JP4951933B2 - Electrolyte for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Description

The present invention is a lithium ion secondary battery example Bei a cathode, an anode, and a lithium ion secondary cell electrolyte used therein.

  In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a digital still camera, a mobile phone, a portable information terminal, or a notebook computer have appeared, and their size and weight have been reduced. Accordingly, as a portable power source for electronic devices, research and development for improving the energy density of batteries, particularly secondary batteries, are being actively promoted. Among these, lithium ion secondary batteries using a carbon material for the negative electrode, a composite material of lithium and a transition metal for the positive electrode, and a carbonate ester for the electrolytic solution are larger than conventional lead batteries and nickel cadmium batteries. Since energy density can be obtained, it is widely used.

Recently, with the improvement in performance of portable electronic devices, further improvement in capacity has been demanded, and it is considered to use tin (Sn) or silicon (Si) instead of carbon material as the negative electrode active material. Has been. This is because the theoretical capacity of tin is 994 mAh / g and the theoretical capacity of silicon is 4199 mAh / g, which is much larger than the theoretical capacity of graphite, 372 mAh / g, and an improvement in capacity can be expected. In particular, it has been reported that a negative electrode in which a thin film of tin or silicon is formed on a current collector can suppress the pulverization of the negative electrode active material and retain a relatively large discharge capacity even by insertion and extraction of lithium ( For example, see Patent Document 1).
International Publication No. WO01 / 031724 Pamphlet

  However, since tin alloys or silicon alloys that occlude lithium have high activity, it is particularly difficult to use a cyclic carbonate, which is a high dielectric constant solvent, and a chain carbonate, which is a low viscosity solvent, as the electrolyte. There was a problem that the formula carbonic acid ester was decomposed and lithium was inactivated. In addition, the effect of suppressing the pulverization of the negative electrode active material due to repeated charge / discharge is not yet sufficient, and as a result, the charge / discharge efficiency is lowered, and sufficient cycle characteristics cannot be obtained.

The present invention has been made in view of such problems, and an object thereof is to provide an electrolyte for a lithium ion secondary battery that can improve cycle characteristics and a lithium ion secondary battery using the same.

An electrolyte for a lithium ion secondary battery according to the present invention contains a solvent containing at least one member selected from the group consisting of a chain carbonate derivative shown in Chemical Formula 1 and a chain carboxylate derivative shown in Chemical Formula 2. It is.

(In the formula, X1 represents chlorine. R1, R2, and R3 each represents hydrogen, fluorine, chlorine, or an alkyl group having 1 to 4 carbon atoms or a group in which at least part of hydrogen is substituted with fluorine or chlorine. To express.)

(In the formula, X2 represents fluorine or chlorine. R4, R5, and R6 each represents hydrogen, fluorine, chlorine, an alkyl group having 1 to 4 carbon atoms, or at least part of hydrogen substituted with fluorine or chlorine. Represents a group.)

The lithium ion secondary battery of the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the electrolyte contains a solvent containing at least one member selected from the group consisting of the chain carbonate ester derivative and the chain carboxylate derivative. Is.

According to the lithium ion secondary battery electrolyte and lithium ion secondary battery of the present invention, the electrolyte includes at least one of the group consisting of the above-described chain carbonate ester derivative and chain carboxylate ester derivative . Therefore, the decomposition reaction of the solvent in the negative electrode can be suppressed, and the cycle characteristics can be improved.

  If a cyclic carbonate derivative having a halogen atom is included, the decomposition reaction of the solvent can be further suppressed, and the cycle characteristics can be further improved.

In particular, when the negative electrode is capable of inserting and extracting lithium ions and contains a negative electrode material containing at least one of a metal element and a metalloid element as a constituent element, or of silicon and tin In the case where a material containing at least one kind as a constituent element is contained, a high effect can be obtained.

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

(First embodiment)
FIG. 1 shows a cross-sectional structure of a secondary battery according to an embodiment of the present invention. This secondary battery is a so-called lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium as an electrode reactant. This secondary battery is a so-called cylindrical type, in which a pair of strip-like positive electrode 21 and negative electrode 22 are stacked and wound inside a substantially hollow cylindrical battery can 11 via a separator 23. A rotating electrode body 20 is provided. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

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

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 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 or one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode active material layer 21B includes, for example, a positive electrode material that can occlude and release lithium as an electrode reactant as a positive electrode active material.

As a cathode material capable of inserting and extracting lithium, for example, lithium cobalt oxide, a solid solution containing lithium nickelate, or these _{(Li (Ni x Co y Mn} z) O 2)) (x, y and z Of 0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1), or lithium composite oxide such as manganese spinel (LiMn ₂ O ₄ ), or lithium iron phosphate A phosphate compound having an olivine structure such as (LiFePO ₄ ) is preferred. This is because a high energy density can be obtained. Examples of positive electrode materials capable of inserting and extracting lithium include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as iron disulfide, titanium disulfide and molybdenum sulfide, polyaniline or Examples also include conductive polymers such as 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 contains, for example, a conductive agent, and may further contain a binder as necessary. Examples of the conductive agent include carbon materials such as graphite, carbon black, and ketjen black, and one 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, and one or more of them are mixed. Used. 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 or one surface of the negative electrode current collector 22A.

  The anode current collector 22A is preferably made of a metal material containing at least one metal element that does not form an intermetallic compound with lithium. This is because when lithium and an intermetallic compound are formed, they expand and contract with charge / discharge, structural breakdown occurs, current collection performance decreases, and the ability to support the negative electrode active material layer 22B decreases. Examples of the metal element that does not form an intermetallic compound with lithium include copper (Cu), nickel, titanium (Ti), iron, and chromium (Cr).

  The negative electrode active material layer 22B includes, for example, a negative electrode material capable of inserting and extracting lithium, which is an electrode reactant, as a negative electrode active material, and a binder such as polyvinylidene fluoride as necessary. Other materials such as an agent and a conductive agent may be included.

  In this secondary battery, the charge capacity of the negative electrode material capable of inserting and extracting lithium is larger than the charge capacity of the positive electrode 21 so that lithium metal does not deposit on the negative electrode 22 during the charge. It has become.

  As a negative electrode material capable of inserting and extracting lithium, a material which can store and release lithium and includes at least one of a metal element and a metalloid element as a constituent element can be given. This is because a high energy density can be obtained by using such a negative electrode material. The negative electrode material may be a single element, alloy or compound of a metal element or metalloid element, or may have at least a part of one or more of these phases. In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of the metal element or metalloid element constituting the negative electrode material include magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), silicon, germanium (which can form an alloy with lithium ( Ge), tin, 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.

  Among these, as the negative electrode material, a material containing a 4B group metal element or a semimetal element in the short-period type periodic table as a constituent element is preferable, and at least one of silicon and tin is particularly preferable as a constituent element. This is because silicon and tin have a large ability to occlude and release lithium, and a high energy density can be obtained.

  Moreover, as this negative electrode material, tin, cobalt, and carbon are included as constituent elements, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the total of tin and cobalt is A SnCoC-containing material having a cobalt ratio Co / (Sn + Co) of 30% by mass to 70% by mass is preferable. This is because a high energy density can be obtained in such a composition range, and excellent cycle characteristics can be obtained.

  This SnCoC-containing material may further contain other constituent elements as necessary. As other constituent elements, for example, silicon, iron, nickel, chromium, indium, niobium, germanium (Ge), titanium, molybdenum, aluminum, phosphorus, gallium, or bismuth is preferable, and two or more kinds may be included. This is because the capacity or cycle characteristics can be further improved.

  This SnCoC-containing material has a phase containing tin, cobalt, and carbon, and this phase preferably has a low crystallinity or an amorphous structure. In this SnCoC-containing material, it is preferable that at least a part of carbon that is a constituent element is bonded to a metal element or a metalloid element that is another constituent element. The decrease in cycle characteristics is thought to be due to the aggregation or crystallization of tin or the like, but this is because such aggregation or crystallization can be suppressed by combining carbon with other elements. .

  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 SnCoC-containing material appears in a region lower than 284.5 eV, at least a part of the carbon contained in the SnCoC-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 SnCoC-containing material. Therefore, by analyzing using, for example, commercially available software, the surface contamination The carbon peak and the carbon peak in the SnCoC-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).

  This SnCoC-containing material is prepared by, for example, mixing raw materials of various constituent elements, melting them in an electric furnace, a high-frequency induction furnace, an arc melting furnace or the like, and then solidifying them. Various atomization methods such as gas atomization or water atomization, various rolls Or a method using a mechanochemical reaction such as a mechanical alloying method or a mechanical milling method. Especially, it is preferable to manufacture by the method using a mechanochemical reaction. This is because the SnCoC-containing material can have a low crystallinity or an amorphous structure. In this method, for example, a production apparatus such as a planetary ball mill apparatus or an attritor can be used.

  As the negative electrode material, a carbon material capable of inserting and extracting lithium may be used, and these carbon materials and the negative electrode material described above may be used together. 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.

  Examples of such carbon materials include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, activated carbon, and carbon black. 1 type (s) or 2 or more types can be used. Among these, cokes include pitch coke, needle coke, and petroleum coke. Organic polymer compound fired bodies are carbonized by firing polymer compounds such as phenol resin and furan resin at an appropriate temperature. What you did.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is made of, for example, a porous film made of synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene or the like, or a multi-hard film made of ceramic, and these two or more kinds of porous films are laminated. It may be made the structure.

  For example, the separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. The electrolytic solution contains, for example, a solvent and an electrolyte salt dissolved in the solvent.

  As the solvent, it is preferable to use a mixture of a high dielectric constant solvent having a relative dielectric constant of 30 or more and a low viscosity solvent having a viscosity of 1 mPa · s or less. This is because high ion conductivity can be obtained.

  Examples of the high dielectric constant solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, or cyclic carbonate derivatives having a halogen atom obtained by substituting at least a part of hydrogen with a halogen. . Among these, a cyclic carbonate derivative having a halogen atom is preferable. This is because the effect of suppressing the decomposition reaction of the solvent is high. Specific examples of the cyclic carbonate derivative having a halogen atom include 4-fluoro-1,3-dioxolan-2-one shown in Chemical Formula 3 (1), and 4- Chloro-1,3-dioxolan-2-one, 4-fluoro-4-methyl-1,3-dioxolan-2-one shown in Chemical formula 3 (3), trans-4-shown in Chemical formula 3 (4) Fluoro-5-methyl-1,3-dioxolan-2-one, cis-4-fluoro-5-methyl-1,3-dioxolan-2-one shown in Chemical formula 3 (5), Chemical formula 3 (6) 4-trifluoromethyl-1,3-dioxolan-2-one and the like shown can be mentioned, among which 4-fluoro-1,3-dioxolan-2-one is preferable. This is because a higher effect can be obtained.

  Preferred examples of the high dielectric constant solvent include cyclic carbonates of unsaturated compounds such as 1,3-dioxol-2-one or 4-vinyl-1,3-dioxolan-2-one. , 3-dioxol-2-one is more preferred. This is because the decomposition reaction of the solvent can be suppressed.

  Examples of the high dielectric constant solvent further include lactones such as γ-butyrolactone and γ-valerolactone, lactams such as N-methylpyrrolidone, cyclic carbamates such as N-methyloxazolidinone, and tetramethylene sulfone. A sulfone compound is also mentioned. A high dielectric constant solvent may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  As the low viscosity solvent, it is preferable to use a compound having the structure shown in Chemical formula 4. This is because it is considered that the C—O—C bond in the structure is not easily broken in the negative electrode 22 because the halogen atom has an electron attractive force. In particular, when the negative electrode 22 is capable of inserting and extracting lithium and contains a negative electrode material containing at least one of a metal element and a metalloid element as a constituent element, decomposition of the solvent in the negative electrode 22 Since the effect which suppresses is high, it is preferable.

（式中、Ｘはハロゲン原子を表す。）

(In the formula, X represents a halogen atom.)

  Examples of the compound having such a structure include a chain carbonate ester derivative shown in Chemical Formula 5 or a chain carboxylic acid ester derivative shown in Chemical Formula 6. One of them may be used alone, or two or more thereof may be mixed and used, or a chain carbonate ester derivative and a chain carboxylic acid ester derivative may be mixed and used.

（式中、Ｘ１は、フッ素または塩素を表す。Ｒ１，Ｒ２，Ｒ３は、水素、フッ素、塩素、または炭素数１から４のアルキル基あるいはそれらの少なくとも一部の水素をフッ素若しくは塩素で置換した基を表す。Ｒ１，Ｒ２，Ｒ３は、同一であっても、異なっていてもよい。）

(In the formula, X1 represents fluorine or chlorine. R1, R2, and R3 each represents hydrogen, fluorine, chlorine, an alkyl group having 1 to 4 carbon atoms, or at least part of hydrogen substituted with fluorine or chlorine. R 1, R 2 and R 3 may be the same or different.

（式中、Ｘ２は、フッ素または塩素を表す。Ｒ４，Ｒ５，Ｒ６は、水素、フッ素、塩素、または炭素数１から４のアルキル基あるいはそれらの少なくとも一部の水素をフッ素若しくは塩素で置換した基を表す。Ｒ４，Ｒ５，Ｒ６は、同一であっても、異なっていてもよい。）

(In the formula, X2 represents fluorine or chlorine. R4, R5, and R6 each represents hydrogen, fluorine, chlorine, an alkyl group having 1 to 4 carbon atoms, or at least part of hydrogen substituted with fluorine or chlorine. R4, R5 and R6 may be the same or different.)

  As the chain carbonic acid ester derivative shown in Chemical formula 5, for example, fluorinated dimethyl carbonate shown in Chemical formula 7 is preferable if X1 is fluorine. This is because the effect of suppressing the decomposition of the solvent is high.

（式中、ｍ，ｎは、０，１または２であり、ｍおよびｎのうちの少なくとも一方は１または２である。）

(In the formula, m and n are 0, 1 or 2, and at least one of m and n is 1 or 2.)

  Specific examples of such fluorinated dimethyl carbonate include (fluoromethyl) methyl carbonate, bisfluoromethyl carbonate, and (difluoromethyl) methyl carbonate. One kind of fluorinated dimethyl carbonate may be used alone, or a plurality of kinds may be mixed and used.

  The content of fluorinated dimethyl carbonate shown in Chemical Formula 7 in the solvent is preferably 5% by mass or more and 30% by mass or less. This is because a higher effect can be obtained within this range.

  In addition to these fluorinated dimethyl carbonates, the chain carbonic acid ester derivatives shown in Chemical formula 5 in which X1 is fluorine include, in addition to (fluoromethyl) ethyl carbonate, (fluoromethyl) propyl carbonate, (fluoromethyl) isopropyl carbonate, (1-fluoroethyl) methyl carbonate, (1-fluoroethyl) ethyl carbonate, (1-fluoroethyl) propyl carbonate, (1-fluoroethyl) isopropyl carbonate, di (1-fluoroethyl) carbonate, carbonate (1-fluoro) Propyl) methyl, (1-fluoropropyl) ethyl carbonate, (1-fluoropropyl) propyl carbonate, (1-fluoropropyl) isopropyl carbonate, di (1-fluoropropyl) carbonate, (2-fluoro-2-propyl) carbonate Methyl, (2-fluoro-2-propyl) ethyl carbonate, carbonic acid (2-fluoro-2-propyl) Pills) propyl carbonate (2-fluoro-2-propyl) isopropyl, or di (2-fluoro-2-propyl) also include chain fluorinated ester carbonate such.

  Specific examples of the chain carbonic acid ester derivatives represented by Chemical formula 5 in which X1 is chlorine include (chloromethyl) methyl carbonate, (chloromethyl) ethyl carbonate, (chloromethyl) propyl carbonate, and (chloromethyl) carbonate Isopropyl, di (chloromethyl) carbonate, (1-chloroethyl) methyl carbonate, (1-chloroethyl) ethyl carbonate, (1-chloroethyl) propyl carbonate, (1-chloroethyl) isopropyl carbonate, di (1-chloroethyl) carbonate, carbonic acid (1-chloropropyl) methyl, (1-chloropropyl) ethyl carbonate, (1-chloropropyl) propyl carbonate, (1-chloropropyl) isopropyl carbonate, di (1-chloropropyl) carbonate, carbonic acid (2-chloro- 2-propyl) methyl, carbonate (2-chloro-2-propyl) ethyl, carbonate (2-chloro-2-propyl) Pills) propyl, and the like carbonate (2-chloro-2-propyl) isopropyl or di (2-chloro-2-propyl) chain carbonic chlorinated esters such as.

  As the chain carbonate derivative shown in Chemical formula 5, a compound having a branched structure is preferable. This is because the effect of suppressing the decomposition reaction of the solvent in the negative electrode 22 is high.

  Specific examples of the chain carboxylic acid ester derivative shown in Chemical formula 6 include fluoromethyl acetate, 1-fluoroethyl acetate, 1-fluoropropyl acetate, 2-fluoro-2-propyl acetate, fluoromethyl propionate, 1-fluoroethyl propionate, 1-fluoropropyl propionate, 2-fluoro-2-propyl propionate, fluoromethyl butyrate, 1-fluoroethyl butyrate, fluoromethyl isobutyrate, 1-fluoroethyl isobutyrate, fluoromethyl pivalate , Carboxylic acid fluorinated esters such as 1-fluoroethyl pivalate, fluoromethyl trifluoroacetate, 1-fluoroethyl trifluoroacetate, 1-fluoropropyl trifluoroacetate or 2-fluoro-2-propyl trifluoroacetate, acetic acid Chloromethyl, 1-chloroethyl acid, 1-chloropropyl acetate, 2-chloro-2-propyl acetate, chloromethyl propionate, 1-chloroethyl propionate, 1-chloropropyl propionate, 2-chloro-2-propyl propionate, chlorobutyrate Methyl, 1-chloroethyl butyrate, chloromethyl isobutyrate, 1-chloroethyl isobutyrate, chloromethyl pivalate, 1-chloroethyl pivalate, chloromethyl trifluoroacetate, 1-chloroethyl trifluoroacetate, 1-chloropropyl trifluoroacetate, Alternatively, there are carboxylic acid chlorinated esters such as 2-chloro-2-propyl trifluoroacetate. Among these, a compound having a branched structure is preferable. This is because the effect of suppressing the decomposition reaction of the solvent in the negative electrode 22 is high.

  These chain carbonate ester derivatives or chain carboxylate derivatives may be mixed with other low-viscosity solvents. Examples of other low viscosity solvents include diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.

As the electrolyte salt, e.g., lithium hexafluorophosphate (LiPF _6), lithium tetrafluoroborate (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium hexafluoro antimonate (LiSbF ₆₎ , Lithium perchlorate (LiClO ₄ ), or lithium tetrachloroaluminate (LiAlCl ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), tris (trifluoromethanesulfonyl) methyllithium ((CF ₃ SO ₂ ) ₃ CLi ) Or lithium salts such as lithium trispentafluoroethyl trifluorophosphate (LiP (C ₂ F ₅ ) ₃ F ₃ ).

Examples of the electrolyte salt include lithium trifluoromethyl trifluoroborate (LiB (CF ₃ ) F ₃ ), lithium pentafluoroethyl trifluoroborate (LiB (C ₂ F ₅ ) F ₃ ), and bis (oxalate) boron. Lithium borate, lithium borate such as difluoro (oxalate) lithium borate, or bis (trifluoromethanesulfonyl) imide lithium (CF ₃ SO ₂ ) ₂ NLi), bis (pentafluoroethanesulfonyl) imide lithium ((C _{2 F 5 SO 2) 2 NLi)} , 1,1,2,2,3,3- hexafluoropropane-1,3-disulfonic imide, trifluoromethyl heptafluoropropyl imide or trifluoromethyl nonafluorobutyl imides, Imidolithium salts such as lithium are preferred Arbitrariness. This is because the cycle characteristics can be improved.

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

  First, for example, the positive electrode active material layer 21B is formed on the positive electrode current collector 21A to produce the positive electrode 21. The positive electrode active material layer 21B is prepared, for example, by mixing a positive electrode material, a conductive agent, and a binder to prepare a positive electrode mixture, and then dispersing the positive electrode mixture in a solvent such as N-methyl-2-pyrrolidone. A paste-like positive electrode mixture slurry is formed, and this positive electrode mixture slurry is applied to the positive electrode current collector 21A, dried, and compression molded.

  Further, for example, the negative electrode active material layer 22B is formed on the negative electrode current collector 22A to produce the negative electrode 22. The negative electrode active material layer 22B is prepared, for example, by mixing a negative electrode material, a conductive agent, and a binder to prepare a negative electrode mixture, and then dispersing the negative electrode mixture in a solvent such as N-methyl-2-pyrrolidone. A paste-like negative electrode mixture slurry is formed, and this negative electrode mixture slurry is applied to the negative electrode current collector 22A, dried, and compression-molded.

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

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution. On the other hand, when discharging is performed, for example, lithium ions are extracted from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution. At that time, since the electrolytic solution includes the compound having the structure shown in Chemical Formula 4 as described above, the decomposition reaction of the solvent in the negative electrode 22 is suppressed.

  As described above, according to the battery according to the present embodiment, since the electrolytic solution includes the compound having the structure shown in Chemical Formula 4, the decomposition reaction of the solvent in the negative electrode 22 can be suppressed, and the cycle characteristics are obtained. Can be improved.

  If a cyclic carbonate derivative having a halogen atom is included, the decomposition reaction of the solvent can be further suppressed, and the cycle characteristics can be further improved.

  In particular, when the negative electrode 22 is capable of inserting and extracting lithium as an electrode reactant and contains a negative electrode material containing at least one of a metal element and a metalloid element as a constituent element, or silicon When a material containing at least one of tin and tin as a constituent element is contained, a high effect can be obtained.

(Second Embodiment)
The secondary battery according to the second embodiment has the same configuration, operation, and effects as the first embodiment except that the configuration of the negative electrode 22 is different, and is manufactured in the same manner. be able to. Therefore, with reference to FIG. 1 and FIG. 2, the same code | symbol is attached | subjected to a corresponding component and description of the same part is abbreviate | omitted.

  Similarly to the first embodiment, the negative electrode 22 has a structure in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A. The negative electrode active material layer 22B is made of silicon and tin. The negative electrode active material containing at least one of these is contained. Specifically, for example, it contains a simple substance, an alloy, or a compound of silicon, or a simple substance, an alloy, or a compound of tin, and may contain two or more of them.

  The negative electrode active material layer 22B is formed by using, for example, a vapor phase method, a liquid phase method, a firing method, or two or more of these methods. The negative electrode active material layer 22B and the negative electrode current collector It is preferable that 22A is alloyed in at least a part of the interface. Specifically, the constituent elements of the negative electrode current collector 22A are diffused in the negative electrode active material layer 22B, the constituent elements of the negative electrode active material layer 22B are diffused in the negative electrode current collector 22A, or they are mutually diffused at the interface. preferable. 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 chemical vapor deposition ( Examples include CVD (Chemical Vapor Deposition), plasma chemical vapor deposition, and thermal spraying. As the liquid phase method, a known method such as electroplating or electroless plating can be used. The firing method is, for example, a method in which a particulate negative electrode active material is mixed with a binder, dispersed in a solvent, applied, and then heat treated at a temperature higher than the melting point of the binder. A known method can also be used for the firing method, for example, an atmospheric firing method, a reactive firing method, or a hot press firing method.

(Third embodiment)
In the secondary battery according to the second embodiment of the present invention, the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is expressed by the sum thereof It is.

  This secondary battery has the same configuration and effects as the secondary battery according to the first or second embodiment except that the configuration of the negative electrode active material layer 22B is different. Can be manufactured. Therefore, here, description will be made with reference to FIGS. 1 and 2 using the same reference numerals. Detailed descriptions of the same parts are omitted.

  For example, the negative electrode active material layer 22B has an open circuit voltage (that is, a battery voltage) in the charging process by making the charge capacity of the negative electrode material capable of occluding and releasing lithium smaller than the charge capacity of the positive electrode 21. When lithium is lower than the overcharge voltage, lithium metal begins to deposit on the negative electrode 22. Therefore, in this secondary battery, both the negative electrode material capable of inserting and extracting lithium and lithium metal function as a negative electrode active material, and the negative electrode material capable of inserting and extracting lithium is lithium metal. It is a base material for precipitation. Examples of the negative electrode material capable of occluding and releasing lithium include the same materials as those in the first embodiment, and among these, a carbon material capable of occluding and releasing lithium is preferable.

  The overcharge voltage refers to the open circuit voltage when the battery is overcharged. For example, the “lithium secondary battery” is one of the guidelines established by the Japan Storage Battery Industry Association (Battery Industry Association). Refers to a voltage that is higher than the open circuit voltage of a “fully charged” battery as defined and defined in the “Safety Evaluation Criteria Guidelines” (SBA G1101). In other words, it refers to a voltage higher than the open circuit voltage after charging using the charging method, standard charging method, or recommended charging method used when determining the nominal capacity of each battery.

  Thereby, in this secondary battery, it is possible to obtain a high energy density and to improve cycle characteristics and quick charge characteristics. This secondary battery is the same as the conventional lithium ion secondary battery in that a negative electrode material capable of inserting and extracting lithium is used for the negative electrode 22, and lithium metal is deposited on the negative electrode 22. Then, it is the same as that of the conventional lithium metal secondary battery.

  In order to obtain these characteristics more effectively, for example, the maximum deposition capacity of the lithium metal deposited on the negative electrode 22 at the maximum voltage before the open circuit voltage becomes the overcharge voltage is to occlude and release lithium. It is preferable that it is 0.05 times or more and 3.0 times or less the charge capacity capability of the negative electrode material capable of being This is because when the amount of deposited lithium metal is too large, the same problem as that of the conventional lithium secondary battery occurs, and when the amount is too small, the charge / discharge capacity cannot be sufficiently increased. Further, for example, the discharge capacity capability of the negative electrode material capable of inserting and extracting lithium is preferably 150 mAh / g or more. This is because the amount of lithium metal deposited becomes relatively smaller as the ability to occlude and release lithium increases. The charge capacity capability of the negative electrode material can be obtained, for example, from the amount of electricity when a negative electrode using lithium metal as a counter electrode and the negative electrode material as a negative electrode active material is charged to 0 V by a constant current / constant voltage method. The discharge capacity capability of the negative electrode material is obtained, for example, from the amount of electricity when the current is discharged to 2.5 V over 10 hours or more by the constant current method.

  In this secondary battery, when charged, lithium ions are released from the positive electrode 21 and are first inserted into the negative electrode material capable of inserting and extracting lithium contained in the negative electrode 22 through the electrolytic solution. When charging is further continued, lithium metal begins to deposit on the surface of the negative electrode material capable of inserting and extracting lithium in a state where the open circuit voltage is lower than the overcharge voltage. After that, lithium metal continues to deposit on the negative electrode 22 until charging is completed. Next, when discharging is performed, first, lithium metal deposited on the negative electrode 22 is eluted as ions, and is occluded in the positive electrode 21 through the electrolytic solution. When the discharge is further continued, lithium ions occluded in the negative electrode material capable of occluding and releasing lithium in the negative electrode 22 are released and inserted in the positive electrode 21 through the electrolytic solution. At that time, since the electrolytic solution includes the compound having the structure shown in Chemical Formula 4 as described above, the decomposition reaction of the solvent in the negative electrode 22 is suppressed.

(Fourth embodiment)
FIG. 3 shows the configuration of the secondary battery according to the third embodiment. In this secondary battery, a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is accommodated in a film-like exterior member 40, and can be reduced in size, weight, and thickness. ing.

  The positive electrode lead 31 and the negative electrode lead 32 are 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, copper, nickel, or stainless steel, and each have a thin plate shape or a mesh shape.

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

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

  FIG. 4 shows a cross-sectional structure taken along 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 side is disposed so as to face the positive electrode active material layer 33B. Yes. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, and the negative electrode current collector 22A. The same as the negative electrode 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. The configuration of the electrolytic solution (that is, the solvent, the electrolyte salt, and the like) is the same as that of the secondary battery according to the first to third embodiments. Examples of the polymer compound include, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate, or an acrylate polymer compound, or polyvinylidene fluoride or vinylidene fluoride. Examples thereof include polymers of vinylidene fluoride such as a copolymer with hexafluoropropylene, and any one of these or a mixture of two or more thereof is used. In particular, from the viewpoint of redox stability, it is desirable to use a fluorine-based polymer compound such as a vinylidene fluoride polymer.

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

  First, the positive electrode 33 and the negative electrode 34 are produced in the same manner as in the first to third embodiments, and a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is added to each of the positive electrode 33 and the negative electrode 34. The electrolyte layer 36 is formed by applying and evaporating the mixed solvent. 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 electrolyte layer 36 is formed are laminated via a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion. Thus, the wound electrode body 30 is formed. 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 FIGS. 3 and 4 is completed.

  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. Rotate and adhere the protective tape 37 to the outermost periphery to form a wound body that is a precursor of the wound electrode body 30. Next, the wound body is sandwiched between the exterior members 40, and the outer peripheral edge portion excluding one side is heat-sealed to form a bag shape, and is stored inside the exterior member 40. Subsequently, an electrolyte composition including an electrolytic solution, 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 interior of the exterior member 40 Inject.

  After injecting the electrolyte composition, the opening of the exterior member 40 is heat-sealed and sealed in a vacuum atmosphere. Next, heat is applied to polymerize the monomer to obtain a polymer compound, thereby forming a gel electrolyte layer 36, and assembling the secondary battery shown in FIG.

  The operation and effect of the secondary battery are the same as those of the secondary battery according to the first to third embodiments.

(Fifth embodiment)
In the secondary battery according to the fifth embodiment, the open circuit voltage (that is, the battery voltage) at the time of full charge can be 4.25V to 6.00V, preferably 4.25V to 4.60V. Except for this, the other components have the same configuration as the secondary battery according to the first to fourth embodiments, and can be manufactured in the same manner.

  In this secondary battery, the amount of lithium released per unit mass increases even when the same positive electrode active material is used, compared with a battery having an open circuit voltage of 4.20 V or more during full charge. The amount of the material and the negative electrode active material is adjusted. As a result, a high energy density can be obtained.

  As the negative electrode active material, a carbon material capable of inserting and extracting lithium is preferable. This is because the energy density of the battery can be easily improved because the charge / discharge potential is low.

  In this secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and occluded or deposited on the negative electrode 22 through the electrolytic solution. On the other hand, when discharging is performed, for example, lithium ions are released or dissolved from the negative electrode 22 and inserted into the positive electrode 21 through the electrolytic solution. Here, since the battery voltage at the time of charging is 4.25 V or more, the electrolytic solution is easily decomposed. However, as described above, since the compound having the structure shown in Chemical Formula 4 is included, The decomposition reaction of the solvent in the negative electrode 22 is suppressed.

  The effect of the secondary battery is the same as that of the secondary battery according to the first to fourth embodiments.

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

(Examples 1-1 to 1-3)
A lithium ion secondary battery was produced. At that time, the coin-type secondary battery shown in FIG. 5 was produced. This secondary battery is formed by laminating a positive electrode 51 and a negative electrode 52 via a separator 53 impregnated with an electrolytic solution, sandwiching between an outer can 54 and an outer cup 55 and caulking via a gasket 56. is there. First, as a positive electrode active material, lithium cobalt composite oxide (LiCoO ₂
) After mixing 94 parts by mass, 3 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder, N-methyl-2-pyrrolidone was added to obtain a positive electrode mixture slurry. Next, the obtained positive electrode mixture slurry was uniformly applied to a positive electrode current collector 51A made of an aluminum foil having a thickness of 20 μm and dried to form a positive electrode active material layer 51B having a thickness of 70 μm. After that, the positive electrode current collector 51A on which the positive electrode active material layer 51B was formed was punched into a circle having a diameter of 15 mm to produce the positive electrode 51.

  A negative electrode active material layer 52B made of silicon having a thickness of 5 μm was formed on the negative electrode current collector 52A made of copper foil having a thickness of 15 μm by sputtering. After that, the negative electrode current collector 52A on which the negative electrode active material layer 52B was formed was punched into a circle having a diameter of 16 mm to produce the negative electrode 52. In addition, the area density ratio between the positive electrode 51 and the negative electrode 52 was designed so that the capacity of the negative electrode 52 is represented by a capacity component due to insertion and extraction of lithium.

  Next, the positive electrode 51 and the negative electrode 52 are laminated via a separator 53 made of a microporous polypropylene film having a thickness of 25 μm, and then 0.1 g of an electrolytic solution is injected into the separator 53, and these are made of an exterior cup 55 made of stainless steel. And the outer can 54 and caulked them to obtain the secondary battery shown in FIG. In the electrolytic solution, a high dielectric constant solvent, a low viscosity solvent, and lithium hexafluorophosphate as an electrolyte salt, high dielectric constant solvent: low viscosity solvent: lithium hexafluorophosphate = 42: 42: 16 What was mixed by mass ratio was used. In this case, the high dielectric constant solvent is ethylene carbonate in Example 1-1, 4-chloro-1,3-dioxolan-2-one in Example 1-2, and 4-fluoro- in Example 1-3. It was 1,3-dioxolan-2-one. The low-viscosity solvent was (1-chloroethyl) ethyl carbonate shown in Chemical Formula 8 as a compound having the structure shown in Chemical Formula 4. Note that (1-chloroethyl) ethyl carbonate is a chain carbonate derivative shown in Chemical formula 5.

  As Comparative Examples 1-1 to 1-3 with respect to Examples 1-1 to 1-3, except that the low-viscosity solvent was diethyl carbonate, the rest was the same as in Examples 1-1 to 1-3. A lithium ion secondary battery was prepared. Further, as Comparative Example 1-4, except that the high dielectric constant solvent was 4-fluoro-1,3-dioxolan-2-one and the low viscosity solvent was methyl pivalate, Example 1-1 to Example 1-1 were used. A coin-type lithium ion secondary battery was produced in the same manner as in 1-3. Further, as Comparative Example 1-5, the high dielectric constant solvent was 4-fluoro-1,3-dioxolan-2-one, and the low viscosity solvent was bis (2,2,2-trichloroethyl) carbonate shown in Chemical Formula 9: Except for this, coin-type lithium ion secondary batteries were produced in the same manner as in Examples 1-1 to 1-3.

  The obtained secondary batteries of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-5 were charged at 1.77 mA with 4.2 V as the upper limit for 12 hours, and then paused for 10 minutes. Charging / discharging of discharging until it reached 2.5 V at .77 mA was repeated, and the discharge capacity maintenance rate at the 50th cycle was determined. The discharge capacity retention ratio at the 50th cycle was calculated as (discharge capacity at the 50th cycle / initial discharge capacity) × 100 (%). The obtained results are shown in Table 1.

  As can be seen from Table 1, according to Examples 1-1 to 1-3 using (1-chloroethyl) ethyl carbonate, which is a chain ester carbonate derivative shown in Chemical Formula 5, Comparative Example 1 not using this The discharge capacity retention ratio was improved from -1 to 1-3. In addition, Comparative Example 1-4 using a chain carbonate ester having no halogen atom or Comparative Example 1-5 using a chain carbonate ester derivative not having the structure of Chemical Example 1 A higher discharge capacity retention rate was obtained for No. 3. Furthermore, according to Examples 1-2 and 1-3 using a cyclic carbonic acid ester derivative having a halogen atom as a high dielectric constant solvent, the discharge capacity retention rate is higher than that of Example 1-1 not using this. Improved.

  That is, if the chain carbonic acid ester derivative shown in Chemical Formula 5 is used as the low-viscosity solvent, cycle characteristics can be improved, and a cyclic carbonate ester derivative having a halogen atom as the high dielectric constant solvent, In particular, it has been found that if 4-fluoro-1,3-dioxolan-2-one is used, cycle characteristics can be further improved.

(Examples 2-1 to 2-3, 3-1 to 3-3)
As Examples 2-1 to 2-3, a negative electrode active material layer 52B made of tin having a thickness of 5 μm was formed on a negative electrode current collector 52A made of copper foil having a thickness of 15 μm by vacuum vapor deposition using tin as the negative electrode active material. Except for the formation, coin-type lithium ion secondary batteries were produced in the same manner as in Examples 1-1 to 1-3.

  As Examples 3-1 to 3-3, a tin-cobalt alloy was used as the negative electrode active material, 94 parts by mass of this tin-cobalt alloy, 3 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder. The negative electrode active material layer 52B having a thickness of 70 μm was formed by adding N-methyl-2-pyrrolidone and uniformly applying to the negative electrode current collector 52A made of a copper foil having a thickness of 15 μm and drying. Otherwise, coin-type lithium ion secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-3.

  As Comparative Examples 2-1 to 2-3, 3-1 to 3-3 for these examples, the high dielectric constant solvent is ethylene carbonate, 4-chloro-1,3-dioxolan-2-one, or 4-fluoro. -1,3-dioxolan-2-one, except that low-viscosity solvent was diethyl carbonate, that is, except that the same electrolytic solution as Comparative Examples 1-1 to 1-3 was used. Coin-type lithium ion secondary batteries were produced in the same manner as in Examples 2-1 to 2-3 and 3-1 to 3-3. Further, as Comparative Examples 2-4 and 3-4, except that the high dielectric constant solvent was 4-fluoro-1,3-dioxolan-2-one and the low viscosity solvent was methyl pivalate, that is, Comparative Example A coin-type lithium ion secondary battery was fabricated in the same manner as in Examples 2-1 to 2-3 and 3-1 to 3-3, except that the same electrolytic solution as in 1-4 was used. Further, as Comparative Examples 2-5 and 3-5, the high dielectric constant solvent was 4-fluoro-1,3-dioxolan-2-one, and the low viscosity solvent was bis (2,2,2-trichloroethyl carbonate). In other words, except that the same electrolytic solution as in Comparative Example 1-5 was used, the rest was the same as in Examples 2-1 to 2-3 and 3-1 to 3-3. An ion secondary battery was produced.

  Regarding the obtained secondary batteries of Examples 2-1 to 2-3, 3-1 to 3-3 and Comparative Examples 2-1 to 2-5, 3-1 to 3-5, Example 1-1 was also performed. The discharge capacity retention rate at the 50th cycle was determined in the same manner as in 1-3. The results are shown in Tables 2 and 3.

  As can be seen from Tables 2 and 3, according to Examples 2-1 to 2-3 and 3-1 to 3-3, Comparative Examples 2-1 to 2 are similar to Examples 1-1 to 1-3. A discharge capacity retention rate higher than −5, 3-1 to 3-5 was obtained, and in particular, Examples 2-2, 2-3, and 3 using cyclic carbonate derivatives having a halogen atom as a high dielectric constant solvent. In 3-2 and 3-3, a higher discharge capacity retention rate was obtained. That is, even when other negative electrode active materials are used, cycle characteristics can be improved by using the chain carbonic acid ester derivative shown in Chemical Formula 5 as a low viscosity solvent. As described above, it was found that the use of a cyclic carbonate derivative having a halogen atom, particularly 4-fluoro-1,3-dioxolan-2-one, can further improve the cycle characteristics.

(Examples 4-1 to 4-3)
A lithium ion secondary battery was produced. A negative electrode made of copper foil having a thickness of 15 μm, using graphite as a negative electrode active material, mixing 97 parts by mass of graphite and 3 parts by mass of polyvinylidene fluoride as a binder, adding N-methyl-2-pyrrolidone. A coin-type lithium ion secondary battery is formed in the same manner as in Examples 1-1 to 1-3 except that the negative electrode active material layer 52B having a thickness of 70 μm is formed by uniformly applying and drying the current collector 52A. A secondary battery was produced. In Examples 4-1 to 4-3, the amounts of the positive electrode active material and the negative electrode active material were adjusted so that the open circuit voltage during complete charging was 4.5V.

  As Comparative Examples 4-1 to 4-5 with respect to Examples 4-1 to 4-3, the high dielectric constant solvent was ethylene carbonate, 4-chloro-1,3-dioxolan-2-one, or 4-fluoro-1, Except that 3-dioxolan-2-one was used and the low-viscosity solvent was diethyl carbonate, that is, except that an electrolytic solution similar to Comparative Examples 1-1 to 1-3 was used, the others were the same as in Example 4- Coin-type lithium ion secondary batteries were produced in the same manner as in 1-4-3. Further, as Comparative Example 4-4, except that the high dielectric constant solvent was 4-fluoro-1,3-dioxolan-2-one and the low viscosity solvent was methyl pivalate, that is, Comparative Example 1-4 and A coin-type lithium ion secondary battery was produced in the same manner as in Examples 4-1 to 4-3 except that the same electrolyte was used. Furthermore, as Comparative Example 4-5, except that the high dielectric constant solvent was 4-fluoro-1,3-dioxolan-2-one and the low viscosity solvent was bis (2,2,2-trichloroethyl carbonate). That is, a coin-type lithium ion secondary battery was fabricated in the same manner as in Examples 4-1 to 4-3 except that the same electrolytic solution as in Comparative Example 1-5 was used.

  For the obtained secondary batteries of Examples 4-1 to 4-3 and Comparative examples 4-1 to 4-5, the discharge capacity retention ratio at the 50th cycle was the same as in Examples 1-1 to 1-3. Asked. The results are shown in Table 4. Charging was performed with 4.5V as the upper limit.

  As can be seen from Table 4, as in Examples 1-1 to 1-3, according to Examples 4-1 to 4-3 in which the battery voltage during charging was 4.5 V, Comparative Examples 4-1 to 4-1 A discharge capacity retention rate higher than 4-5 was obtained, and in particular, in Examples 4-2 and 4-3 using a cyclic carbonate derivative having a halogen atom as a high dielectric constant solvent, a higher discharge capacity retention rate was obtained. Obtained. That is, even when the battery voltage at the time of charging is increased, cycle characteristics can be improved by using the chain carbonate ester derivative shown in Chemical Formula 5 as a low viscosity solvent, and further, a high dielectric constant solvent. As described above, it was found that the use of a cyclic carbonate derivative having a halogen atom, particularly 4-fluoro-1,3-dioxolan-2-one, can further improve the cycle characteristics.

(Examples 5-1 to 5-3)
A secondary battery in which the capacity of the negative electrode 52 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium and is expressed by the sum thereof was produced. At that time, graphite is used as the negative electrode material, 97 parts by mass of this graphite and 3 parts by mass of polyvinylidene fluoride as a binder are mixed, N-methyl-2-pyrrolidone is added, and a copper foil having a thickness of 15 μm is used. In the same manner as in Examples 1-1 to 1-5, except that a negative electrode active material layer 52B having a thickness of 50 μm was formed by uniformly applying to a negative electrode current collector 52A and drying, a coin-type two A secondary battery was produced. The area density ratio between the positive electrode 51 and the negative electrode 52 is designed so that the capacity of the negative electrode 52 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. did.

  As Comparative Examples 5-1 to 5-3 with respect to Examples 5-1 to 5-3, the high dielectric constant solvent is ethylene carbonate, 4-chloro-1,3-dioxolan-2-one, or 4-fluoro-1, Except that 3-dioxolan-2-one was used and the low-viscosity solvent was diethyl carbonate, ie, the same electrolytic solution as in Comparative Examples 1-1 to 1-3 was used. Coin-type secondary batteries were produced in the same manner as in 1-5-3. Further, as Comparative Example 5-4, except that the high dielectric constant solvent was 4-fluoro-1,3-dioxolan-2-one and the low viscosity solvent was methyl pivalate, that is, Comparative Example 1-4 and Other than using the same electrolyte, coin-type secondary batteries were fabricated in the same manner as in Examples 5-1 to 5-3.

  For the obtained secondary batteries of Examples 5-1 to 5-3 and Comparative examples 5-1 to 5-4, the discharge capacity retention ratio at the 50th cycle was the same as in Examples 1-1 to 1-3. Asked. The results are shown in Table 5.

  Separately, secondary batteries of Examples 5-1 to 5-3 and Comparative Examples 5-1 to 5-4 prepared in the same manner are prepared, and whether or not lithium metal is deposited by disassembly. As a result, it was confirmed that lithium metal was deposited on the surface of the negative electrode 52 during full charge. In addition, lithium metal disappeared from the surface of the negative electrode 52 during complete discharge. That is, it was confirmed that the capacity of the negative electrode 52 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof.

  As can be seen from Table 5, similarly to Examples 1-1 to 1-3, according to Examples 5-1 to 5-3, a higher discharge capacity retention rate than Comparative Examples 5-1 to 5-4 was obtained. In particular, in Examples 5-2 and 5-3 using a cyclic carbonate derivative having a halogen atom as a high dielectric constant solvent, a higher discharge capacity retention rate was obtained. That is, when the capacity of the negative electrode 52 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is used for a battery represented by the sum thereof, By using the chain ester carbonate derivative shown, cycle characteristics can be improved, and as a high dielectric constant solvent, a cyclic carbonate ester derivative having a halogen atom, particularly 4-fluoro-1,3- It has been found that the use of dioxolan-2-one can improve the cycle characteristics.

(Examples 6-1, 6-2, 7-1, 7-2, 8-1, 8-2, 9-1, 9-2, 10-1, 10-2)
Except that the low-viscosity solvent was replaced with chloromethyl pivalate shown in Chemical Formula 10 or (1-chloroethyl) isopropyl carbonate shown in Chemical Formula 11, the others were the same as in Examples 1-3, 2-3, and 3-3. , 4-3, and 5-3, coin-type secondary batteries were fabricated. Note that chloromethyl pivalate is a chain carboxylic acid ester derivative shown in Chemical formula 6. Further, (1-chloroethyl) isopropyl carbonate is a chain carbonate derivative shown in Chemical formula 5 and has a branched structure.

  Also for the obtained secondary batteries of Examples 6-1, 6-2, 7-1, 7-2, 8-1, 8-2, 9-1, 9-2, 10-1, and 10-2. The discharge capacity retention ratio at the 50th cycle was determined in the same manner as in Examples 1-1 to 1-3. The results are shown in Tables 6-10. In addition, about the secondary battery of Examples 9-1 and 9-2, charge was performed by making 4.5V into an upper limit.

  As can be seen from Tables 6 to 10, Examples 6-1, 6-2, and 7-1 using the chain carbonate ester derivatives shown in Chemical Formula 5 or the chain carboxylate derivatives shown in Chemical Formula 6 were used. , 7-2, 8-1, 8-2, 9-1, 9-2, 10-1, 10-2 also in Examples 1-3, 2-3, 3-3, 4-3, 5 As with -3, the discharge capacity retention rate was improved. In addition, according to Examples 6-2, 7-2, 8-2, and 10-2 using a chain carbonic acid ester derivative having a branched structure, Examples using a chain carbonic acid ester derivative having no branched structure The discharge capacity retention rate was improved as compared with 1-3, 2-3, 3-3, and 5-3.

  That is, it was found that cycle characteristics can be improved by using a compound having the structure shown in Chemical Formula 4 as the low viscosity solvent. In particular, the negative electrode 52 can occlude and release lithium and includes a negative electrode material containing at least one of a metal element and a metalloid element as a constituent element, or the negative electrode 52 has a capacity of lithium. It has been found that it is preferable if the compound has a branched structure when used in a battery that includes a capacity component due to occlusion and release and a capacity component due to lithium precipitation and dissolution, and is represented by the sum thereof. .

(Examples 11-1, 12-1, 13-1, 14-1, 15-1)
Examples 1-3, 2-3, 3-3, 4-3, except that diethyl carbonate was used in addition to (1-chloroethyl) ethyl carbonate shown in Chemical Formula 8 as the low-viscosity solvent. A coin-type secondary battery was produced in the same manner as in 5-3. At that time, the mass ratio of (1-chloroethyl) ethyl carbonate to diethyl carbonate was (1-chloroethyl) ethyl carbonate: diethyl carbonate = 5: 37.

  For the obtained secondary batteries of Examples 11-1, 12-1, 13-1, 14-1, and 15-1, the discharge capacity at the 50th cycle was the same as in Examples 1-1 to 1-3. The maintenance rate was determined. The results are shown in Tables 11-15. In addition, about the secondary battery of Example 14-1, charge was performed by making 4.5V into an upper limit.

  As can be seen from Tables 11 to 15, according to Examples 11-1, 12-1, 13-1, 14-1, and 15-1, a low-viscosity solvent obtained by mixing a small amount of the compound having the structure shown in Chemical Formula 4 The discharge capacity retention rate could be improved even in the same manner as in Examples 1-3, 2-3, 3-3, 4-3, and 5-3.

  That is, it was found that cycle characteristics can be improved even when a small amount of a compound having the structure shown in Chemical Formula 4 is mixed as a low viscosity solvent.

(Examples 16-1 to 16-5, 17-1 to 17-5)
In Examples 16-1 to 16-5, silicon was used as the negative electrode active material, and the negative electrode active material layer 52B made of silicon having a thickness of 5 μm was formed on the negative electrode current collector 52A made of copper foil having a thickness of 15 μm by the electron beam method. In the same manner as in Examples 1-1 to 1-3, except that the fluorinated dimethyl carbonate shown in Chemical Formula 7 was used as the compound having the structure shown in Chemical Formula 4 and a coin-type lithium ion was formed. A secondary battery was produced. At that time, in the electrolyte solution, lithium hexafluorophosphate was dissolved in a solvent obtained by mixing ethylene carbonate as a high dielectric constant solvent and a low-viscosity solvent at a mass ratio of 50:50 so as to be 1 mol / kg. What was done was used. Further, the low-viscosity solvents are fluorinated dimethyl carbonate shown in Chemical formula 7 (fluoromethyl) methyl carbonate shown in Chemical formula 12, bisfluoromethyl carbonate shown in Chemical formula 13, and carbonic acid (difluoromethyl carbonate shown in Chemical formula 14). ) Methyl and dimethyl carbonate, (fluoromethyl) methyl carbonate: bisfluoromethyl carbonate: methyl (difluoromethyl) carbonate: dimethyl carbonate = 3.6: 1.3: 0.1: 45, or 9.4: 3.2: 0.4: 37, or 13.1: 4.4: 0.5: 32, or 21.8: 7.4: 0.8: 20, or 26.9: 9.1: 1 It was mixed at a mass ratio of 0.0: 13. In addition, the fluorinated dimethyl carbonate shown in Chemical formula 7 in the solvent is 5% by mass, 13% by mass, 18% by mass, 30% by mass or 37% by mass.

  In Examples 17-1 to 17-5, an SnCoC-containing material was used as the negative electrode active material, this SnCoC-containing material, graphite as a conductive agent, and polyvinylidene fluoride as a binder were mixed, and N-methyl-2 -Pyrrolidone was added and uniformly applied to the negative electrode current collector 52A made of copper foil and dried to form the negative electrode active material layer 52B, and the compound having the structure shown in Chemical formula 4 was shown in Chemical formula 7 Other than using fluorinated dimethyl carbonate, coin type lithium ion secondary batteries were produced in the same manner as in Examples 1-1 to 1-3. At that time, the same electrolyte solution as in Examples 16-1 to 16-5 was used.

  In addition, as the SnCoC-containing material, tin / cobalt / indium / titanium alloy powder and carbon powder were mixed, and the SnCoC-containing material was synthesized using a mechanochemical reaction. When the composition of the obtained SnCoC-containing material was analyzed, the tin content was 48 mass%, the cobalt content was 23 mass%, the carbon content was 20 mass%, and the cobalt relative to the total of tin and cobalt The ratio Co / (Sn + Co) was 32.4% by mass. The carbon content was measured by a carbon / sulfur analyzer, and the tin and cobalt contents were measured by ICP (Inductively Coupled Plasma) emission analysis. Further, when X-ray diffraction was performed on the obtained SnCoC-containing material, a diffraction peak having a wide half-width with a diffraction angle 2θ of 1.0 ° or more was observed between the diffraction angle 2θ = 20 ° and 50 °. It was. Further, when XPS was performed on this SnCoC-containing material, a peak P1 was obtained as shown in FIG. When the peak P1 was analyzed, a peak P2 of surface contamination carbon and a peak P3 of C1s in the SnCoC-containing material on the lower energy side than the peak P2 were obtained. This peak P3 was obtained in a region lower than 284.5 eV. That is, it was confirmed that carbon in the SnCoC-containing material was bonded to other elements.

  As Comparative Examples 16-1 and 17-1 to Examples 16-1 to 16-5 and 17-1 to 17-5, except that the fluorinated dimethyl carbonate shown in Chemical Formula 7 was not used, that is, high dielectric The secondary solution was the same as in Examples 16-1 and 17-1, except that a solvent obtained by mixing ethylene carbonate as a low-rate solvent and dimethyl carbonate as a low viscosity solvent at a mass ratio of 50:50 was used. A battery was produced.

  The obtained secondary batteries of Examples 16-1 to 16-5, 17-1 to 17-5 and Comparative Examples 16-1 and 17-1 were also the same as in Examples 1-1 to 1-3. The discharge capacity retention rate at the 50th cycle was determined. The results are shown in Tables 16 and 17 and FIGS.

  As can be seen from Tables 16 and 17 and FIGS. 6 and 7, the discharge capacity retention rate increases as the content of fluorinated dimethyl carbonate shown in Chemical Formula 7 in the solvent increases, decreases after showing a maximum value. A trend was observed.

  That is, it was found that the cycle characteristics can be improved even when fluorinated dimethyl carbonate shown in Chemical formula 7 is used, and it is preferable that the content in the solvent is 5 mass% or more and 30 mass% or less.

(Examples 18-1 to 18-4, 19-1 to 19-4)
In Examples 18-1 and 19-1, except that lithium trifluoromethyltrifluoroborate (LiB (CF ₃ ) F ₃ ), which is a lithium borate salt, was used instead of lithium hexafluorophosphate. Other than that, secondary batteries were fabricated in the same manner as in Examples 16-2 and 17-2.

In Examples 18-2 and 19-2, in addition to lithium hexafluorophosphate, bis (trifluoromethanesulfonyl) imide lithium (CF ₃ SO ₂ ) ₂ NLi) which is an imide lithium salt was used, Otherwise, secondary batteries were fabricated in the same manner as in Examples 16-2 and 17-2. The content of bis (trifluoromethanesulfonyl) imide lithium in the electrolytic solution was set to 1% by mass. In Examples 18-3 and 19-3, in addition to lithium hexafluorophosphate, 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimide which is an imide lithium salt A secondary battery was fabricated in the same manner as in Examples 16-2 and 17-2, except that lithium was used. The content of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonimidolithium in the electrolytic solution was 1% by mass.

  Furthermore, in Examples 18-4 and 19-4, in addition to ethylene carbonate as a high dielectric constant solvent, except that 1,3-dioxol-2-one, which is a cyclic carbonate of an unsaturated compound, was used, Otherwise, secondary batteries were fabricated in the same manner as in Examples 16-2 and 17-2. Ethylene carbonate and 1,3-dioxol-2-one are mixed at a mass ratio of ethylene carbonate: 1,3-dioxol-2-one = 49: 1, and the ratio of the high dielectric constant solvent in the solvent is 50% by mass. It was.

  For the obtained secondary batteries of Examples 18-1 to 18-4 and 19-1 to 19-4, the discharge capacity maintenance ratio at the 50th cycle was obtained in the same manner as in Examples 1-1 to 1-3. It was. The results are shown in Tables 18 and 19.

  As can be seen from Tables 18 and 19, according to Examples 18-1 and 19-1 using lithium trifluoromethyltrifluoroborate, compared to Examples 16-2 and 17-2 not using this, The discharge capacity retention rate improved. Further, in addition to lithium hexafluorophosphate, Examples 18-2 and 19-2 using bis (trifluoromethanesulfonyl) imide lithium, or in addition to lithium hexafluorophosphate, 1,1,2, According to Examples 18-3 and 19-3 using lithium 2,3,3-hexafluoropropane-1,3-disulfonimido, Examples 16-2 and 17 using only lithium hexafluorophosphate As compared with -2, the discharge capacity retention rate improved. Furthermore, according to Examples 18-4 and 19-4 using 1,3-dioxol-2-one, the discharge capacity retention rates were respectively higher than those of Examples 16-2 and 17-2 not using this. Improved.

  That is, it has been found preferable to use a cyclic carbonate, lithium borate or imide lithium salt of an unsaturated compound.

Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, a coin-type secondary battery and a wound-structure secondary battery have been specifically described. However, the present invention is not limited to a square-type, sheet-type or card-type, or The present invention can be similarly applied to a secondary battery having a stacked structure in which a plurality of positive electrodes and negative electrodes are stacked .

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

It is sectional drawing showing the structure of the secondary battery which concerns on 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 secondary battery which concerns on other 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 secondary battery produced in the Example. 1 shows an example of a peak obtained by X-ray photoelectron spectroscopy relating to a SnCoC-containing material produced in an example. It is a characteristic view showing the relationship between the content of fluorinated dimethyl carbonate shown in Chemical formula 7 in the solvent and the discharge capacity retention rate. It is another characteristic view showing the relationship between the content of fluorinated dimethyl carbonate shown in Chemical formula 7 in the solvent and the discharge capacity retention rate.

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, 56 ... Gasket, 20, 30 ... Winding electrode body, 21 , 33, 51 ... positive electrode, 21A, 33A, 51A ... positive electrode current collector, 21B, 33B, 51B ... positive electrode active material layer, 22, 34, 52 ... negative electrode, 22A, 34A, 52A ... negative electrode current collector, 22B, 34B, 52B ... negative electrode active material layer, 23, 35, 53 ... separator, 24 ... center pin, 25, 31 ... positive electrode lead, 26, 32 ... negative electrode lead, 36 ... electrolyte layer, 37 ... protective tape, 40 ... exterior member 41 ... Adhesion film, 54 ... Exterior can, 55 ... Exterior cup

Claims (20)

An electrolyte for a lithium ion secondary battery, comprising a solvent containing at least one member selected from the group consisting of a chain carbonate derivative shown in Chemical Formula 2 and a chain carboxylate derivative shown in Chemical Formula 3 .

(In the formula, X1 represents chlorine. R1, R2, and R3 each represents hydrogen, fluorine, chlorine, or an alkyl group having 1 to 4 carbon atoms or a group in which at least part of hydrogen is substituted with fluorine or chlorine. To express.)

(In the formula, X2 represents fluorine or chlorine. R4, R5, and R6 each represents hydrogen, fluorine, chlorine, an alkyl group having 1 to 4 carbon atoms, or at least part of hydrogen substituted with fluorine or chlorine. Represents a group.) The chain carbonic ester derivatives and the chain carboxylic acid ester derivative having a branched structure, according to claim 1 for a lithium ion secondary battery electrolyte according. The chain carbonic acid ester derivatives shown in Chemical Formula 2 are (chloromethyl) methyl carbonate, (chloromethyl) ethyl carbonate, (chloromethyl) propyl carbonate, (chloromethyl) isopropyl carbonate, di (chloromethyl) carbonate, carbonic acid ( 1-chloroethyl) methyl, (1-chloroethyl) ethyl carbonate, (1-chloroethyl) propyl carbonate, (1-chloroethyl) isopropyl carbonate, di (1-chloroethyl) carbonate, (1-chloropropyl) methyl carbonate, carbonate (1 -Chloropropyl) ethyl, (1-chloropropyl) propyl carbonate, (1-chloropropyl) isopropyl carbonate, di (1-chloropropyl) carbonate, (2-chloro-2-propyl) methyl carbonate, (2-chloro) -2-propyl) ethyl, carbonic acid (2-chloro-2-propyl) propyl, carbonic acid (2-chloro-2) Comprises at least one selected from the group consisting of propyl) isopropyl, and di (2-chloro-2-propyl)
The chain carboxylic acid ester derivatives shown in Chemical Formula 3 are fluoromethyl acetate, 1-fluoroethyl acetate, 1-fluoropropyl acetate, 2-fluoro-2-propyl acetate, fluoromethyl propionate, 1-fluoroethyl propionate. 1-fluoropropyl propionate, 2-fluoro-2-propyl propionate, fluoromethyl butyrate, 1-fluoroethyl butyrate, fluoromethyl isobutyrate, 1-fluoroethyl isobutyrate, fluoromethyl pivalate, 1-fluoro pivalate Ethyl, fluoromethyl trifluoroacetate, 1-fluoroethyl trifluoroacetate, 1-fluoropropyl trifluoroacetate, 2-fluoro-2-propyl trifluoroacetate, chloromethyl acetate, 1-chloroethyl acetate, 1-chloropropyl acetate, 2-chloro-acetic acid -Propyl, chloromethyl propionate, 1-chloroethyl propionate, 1-chloropropyl propionate, 2-chloro-2-propyl propionate, chloromethyl butyrate, 1-chloroethyl butyrate, chloromethyl isobutyrate, 1-chloroethyl isobutyrate Chloromethyl pivalate, 1-chloroethyl pivalate, chloromethyl trifluoroacetate, 1-chloroethyl trifluoroacetate, 1-chloropropyl trifluoroacetate, and 2-chloro-2-propyl trifluoroacetate including,
The electrolyte for lithium ion secondary batteries according to claim 1. Containing a solvent containing at least one member selected from the group consisting of (1-chloroethyl) ethyl carbonate shown in Chemical Formula 4, (1-chloroethyl) isopropyl carbonate shown in Chemical Formula 5 and chloromethyl pivalate shown in Chemical Formula 6 to claim 1 for a lithium ion secondary battery electrolyte according.

Further comprises a solvent containing a cyclic carbonate derivative having halogen atom, according to claim 1 for a lithium ion secondary battery electrolyte according. Of 7 containing fluorinated solvent containing dimethyl carbonate as shown in, the content of the fluorinated dimethyl carbonate in the solvent is less than 5% by weight to 30% by weight, the lithium ion secondary battery according to claim 1, wherein For electrolyte.

(In the formula, m and n are 0, 1 or 2, and at least one of m and n is 1 or 2.) Of 8 illustrates carbonate (fluoromethyl) methyl, contains a solvent comprising at least one selected from the group consisting of carbonate (difluoromethyl) methyl illustrated in carbonate bisfluoromethyl and reduction 10 shown in Chemical formula 9, wherein Item 2. The electrolyte for a lithium ion secondary battery according to Item 1.

Furthermore, at least one including, claim 1 for a lithium ion secondary battery electrolyte according of lithium borate and imide salts. Further comprises a solvent containing a cyclic carbonate of the unsaturated compound, according to claim 1 for a lithium ion secondary battery electrolyte according. An electrolyte is provided with a positive electrode and a negative electrode ,
The electrolyte contains a solvent containing at least one member selected from the group consisting of a chain carbonate derivative shown in Chemical formula 12 and a chain carboxylate derivative shown in Chemical formula 13 ,
Lithium ion secondary battery.

(In the formula, X1 represents chlorine. R1, R2, and R3 each represents hydrogen, fluorine, chlorine, or an alkyl group having 1 to 4 carbon atoms or a group in which at least part of hydrogen is substituted with fluorine or chlorine. To express.)

(In the formula, X2 represents fluorine or chlorine. R4, R5, and R6 each represents hydrogen, fluorine, chlorine, an alkyl group having 1 to 4 carbon atoms, or at least part of hydrogen substituted with fluorine or chlorine. Represents a group.) The lithium ion secondary battery according to claim 10 , wherein the chain carbonic acid ester derivative and the chain carbonic acid ester derivative have a branched structure. The chain carbonate derivatives shown in Chemical Formula 12 are (chloromethyl) methyl carbonate, (chloromethyl) ethyl carbonate, (chloromethyl) propyl carbonate, (chloromethyl) isopropyl carbonate, di (chloromethyl) carbonate, carbonic acid ( 1-chloroethyl) methyl, (1-chloroethyl) ethyl carbonate, (1-chloroethyl) propyl carbonate, (1-chloroethyl) isopropyl carbonate, di (1-chloroethyl) carbonate, (1-chloropropyl) methyl carbonate, carbonate (1 -Chloropropyl) ethyl, (1-chloropropyl) propyl carbonate, (1-chloropropyl) isopropyl carbonate, di (1-chloropropyl) carbonate, (2-chloro-2-propyl) methyl carbonate, (2-chloro) -2-propyl) ethyl, carbonic acid (2-chloro-2-propyl) propyl, carbonic acid (2-chloro- - propyl) comprises isopropyl, and at least one selected from the group consisting of di (2-chloro-2-propyl)
The chain carboxylic acid ester derivatives shown in Chemical Formula 13 are fluoromethyl acetate, 1-fluoroethyl acetate, 1-fluoropropyl acetate, 2-fluoro-2-propyl acetate, fluoromethyl propionate, 1-fluoroethyl propionate. 1-fluoropropyl propionate, 2-fluoro-2-propyl propionate, fluoromethyl butyrate, 1-fluoroethyl butyrate, fluoromethyl isobutyrate, 1-fluoroethyl isobutyrate, fluoromethyl pivalate, 1-fluoro pivalate Ethyl, fluoromethyl trifluoroacetate, 1-fluoroethyl trifluoroacetate, 1-fluoropropyl trifluoroacetate, 2-fluoro-2-propyl trifluoroacetate, chloromethyl acetate, 1-chloroethyl acetate, 1-chloropropyl acetate, 2-chloroacetate 2-propyl, chloromethyl propionate, 1-chloroethyl propionate, 1-chloropropyl propionate, 2-chloro-2-propyl propionate, chloromethyl butyrate, 1-chloroethyl butyrate, chloromethyl isobutyrate, 1-isobutyrate At least one of chloroethyl, chloromethyl pivalate, 1-chloroethyl pivalate, chloromethyl trifluoroacetate, 1-chloroethyl trifluoroacetate, 1-chloropropyl trifluoroacetate, and 2-chloro-2-propyl trifluoroacetate Including species,
The lithium ion secondary battery according to claim 10. The electrolyte includes at least one selected from the group consisting of (1-chloroethyl) ethyl carbonate shown in Chemical formula 14, (1-chloroethyl) isopropyl carbonate shown in Chemical formula 15, and chloromethyl pivalate shown in Chemical formula 16. containing solvent containing a lithium ion secondary battery according to claim 10, wherein.

The lithium ion secondary battery according to claim 10 , wherein the electrolyte further contains a solvent containing a cyclic carbonate derivative having a halogen atom. 11. The lithium according to claim 10 , wherein the electrolyte contains a solvent containing fluorinated dimethyl carbonate shown in Chemical Formula 17, and the content of the fluorinated dimethyl carbonate in the solvent is 5% by mass or more and 30% by mass or less. Ion secondary battery.

(In the formula, m and n are 0, 1 or 2, and at least one of m and n is 1 or 2.) The electrolyte includes a solvent containing at least one member selected from the group consisting of (fluoromethyl) methyl carbonate shown in Chemical formula 18, bisfluoromethyl carbonate shown in Chemical formula 19 and (difluoromethyl) methyl carbonate shown in Chemical formula 20. containing lithium ion secondary battery according to claim 10, wherein.

The lithium ion secondary battery according to claim 10 , wherein the electrolyte further includes at least one of a lithium borate salt and an imide lithium salt. Further comprises a solvent containing a cyclic carbonate of the unsaturated compound, a lithium ion secondary battery according to claim 10, wherein. The negative electrode is capable of storing and releasing lithium ions, containing a negative electrode material containing at least one of metal elements and metalloid elements as an element, a lithium ion secondary battery according to claim 10, wherein . The negative electrode of silicon (Si) and at least one of which contains a material containing as a constituent element, a lithium ion secondary battery according to claim 10, wherein one of tin (Sn).

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