefore, side reactions in the negative electrode can be suppressed, and charge / discharge efficiency can be improved.

  In particular, if the content of the acetophenone derivative in the solvent is in the range of 0.05% by mass or more and 10% by mass or less, a higher effect can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, a so-called lithium ion secondary battery using lithium as an electrode reactant will be described.

[First Embodiment]
FIG. 1 shows a cross-sectional structure of a secondary battery according to the first embodiment of the present invention. This secondary battery is a so-called cylindrical type, and a wound electrode body 20 in which a belt-like positive electrode 21 and a negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. have. 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 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.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. 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.

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. Although not shown, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

The positive electrode active material layer 21B includes a positive electrode material capable of inserting and extracting lithium, which is an electrode reactant, for example, as a positive electrode active material. As the positive electrode material capable of inserting and extracting lithium, for example, lithium-containing compounds such as lithium oxide, lithium phosphorus oxide, lithium sulfide, or an intercalation compound containing lithium are suitable, and two or more kinds are mixed. May be used. In particular, in order to increase the energy density, a lithium composite oxide or lithium phosphorus oxide represented by the general formula Li _x MIO ₂ or Li _y MIIPO ₄ is preferable. In the formula, MI and MII represent one or more transition metals, for example, at least one of cobalt (Co), nickel, manganese (Mn), iron, aluminum, vanadium (V), and titanium (Ti). Species are preferred. 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 include lithium cobalt composite oxide (LiCoO ₂ ), lithium nickel composite oxide (LiNiO ₂ ), lithium nickel cobalt composite oxide (LiNi _v Co _1-v O ₂ ; 0.7 < v <1.0), or lithium manganese composite oxide (LiMn ₂ O ₄ ) having a spinel crystal structure. Specific examples of the lithium phosphorus oxide include LiFePO ₄ or LiFe _0.5 Mn _0.5 PO ₄ .

  The positive electrode active material layer 21B also contains, for example, a conductive agent, and may further contain a binder as necessary. Examples of the conductive agent include carbon materials such as graphite, carbon black, and ketjen black, and one kind or a mixture of two or more kinds is used. In addition to the carbon material, a metal material or a conductive polymer material may be used as long as it is a conductive material. Examples of the binder include synthetic rubber such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene rubber, or a polymer material such as polyvinylidene fluoride, and one or two or more kinds are used in combination. It is done.

  The negative electrode 22 has, for example, a configuration in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer 22B includes, for example, one or more negative electrode materials capable of inserting and extracting lithium, which is an electrode reactant, as a negative electrode active material. For example, the binder similar to the positive electrode active material layer 13B may be included.

  Examples of the negative electrode material capable of inserting and extracting lithium include carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon. These carbon materials are preferable because the change in crystal structure that occurs during charge / discharge is very small, a high charge / discharge capacity can be obtained, and good charge / discharge cycle characteristics can be obtained. In particular, graphite is preferable because the electrochemical equivalent is large and a high energy density can be obtained. The graphite may be artificial graphite or natural graphite.

  Examples of the negative electrode material capable of inserting and extracting lithium include those containing at least one of a metal element and a metalloid element capable of forming an alloy with lithium as a constituent element. This negative electrode material may be a single element or an alloy or a compound of a metal element or a metalloid element, or may have at least a part of one or more of these phases. These are preferable because a high energy density can be obtained. In particular, when used together with a carbon material, a high energy density can be obtained and excellent charge / discharge cycle characteristics can be obtained. 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 capable of forming an alloy with lithium include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth ( Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium ( Hf). Among these, a group 14 metal element or metalloid element in the long-period type periodic table is preferable, and silicon or tin is particularly preferable.

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

  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 composed of, for example, a porous film made of a synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a porous film made of an inorganic material such as a ceramic nonwoven fabric. The porous film may be laminated.

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. The electrolytic solution includes an electrolyte salt and a solvent that dissolves the electrolyte salt.

Examples of the electrolyte salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiB (C ₆ H ₅ ) ₄ , CH _3. Examples thereof include lithium salts such as SO ₃ Li, CF ₃ SO ₃ Li, LiCl, and LiBr. As the electrolyte salt, one kind may be used alone, or two or more kinds may be mixed and used.

  Solvents include ethylene carbonate, propylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, γ-valerolactone, tetrahydrofuran, 2 -Methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetate ester, butyrate ester, propionate ester or fluorobenzene Non-aqueous solvents are mentioned. As the solvent, one kind may be used alone, or two or more kinds may be mixed and used.

  Among them, the solvent preferably contains a cyclic carbonate, and for example, preferably contains at least one of ethylene carbonate, propylene carbonate, and vinylene carbonate. This is because excellent charge / discharge capacity and charge / discharge cycle characteristics can be obtained.

  In this embodiment mode, the solvent contains an acetophenone derivative having a polyfluoroalkyl group. This is because the charge / discharge efficiency can be improved by forming a good film on the negative electrode 22. The acetophenone derivative having this polyfluoroalkyl group refers to one obtained by substituting a functional group having a polyfluoroalkyl group with the acetophenone shown in Chemical Formula 1 or by substituting the hydrogen of the methyl group of acetophenone with fluorine, Furthermore, you may have another substituent.

  The functional group having a polyfluoroalkyl group may be substituted with hydrogen of a phenyl group or may be substituted with hydrogen of a methyl group. In addition, other substituents may be substituted with hydrogen of the phenyl group or may be substituted with hydrogen of the methyl group, such as 1-acetonaphthone shown in Chemical Formula 2 or 2-acetonaphthone shown in Chemical Formula 3. A condensed ring may be formed.

  Examples of the functional group having a polyfluoroalkyl group include trifluoromethyl group, pentafluoroethyl group, 2,2,2-trifluoroethyl group, n-pentafluoropropyl group, iso-heptafluoropropyl group, 2, 2,3,3,3-pentafluoropropyl group, 1,1,2,3,3,3-hexafluoropropyl group, trifluoromethoxy group, 2,2,2-trifluoroethoxy group, or n-penta A fluoropropoxy group is mentioned. The number of carbon atoms of the polyfluoroalkyl group is preferably 1 to 3. As the number of carbons increases and the molecular weight increases, the excluded volume of the molecules increases, the molecular mobility decreases, and the movement of the molecules in the electrolytic solution is not performed smoothly. This is because the forming ability is weakened.

  Specific examples of such an acetophenone derivative include, for example, 3 ′-(trifluoromethyl) acetophenone shown in Chemical formula 4, 2 ′-(trifluoromethoxy) acetophenone shown in Chemical formula 5, and 3 ′ shown in Chemical formula 6. -(Trifluoromethoxy) acetophenone, 4 '-(trifluoromethoxy) acetophenone shown in Chemical formula 7, 3'-(2,2,2-trifluoroethyl) acetophenone shown in Chemical formula 8, 7 shown in Chemical formula 9 Examples include '-(trifluoromethoxy) acetonaphthone, or 6'-(trifluoromethoxy) acetonaphthone shown in Chemical formula 10. These acetophenone derivatives may be used alone or in combination of two or more.

  Of these, those having a polyfluoroalkoxy group are preferred as the functional group having a polyfluoroalkyl group. This is because the impurity ions can be stably solvated by the ether bond and deterioration of the battery characteristics can be suppressed. The introduction position of the polyfluoroalkoxy group is preferably the 2- or 3-position of the benzene ring, and most preferably the 2-position. This is because ions can be coordinated between oxygen of the carbonyl group and oxygen of the ether group.

  The content of the acetophenone derivative in the solvent is preferably 0.05% by mass to 10% by mass, and more preferably 0.1% by mass to 9% by mass. This is because a higher effect can be obtained within this range.

  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 the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like material. A positive electrode mixture slurry is obtained. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21A and the solvent is dried. Then, the positive electrode active material layer 21B is formed by compression molding using a roll press or the like, and the positive electrode 21 is manufactured.

  Next, 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-methyl-2-pyrrolidone to obtain a paste-like negative electrode mixture slurry. And Subsequently, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, and the solvent is dried. Then, the negative electrode active material layer 22B is formed by compression molding using a roll press or the like, and the negative electrode 22 is manufactured.

  Next, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A 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. 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 FIGS. 1 and 2 is completed.

  This secondary battery operates as follows.

  In the secondary battery, when charged, for example, lithium ions are released from the positive electrode active material layer 21B and inserted into the negative electrode active material layer 22B through the electrolytic solution. In addition, when discharging is performed, for example, lithium ions are released from the negative electrode active material layer 22B and inserted into the positive electrode active material layer 21B through the electrolytic solution. At that time, a film made of the above-described acetophenone derivative is formed on the negative electrode 22, and an irreversible reaction occurring between the negative electrode 22 and the electrolytic solution is suppressed.

  As described above, according to the present embodiment, since the acetophenone derivative having a polyfluoroalkyl group is included, a favorable film can be formed on the negative electrode 22 and side reactions in the negative electrode 22 can be suppressed. . Therefore, charge / discharge efficiency can be improved, and battery characteristics such as cycle characteristics can be improved.

  In particular, if an acetophenone derivative having a polyfluoroalkoxy group, particularly an acetophenone derivative having a polyfluoroalkoxy group at the 2-position of the benzene ring is included, a higher effect can be obtained.

  Further, if the content of the acetophenone derivative in the solvent is 0.05% by mass or more and 10% by mass or less, and further 0.1% by mass or more and 9% by mass or less, a higher effect can be obtained. it can.

[Second Embodiment]
FIG. 3 shows the configuration of the secondary battery according to the second embodiment of the present invention. This secondary battery is a so-called laminate film type, and has a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached accommodated in a film-shaped exterior member 40.

  The positive electrode lead 31 and the negative electrode lead 32 are led out, for example, in the same direction from the inside of the exterior member 40 to the outside, and are each made of a metal material such as aluminum, copper, nickel, or stainless steel.

  The exterior member 40 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. For example, the exterior member 40 is disposed so that the polyethylene film side and the wound electrode body 30 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 40 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 4 shows an enlarged part of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is obtained by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte layer 36 interposed therebetween.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on both surfaces of a positive electrode current collector 33A, and the negative electrode 34 also has a structure in which a negative electrode active material layer 34B is provided on both surfaces of the negative electrode current collector 34A. have. The positive electrode 33 and the negative electrode 34 are disposed so that the positive electrode active material layer 33B and the negative electrode active material layer 34B face each other. The specific configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are the same as those of the positive electrode current collector 21A, the positive electrode active material layer in the first embodiment. This is the same as 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound that holds the electrolytic solution, and has a so-called gel shape. A gel electrolyte is preferable because high ion conductivity can be obtained and battery leakage can be prevented. The configuration of the electrolytic solution (that is, the solvent, the electrolyte salt, and the like) is the same as that in the first embodiment described above. Examples of the polymer material include, for example, an ether-based polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, a polymer of vinylidene fluoride such as polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropropylene, Or a polyacrylonitrile is mentioned, Any 1 type or 2 types or more of these are mixed and used. In particular, from the viewpoint of redox stability, it is desirable to use a fluorine-based polymer compound such as a vinylidene fluoride polymer.

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

  First, after forming the positive electrode 33 and the negative electrode 34 in the same manner as in the first embodiment, the electrolyte layer 36 in which the electrolytic solution is held in the polymer compound is formed on each of the positive electrode 33 and the negative electrode 34. Next, the positive electrode lead 31 is attached to the end portion of the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the end portion of the negative electrode current collector 34A. Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are stacked via the separator 35, and then wound in the longitudinal direction to form the wound electrode body 30. After that, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edge portions of the exterior members 40 are sealed and sealed by thermal fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  Further, in this secondary battery, the positive electrode 33 and the negative electrode 34 are laminated and wound via the separator 35 and sandwiched between the exterior members 40, and then the electrolytic solution and the polymer compound are opened from the opening of the exterior member 40. The electrolyte layer 36 may be formed by injecting an electrolyte composition containing a monomer as a raw material and polymerizing the monomer.

  This secondary battery operates in the same manner as in the first embodiment, and has the same effect as in the first embodiment.

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

(Examples 1-1 to 1-9)
The laminate film type secondary battery shown in FIGS. First, lithium-cobalt composite oxide (LiCoO ₂ ) is used as a positive electrode active material, and the lithium-cobalt composite oxide, graphite as a conductive agent, and polyvinylidene fluoride as a binder are mixed to form a positive electrode composite. An agent was prepared. Next, this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, and then uniformly applied to the positive electrode current collector 33A made of aluminum foil and dried, and a roll press machine The positive electrode active material layer 33B was formed by compression molding to produce the positive electrode 33.

  Further, artificial graphite was prepared as a negative electrode active material, and this negative graphite was mixed with polyvinylidene fluoride as a binder to prepare a negative electrode mixture. Next, this negative electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, and then uniformly applied to the negative electrode current collector 34A made of copper foil and dried, and a roll press machine The negative electrode active material layer 34B was formed by compression molding, and the negative electrode 34 was produced.

Subsequently, the positive electrode lead 31 was attached to the positive electrode current collector 33A, the negative electrode lead 32 was attached to the negative electrode current collector 34A, and the electrolyte layer 36 was formed on the positive electrode active material layer 33B and the negative electrode active material layer 34B. The electrolyte layer 36 is a mixture of ethylene carbonate and propylene carbonate at a mass ratio of 6: 4, to which 3 ′-(trifluoromethoxy) acetophenone shown in Chemical Formula 6 which is an acetophenone derivative and LiPF ₆ which is an electrolyte salt. And an electrolyte solution prepared by adding a gel electrolyte held in a copolymer of hexafluoropropylene and vinylidene fluoride.

At that time, the content of 3 ′-(trifluoromethoxy) acetophenone in the solvent was within the range of 0.05% by mass to 10.0% by mass as shown in Table 1 in Examples 1-1 to 1-9. It was changed with. The content of LiPF ₆ was 0.7 mol / kg, and the ratio of hexafluoropropylene in the copolymer was 6.9% by mass.

  Next, the separator 35, the positive electrode 33, the separator 35, and the negative electrode 34 were stacked and wound in this order to form the wound electrode body 30, and then the wound electrode body 30 was sealed between the exterior members 40. This obtained the secondary battery of Examples 1-1 to 1-9.

  As Comparative Example 1-1 with respect to Examples 1-1 to 1-9, secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-9, except that no acetophenone derivative was added to the electrolytic solution. . In addition, as Comparative Examples 1-2 to 1-4, secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-9, except that 3-methoxyacetophenone was added to the electrolytic solution. At that time, in Comparative Examples 1-2 to 1-4, the content of 3-methoxyacetophenone in the solvent was changed to 0.1 mass%, 1.0 mass%, or 9.0 mass%.

  About the produced secondary battery of Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-4, charging / discharging was performed and initial charge / discharge efficiency was investigated. Charging was performed at a constant current and constant voltage of 0.08 A and an upper limit of 4.2 V at 23 ° C., and discharging was performed at a constant current of 0.16 A at 23 ° C. to a final voltage of 3.0 V. The initial charge / discharge efficiency was determined from the ratio of the discharge capacity to the charge capacity at the first cycle, that is, (discharge capacity at the first cycle / charge capacity at the first cycle) × 100. The obtained results are shown in Table 1.

  As shown in Table 1, according to Examples 1-1 to 1-9 to which an acetophenone derivative having a polyfluoroalkoxy group was added, the initial charge / discharge efficiency was higher than that of Comparative Example 1-1 to which no acetophenone derivative was added. Was able to greatly improve. On the other hand, in Comparative Examples 1-2 to 1-4 to which an acetophenone derivative having no polyfluoroalkoxy group was added, the improvement was not observed as much as Examples 1-1 to 1-9. That is, it was found that the charge / discharge efficiency can be improved by including an acetophenone derivative having a polyfluoroalkoxy group in the electrolytic solution.

  Further, as can be seen by comparing Examples 1-1 to 1-9, when the content of the acetophenone derivative was increased, the initial charge / discharge efficiency was improved and then decreased. That is, it was found that the content of the acetophenone derivative in the solvent is preferably 0.05% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 9.0% by mass or less.

(Examples 2-1 to 2-6)
A secondary battery was made in the same manner as Example 1-4 except that the type of acetophenone derivative was changed. At that time, 3 ′-(trifluoromethyl) acetophenone shown in Chemical Formula 4 was used in Example 2-1, and 2 ′-(trifluoromethoxy) acetophenone shown in Chemical Formula 5 was used in Example 2-2. In Example 2-3, 4 ′-(trifluoromethoxy) acetophenone shown in Chemical Formula 7 was used, and in Example 2-4, 3 ′-(2,2,2-trifluoroethyl) acetophenone shown in Chemical Formula 8 was used. In Example 2-5, 7 ′-(trifluoromethoxy) acetonaphthone shown in Chemical Formula 9 was used, and in Example 2-6, 6 ′-(trifluoromethoxy) acetonaphthone shown in Chemical Formula 10 was used. In addition, content in the solvent of an acetophenone derivative is 1 mass%.

  For the fabricated secondary batteries of Examples 2-1 to 2-6, a charge / discharge test was performed in the same manner as in Example 1-4 to examine the initial charge / discharge efficiency. The results are shown in Table 2 together with the results of Example 1-4 and Comparative Examples 1-1 and 1-3.

  As shown in Table 2, also in Examples 2-1 to 2-6, the initial charge and discharge efficiency can be improved as compared with Comparative Examples 1-1 and 1-3, as in Example 1-4. It was. That is, it was found that the same effect can be obtained even when other acetophenone derivatives having a polyfluoroalkoxy group are used.

  Moreover, as can be seen by comparing Examples 1-4 and 2-1 to 2-6, the highest value was obtained in Example 2-2 using 2 ′-(trifluoromethoxy) acetophenone. . That is, it was found that it is more preferable to use an acetophenone derivative having a polyfluoroalkoxy group at the 2-position of the benzene ring.

(Examples 3-1 to 3-9)
A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-9, except that a tin alloy containing 45% by mass of tin was used instead of artificial graphite as the negative electrode active material. At that time, the content of the acetophenone derivative in the solvent was changed within the range of 0.05% by mass to 10.0% by mass as shown in Table 3 in Examples 3-1 to 3-9.

  As Comparative Example 3-1 with respect to Examples 3-1 to 3-9, a secondary battery was fabricated in the same manner as in Examples 3-1 to 3-9, except that no acetophenone derivative was added to the electrolytic solution. . As Comparative Examples 3-2 to 3-4, secondary batteries were fabricated in the same manner as in Examples 3-1 to 3-9, except that 3-methoxyacetophenone was added to the electrolytic solution. At that time, in Comparative Examples 3-2 to 3-4, the content of 3-methoxyacetophenone in the solvent was changed to 0.1 mass%, 1.0 mass%, or 9.0 mass%.

  For the fabricated secondary batteries of Examples 3-1 to 3-9 and Comparative Examples 3-1 to 3-4, a charge / discharge test was performed in the same manner as in Examples 1-1 to 1-9, and the initial charge / discharge was performed. The efficiency was examined. The results are shown in Table 3.

  As shown in Table 3, also in Examples 3-1 to 3-9, as with Examples 1-1 to 1-9, the initial charge / discharge efficiency was improved as compared with Comparative Examples 1-1 to 1-4. I was able to. That is, it was found that the same effect can be obtained even when other negative electrode active materials are used. Similarly, the content of the acetophenone derivative in the solvent is preferably 0.05% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 9.0% by mass or less.

(Examples 4-1 to 4-9)
The cylindrical secondary battery shown in FIGS. At that time, secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-9 except that the electrolytic solution was used as it was without being held in the polymer compound. At that time, the content of the acetophenone derivative in the solvent was changed within the range of 0.05% by mass to 10.0% by mass as shown in Table 4 in Examples 4-1 to 4-9.

  As Comparative Example 4-1 with respect to Examples 4-1 to 4-9, secondary batteries were fabricated in the same manner as in Examples 4-1 to 4-9, except that no acetophenone derivative was added to the electrolytic solution. . In addition, as Comparative Examples 4-2 to 4-4, secondary batteries were fabricated in the same manner as in Examples 4-1 to 4-9, except that 3-methoxyacetophenone was added to the electrolytic solution. At that time, in Comparative Examples 4-2 to 4-4, the content of 3-methoxyacetophenone in the solvent was changed to 0.1 mass%, 1.0 mass%, or 9.0 mass%.

  For the fabricated secondary batteries of Examples 4-1 to 4-9 and Comparative Examples 4-1 to 4-4, a charge / discharge test was performed in the same manner as in Examples 1-1 to 1-9, and the initial charge / discharge was performed. The efficiency was examined. The results are shown in Table 4.

  As shown in Table 4, also in Examples 4-1 to 4-9, the initial charge / discharge efficiency was improved as compared with Comparative Examples 4-1 to 4-4, similarly to Examples 1-1 to 1-9. I was able to. That is, it has been found that charging / discharging efficiency can be improved by including an acetophenone derivative having a polyfluoroalkoxy group, whether the electrolytic solution is used as it is or held in a polymer compound. Similarly, the content of the acetophenone derivative in the solvent is preferably 0.05% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 9.0% by mass or less.

  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 the electrolyte solution or the gel electrolyte in which the electrolyte solution is held in the polymer compound is used as the electrolyte has been described, but the electrolyte solution may be held in the inorganic conductor, Moreover, you may make it hold | maintain electrolyte solution in the mixture of a high molecular compound and an inorganic conductor. Examples of inorganic conductors include polycrystals of lithium nitride, lithium iodide or lithium hydroxide, a mixture of lithium iodide and dichromium trioxide, or a mixture of lithium iodide, thilium sulfide and diphosphorous subsulfide. The thing containing is mentioned.

  Moreover, although the said embodiment and Example demonstrated the case where the positive electrodes 21 and 33 and the negative electrodes 22 and 34 were wound, you may make it fold or stack | stack a positive electrode and a negative electrode. Furthermore, in the above-described embodiments and examples, a cylindrical or laminated film type secondary battery has been described. For example, other types such as an elliptical type, a polygonal type, a coin type, a button type, a square type, and a large type The present invention can also be applied to a secondary battery having a shape. In addition, the present invention can be applied not only to secondary batteries but also to primary batteries.

  Furthermore, in the above-described embodiments and examples, a so-called lithium ion secondary battery, that is, a secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium has been described. The present invention can be similarly applied to the used battery. As a battery using another electrode reaction, for example, a battery in which the capacity of the negative electrode is represented by the sum of the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium, or the capacity of the negative electrode is A so-called lithium metal battery represented by a capacity component due to precipitation and dissolution of lithium can be given.

  Among these, a battery in which the capacity of the negative electrode is represented by the sum of the capacity component due to insertion and extraction of lithium and the capacity component due to precipitation and dissolution of lithium has, for example, a charge capacity of a negative electrode material capable of inserting and extracting lithium. The lithium ion secondary battery has the same configuration as the above-described lithium ion secondary battery except that lithium metal is deposited on the negative electrode during charging by being adjusted to be smaller than the charging capacity of the positive electrode. . In addition, the lithium metal battery has the same configuration as the lithium ion secondary battery described above except that the negative electrode is made of lithium metal and the like, and the precipitation and dissolution reaction of lithium is used in the negative electrode. Yes.

  Furthermore, in the above-described embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, other alkali metals such as sodium (Na) or potassium (K), magnesium or calcium (Ca), etc. The present invention can also be applied to the case of using other light metals such as alkaline earth metals or aluminum.

It is sectional drawing showing the structure of the secondary battery which concerns on the 1st Embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is a partial exploded perspective view showing the structure of the secondary battery which concerns on the 2nd Embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG.

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, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode current collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode current collector, 22B, 34B ... Negative electrode active material layer, 23, 35 ... Separator , 24 ... center pin, 25, 31 ... positive electrode lead, 26, 32 ... negative electrode lead, 36 ... electrolyte layer, 40 ... exterior member, 41 ... adhesion film.

Claims (6)

  An electrolyte comprising a solvent containing an acetophenone derivative having a polyfluoroalkyl group.   2. The electrolyte according to claim 1, wherein the content of the acetophenone derivative in the solvent is in the range of 0.05% by mass to 10% by mass.   2. 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, wherein the electrolyte contains a solvent containing an acetophenone derivative having a polyfluoroalkyl group.   The battery according to claim 4, wherein the content of the acetophenone derivative in the solvent is in the range of 0.05% by mass to 10% by mass. The battery according to claim 4, wherein the electrolyte further contains a polymer compound.

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