JP2008016422A - Electrolyte and battery using the same, electrolyte for square battery, and square battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte capable of obtaining superior cycle characteristics and low-temperature discharge characteristics, and to provide a battery that uses the same. <P>SOLUTION: The secondary battery that uses the electrolyte has a wound electrode body 20, in which a belt-like positive electrode 21 and a negative electrode 22 are laminated and wound around via a separator 23 in a battery can 11 of hollow cylindrical shape. An electrolytic solution, containing a solvent and an electrolytic salt, is impregnated in this separator 23. As the solvent, the solvent which includes a first solvent made of at least one kind selected out of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, a second solvent made of at least one kind selected from among diethyl carbonate, dimethyl carbonate, and ethyl-methyl carbonate, and 4, 5-difluoro-1,3-dioxolane-2-on is used. The volume of the first solvent is 5 vol% or larger and 40 vol% or smaller with respect to the solvent as a whole, and the volume of 4,5-difluoro-1,3-dioxolane-2-on is 0.05 vol% or larger and 20 vol% or smaller with respect to the whole solvent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrolyte, a battery using the same, a prismatic battery electrolyte, and a prismatic battery using the electrolyte, and more specifically, a nonaqueous electrolyte including a nonaqueous solvent and an electrolyte salt, and a non-aqueous electrolyte using the nonaqueous electrolyte. The present invention relates to a water electrolyte battery, a nonaqueous electrolyte for a prismatic battery, and a prismatic nonaqueous electrolyte battery using the same.

  In recent years, portable electronic devices typified by a camera-integrated VTR (video tape recorder), mobile phone device, or laptop computer have become widespread, and their miniaturization, weight reduction, and long-term continuous driving are strongly demanded. . Accordingly, research and development for improving the energy density of a battery, particularly a secondary battery, as a power source has been actively promoted. Among these, lithium ion secondary batteries or lithium metal secondary batteries are expected because a large energy density can be obtained as compared with lead batteries and nickel cadmium batteries, which are conventional nonaqueous electrolyte secondary batteries.

  In such a lithium ion secondary battery or a lithium metal secondary battery, since the negative electrode becomes a strong reducing agent in a charged state, the electrolytic solution is easily decomposed in the negative electrode, thereby reducing the discharge capacity. Therefore, various studies have been made on the composition of the electrolytic solution in order to improve battery characteristics such as cycle characteristics. For example, Patent Document 1 proposes using an electrolytic solution containing 4-fluoro-1,3-dioxolan-2-one.

JP 2006-134834 A

  However, as the use of portable electronic devices increases, recently, they are often placed under low temperature conditions during use and the like, and deterioration of battery characteristics due to this has become a problem. Therefore, it has been desired to develop an electrolyte that can improve not only cycle characteristics but also characteristics at low temperatures.

  In addition, since the electrolytic solution described in Patent Document 1 contains 4-fluoro-1,3-dioxolan-2-one, the viscosity becomes high and the lithium salt is difficult to dissociate, and the characteristics at low temperature are high. There was a problem of lowering.

  Further, the battery having a square shape has a problem that the battery swells due to a gas generated by a decomposition reaction of the electrolytic solution.

  Accordingly, an object of the present invention is to provide an electrolyte capable of obtaining excellent cycle characteristics and low-temperature discharge characteristics, and a battery using the electrolyte.

  Another object of the present invention is to provide a prismatic battery electrolyte capable of suppressing battery swelling during high-temperature storage and a prismatic battery using the same.

In order to solve the above-described problem, the first invention
A first solvent comprising at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone;
A second solvent comprising at least one selected from diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate;
4,5-difluoro-1,3-dioxolan-2-one;
Including
The volume of the first solvent is 5% by volume or more and 40% by volume or less with respect to the entire solvent,
The volume of 4,5-difluoro-1,3-dioxolan-2-one is an electrolyte characterized by being 0.05 volume% or more and 20 volume% or less.

The second invention is
A first solvent comprising ethylene carbonate;
A second solvent comprising at least one of diethyl carbonate and ethyl methyl carbonate;
4,5-difluoro-1,3-dioxolan-2-one;
Including
The volume of the first solvent is 5% by volume or more and 30% by volume or less with respect to the entire solvent,
The volume of 4,5-difluoro-1,3-dioxolan-2-one is 0.05% by volume or more and 10% by volume or less.

The third invention is
A battery comprising a positive electrode and a negative electrode, and an electrolyte,
The electrolyte
A first solvent comprising at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone;
A second solvent comprising at least one selected from diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate;
4,5-difluoro-1,3-dioxolan-2-one;
Including
The volume of the first solvent is 5% by volume or more and 40% by volume or less with respect to the entire solvent,
The battery is characterized in that the volume of 4,5-difluoro-1,3-dioxolan-2-one is 0.05% by volume or more and 20% by volume or less.

The fourth invention is:
A positive electrode, a negative electrode, and an electrolyte;
The electrolyte
A first solvent comprising ethylene carbonate;
A second solvent comprising at least one of diethyl carbonate and ethyl methyl carbonate;
4,5-difluoro-1,3-dioxolan-2-one;
Including
The volume of the first solvent is 5% by volume or more and 30% by volume or less with respect to the entire solvent,
The volume of 4,5-difluoro-1,3-dioxolan-2-one is 0.05% by volume or more and 10% by volume or less.

  In the first invention, a first solvent comprising at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone, and diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. A second solvent composed of at least one selected from the above, and 4,5-difluoro-1,3-dioxolan-2-one, and the volume of the first solvent relative to the whole solvent is: Viscosity is reduced because the volume of 5,5-difluoro-1,3-dioxolan-2-one is 0.05 vol% or more and 20 vol% or less. The decomposition reaction can be suppressed even at room temperature.

  In the second invention, a first solvent composed of ethylene carbonate, a second solvent composed of at least one of diethyl carbonate and ethyl methyl carbonate, and 4,5-difluoro-1,3-dioxolane-2- The volume of the first solvent is 5% by volume or more and 30% by volume or less, and the volume of 4,5-difluoro-1,3-dioxolan-2-one is Since it is made 0.05 volume% or more and 10 volume% or less, when it uses for a square battery, the swelling at the time of a preservation | save can be suppressed.

  In the third invention, as an electrolyte, a first solvent consisting of at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone, diethyl carbonate, dimethyl carbonate, ethyl A second solvent composed of at least one selected from methyl carbonate and 4,5-difluoro-1,3-dioxolan-2-one, and the first solvent The volume is 5 volume% or more and 40 volume% or less, and the volume of 4,5-difluoro-1,3-dioxolan-2-one is 0.05 volume% or more and 20 volume% or less. Since it is used, a decomposition reaction or the like can be suppressed even at room temperature, and excellent cycle characteristics and low-temperature discharge characteristics can be obtained.

  In the fourth invention, as the electrolyte, a first solvent made of ethylene carbonate, a second solvent made of at least one of diethyl carbonate and ethyl methyl carbonate, and 4,5-difluoro-1,3-dioxolane are used. And the volume of the first solvent is 5% by volume or more and 30% by volume or less with respect to the entire solvent, and the amount of 4,5-difluoro-1,3-dioxolan-2-one Since the volume used is 0.05 volume% or more and 10 volume% or less, it is possible to suppress swelling during storage in a rectangular battery.

  According to the present invention, excellent cycle characteristics and low temperature discharge characteristics can be obtained. Moreover, in a square battery, swelling during storage can be suppressed.

  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 includes a so-called liquid electrolytic solution including, for example, a solvent and an electrolyte salt dissolved in the solvent.

  The solvent is preferably a non-aqueous solvent such as an organic solvent, for example, a first solvent comprising at least one of ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone, diethyl carbonate, dimethyl carbonate And a second solvent comprising at least one of ethyl methyl carbonate and 4,5-difluoro-1,3-dioxolan-2-one. The volume of the first solvent is 5% by volume or more and 40% by volume or less with respect to the whole solvent. The volume of 4,5-difluoro-1,3-dioxolan-2-one is 0.05% by volume or more and 20% by volume or less with respect to the whole solvent. By using this solvent in a battery, excellent room temperature cycle characteristics and low temperature discharge characteristics can be obtained. In addition, the volume of the first solvent is more preferably 5% by volume or more and 30% by volume or less with respect to the whole solvent from the viewpoint that more excellent characteristics can be obtained, and 4,5-difluoro-1,3- The volume of dioxolan-2-one is more preferably 0.05% by volume or more and 15% by volume or less with respect to the whole solvent. This is because, with these compositions, decomposition reactions and the like can be further suppressed even at room temperature, and more excellent cycle characteristics and low-temperature discharge characteristics can be obtained.

  As a solvent for the prismatic battery, ethylene carbonate as the first solvent, at least one of diethyl carbonate and ethyl methyl carbonate as the second solvent, and 4,5-difluoro-1,3-dioxolane It is preferable to use those containing 2-one. The volume of the 1st solvent which consists of ethylene carbonate is 5 volume% or more and 30 volume% or less with respect to the whole solvent. The volume of 4,5-difluoro-1,3-dioxolan-2-one is 0.05% by volume or more and 10% by volume or less. The electrolyte containing such a solvent can improve the chemical stability even in a high temperature environment. When the electrolyte containing this solvent is used for a prismatic battery, it is a battery that becomes a problem particularly when stored at a high temperature. Can suppress blistering. In addition to ethylene carbonate, the solvent for the prismatic battery may further contain at least one of propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone, in addition to ethylene carbonate. . This is because a more excellent battery swelling suppression effect can be obtained.

  Furthermore, as 4,5-difluoro-1,3-dioxolan-2-one, a trans isomer is preferable to a cis isomer from the viewpoint of obtaining superior low-temperature discharge characteristics. Furthermore, in the case of using for a rectangular battery, it is preferable to use a trans form of 4,5-difluoro-1,3-dioxolan-2-one because a more excellent battery swelling suppression effect can be obtained.

  Furthermore, the volume of the second solvent is preferably 40% by volume to 94.95% by volume with respect to the whole solvent. Further, when the solvent further contains other solvent species in addition to the first solvent and 4,5-difluoro-1,3-dioxolan-2-one, the volume of the second solvent is 50 Volume% to 90 volume% is preferred. It is because better battery characteristics can be obtained by setting it as these ranges.

  Furthermore, when this electrolyte is used for a battery, the negative electrode preferably has a material containing silicon (Si) as a constituent element or lithium metal. This is because the room temperature cycle characteristics can be further improved. Further, when the prismatic electrolyte is used for a prismatic battery, it is more effective that the negative electrode has a material containing at least one of silicon (Si) and (Sn) as a constituent element. It is preferable in that it can be performed.

  Furthermore, as a solvent, it is preferable that the cyclic carbonate which has unsaturated bonds, such as vinylene carbonate (VC) and vinyl ethylene carbonate (VEC), is further included. This is because the chemical stability of the electrolytic solution can be improved, and more excellent cycle characteristics can be obtained. Furthermore, the content of the cyclic carbonate having an unsaturated bond is preferably 0.01% by weight or more and 5% by weight or less. This is because particularly excellent cycle characteristics can be obtained.

  Furthermore, it is preferable that the solvent further contains an acid anhydride. This is because more excellent cycle characteristics can be obtained. Examples of the acid anhydride include succinic anhydride, glutaric anhydride, maleic anhydride and the like. Furthermore, the addition amount of the acid anhydride is preferably 0.5% by weight to 3% by weight. This is because particularly excellent cycle characteristics can be obtained. When used as a solvent for a prismatic battery, it is preferable to further include an acid anhydride because the battery bulge during high-temperature storage can be further suppressed.

  Further, the solvent for the prismatic battery preferably contains a compound having a sulfone structure such as propane sultone, propene sultone, divinyl sulfone, and the like. Furthermore, the content of the compound having a sulfone structure is preferably in the range of 0.01% by weight to 5% by weight. This is because battery swelling during high-temperature storage can be further suppressed.

[Electrolyte salt]
The electrolyte salt preferably includes a light metal salt represented by Chemical Formula 1. This is because the light metal salt represented by Chemical Formula 1 can form a stable film on the surface of the negative electrode 22 and suppress the decomposition reaction of the solvent. The light metal salt represented by Chemical Formula 1 may be used alone or in combination of two or more.

（式中、Ｒ１１は化２、化３または化４に示した基を表し、Ｒ１２はハロゲン基、アルキル基、ハロゲン化アルキル基、アリール基またはハロゲン化アリール基を表し、Ｘ１１およびＸ１２は酸素（Ｏ）または硫黄（Ｓ）をそれぞれ表し、Ｍ１１は遷移金属元素または短周期型周期表における３Ｂ族元素、４Ｂ族元素あるいは５Ｂ族元素を表し、Ｍ２１は短周期型周期表における１Ａ族元素あるいは２Ａ族元素またはアルミニウム（Ａｌ）を表し、ａは１〜４の整数であり、ｂは０〜８の整数であり、ｃ、ｄ、ｅおよびｆはそれぞれ１〜３の整数である。）

(Wherein R11 represents the group shown in Chemical Formula 2, Chemical Formula 3 or Chemical Formula 4, R12 represents a halogen group, an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, and X11 and X12 represent oxygen ( O) or sulfur (S), respectively, M11 represents a transition metal element or a group 3B element, 4B element or 5B element in the short periodic table, and M21 represents a group 1A element or 2A in the short periodic table Represents a group element or aluminum (Al), a is an integer of 1 to 4, b is an integer of 0 to 8, and c, d, e, and f are each an integer of 1 to 3.)

（式中、Ｒ２１は、アルキレン基、ハロゲン化アルキレン基、アリーレン基またはハロゲン化アリーレン基を表す。）

(In the formula, R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group.)

（式中、Ｒ２３、Ｒ２４は、アルキル基、ハロゲン化アルキル基、アリール基またはハロゲン化アリール基を表す。）

(Wherein R23 and R24 represent an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group.)

  As the light metal salt represented by Chemical Formula 1, the compound represented by Chemical Formula 5 is preferable.

（式中、Ｒ１１は化６、化７または化８に示した基を表し、Ｒ１３はハロゲンを表し、Ｍ１２はリン（Ｐ）またはホウ素（Ｂ）を表し、Ｍ２１は短周期型周期表における１Ａ族元素あるいは２Ａ族元素またはアルミニウム（Ａｌ）を表し、ａ１は１〜４の整数であり、ｂ１は０、２または４であり、ｃ、ｄ、ｅおよびｆはそれぞれ１〜３の整数である。）

(In the formula, R11 represents the group shown in Chemical Formula 6, Chemical Formula 7, or Chemical Formula 8, R13 represents halogen, M12 represents phosphorus (P) or boron (B), and M21 represents 1A in the short periodic table. Represents a group element or a group 2A element or aluminum (Al), a1 is an integer of 1 to 4, b1 is 0, 2 or 4, and c, d, e and f are each an integer of 1 to 3. .)

（式中、Ｒ２１は、アルキレン基、ハロゲン化アルキレン基、アリーレン基またはハロゲン化アリーレン基を表す。）

(In the formula, R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group.)

（式中、Ｒ２２は、アルキル基、ハロゲン化アルキル基、アリール基またはハロゲン化アリール基を表す。）

(Wherein R22 represents an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group.)

  More specifically, as the light metal salt represented by Chemical Formula 1, more specifically, difluoro [oxolato-O, O ′] lithium borate represented by Chemical Formula 9, difluorobis [oxolato-O, O ′ represented by Chemical Formula 10 ] Lithium phosphate, difluoro [3,3,3-trifluoro-2-oxide-2-trifluoromethylpropionate (2-)-O, O '] lithium borate represented by formula 11 Bis [3,3,3-trifluoro-2-oxide-2-trifluoromethylpropionate (2-)-O, O ′] lithium borate represented, tetrafluoro [oxolato- O, O ′] lithium phosphate and bis [oxolato-O, O ′] lithium borate represented by the formula 14 can be mentioned.

  Furthermore, as the electrolyte salt, in addition to the above-described light metal salt, any one or more of other light metal salts are preferably mixed and used. This is because battery characteristics such as storage characteristics can be improved and internal resistance can be reduced.

Examples of other light metal salts include LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, LiBr, LiPF ₆ , LiBF ₄ , LiB (OCOCF ₃ ) _4. , LiB (OCOC ₂ F ₅ ) ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ or LiN (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ )) or a lithium salt represented by Chemical Formula 16 such as LiC (CF ₃ SO ₂ ) ₃ .

  Other light metal salts include, for example, a lithium salt represented by Chemical Formula 17, and examples of the lithium salt represented by Chemical Formula 17 include 1,2-perfluoroethane represented by Chemical Formula 18 Disulfonylimide lithium, 1,3-perfluoropropane disulfonylimide lithium represented by Chemical Formula 19, 1,3-perfluorobutane disulfonylimide lithium represented by Chemical Formula 20, 1,4 represented by Chemical Formula 21 -More preferred is perfluorobutanedisulfonylimide lithium. Furthermore, lithium salts such as perfluoroheptanedioic acid lithium represented by Chemical Formula 22 can be mentioned.

（式中、ｍおよびｎは１以上の整数である。）

(In the formula, m and n are integers of 1 or more.)

（式中、ｐ、ｑおよびｒは１以上の整数である。）

(In the formula, p, q and r are integers of 1 or more.)

(式中、Ｒは炭素数２〜４の直鎖状または分岐状パーフルオロアルキレン基を表す。)

(In the formula, R represents a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms.)

Among them, at least one selected from the group consisting of LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , lithium salt represented by Chemical formula 15, lithium salt represented by Chemical formula 16 and lithium salt represented by Chemical formula 17 If included, a higher effect can be obtained and a high conductivity can be obtained, which is preferable. LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , a lithium salt represented by Chemical formula 15 It is more preferable to use a mixture of at least one selected from the group consisting of the lithium salt represented by Formula 16 and the lithium salt represented by Formula 17.

Furthermore, as the electrolyte salt, it is particularly preferable to include LiBF ₄ from the viewpoint that gas generation can be further suppressed in the negative electrode, and that excellent low-temperature discharge characteristics can be obtained without deteriorating the normal temperature cycle characteristics.

In addition, when used in a prismatic battery, the electrolyte salt more preferably contains LiBF ₄ because it can further suppress battery swelling during high-temperature storage. Further, when used in a prismatic battery, it is particularly preferable that LiBF ₄ is included as an electrolyte salt, and further, for example, a compound having a sulfone structure such as propene sultone (PRS) is included. This is because battery swelling during high temperature storage can be significantly suppressed.

  The content (concentration) of the electrolyte salt is preferably in the range of 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent. Outside this range, there is a risk that sufficient battery characteristics may not be obtained due to an extreme decrease in ionic conductivity. Among them, the content of the light metal salt shown in Chemical Formula 1 is preferably in the range of 0.01 mol / kg to 2.0 mol / kg with respect to the solvent. This is because a higher effect can be obtained within this range.

  Note that the electrolyte may be a gel electrolyte in which an electrolytic solution is held in a polymer compound. The gel electrolyte is not particularly limited as long as the ion conductivity is 1 mS / cm or more at room temperature, and the composition and the structure of the polymer compound are not particularly limited. The electrolyte solution (that is, liquid solvent and electrolyte salt) is as described above. Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride (PVdF) and polyhexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, and polypropylene oxide. , Polyphosphazene, polysiloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene or polycarbonate. In particular, from the viewpoint of electrochemical stability, it is desirable to use a polymer compound having a structure of polyacrylonitrile, polyvinylidene fluoride (PVdF), polyhexafluoropropylene or polyethylene oxide. The amount of the polymer compound added to the electrolytic solution varies depending on the compatibility between the two, but it is usually preferable to add a polymer compound corresponding to 5% by mass or more and less than 50% by mass of the electrolytic solution.

  The content of the electrolyte salt is the same as that in the case of the electrolytic solution. However, the term “solvent” here means not only a liquid solvent but also a concept that can dissociate the electrolyte salt and has a wide range of ionic conductivity. Therefore, when using what has ion conductivity for a high molecular compound, the high molecular compound is also contained in a solvent.

  Using the electrolyte as described above, for example, secondary batteries such as lithium batteries of various shapes and sizes can be manufactured. A first example of a battery using an electrolyte according to an embodiment of the present invention will be described below.

(First example of battery)
FIG. 1 shows a cross-sectional structure of a first example of a secondary battery using an electrolyte 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 negative electrode 22 are laminated and wound inside a substantially hollow cylindrical battery can 11 via a separator 23. 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, 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 (Ni) 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 includes, for example, a positive electrode current collector 21A having a pair of opposed surfaces, and a positive electrode active material layer 21B provided on both surfaces of the positive electrode current collector 21A. The positive electrode active material layer 21B may have a region that exists only on one side. 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, for example, a positive electrode material that can occlude and release lithium (Li) as an electrode reactant as a positive electrode active material.

Lithium as the positive electrode material capable of a (Li) of absorbing and releasing, for example, a solid solution _{(Li (Ni x Co y Mn} z) O 2 containing lithium cobaltate, lithium nickelate, or those having a layered rock salt structure (The values of x, y and z are 0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1), or a lithium composite such as LiMn ₂ O ₄ having a manganese spinel structure An oxide or a phosphate compound having an olivine structure such as lithium iron phosphate (LiFePO ₄ ) is preferable. This is because a high energy density can be obtained.

  Examples of the positive electrode material capable of inserting and extracting lithium (Li) include oxides such as titanium oxide, vanadium oxide and manganese dioxide, and disulfides such as iron disulfide, titanium disulfide and molybdenum sulfide. And conductive polymers such as polyaniline and polythiophene. As the positive electrode material, one kind may be used alone, or two or more kinds may be mixed and used.

  The positive electrode active material layer 21B also includes, for example, a conductive agent, and may further include a binder as necessary. Examples of the conductive agent include carbon materials such as graphite, carbon black, and ketjen black, and one or more of them are used in combination. 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 rubbers such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene rubber, or polymer materials such as polyvinylidene fluoride (PVdF), and one or more of them are used. Are used as a mixture. For example, when the positive electrode 21 and the negative electrode 22 are wound as shown in FIG. 1, it is preferable to use a styrene butadiene rubber or a fluorine rubber having high flexibility as the binder.

  The negative electrode 22 includes, for example, a negative electrode current collector 22A having a pair of opposed surfaces and a negative electrode active material layer 22B provided on both surfaces of the negative electrode current collector 22A. The negative electrode active material layer 22B may have a region where only one side exists.

  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 having good electrochemical stability, electrical conductivity, and mechanical strength. In particular, copper foil is most preferable because it has high electrical conductivity.

  Further, the negative electrode current collector 22A may be preferably made of a metal material containing at least one metal element that does not form an intermetallic compound with lithium (Li). When an intermetallic compound is formed with lithium (Li), it expands and contracts with charge and discharge, structural breakdown occurs, current collection performance decreases, and the ability to support the negative electrode active material layer 22B decreases, and the negative electrode active material layer This is because 22B may fall off from the negative electrode current collector 22A. Note that in this specification, the metal material includes not only a single metal element but also an alloy composed of two or more metal elements or one or more metal elements and one or more metalloid elements. Examples of the metal element that does not form an intermetallic compound with lithium (Li) include copper (Cu), nickel (Ni), titanium (Ti), iron, and chromium (Cr).

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of inserting and extracting lithium (Li) as a negative electrode active material. The binder similar to the positive electrode active material layer 21B may be included.

  Examples of the negative electrode material capable of inserting and extracting lithium (Li) include a carbon material, a metal oxide, and a polymer compound. Examples of the carbon material include graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, and graphite having a (002) plane spacing of 0.340 nm or less. More specifically, there are pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers or activated carbon. Among these, coke includes pitch coke, needle coke, and petroleum coke. Organic polymer compound fired bodies are carbonized by firing polymer compounds such as phenol resin and furan resin at an appropriate temperature. What you did. In addition, examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide, and examples of the polymer compound include polyacetylene and polypyrrole.

  Further, the negative electrode active material layer 22B, for example, as a negative electrode active material, a simple substance, an alloy, and a compound of a metal element capable of inserting and extracting lithium (Li) as an electrode reactant, and lithium (Li) are occluded. And at least one negative electrode material selected from the group consisting of simple substances, alloys and compounds of metalloid elements that can be released. Thereby, a high energy density can be obtained. Furthermore, you may make it use this negative electrode material with the carbon material mentioned above. The carbon material has very little change in the crystal structure that occurs during charging and discharging. For example, if used together with the negative electrode material described above, a high energy density can be obtained and excellent cycle characteristics can be obtained. This is preferable because it can function as a conductive agent. Note that in this specification, alloys include those composed of 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. Some of the structures include a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them.

  As the metal element or metalloid element constituting this negative electrode material, magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), Tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd) or Platinum (Pt) is mentioned. These may be crystalline or amorphous.

As the alloy or compound of these metal element or a metalloid element, 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 metal elements and metalloid elements capable of forming an alloy with lithium (Li), and Mb represents metal elements other than lithium (Li) and Ma and metalloid elements. 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 these, as the negative electrode material, a simple substance, an alloy or a compound of a 4B group metal element or a semimetal element in the short-period type periodic table is preferable, and silicon (Si) or tin (Sn) simple substance or these are particularly preferable. It is an alloy or compound. Silicon (Si) or tin (Sn) simple substances, alloys and compounds have a large ability to occlude and release lithium (Li), and depending on the combination, the energy density of the anode 22 should be higher than that of conventional graphite. Because you can.

Specific examples of such alloys or compounds include SiB ₄ , SiB ₆ , Mg ₂ Si, 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, LiSnO, Mg ₂ Sn, or an alloy containing tin (Sn) and cobalt (Co).

  Among these, as this negative electrode material, tin (Sn), cobalt (Co), and carbon (C) are included as constituent elements, and the carbon content is 9.9 mass% or more and 29.7 mass% or less. And the ratio Co / (Sn + Co) of cobalt (Co) with respect to the sum total of tin (Sn) and cobalt (Co) is preferably 30% by mass or more and 70% by mass or less. This is because a high energy density can be obtained in such a composition range, and excellent cycle characteristics can be obtained.

  This CoSnC-containing material may further contain other constituent elements as necessary. Examples of other constituent elements include silicon (Si), iron (Fe), nickel (Ni), chromium (Cr), indium (In), niobium (Nb), germanium (Ge), titanium (Ti), and molybdenum. (Mo), aluminum (Al), phosphorus (P), gallium (Ga) or bismuth (Bi) are preferable and may contain two or more. This is because the capacity or cycle characteristics can be further improved.

  The CoSnC-containing material has a phase containing tin (Sn), cobalt (Co), and carbon (C), and this phase has a low crystallinity or an amorphous structure. It is preferable. In this CoSnC-containing material, it is preferable that at least a part of carbon as a constituent element is bonded to a metal element or a semimetal element as another constituent element. The decrease in cycle characteristics is thought to be due to aggregation or crystallization of tin (Sn) or the like, but such aggregation or crystallization can be suppressed by combining carbon with other elements. Because.

  As a measuring method for examining the bonding state of elements, for example, X-ray photoelectron spectroscopy (XPS) can be cited. In XPS, the peak of the carbon 1s orbital (C1s) appears at 284.5 eV in an energy calibrated apparatus so that the peak of the gold atom 4f orbital (Au4f) is obtained at 84.0 eV if it is graphite. . Moreover, if it is surface contamination carbon, it will appear at 284.8 eV. On the other hand, when the charge density of the carbon element increases, for example, when carbon is bonded to a metal element or a metalloid element, the C1s peak appears in a region lower than 284.5 eV. That is, when the peak of the synthetic wave of C1s obtained for the CoSnC-containing material appears in a region lower than 284.5 eV, at least a part of the carbon contained in the CoSnC-containing material is a metal element or a half of other constituent elements. Combined with metal elements.

  In XPS measurement, for example, the C1s peak is used to correct the energy axis of the spectrum. Usually, since surface-contaminated carbon exists on the surface, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, which is used as an energy standard. In the XPS measurement, the waveform of the C1s peak is obtained as a shape including the surface contamination carbon peak and the carbon peak in the CoSnC-containing material. For example, by analyzing using a commercially available software, the surface contamination The carbon peak and the carbon peak in the CoSnC-containing material are separated. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  The negative electrode active material layer 22B may be formed by, for example, any one of a vapor phase method, a liquid phase method, a baking method, and coating, or a combination of two or more thereof. The firing method is a method in which a particulate negative electrode active material is mixed with a binder or a solvent and molded, and then heat-treated at a temperature higher than the melting point of the binder, for example.

  In the case of forming by a vapor phase method, a liquid phase method or a firing method, the negative electrode active material layer 22B and the negative electrode current collector 22A may be alloyed at least at a part of the interface during the formation. Furthermore, heat treatment may be performed in a vacuum atmosphere or a non-oxidizing atmosphere to form an alloy. Specifically, it is preferable that the constituent element of the negative electrode current collector 22A is diffused in the negative electrode active material layer 22B, the constituent element of the negative electrode active material is diffused in the negative electrode current collector 22A, or they are mutually diffused at the interface. This is because breakage due to expansion / contraction of the negative electrode active material layer 22B due to charging / discharging can be suppressed, and electronic conductivity between the negative electrode active material layer 22B and the negative electrode current collector 22A can be improved. .

  As the vapor phase method, for example, a physical deposition method or a chemical deposition method can be used. Specifically, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a thermal CVD (Chemical Vapor Deposition; A vapor phase growth) method or a plasma CVD method can be used. As the liquid phase method, a known method such as electrolytic plating or electroless plating can be used. A known method can also be used for the firing method, and for example, an atmosphere firing method, a reaction firing method, or a hot press firing method can be used. In the case of application, it can be formed in the same manner as the positive electrode 21.

  Moreover, you may form the negative electrode active material layer 22B with the lithium metal which is a negative electrode active material, for example. This is because a high energy density can be obtained. In this case, the negative electrode active material layer 22B may be configured to be already provided from the time of assembly, but may be configured by lithium metal which is not present at the time of assembly and is deposited during charging. Alternatively, the negative electrode active material layer 22B may be used as a current collector, and the negative electrode current collector 22A may be deleted.

  The separator 23 is made of, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and has a structure in which two or more kinds of porous films are laminated. May be. Among these, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve the safety of the battery due to the shutdown effect. In particular, polyethylene is preferable as a material constituting the separator 23 because a shutdown effect can be obtained within a range of 100 ° C. or higher and 160 ° C. or lower and the electrochemical stability is excellent. Polypropylene is also preferable, and any other resin having chemical stability can be used by copolymerizing or blending with polyethylene or polypropylene.

  Furthermore, the separator 23 may have a structure in which polyvinylidene fluoride (PVdF) is applied to both surfaces of the porous film. This is because more excellent room temperature cycle characteristics and low temperature discharge characteristics can be obtained.

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. This electrolytic solution contains a liquid solvent, for example, a nonaqueous solvent such as an organic solvent, and an electrolyte salt dissolved in the nonaqueous solvent, and may contain various additives as necessary. The liquid non-aqueous solvent is made of, for example, a non-aqueous compound and has an intrinsic viscosity at 25 ° C. of 10.0 mPa · s or less. In addition, the intrinsic viscosity in a state where the electrolyte salt is dissolved may be 10.0 mPa · s or less. When a solvent is formed by mixing a plurality of types of nonaqueous compounds, the intrinsic viscosity in the mixed state is What is necessary is just 10.0 mPa * s or less.

  Next, the manufacturing method of the 1st example of a battery is demonstrated. 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-methyl-2-pyrrolidone (NMP). A paste-like positive electrode mixture slurry is prepared. Next, the positive electrode mixture slurry is applied to the positive electrode current collector 21A, the solvent is dried, and the positive electrode active material layer 21B is formed by compression molding using a roll press or the like. Thereby, the positive electrode 31 is obtained.

  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-methyl-2-pyrrolidone (NMP) to form a paste-like negative electrode A mixture slurry is prepared. Next, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, the solvent is dried, and the negative electrode active material layer 22B is formed by compression molding using a roll press or the like. Thereby, the negative electrode 22 is obtained.

  Subsequently, 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 device 15, and the heat sensitive resistance element 16 are fixed to the opening end portion of the battery can 11 by caulking through the gasket 17. Thereby, the secondary battery shown in FIG. 2 is obtained.

  In this secondary battery, for example, when charged, lithium ions are released from the positive electrode active material layer 21B, and lithium (Li) contained in the negative electrode active material layer 22B can be occluded and released through the electrolytic solution. Occluded in possible negative electrode materials. Next, when discharge is performed, lithium ions occluded in the negative electrode material capable of inserting and extracting lithium (Li) in the negative electrode active material layer 22B are released, and the positive electrode active material layer 21B is passed through the electrolytic solution. Occluded.

(Second example of battery)
Next, a second example of the battery will be described. FIG. 3 is a cross-sectional view showing a configuration example of the second example of the battery. This secondary battery has a rectangular shape, and the wound electrode body 30 to which the positive electrode lead 31 and the negative electrode lead 32 are attached is housed in a film-like exterior member 40, and is reduced in size and weight. And it is possible to reduce the thickness.

  Each of the positive electrode lead 31 and the negative electrode lead 32 is led out from the inside of the exterior member 40 to the outside, for example, in the same direction. The positive electrode lead 31 and the negative electrode lead 32 are each made of a metal material such as aluminum (Al), copper (Cu), nickel (Ni), or stainless steel (SUS), and each have a thin plate shape or a mesh shape. Yes.

  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 is a cross-sectional view taken along the line II 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, and the outermost peripheral portion is protected by a protective tape 37.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on one or both surfaces of a positive electrode current collector 33A. The negative electrode 34 has a structure in which a negative electrode active material layer 34B is provided on one surface or both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B and the positive electrode active material layer 33B are arranged to face each other. Yes. The configuration 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 is the same as that of the positive electrode current collector 21A, the positive electrode active material layer 21B described in the first example, This is the same as the anode current collector 22A, the anode active material layer 22B, and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. The gel electrolyte layer 36 is preferable because high ion conductivity can be obtained and battery leakage can be prevented. In addition, you may use for electrolyte as it is as a liquid electrolyte, without hold | maintaining electrolyte solution to a high molecular compound.

  Next, an example of the manufacturing method of the 2nd example of a battery is demonstrated. First, a precursor solution containing a solvent, an electrolyte salt, a polymer compound, and a mixed solvent is applied to each of the positive electrode 33 and the negative electrode 34, and the mixed solvent is volatilized to form a gel electrolyte layer 36. After that, the positive electrode lead 31 is attached to the end of the positive electrode current collector 33A by welding, and the negative electrode lead 32 is attached to the end of the negative electrode current collector 34A by welding.

  Next, the positive electrode 33 and the negative electrode 34 on which the gel electrolyte layer 36 is formed are laminated through a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction to protect the outermost peripheral portion. The wound electrode body 30 is formed by adhering the tape 37. Finally, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edges of the exterior members 40 are sealed and sealed by heat 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 FIG. 3 and FIG. 4 is obtained.

  Further, this secondary battery may be manufactured as follows. First, the positive electrode 33 and the negative electrode 34 are prepared as described above, and after the positive electrode lead 31 and the negative electrode lead 32 are attached to the positive electrode 33 and the negative electrode 34, the positive electrode 33 and the negative electrode 34 are stacked via the separator 35 and wound. The wound electrode body 30 is formed by rotating and bonding the protective tape 37 to the outermost periphery. Next, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer peripheral edge except for one side is heat-sealed to form a bag shape and housed inside the exterior member 40. Subsequently, an electrolyte composition including a solvent, an electrolyte salt, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared, and the exterior member Inject into 40.

  After injecting the electrolyte composition, the opening of the exterior member 40 is heat-sealed and sealed in a vacuum atmosphere. Next, the gelled electrolyte layer 36 is formed by applying heat to polymerize the monomer to obtain a polymer compound. Thus, the secondary battery shown in FIG. 4 is obtained.

(Third example of battery)
Next, a third example of the battery will be described. FIG. 5 shows a configuration example of the third example of the battery. This battery is a square battery having a square shape. In this rectangular battery, the wound electrode body 53 is accommodated in an outer can 51 made of a metal such as aluminum (Al) or iron (Fe), for example, and an electrode pin 54 provided on the battery lid 52 and a battery element 53 are provided. The electrode terminal 55 is connected to the electrode terminal 55 and then sealed with the battery lid 52, and is produced by injecting the electrolyte from the electrolyte inlet 56 and sealing with the sealing member 57. .

  Further, a specific embodiment of the present invention will be described with reference to FIGS. However, the present invention is not limited to these examples.

<Example 1-1 to Example 1-24, Comparative Example 1-1 to Comparative Example 1-7>
First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a ratio of Li ₂ CO ₃ : CoCO ₃ = 0.5: 1 (molar ratio), and 5 ° C. at 900 ° C. in the air. After firing for a time, lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode material was obtained.

  Next, 91 parts by mass of this lithium-cobalt composite oxide, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed to prepare a positive electrode mixture. . Subsequently, this positive electrode mixture is dispersed in N-methyl-2-pyrrolidone (NMP) as a solvent to form a positive electrode mixture slurry, which is uniformly applied to both surfaces of a positive electrode current collector 33A made of a strip-shaped aluminum foil having a thickness of 12 μm. Then, it was dried and compression molded by a roll press machine to form the positive electrode active material layer 33B to produce the positive electrode 33. After that, the positive electrode lead 31 made of aluminum was attached to one end of the positive electrode current collector 33A.

  In Example 1-1 to Example 1-24 and Comparative Example 1-1 to Comparative Example 1-7, the negative electrode 34 was produced as described below.

  A negative electrode active material layer 34B was formed on a negative electrode current collector 34A made of a copper foil having a thickness of 15 μm by using silicon (Si) as a negative electrode active material and using an electron beam evaporation method. Thereby, the negative electrode 34 was obtained.

  Next, the produced positive electrode 33 and the negative electrode 34 were laminated | stacked through the separator 35 which consists of porous polyethylene films, and the flat electrode was wound, and the winding electrode body 30 was obtained. In Examples 1-22 and 1-23, separators 35 having a thickness of 16 μm and 2 μm of polyvinylidene fluoride (PVdF) applied on both sides thereof were used.

  Next, the obtained wound electrode body 30 is sandwiched between exterior members 40 made of a laminate film, and the outer peripheral edge except for one side is heat-sealed into a bag shape and stored inside the exterior member 40. The electrolyte solution to be described was injected into the exterior member 40. Next, the opening of the exterior member 40 was heat-sealed and sealed in a vacuum atmosphere. As described above, secondary batteries of Example 1-1 to Example 1-24 and Comparative Example 1-1 to Comparative Example 1-7 were produced. The laminate film was made of nylon-aluminum-unstretched polypropylene from the outside, and the thicknesses thereof were 30 μm, 40 μm, and 30 μm, respectively, and the total was 100 μm.

In Example 1-1, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 20:70:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-2, as an electrolytic solution, propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (PC:: DEC trans-DFEC ) 20:70:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-3, as an electrolytic solution, butylene carbonate (BC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt was used in a solvent mixed with a composition of volume ratio (BC: DEC: trans-DFEC) 20:70:10.

In Example 1-4, as an electrolytic solution, γ-butyrolactone (GBL), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used. A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed at a volume ratio (GBL: DEC: trans-DFEC) of 20:70:10 was used.

In Example 1-5, as an electrolytic solution, γ-valerolactone (GVL), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) Was dissolved in LiPF ₆ as an electrolyte salt in a volume ratio (GVL: DEC: trans-DFEC) 20:70:10 in an amount of 1.0 mol / kg as an electrolyte salt.

In Example 1-6, as an electrolytic solution, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used. A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed at a volume ratio (EC: EMC: trans-DFEC) of 20:70:10 was used.

In Example 1-7, as an electrolytic solution, ethylene carbonate (EC), dimethyl carbonate (DMC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DMC trans-DFEC ) 20:70:10, as an electrolyte salt, it was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-8, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved to 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20: 79.95: 0.05 was used. It was.

In Example 1-9, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio (EC: DEC: trans-DFEC ) 20: 75: mixed solvent of a composition of 5, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-10, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 20:60:20, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-11, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 5:85:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-12, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 40:50:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-13, as an electrolytic solution, propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (PC:: DEC trans-DFEC ) 5:85:10, as an electrolyte salt, it was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-14, as an electrolytic solution, propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (PC:: DEC trans-DFEC ) 40:50:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-15, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of vinylene carbonate (VC) to a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 20:70:10, LiPF ₆ was added at 1.0 mol / kg as an electrolyte salt. What was dissolved was used.

In Example 1-16, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of vinyl ethylene carbonate (VEC) to a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, 1.0 mol / kg of LiPF ₆ is used as an electrolyte salt. What was melt | dissolved so that it might become was used.

In Example 1-17, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of SCAH (succinic anhydride) to a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 20:70:10, LiPF ₆ was added at 1.0 mol / kg as an electrolyte salt. What was melt | dissolved so that it might become was used.

In Example 1-18, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), In a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, as an electrolyte salt, LiPF ₆ was dissolved at 1.0 mol / kg and LiBF ₄ was dissolved at 0.1 mol / kg. What was made to use was used.

In Example 1-19, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), In a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, as an electrolyte salt, LiPF ₆ was dissolved at 0.9 mol / kg and chemical 9 was dissolved at 0.1 mol / kg. What was made to use was used.

In Example 1-20, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), In a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, LiPF ₆ is dissolved as an electrolyte salt to 0.9 mol / kg and chemical 14 is 0.1 mol / kg. What was made to use was used.

In Example 1-21, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), In a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, LiPF ₆ was dissolved as an electrolyte salt to 0.9 mol / kg and chemical 19 to 0.1 mol / kg. What was let was used.

In Example 1-22, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 20:70:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-23, as an electrolytic solution, propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (PC:: DEC trans-DFEC ) 20:70:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 1-24, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a cis isomer of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition of volume ratio (EC: DEC: cis-DFEC) 20:70:10 was used.

In Comparative Example 1-1, as an electrolyte, LiPF was used as an electrolyte salt in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio (EC: DEC) of 30:70. What dissolved ₆ so that it might become 1.0 mol / kg was used.

In Comparative Example 1-2, as the electrolytic solution, vinylene carbonate (VC) was added to a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio (EC: DEC) of 30:70. After adding 1% by weight, an electrolyte salt in which LiPF ₆ was dissolved at 1.0 mol / kg was used.

In Comparative Example 1-3, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used as an electrolytic solution. A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed at a ratio (EC: DEC: trans-DFEC) of 25: 74.99: 0.01 was used. .

In Comparative Example 1-4, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition having a ratio (EC: DEC: trans-DFEC) of 25:50:25 was used.

In Comparative Example 1-5, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed at a ratio (EC: DEC: trans-DFEC) of 0:90:10 was used.

In Comparative Example 1-6, ethylene electrolyte (EC), diethyl carbonate (DEC), and a trans isomer of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used as an electrolyte solution. A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition having a ratio (EC: DEC: trans-DFEC) of 50:40:10 was used.

In Comparative Example 1-7, as an electrolyte, LiPF ₆ was used as an electrolyte salt in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio (EC: DEC) of 30:70. Was dissolved to 0.9 mol / kg and chemical 9 was dissolved to 0.1 mol / kg.

  Next, charge / discharge tests were performed on the fabricated secondary batteries of Example 1-1 to Example 1-24 and Comparative Example 1-1 to Comparative Example 1-7, and room temperature cycle characteristics and low temperature discharge characteristics were examined. .

  The room temperature cycle characteristics are as follows: after charging and discharging at 23 ° C. for 2 cycles, charging and discharging at 23 ° C. for 100 cycles, the ratio to the discharge capacity at the second cycle at 23 ° C., that is, “discharge at the 100th cycle at 23 ° C. Capacity ”/“ Discharge capacity at the second cycle at 23 ° C. ”) × 100. The obtained results are shown in Table 1.

  The low-temperature discharge characteristics are as follows. First, charge / discharge is performed at 23 ° C. for 2 cycles, the discharge capacity at the second cycle (discharge capacity at 23 ° C.) is obtained, and then charged at 23 ° C. in a constant temperature bath at −20 ° C. Then, discharge was performed to determine a discharge capacity (discharge capacity at −20 ° C.) and (“discharge capacity at −20 ° C.” / “Discharge capacity at 23 ° C.”) × 100. The obtained results are shown in Table 1.

  The charging and discharging are performed under the same conditions. Charging is performed by constant current constant voltage charging at 0.2 C up to an upper limit voltage of 4.2 V, and discharging is performed by constant current discharging at 0.2 C at a final voltage of 2.5 V. Went up.

  As shown in Table 1, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), γ-butyrolactone (GBL) or γ-valerolactone (GVL), diethyl carbonate (DEC), According to Examples 1-1 to 1-5 using an electrolyte containing three components of 5-difluoro-1,3-dioxolan-2-one (DFEC) and a trans isomer as a solvent, ethylene carbonate (EC ) And diethyl carbonate (DEC) were improved in room temperature cycle characteristics and low temperature discharge characteristics as compared with Comparative Example 1-1 using an electrolytic solution containing two components as solvents.

  In addition, three components of ethylene carbonate (EC), ethyl methyl carbonate (EMC) or dimethyl carbonate (DMC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) are used as a solvent. According to Examples 1-6 to 1-7 using an electrolytic solution containing as Comparative Example 1 using an electrolytic solution containing two components of ethylene carbonate (EC) and diethyl carbonate (DEC) as a solvent Compared with 1, the normal temperature cycle characteristics were improved while maintaining the low temperature discharge characteristics substantially.

  Furthermore, according to Example 1-1, Example 1-8 to Example 1-12, Comparative Example 1-3, and Comparative Example 1-6, ethylene carbonate (EC) is 40 volume% with respect to the whole solvent. When it exceeded, the low temperature discharge characteristic fell. Furthermore, when ethylene carbonate (EC) was less than 5% by volume with respect to the entire solvent, the low-temperature discharge characteristics deteriorated. Furthermore, when the trans isomer of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) exceeds 20% by volume with respect to the whole solvent, the low-temperature discharge characteristics deteriorated. Furthermore, when the trans isomer of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) was less than 0.05% by volume with respect to the whole solvent, the room temperature cycle characteristics were deteriorated. Furthermore, according to Example 1-13 to Example 1-14, the propylene carbonate (PC) was 5 volume% or more and 40 volume% or less with respect to the whole solvent, and excellent room temperature cycle characteristics and cycle characteristics were obtained. .

Furthermore, in Example 1-1, Example 1-8 to Example 1-12, Comparative Example 1-3 to Comparative Example 1-6, instead of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate Similar results tend to be obtained using (BC), γ-butyrolactone (GBL) or γ-valerolactone (GVL). Further, in Example 1-1, Example 1-8 to Example 1-12, Comparative Example 1-3 to Comparative Example 1-6, instead of ethylene carbonate (EC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), γ-butyrolactone (GBL), γ-valerolactone (GVL)
Even when any two or more of these are mixed and used, the same result tends to be obtained.

  Furthermore, in Example 1-1, Example 1-8 to Example 1-12, and Comparative Example 1-3 to Comparative Example 1-6, instead of diethyl carbonate (DEC), ethyl methyl carbonate (EMC) or dimethyl Even when carbonate (DMC) is used, similar results tend to be obtained. Further, in Example 1-1, Example 1-8 to Example 1-12, and Comparative Example 1-3 to Comparative Example 1-6, instead of diethyl carbonate (DEC), diethyl carbonate (DEC), ethyl methyl Even if any two or more of carbonate (EMC) and dimethyl carbonate (DMC) are mixed and used, the same result tends to be obtained.

  That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, the solvent is at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone. A first solvent composed of a seed, a second solvent composed of at least one selected from diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate, and 4,5-difluoro-1,3-dioxolan-2-one The volume of the first solvent is 5% by volume or more and 40% by volume or less, and the volume of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) is 0.05% with respect to the whole solvent. Excellent room temperature cycle by using electrolyte containing one selected from volume% to 20 volume% Characteristics and low-temperature discharge characteristics were obtained.

  Furthermore, according to Example 1-15 to Example 1-16 and Comparative Example 1-2, the room temperature cycle characteristics were further improved by further adding vinylene carbonate (VC) and vinyl ethylene carbonate (VEC). That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, more excellent cycle characteristics can be obtained by adding a cyclic carbonate having an unsaturated bond to the electrolytic solution having the solvent composition described above. I found out that

  Furthermore, according to Example 1-17, the room temperature cycle characteristics were further improved by further adding succinic anhydride (SCAH). That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, more excellent cycle characteristics can be obtained by further adding an acid anhydride to the electrolytic solution having the above solvent composition. all right.

Furthermore, according to Example 1-18, the addition of LiBF ₄ improved the low-temperature discharge characteristics without deteriorating the normal temperature cycle characteristics. That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, by adding LiBF ₄ to the electrolytic solution having the above-described solvent composition, the room temperature cycle characteristics can be further reduced. It was found that excellent low-temperature discharge characteristics can be obtained.

  Furthermore, according to Example 1-19 to Example 1-20 and Comparative Example 1-7, the ambient temperature cycle characteristics were further improved by further including the light metal salt shown in Chemical formula 9 or the light metal salt shown in Chemical formula 14. . That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, more excellent cycle characteristics can be obtained by further including the light metal salt represented by Chemical Formula 1 in the electrolytic solution having the solvent composition described above. I found out that

  Further, according to Example 1-21, the room temperature cycle characteristics and the low temperature discharge characteristics were further improved by further including the light metal salt shown in Chemical formula 19. That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, more excellent cycle characteristics can be obtained by further including a light metal salt represented by Chemical Formula 17 in the electrolytic solution having the solvent composition described above. It was also found that low temperature discharge characteristics can be obtained.

  Furthermore, according to Examples 1-22 to 1-23, by using a separator having a structure in which polyvinylidene fluoride (PVdF) is applied to both sides of a porous polyethylene film, the room temperature cycle characteristics are further increased. And the low temperature discharge characteristics improved. That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, the electrolytic solution having the above-described solvent composition is used, and further, the separator is polyvinylidene fluoride (PVdF) on both surfaces of the porous film. It was found that more excellent cycle characteristics and low-temperature discharge characteristics can be obtained by using those having a structure coated with.

  Furthermore, according to Example 1-1 and Example 1-24, Example 1-1 using an electrolytic solution containing a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) The improved low-temperature discharge characteristics. That is, it was found that a trans isomer is preferable as 4,5-difluoro-1,3-dioxolan-2-one (DFEC) from the viewpoint of obtaining superior low-temperature discharge characteristics.

<Example 2-1 to Example 2-18, Comparative Example 2-1 to Comparative Example 2-7>
In Example 2-1 to Example 2-18 and Comparative Example 2-1 to Comparative Example 2-7, the negative electrode 34 was produced as described below. Moreover, the electrolyte solution demonstrated below was used. In Example 2-17 and Example 2-18, the separator 35 having a thickness of 16 μm and polyvinylidene fluoride (PVdF) applied to each side by 2 μm was used.

  90 parts by weight of silicon powder with an average particle diameter of 2 μm and 10 parts by weight of polyvinylidene fluoride (PVdF) powder are mixed, and N-methyl-2-pyrrolidone (NMP) outside the amount is added and kneaded to prepare a negative electrode slurry. Was made. This negative electrode slurry was applied to both surfaces of an electrolytic copper foil having a thickness of 20 μm, dried, and then pressed with a roll press so that the negative electrode active material layer 34B had a thickness of 15 μm (one surface). The obtained electrode was heat-treated at 350 ° C. for 3 hours, cut to a predetermined width and length after cooling, and welded with a nickel lead to form a negative electrode 34.

In Example 2-1, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 20:70:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 2-2, as an electrolytic solution, propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (PC:: DEC trans-DFEC ) 20:70:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 2-3, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved to 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20: 79.95: 0.05 was used. It was.

In Example 2-4, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio (EC: DEC: trans-DFEC ) 20: 75: mixed solvent of a composition of 5, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 2-5, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 20:60:20, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 2-6, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 5:85:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 2-7, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 40:50:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 2-8, as an electrolytic solution, propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (PC:: DEC trans-DFEC ) 5:85:10, as an electrolyte salt, it was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 2-9, as an electrolytic solution, propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (PC:: DEC trans-DFEC ) 40:50:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 2-10, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of vinylene carbonate (VC) to a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 20:70:10, LiPF ₆ was added at 1.0 mol / kg as an electrolyte salt. What was dissolved was used.

In Example 2-11, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of vinyl ethylene carbonate (VEC) to a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, 1.0 mol / kg of LiPF ₆ is used as an electrolyte salt. What was melt | dissolved so that it might become was used.

In Example 2-12, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of SCAH to a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, LiPF ₆ is dissolved as an electrolyte salt to 1.0 mol / kg. What was let was used.

In Example 2-13, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used. In a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, as an electrolyte salt, LiPF ₆ was dissolved at 1.0 mol / kg and LiBF ₄ was dissolved at 0.1 mol / kg. What was made to use was used.

In Example 2-14, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), In a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, as an electrolyte salt, LiPF ₆ was dissolved at 0.9 mol / kg and chemical 9 was dissolved at 0.1 mol / kg. What was made to use was used.

In Example 2-15, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), In a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, LiPF ₆ is dissolved as an electrolyte salt to 0.9 mol / kg and chemical 14 is 0.1 mol / kg. What was let was used.

In Example 2-16, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), In a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20:70:10, LiPF ₆ was dissolved as an electrolyte salt to 0.9 mol / kg and chemical 19 to 0.1 mol / kg. What was made to use was used.

In Example 2-17, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 20:70:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 2-18, as an electrolytic solution, propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 20:70:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Comparative Example 2-1, as an electrolyte, LiPF was used as an electrolyte salt in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio (EC: DEC) of 30:70. What dissolved ₆ so that it might become 1.0 mol / kg was used.

In Comparative Example 2-2, as the electrolyte, vinylene carbonate (VC) was added to a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio (EC: DEC) of 30:70. After adding 1% by weight, an electrolyte salt in which LiPF ₆ was dissolved at 1.0 mol / kg was used.

In Comparative Example 2-3, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were added in volume. A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed at a ratio (EC: DEC: trans-DFEC) of 25: 74.99: 0.01 was used. .

In Comparative Example 2-4, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were added in volume. A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition having a ratio (EC: DEC: trans-DFEC) of 25:50:25 was used.

In Comparative Example 2-5, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used as an electrolytic solution in a volume. A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed at a ratio (EC: DEC: trans-DFEC) of 0:90:10 was used.

In Comparative Example 2-6, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used as an electrolytic solution. A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition having a ratio (EC: DEC: trans-DFEC) of 50:40:10 was used.

In Comparative Example 2-7, as an electrolyte, LiPF ₆ was used as an electrolyte salt in a solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at a composition of volume ratio (EC: DEC) 30:70. Was dissolved to 0.9 mol / kg and chemical 9 was dissolved to 0.1 mol / kg.

  For the fabricated secondary batteries of Example 2-1 to Example 2-18 and Comparative Example 2-1 to Comparative Example 2-7, Example 1-1 to Example 1-24 and Comparative Example 1-1 to Comparative Example 1-1 were compared. A charge / discharge test was conducted in the same manner as in Example 1-7, and the room temperature cycle characteristics and the low temperature discharge characteristics were examined. The obtained results are shown in Table 2.

  As shown in Table 2, ethylene carbonate (EC) or propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) According to Example 2-1 to Example 2-2 using an electrolytic solution containing three components as a solvent, an electrolytic solution containing two components of ethylene carbonate (EC) and diethyl carbonate (DEC) as a solvent was used. Room temperature cycle characteristics and low temperature discharge characteristics were improved as compared with Comparative Example 2-1.

  Further, according to Example 2-1, Example 2-3 to Example 2-7, Comparative Example 2-3 to Comparative Example 2-6, when ethylene carbonate (EC) exceeds 40% by volume, low temperature discharge characteristics Decreased. Furthermore, when ethylene carbonate (EC) became less than 5 volume%, the low-temperature discharge characteristic fell. Furthermore, when the trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) exceeds 20% by volume, the low-temperature discharge characteristics deteriorated. Furthermore, when the trans isomer of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) was less than 0.05% by volume, the room temperature cycle characteristics deteriorated. Furthermore, according to Example 2-8 to Example 2-9, propylene carbonate (PC) was 5% by volume or more and 40% by volume or less, and excellent room temperature cycle characteristics and cycle characteristics were obtained.

  Furthermore, in Example 2-1, Example 2-3 to Example 2-7, Comparative Example 2-3 to Comparative Example 2-6, instead of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate Similar results tend to be obtained using (BC), γ-butyrolactone (GBL) or γ-valerolactone (GVL). Further, in Example 2-1, Example 2-3 to Example 2-7, Comparative Example 2-3 to Comparative Example 2-6, instead of ethylene carbonate (EC), ethylene carbonate (EC), propylene carbonate The same result tends to be obtained even when two or more of (PC), butylene carbonate (BC), γ-butyrolactone (GBL), and γ-valerolactone (GVL) are used in combination.

  Further, in Example 2-1, Example 2-3 to Example 2-7, Comparative Example 2-3 to Comparative Example 2-6, instead of diethyl carbonate (DEC), ethyl methyl carbonate (EMC) or dimethyl Even when carbonate (DMC) is used, similar results tend to be obtained. Further, in Example 2-1, Example 2-3 to Example 2-7, Comparative Example 2-3 to Comparative Example 2-6, instead of diethyl carbonate (DEC), diethyl carbonate (DEC), ethyl methyl Even if any two or more of carbonate (EMC) and dimethyl carbonate (DMC) are mixed and used, the same result tends to be obtained.

  That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, the solvent is at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone. A first solvent composed of a seed, a second solvent composed of at least one selected from diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate, and 4,5-difluoro-1,3-dioxolan-2-one The volume of the first solvent is 5% by volume or more and 40% by volume or less, and the volume of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) is 0.05% with respect to the whole solvent. Excellent room temperature cycle by using electrolyte containing one selected from volume% to 20 volume% Characteristics and low-temperature discharge characteristics were obtained.

  Furthermore, according to Example 2-10 to Example 2-11 and Comparative Example 2-2, the room temperature cycle characteristics were further improved by further adding vinylene carbonate (VC) and vinyl ethylene carbonate (VEC). That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, more excellent cycle characteristics can be obtained by adding a cyclic carbonate having an unsaturated bond to the electrolytic solution having the solvent composition described above. I found out that

  Furthermore, according to Example 2-12, the room temperature cycle characteristics were further improved by further adding SCAH. That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, more excellent cycle characteristics can be obtained by further adding an acid anhydride to the electrolytic solution having the above solvent composition. all right.

Furthermore, according to Example 2-13, the addition of LiBF ₄ improved the low temperature discharge characteristics without deteriorating the normal temperature cycle characteristics. That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, by adding LiBF ₄ to the electrolytic solution having the above-described solvent composition, the room temperature cycle characteristics can be further reduced. It was found that excellent low-temperature discharge characteristics can be obtained.

  Furthermore, according to Example 2-14 to Example 2-15 and Comparative Example 2-7, the room temperature cycle characteristics were further improved by further including the light metal salt shown in Chemical formula 9 or the light metal salt shown in Chemical formula 14. . That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, more excellent cycle characteristics can be obtained by further including the light metal salt represented by Chemical Formula 1 in the electrolytic solution having the solvent composition described above. I found out that

  Furthermore, according to Example 2-16, by further including the light metal salt shown in Chemical formula 19, the room temperature cycle characteristics and the low temperature discharge characteristics were further improved. That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, more excellent cycle characteristics can be obtained by further including a light metal salt represented by Chemical Formula 17 in the electrolytic solution having the solvent composition described above. It was also found that low temperature discharge characteristics can be obtained.

  Furthermore, according to Example 2-17 to Example 2-18, by using a separator having a structure in which polyvinylidene fluoride (PVdF) is applied to both surfaces of a porous polyethylene film, further room temperature cycle characteristics And the low temperature discharge characteristics improved. That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, the electrolytic solution having the above-described solvent composition is used, and further, the separator is polyvinylidene fluoride (PVdF) on both surfaces of the porous film. It was found that more excellent cycle characteristics and low-temperature discharge characteristics can be obtained by using those having a structure coated with.

<Example 3-1 to Example 3-18, Comparative Example 3-1 to Comparative Example 3-7>
In Example 3-1 to Example 3-18 and Comparative Example 3-1 to Comparative Example 3-7, the negative electrode 34 was fabricated as described below. Moreover, as shown in Table 3, the electrolyte solution similar to Example 2-1 to Example 2-18 and Comparative Example 2-1 to Comparative Example 2-7 was used. In Examples 3-17 and 3-18, as the separator 35, a porous polyethylene film having a thickness of 16 μm and polyvinylidene fluoride (PVdF) applied to each side by 2 μm was used.

  A negative electrode active material layer 34B was formed by attaching lithium metal having a thickness of 30 μm to a negative electrode current collector 34A made of a strip-shaped copper foil having a thickness of 8 μm.

  Regarding the fabricated secondary batteries of Example 3-1 to Example 3-18 and Comparative Example 3-1 to Comparative Example 3-7, Example 1-1 to Example 1-24 and Comparative Example 1-1 to Comparative Example 1-1 were compared. A charge / discharge test was conducted in the same manner as in Example 1-7, and the room temperature cycle characteristics and the low temperature discharge characteristics were examined. The obtained results are shown in Table 3. In Examples 3-17 and 3-18, the separator 35 having a thickness of 16 μm and 2 μm of polyvinylidene fluoride (PVdF) applied to both sides thereof was used.

  As shown in Table 3, ethylene carbonate (EC) or propylene carbonate (PC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) According to Example 3-1 to Example 3-2 using an electrolyte containing three components as a solvent, an electrolyte containing two components of ethylene carbonate (EC) and diethyl carbonate (DEC) was used. Room temperature cycle characteristics and low temperature discharge characteristics were improved as compared with Comparative Example 3-1.

  Further, according to Example 3-1, Example 3-3 to Example 3-7, Comparative Example 3-3 to Comparative Example 3-6, when ethylene carbonate (EC) exceeds 40% by volume, low temperature discharge characteristics Decreased. Furthermore, when ethylene carbonate (EC) became less than 5 volume%, the low-temperature discharge characteristic fell. Furthermore, when the trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) exceeds 20% by volume, the low-temperature discharge characteristics deteriorated. Furthermore, when the trans isomer of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) was less than 0.05% by volume, the room temperature cycle characteristics deteriorated. Furthermore, according to Example 3-8 to Example 3-9, propylene carbonate (PC) was 5% by volume or more and 40% by volume or less, and excellent room temperature cycle characteristics and cycle characteristics were obtained.

  Furthermore, in Example 3-1, Example 3-3 to Example 3-7, Comparative Example 3-3 to Comparative Example 3-6, instead of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate Similar results tend to be obtained using (BC), γ-butyrolactone (GBL) or γ-valerolactone (GVL). Further, in Example 3-1, Example 3-3 to Example 3-7, Comparative Example 3-3 to Comparative Example 3-6, instead of ethylene carbonate (EC), ethylene carbonate (EC), propylene carbonate The same result tends to be obtained even when two or more of (PC), butylene carbonate (BC), γ-butyrolactone (GBL), and γ-valerolactone (GVL) are used in combination.

  Further, in Example 3-1, Example 3-3 to Example 3-7, Comparative Example 3-3 to Comparative Example 3-6, instead of diethyl carbonate (DEC), ethyl methyl carbonate (EMC) or dimethyl Even when carbonate (DMC) is used, similar results tend to be obtained. Furthermore, in Example 3-1, Example 3-3 to Example 3-7, Comparative Example 3-3 to Comparative Example 3-6, instead of diethyl carbonate (DEC), diethyl carbonate (DEC), ethyl methyl Even if any two or more of carbonate (EMC) and dimethyl carbonate (DMC) are mixed and used, the same result tends to be obtained.

  That is, in the case of using lithium metal as the negative electrode active material, the solvent is a first solvent consisting of at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone, A second solvent comprising at least one selected from diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate, and 4,5-difluoro-1,3-dioxolan-2-one, and The volume of the first solvent is selected from 5% by volume to 40% by volume, and the volume of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) is selected from 0.05% by volume to 20% by volume. By using an electrolyte containing the above, excellent room temperature cycle characteristics and low temperature discharge characteristics can be obtained. I found out.

  Furthermore, according to Example 3-10 to Example 3-11 and Comparative Example 3-2, the room temperature cycle characteristics were further improved by further adding vinylene carbonate (VC) and vinyl ethylene carbonate (VEC). That is, when lithium metal was used as the negative electrode active material, it was found that better cycle characteristics can be obtained by adding a cyclic carbonate having an unsaturated bond to the electrolytic solution having the solvent composition described above.

  Furthermore, according to Example 3-12, the room temperature cycle characteristics were further improved by further adding succinic anhydride (SCAH). That is, when lithium metal was used as the negative electrode active material, it was found that more excellent cycle characteristics can be obtained by adding an acid anhydride to the electrolytic solution having the above solvent composition.

Furthermore, according to Example 3-13, the addition of LiBF ₄ improved the low temperature discharge characteristics without deteriorating the normal temperature cycle characteristics. That is, when lithium metal is used as the negative electrode active material, by adding LiBF ₄ to the electrolytic solution having the above solvent composition, more excellent low-temperature discharge characteristics can be obtained without deteriorating the normal temperature cycle characteristics. I understood.

  Furthermore, according to Example 3-14 to Example 3-15 and Comparative Example 3-7, the room temperature cycle characteristics were further improved by further including the light metal salt shown in Chemical Formula 9 or the light metal salt shown in Chemical Formula 14. . That is, when lithium metal was used as the negative electrode active material, it was found that better cycle characteristics can be obtained by further including the light metal salt represented by Chemical Formula 1 in the electrolytic solution having the above solvent composition.

  Furthermore, according to Example 3-16, by further including the light metal salt shown in Chemical formula 19, the room temperature cycle characteristics and the low temperature discharge characteristics were further improved. That is, in the case where lithium metal is used as the negative electrode active material, it is possible to obtain more excellent cycle characteristics and low temperature discharge characteristics by further including the light metal salt represented by Chemical Formula 17 in the electrolytic solution having the above-described solvent composition. all right.

  Furthermore, according to Example 3-17 to Example 3-18, by using a separator having a structure in which polyvinylidene fluoride (PVdF) is applied to both sides of a porous polyethylene film, further room temperature cycle characteristics And the low temperature discharge characteristics improved. That is, when lithium metal is used as the negative electrode active material, an electrolyte having the above-described solvent composition is used, and a separator having a structure in which polyvinylidene fluoride (PVdF) is applied to both surfaces of the porous film is used. Thus, it was found that better cycle characteristics and low temperature discharge characteristics can be obtained.

<Example 4-1 and Comparative Example 4-1>
In Example 4-1 and Comparative Example 4-1, the negative electrode 34 was produced as described below. Moreover, the electrolyte solution demonstrated below was used.

  Artificial graphite powder was prepared as a negative electrode material, and 90 parts by mass of the artificial graphite powder and 10 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed 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 both surfaces of the negative electrode current collector 34A made of a strip-shaped copper foil having a thickness of 15 μm. The negative electrode 34 was produced by compression molding with a roll press to form a negative electrode active material layer 34B.

In Example 4-1, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio (EC: DEC: trans-DFEC ) 25: 70: mixed solvent of a composition of 5, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Comparative Example 4-1, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved in an amount of 1.0 mol / kg as an electrolyte salt in a solvent mixed at a volume ratio (EC: DEC) of 30:70 was used.

  For the fabricated secondary batteries of Example 4-1 and Comparative Example 4-1, a charge / discharge test was performed in the same manner as in Example 1-1 to Example 23 and Comparative Example 1-1 to Comparative Example 1-7. The room temperature cycle characteristics and the low temperature discharge characteristics were investigated. Table 4 shows the measurement results.

  As shown in Table 4, in Example 4-1, superior room temperature cycle characteristics and low temperature discharge characteristics are obtained as compared with Comparative Example 4-1, which uses an electrolytic solution containing only ethylene carbonate (EC) and diethyl carbonate (DEC). I was able to. Further, even when a carbon material is used as the negative electrode active material, Examples 1-1 to 3-18 and Comparative Examples using a material containing silicon (Si) as a constituent element or lithium metal as the negative electrode active material The results similar to those obtained in 1-1 to Comparative Example 3-7 tend to be obtained.

  That is, in the case where a carbon material is used as the negative electrode active material, the solvent is a first solvent composed of at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone. A second solvent composed of at least one selected from diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate, and 4,5-difluoro-1,3-dioxolan-2-one, The volume of the first solvent is 5% by volume to 40% by volume, and the volume of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) is 0.05% by volume to 20% by volume. By using an electrolyte containing the selected one, excellent room temperature cycle characteristics and low temperature discharge characteristics can be obtained. I understand that

  Further, according to Tables 1 to 4, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, and when lithium metal is used as the negative electrode active material, By using an electrolytic solution containing a solvent, the room temperature cycle characteristics were significantly improved. That is, by using an electrolytic solution containing a solvent having the above-described solvent composition, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, and when lithium metal is used as the negative electrode active material In particular, it was found that the room temperature cycle characteristics can be remarkably improved.

  Furthermore, according to Tables 1 and 2, when a material containing silicon (Si) as a constituent element was used as the negative electrode active material, the room temperature cycle characteristics were further improved when the negative electrode active material layer was formed by vapor deposition. That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, it is preferable to form the negative electrode active material layer by a vapor deposition method from the viewpoint of obtaining better room temperature cycle characteristics. all right.

<Example 5-1 to Example 5-26, Comparative Example 5-1 to Comparative Example 5-5>
In Example 5-1 to Example 5-26, the negative electrode 34 was produced as described below. Moreover, the electrolyte solution demonstrated below was used.

  A negative electrode active material layer 34B was formed on a negative electrode current collector 34A made of a copper foil having a thickness of 15 μm by using silicon (Si) as a negative electrode active material and using an electron beam evaporation method. Thereby, the negative electrode 34 was obtained.

In Example 5-1, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved to 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 30: 69.95: 0.05 was used. .

In Example 5-2, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 30: 69: 1 was used.

In Example 5-3, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 30: 68: 2 was used.

In Example 5-4, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 30: 65: 5 was used.

In Example 5-5, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 30:60:10 was used.

In Example 5-6, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a cis isomer of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed at a volume ratio (EC: DEC: cis-DFEC) of 30:60:10 was used.

In Example 5-7, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 5: 90: 5 was used.

In Example 5-8, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 10: 85: 5 was used.

In Example 5-9, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 20: 75: 5 was used.

In Example 5-10, as an electrolytic solution, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used. A solution in which LiPF ₆ was dissolved at 1.0 mol / kg as an electrolyte salt in a solvent mixed at a volume ratio (EC: EMC: trans-DFEC) of 30: 65: 5 was used.

In Example 5-11, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 4,5-difluoro-1,3-dioxolan-2-one (DFEC) ) In a volume ratio (EC: DEC: EMC: trans-DFEC) of 30: 40: 25: 5 as an electrolyte salt, so that LiPF ₆ is 1.0 mol / kg. What was dissolved was used.

In Example 5-12, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and 4,5-difluoro-1,3-dioxolan-2-one (DFEC) LiPF ₆ was dissolved as an electrolyte salt in a solvent obtained by mixing the trans isomer of 1 with a composition having a volume ratio (EC: DEC: DMC: trans-DFEC) of 30: 40: 25: 5 to 1.0 mol / kg. What was let was used.

In Example 5-13, the electrolytes included ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and 4,5-difluoro-1,3-dioxolan-2-one (DFEC). LiPF ₆ was dissolved as an electrolyte salt in a solvent obtained by mixing the trans isomer of 1 with a composition having a volume ratio (EC: PC: DEC: trans-DFEC) of 10: 10: 75: 5 to 1.0 mol / kg. What was made to use was used.

In Example 5-14, as an electrolytic solution, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), 4,5-difluoro-1,3-dioxolan-2-one (DFEC) LiPF ₆ was dissolved as an electrolyte salt in a solvent obtained by mixing the trans isomer of 1 with a composition having a volume ratio (EC: PC: DEC: trans-DFEC) of 10: 20: 65: 5 to 1.0 mol / kg. What was made to use was used.

In Example 5-15, as an electrolytic solution, ethylene carbonate (EC), butylene carbonate (BC), diethyl carbonate (DEC), and 4,5-difluoro-1,3-dioxolan-2-one (DFEC) LiPF ₆ as an electrolyte salt was dissolved in a solvent in which the trans isomer was mixed with a composition having a volume ratio (EC: BC: DEC: trans-DFEC) of 10: 20: 65: 5 so as to be 1.0 mol / kg. What was made to use was used.

In Example 5-16, as an electrolytic solution, ethylene carbonate (EC), γ-butyrolactone (GBL), diethyl carbonate (DEC), and 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used. ) In a volume ratio (EC: GBL: DEC: trans-DFEC) 10: 20: 65: 5 as an electrolyte salt, so that LiPF ₆ is 1.0 mol / kg. What was dissolved was used.

In Example 5-17, as an electrolytic solution, ethylene carbonate (EC), γ-valerolactone (GVL), diethyl carbonate (DEC), 4,5-difluoro-1,3-dioxolan-2-one ( DFEC) trans isomer was mixed with a composition of volume ratio (EC: GVL: DEC: trans-DFEC) 10: 20: 65: 5 as an electrolyte salt so that LiPF ₆ would be 1.0 mol / kg. What was dissolved in was used.

In Example 5-18, as an electrolytic solution, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and 4,5-difluoro-1,3-dioxolan-2-one (DFEC) LiPF ₆ was dissolved as an electrolyte salt in a solvent in which the trans isomer was mixed in a volume ratio (EC: PC: DEC: trans-DFEC) with a composition of 10: 10: 70: 10 so as to be 1.0 mol / kg. What was made to use was used.

In Example 5-19, as an electrolytic solution, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and 4,5-difluoro-1,3-dioxolan-2-one (DFEC) LiPF ₆ was dissolved as an electrolyte salt in a solvent in which the trans isomer was mixed in a volume ratio (EC: PC: DEC: trans-DFEC) 10: 20: 60: 10 composition to an electrolyte salt of 1.0 mol / kg. What was made to use was used.

In Example 5-20, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of vinylene carbonate (VC) to a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 30: 65: 5, LiPF ₆ was added at 1.0 mol / kg as an electrolyte salt. What was dissolved was used.

In Example 5-21, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of propene sultone (PRS) to a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 30:60:10, LiPF ₆ was added at 1.0 mol / kg as an electrolyte salt. What was dissolved was used.

In Example 5-22, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of divinyl sulfone (DVS) to a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 30:60:10, LiPF ₆ was added at 1.0 mol / kg as an electrolyte salt. What was dissolved was used.

In Example 5-23, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of succinic anhydride (SCAH) to a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 30:60:10, LiPF ₆ was added at 1.0 mol / kg as an electrolyte salt. What was melt | dissolved so that it might become was used.

In Example 5-24, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), LiPF ₆ is dissolved at 1.0 mol / kg and LiBF ₄ is dissolved at 0.1 mol / kg as an electrolyte salt in a solvent mixed with a composition of volume ratio (EC: DEC: trans-DFEC) 30:60:10. Used.

In Example 5-25, as an electrolytic solution, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), 4,5-difluoro-1,3-dioxolan-2-one (DFEC) 1% by weight of propene sultone (PRS) to a solvent prepared by mixing the trans isomer with a composition of volume ratio (EC: PC: DEC: trans-DFEC) 10: 20: 60: 10, and then adding an electrolyte salt. As a solution, LiPF ₆ dissolved at 1.0 mol / kg was used.

In Example 5-26, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of propene sultone (PRS) to a solvent mixed at a composition of volume ratio (EC: DEC: trans-DFEC) 30: 65: 5, 1.0 mol / kg of LiPF ₆ is used as an electrolyte salt. the LiBF ₄ was used dissolved at a 0.1 mol / kg.

In Comparative Example 5-1, as an electrolyte, LiPF was used as an electrolyte salt in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio (EC: DEC) of 30:70. What dissolved ₆ so that it might become 1.0 mol / kg was used.

In Comparative Example 5-2, as the electrolytic solution, propene sultone (PRS) was added to a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio (EC: DEC) of 30:70. After adding 1% by weight of LiPF ₆ , LiPF ₆ dissolved at 1.0 mol / kg was used as the electrolyte salt.

In Comparative Example 5-3, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 30:55:15, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Comparative Example 5-4, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 40:50:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Comparative Example 5-5, as an electrolytic solution, ethylene carbonate (EC), dimethyl carbonate (DMC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio (EC: DMC: trans-DFEC ) 30: 65: mixed solvent of a composition of 5, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

  The fabricated secondary batteries of Example 5-1 to Example 5-26 and Comparative Example 5-1 to Comparative Example 5-5 are the same as in Example 1-1 to Example 1-24 and Comparative Example 1-7. Thus, a charge / discharge test was conducted to examine room temperature cycle characteristics.

  In addition, as described below, the high-temperature storage swelling characteristics were examined. At 23 ° C., charging and discharging were performed for 2 cycles. Subsequently, the battery was charged to 4.2 V at 23 ° C., and the thickness (initial thickness) of the battery was measured. Thereafter, a storage test was conducted in a high-temperature bath at 90 ° C., the thickness of the battery after 4 hours was determined, and the difference from the initial thickness was determined. In addition, charge performed 0.2 C constant current constant voltage charge to the upper limit voltage 4.2V, and discharge performed 0.2 C constant current discharge to final voltage 2.5V. The results obtained are shown in Table 5.

  As shown in Table 5, a first solvent made of ethylene carbonate (EC), a second solvent made of at least one of diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), and 4,5- According to Example 5-1 to Example 5-26 using an electrolyte containing three components of difluoro-1,3-dioxolan-2-one (DFEC) as a solvent, ethylene carbonate (EC) And the normal temperature cycle characteristic improved from the comparative example 5-1 using the electrolyte solution which contains two components, and diethyl carbonate (DEC), as a solvent.

  In addition, according to Example 5-1 to Example 5-5 and Comparative Example 5-3, when 4,5-difluoro-1,3-dioxolan-2-one exceeds 10% by volume, high-temperature storage swelling characteristics are exhibited. Remarkably worsened.

  Furthermore, according to Example 5-5, Example 5-7 to Example 5-9, and Comparative Example 5-4, when the amount of ethylene carbonate (EC) exceeds 30% by volume with respect to the entire solvent, The storage blistering property was deteriorated.

  Furthermore, according to Example 5-10, even when ethyl methyl carbonate (EMC) was used instead of diethyl carbonate (DEC) as the second solvent, excellent room temperature cycle characteristics and high temperature storage swelling characteristics could be obtained. . Further, according to Example 5-11, even when diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) are mixed and used as the second solvent, excellent room temperature cycle characteristics and high temperature storage blister characteristics can be obtained. did it.

  That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, a first solvent made of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) are used as the solvent. A second solvent consisting of at least one of the following, and 4,5-difluoro-1,3-dioxolan-2-one (DFEC), and the volume of the first solvent relative to the total solvent is An electrolytic solution containing 5% by volume to 30% by volume and a volume of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) selected from 0.05% by volume to 10% by volume By using it, it was found that excellent room temperature cycle characteristics and high temperature storage swell characteristics can be obtained.

  Furthermore, according to Example 5-6, even when a cis isomer of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) is used, excellent room temperature cycle characteristics and high temperature storage blister characteristics can be obtained. I was able to. Furthermore, instead of the trans isomer of Example 5-5 and 4,5-difluoro-1,3-dioxolan-2-one (DFEC), 4,5-difluoro-1,3-dioxolan-2-one (DFEC) According to the comparison with Example 5-6 which differs only in using the cis isomer of Example 5-5, the high temperature storage swell characteristic was improved in Example 5-5. That is, it was found that a trans isomer is preferable as 4,5-difluoro-1,3-dioxolan-2-one (DFEC) from the viewpoint of obtaining superior high-temperature storage swelling characteristics.

  Further, according to Examples 5-13 to 5-19, as the first solvent, in addition to ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), γ-butyrolactone (GBL), When a solvent containing at least one of γ-valerolactone (GVL) was used, it was possible to obtain more excellent high-temperature storage swelling characteristics.

  That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, propylene in addition to ethylene carbonate (EC) as the first solvent in addition to the electrolytic solution having the above solvent composition. By using an electrolytic solution having a solvent containing at least one of carbonate (PC), butylene carbonate (BC), γ-butyrolactone (GBL), and γ-valerolactone (GVL), more excellent high temperature storage swell characteristics I found out that

  Furthermore, according to Example 5-20, the room temperature cycle characteristics were further improved by further adding vinylene carbonate (VC). That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, more excellent cycle characteristics can be obtained by including a cyclic carbonate having an unsaturated bond in the electrolytic solution having the solvent composition described above. I found out that

  Furthermore, according to Example 5-21, the addition of propene sultone (PRS) further improved the high temperature storage blister characteristics. Furthermore, according to Example 5-22, the high temperature storage blistering property was further improved by further adding divinyl sulfone (DVS). That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, the electrolyte solution having the above-described solvent composition further includes a compound having a sulfone structure, so that more excellent high-temperature storage swell characteristics can be obtained. It turns out that it is obtained.

  Furthermore, according to Example 5-23, the high temperature storage blistering property was further improved by further adding succinic anhydride (SCAH). That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, further excellent high-temperature storage swell characteristics can be obtained by further containing an acid anhydride in the electrolytic solution having the above solvent composition. I understood it.

Furthermore, according to Example 5-24, the addition of LiBF ₄ greatly improved the high temperature storage swell characteristics. That is, in the case where a material containing silicon (Si) as a constituent element is used as the negative electrode active material, the electrolyte solution having the above solvent composition contains LiBF ₄ as a lithium salt, so that more excellent high-temperature storage swell characteristics can be obtained. It turns out that it is obtained.

  Furthermore, according to Example 5-25, the high temperature storage blistering property was improved by adding propylene carbonate (PC) as a first solvent and further adding propene sultone (PRS). That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, the electrolyte solution having the above-described solvent composition further includes a compound having a sulfone structure, so that more excellent high-temperature storage swell characteristics can be obtained. It turns out that it is obtained.

Furthermore, according to Example 5-26, the high temperature storage blistering property was remarkably improved by adding LiBF ₄ and further adding propene sultone (PRS). That is, when a material containing silicon (Si) as a constituent element is used as the negative electrode active material, the electrolytic solution having the above solvent composition contains LiBF ₄ as a lithium salt and further contains a compound having a sulfone structure. Thus, it was found that particularly excellent high-temperature storage blister characteristics can be obtained.

<Example 6-1 to Example 6-4, Comparative Example 6-1 to Comparative Example 6-3>
In Example 6-1 to Example 6-4, the negative electrode 34 was produced as described below. Moreover, the electrolyte solution demonstrated below was used.

  Artificial graphite powder was prepared as a negative electrode material, and 90 parts by mass of the artificial graphite powder and 10 parts by mass of polyvinylidene fluoride (PVdF) as a binder were mixed 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 both surfaces of the negative electrode current collector 34A made of a strip-shaped copper foil having a thickness of 15 μm. The negative electrode 34 was produced by compression molding with a roll press to form a negative electrode active material layer 34B.

In Example 6-1, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio (EC: DEC: trans-DFEC ) 30: 65: mixed solvent of a composition of 5, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Example 6-2, as an electrolytic solution, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), 4,5-difluoro-1,3-dioxolan-2-one (DFEC) ) In a volume ratio (EC: PC: DEC: trans-DFEC) 10: 10: 75: 5, and the electrolyte salt is LiPF ₆ at 1.0 mol / kg. What was dissolved in was used.

In Example 6-3, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of propene sultone (PRS) to a solvent mixed at a volume ratio (EC: DEC: trans-DFEC) of 30: 65: 5, LiPF ₆ was added at 1.0 mol / kg as an electrolyte salt. What was dissolved was used.

In Example 6-4, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), After adding 1% by weight of propene sultone (PRS) to a solvent mixed at a composition of volume ratio (EC: DEC: trans-DFEC) 30: 65: 5, 1.0 mol / kg of LiPF ₆ is used as an electrolyte salt. the LiBF ₄ was used dissolved at a 0.1 mol / kg.

In Comparative Example 6-1, as an electrolyte, LiPF was used as an electrolyte salt in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio (EC: DEC) of 30:70. What dissolved ₆ so that it might become 1.0 mol / kg was used.

In Comparative Example 6-2, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC), volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 30:55:15, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

In Comparative Example 6-3, as an electrolytic solution, ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used. volume ratio mixed solvent of a composition of (EC:: DEC trans-DFEC ) 40:50:10, as an electrolyte salt, was used by dissolving LiPF ₆ so that 1.0 mol / kg.

  Regarding the fabricated secondary batteries of Example 6-1 to Example 6-4 and Comparative Example 6-1 to Comparative Example 6-3, Examples 5-1 to 5-26 and Comparative Examples 5-1 to 5-1 were compared. In the same manner as in Example 5-5, the room temperature cycle characteristics and the high temperature storage swell characteristics were examined. The results obtained are shown in Table 6.

  As shown in Table 6, three components of ethylene carbonate (EC), diethyl carbonate (DEC), and a trans form of 4,5-difluoro-1,3-dioxolan-2-one (DFEC) were used as a solvent. According to Example 6-1 to Example 6-2 using an electrolytic solution containing Comparative Example 6-1 using an electrolytic solution containing two components of ethylene carbonate (EC) and diethyl carbonate (DEC) as a solvent More room temperature cycle characteristics were improved.

  Further, according to Example 6-1 to Example 6-2 and Comparative Example 6-2, when 4,5-difluoro-1,3-dioxolan-2-one (DFEC) exceeds 10% by volume, it is stored at high temperature. The blistering property was significantly deteriorated.

  Furthermore, according to Example 6-1 to Example 6-2, Comparative Example 6-1 and Comparative Example 6-3, when the amount of ethylene carbonate (EC) exceeds 30% by volume with respect to the whole solvent, the temperature is high. The storage blistering property was deteriorated.

  Furthermore, even if ethyl methyl carbonate (EMC) is used as the second solvent instead of diethyl carbonate (DEC), excellent room temperature cycle characteristics and high temperature storage blister characteristics tend to be obtained. Even when diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) are mixed and used as the second solvent, excellent room temperature cycle characteristics and high temperature storage swelling characteristics tend to be obtained.

  That is, when a carbon material is used as the negative electrode active material, the solvent is composed of at least one of a first solvent made of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). A second solvent and 4,5-difluoro-1,3-dioxolan-2-one (DFEC), wherein the volume of the first solvent is 5% by volume or more and 30% by volume or less based on the whole solvent. , 4,5-difluoro-1,3-dioxolan-2-one (DFEC) has an excellent room temperature cycle by using an electrolyte containing a volume selected from 0.05% by volume to 10% by volume It was found that characteristics and high temperature storage blister characteristics can be obtained.

  Furthermore, according to Example 6-3, the room temperature cycle characteristics were further improved by further adding propene sultone (PRS). That is, when a carbon material is used as the negative electrode active material, it was found that more excellent cycle characteristics can be obtained by further including a compound having a sulfone structure in the electrolytic solution having the above solvent composition.

Furthermore, according to Example 6-4, the high temperature storage blistering property was remarkably improved by adding LiBF ₄ and further adding propene sultone (PRS). That is, when a carbon material is used as the negative electrode active material, the electrolyte solution having the above-described solvent composition contains LiBF ₄ as the lithium salt and further contains propene sultone (PRS). It was found that characteristics can be obtained.

  In addition, even when a carbon material is used as the negative electrode active material, Examples 5-1 to 5-26 and Comparative Example 5-1 using a material containing silicon (Si) as a constituent element as the negative electrode active material. -A result similar to the result obtained in Comparative Example 5-5 tends to be obtained.

  Further, even when a material containing tin (Sn) as a constituent element is used as the negative electrode active material, Examples 5-1 to 5-26 using a material containing (Si) as a constituent element as the negative electrode active material The results similar to those obtained in Comparative Examples 5-1 to 5-5 tend to be obtained.

  Furthermore, in the above-described embodiment, the case where the electrolytic solution is used has been described. However, 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-described embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, a secondary battery having a wound structure has been specifically described. However, the present invention is a rectangular type, a sheet type or a card type, or a laminate in which a plurality of positive and negative electrodes are laminated. The present invention can be similarly applied to a secondary battery having a structure. Further, the present invention is not limited to the secondary battery but can be similarly applied to other batteries such as a primary battery.

  Moreover, in embodiment mentioned above, although the cylindrical battery, the battery which used the laminate film for the exterior material, and the battery using the metal exterior can were mentioned as an example, it was not limited to these. . For example, the present invention can be applied to non-aqueous electrolyte batteries having various shapes and sizes, such as a coin type, a button type, and a thin battery.

  Further, in the above-described embodiments and examples, the case where lithium (Li) is used as the electrode reactant has been described, but other group 1 elements in the long-period periodic table such as sodium (Na) or potassium (K) are used. Or when using a group 2 element in the long-period periodic table such as magnesium (Mg) or calcium (Ca), or other light metal such as aluminum (Al), or lithium (Li) or an alloy thereof, The present invention can be applied and the same effect can be obtained. At that time, as the negative electrode active material, the negative electrode material described in the embodiment can be used in the same manner.

It is sectional drawing showing the structure of the 1st example of the secondary battery using the electrolyte by one 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 disassembled perspective view showing the structure of the 2nd example of the secondary battery using the electrolyte by one Embodiment of this invention. It is sectional drawing along the II line | wire of the winding electrode body shown in FIG. It is sectional drawing showing the structure of the 3rd example of the secondary battery using the electrolyte by one Embodiment 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, 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 37 ... protective tape DESCRIPTION OF SYMBOLS 40 ... Exterior member 41 ... Adhesion film 51 ... Exterior can 52 ... Battery cover 53 ... Winding electrode body 54 ... Electrode pin 55 ... Battery terminal 57 ... Sealing Element

Claims (34)

A first solvent comprising at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone;
A second solvent comprising at least one selected from diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate;
4,5-difluoro-1,3-dioxolan-2-one;
Including
The volume of the first solvent is 5% by volume or more and 40% by volume or less with respect to the entire solvent,
The electrolyte characterized in that the volume of the 4,5-difluoro-1,3-dioxolan-2-one is 0.05 vol% or more and 20 vol% or less. The electrolyte according to claim 1, wherein the 4,5-difluoro-1,3-dioxolan-2-one is a trans isomer. The electrolyte according to claim 1, further comprising a cyclic carbonate compound having an unsaturated bond. The electrolyte according to claim 1, further comprising an acid anhydride. 2. The electrolyte according to claim 1, further comprising at least one light metal salt represented by Chemical Formula 1.

(Wherein R11 represents a —C (═O) —R21—C (═O) — group (R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group), —C (═O ) -C (R23) (R24)-group (R23, R24 represents an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group), or -C (= O) -C (= O) -Represents a group, R12 represents a halogen group, an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, X11 and X12 each represent oxygen (O) or sulfur (S), and M11 represents a transition metal element Or represents a group 3B element, a group 4B element or a group 5B element in the short period type periodic table, and M21 represents a group 1A element, group 2A element or aluminum in the short period type periodic table. Represents (Al), a is an integer from 1 to 4, b is an integer of 0~8, c, d, e and f is an integer of 1 to 3, respectively.) 2. The electrolyte according to claim 1, further comprising at least one light metal salt represented by Chemical Formula 2.

(Wherein R11 represents a —C (═O) —R21—C (═O) — group (R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group), —C (═O ) —C (═O) — group or —C (═O) —C— (R22) ₂ (R22 represents an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group) — group. , R13 represents halogen, M12 represents phosphorus (P) or boron (B), M21 represents a group 1A element or group 2A element or aluminum (Al) in the short-period periodic table, and a1 is 1 to 4 An integer, b1 is 0, 2 or 4, and c, d, e and f are each an integer of 1 to 3.) Further, difluoro [oxolato-O, O ′] lithium borate represented by Chemical Formula 3, difluorobis [oxolato-O, O ′] lithium phosphate represented by Chemical Formula 4, difluoro [3, 3,3-trifluoro-2-oxide-2-trifluoromethylpropionate (2-)-O, O ′] lithium borate, bis [3,3,3-trifluoro-2 represented by Formula 6 -Oxide-2-trifluoromethylpropionate (2-)-O, O '] lithium borate, tetrafluoro [oxolato-O, O'] lithium phosphate represented by Chemical formula 7, represented by Chemical formula 8 2. The electrolyte according to claim 1, comprising at least one light metal salt selected from the group consisting of lithium bis [oxolato-O, O ′] lithium borate.

Further, at least one selected from the group consisting of LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , a lithium salt represented by Chemical Formula 9, a lithium salt represented by Chemical Formula 10 and a lithium salt represented by Chemical Formula 11 The electrolyte according to claim 1, comprising:

(In the formula, m and n are integers of 1 or more.)

(In the formula, R represents a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms.)

(In the formula, p, q and r are integers of 1 or more.) A first solvent comprising ethylene carbonate;
A second solvent comprising at least one of diethyl carbonate and ethyl methyl carbonate;
4,5-difluoro-1,3-dioxolan-2-one;
Including
The volume of the first solvent is 5% by volume or more and 30% by volume or less with respect to the entire solvent,
The electrolyte for a prismatic battery, wherein the volume of the 4,5-difluoro-1,3-dioxolan-2-one is 0.05% by volume or more and 10% by volume or less. The electrolyte for a prismatic battery according to claim 9, further comprising at least one of propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone as the first solvent. 10. The electrolyte for a prismatic battery according to claim 9, wherein the 4,5-difluoro-1,3-dioxolan-2-one is a trans isomer. The electrolyte for a prismatic battery according to claim 9, further comprising a cyclic carbonate compound having an unsaturated bond. The electrolyte for a prismatic battery according to claim 9, further comprising an acid anhydride. The electrolyte for a prismatic battery according to claim 9, further comprising a compound having a sulfone structure. 15. The prismatic battery electrolyte according to claim 14, wherein the compound having a sulfone structure is at least one selected from the group consisting of propane sultone, propene sultone, and divinyl sulfone. Further prismatic cell electrolyte according to claim 9, characterized in that it comprises a LiBF _4. A battery comprising a positive electrode and a negative electrode, and an electrolyte,
The electrolyte is
A first solvent comprising at least one selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone;
A second solvent comprising at least one selected from diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate;
4,5-difluoro-1,3-dioxolan-2-one;
Including
The volume of the first solvent is 5% by volume or more and 40% by volume or less with respect to the entire solvent,
The battery characterized in that the volume of the 4,5-difluoro-1,3-dioxolan-2-one is 0.05 vol% or more and 20 vol% or less. The battery according to claim 17, wherein the 4,5-difluoro-1,3-dioxolan-2-one is in a trans form. The electrolyte is
18. The battery according to claim 17, further comprising a cyclic carbonate compound having an unsaturated bond. The electrolyte is
The battery according to claim 17, further comprising an acid anhydride. The electrolyte is
The battery according to claim 17, further comprising at least one light metal salt represented by Chemical formula 12.

(Wherein R11 represents a —C (═O) —R21—C (═O) — group (R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group), —C (═O ) -C (R23) (R24)-group (R23, R24 represents an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group), or -C (= O) -C (= O) -Represents a group, R12 represents a halogen group, an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, X11 and X12 each represent oxygen (O) or sulfur (S), and M11 represents a transition metal element Or represents a group 3B element, a group 4B element or a group 5B element in the short period type periodic table, and M21 represents a group 1A element, group 2A element or aluminum in the short period type periodic table. Represents (Al), a is an integer from 1 to 4, b is an integer of 0~8, c, d, e and f is an integer of 1 to 3, respectively.) The electrolyte is
The battery according to claim 17, further comprising at least one light metal salt represented by Chemical formula 13.

(Wherein R11 represents a —C (═O) —R21—C (═O) — group (R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group), —C (═O ) —C (═O) — group or —C (═O) —C— (R22) ₂ (R22 represents an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group) — group. , R13 represents halogen, M12 represents phosphorus (P) or boron (B), M21 represents a group 1A element or group 2A element or aluminum (Al) in the short-period periodic table, and a1 is 1 to 4 An integer, b1 is 0, 2 or 4, and c, d, e and f are each an integer of 1 to 3.) The electrolyte is
Further, lithium difluoro [oxolato-O, O ′] lithium borate represented by Chemical formula 14, difluorobis [oxolato-O, O ′] lithium phosphate represented by Chemical formula 15, difluoro [3, 3,3-trifluoro-2-oxide-2-trifluoromethylpropionate (2-)-O, O ′] lithium borate, bis [3,3,3-trifluoro-2 represented by formula 17 -Oxide-2-trifluoromethylpropionate (2-)-O, O '] lithium borate, tetrafluoro [oxolato-O, O'] lithium phosphate represented by Chemical formula 18, represented by Chemical formula 19 The battery according to claim 17, comprising at least one light metal salt selected from the group consisting of lithium bis [oxolato-O, O ′] lithium borate.

The electrolyte is
Further, at least one selected from the group consisting of LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , a lithium salt represented by Chemical Formula 20, a lithium salt represented by Chemical Formula 21 and a lithium salt represented by Chemical Formula 22 The battery according to claim 17, comprising:

(In the formula, m and n are integers of 1 or more.)

(In the formula, R represents a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms.)

(In the formula, p, q and r are integers of 1 or more.) The battery according to claim 17, wherein the negative electrode includes a material containing lithium metal or silicon (Si). A positive electrode, a negative electrode, and an electrolyte;
The electrolyte is
A first solvent comprising ethylene carbonate;
A second solvent comprising at least one of diethyl carbonate and ethyl methyl carbonate;
4,5-difluoro-1,3-dioxolan-2-one;
Including
The volume of the first solvent is 5% by volume or more and 30% by volume or less with respect to the entire solvent,
The prismatic battery characterized in that the volume of the 4,5-difluoro-1,3-dioxolan-2-one is 0.05 vol% or more and 10 vol% or less. The electrolyte is
27. The prismatic battery according to claim 26, further comprising at least one of propylene carbonate, butylene carbonate, γ-butyrolactone, and γ-valerolactone as the first solvent. 27. The prismatic battery according to claim 26, wherein the 4,5-difluoro-1,3-dioxolan-2-one is a trans isomer. The electrolyte is
27. The prismatic battery according to claim 26, further comprising a cyclic carbonate compound having an unsaturated bond. The electrolyte is
27. The prismatic battery according to claim 26, further comprising an acid anhydride. The electrolyte is
27. The prismatic battery according to claim 26, further comprising a compound having a sulfone structure. The electrolyte is
32. The prismatic battery according to claim 31, wherein the compound having a sulfone structure is at least one selected from the group consisting of propane sultone, propene sultone, and divinyl sulfone. The electrolyte is
Furthermore the prismatic battery according to claim 26, characterized in that it comprises a LiBF _4. 27. The prismatic battery according to claim 26, wherein the negative electrode has a material containing at least one of silicon (Si) and tin (Sn) as a constituent element.

Images