JP2006318760A - Electrolyte and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte capable of enhancing cycle characteristics by enhancing charge/discharge efficiency and to provide a battery. <P>SOLUTION: A separator 23 is impregnated with the electrolyte. The electrolyte contains a cyclic carbonate derivative having halogen atoms, such as 4-fluoro-1,3-dioxolane-2-one or 4-chloro-1,3-dioxolane-2-one, and lactone such as ε-caprolactone or δ-caprolactone. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrolytic solution containing a cyclic carbonate derivative having a halogen atom and a battery using the same.

  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 maintain a relatively large discharge capacity without pulverization of the negative electrode active material 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 (Li) are highly active, the use of carbonates or the like that have been used in the electrolyte solution will cause them to be decomposed, and lithium is inactivated. There was a problem that. Therefore, it has been studied to suppress the decomposition reaction of the solvent in the negative electrode and improve the charge / discharge efficiency by using a cyclic carbonate derivative having a halogen atom in the electrolytic solution. However, the effect of suppressing the decomposition reaction of the electrolytic solution is not sufficient, and further improvement in charge / discharge efficiency has been desired.

  This invention is made | formed in view of this problem, The objective is to provide the battery which can improve cycling characteristics by improving charging / discharging efficiency, and the electrolyte solution used therewith.

  The electrolytic solution according to the present invention contains a cyclic carbonate derivative having a halogen atom and a lactone.

  A battery according to the present invention includes an electrolyte solution together with a positive electrode and a negative electrode, and the negative electrode can occlude and release an electrode reactant, and at least one of a metal element and a metalloid element as a constituent element. The electrolyte contains a material containing one kind, and the electrolytic solution contains a cyclic carbonate derivative having a halogen atom and a lactone.

  According to the electrolytic solution of the present invention, since the cyclic carbonate derivative having a halogen atom and the lactone are included, the stability of the electrolytic solution can be improved. Therefore, according to the battery of the present invention using this electrolytic solution, the charge / discharge efficiency can be improved and the cycle characteristics can be improved.

  In particular, as a lactone, a compound having a 4-membered lactone ring, a compound having a 6-membered lactone ring, a compound having a 7-membered lactone ring, or a compound having a double bond in the lactone ring may be used. High effects can be obtained.

  Further, if the lactone content in the electrolytic solution is in the range of 0.1% by mass or more and 2% by mass or less, a higher effect can be obtained.

  Furthermore, it is possible to occlude and release electrode reactants in the negative electrode, and when containing a material containing at least one of a metal element and a metalloid element as a constituent element, or tin and silicon as constituent elements A particularly high effect can be obtained when the negative electrode material containing at least one of them is contained.

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

  The electrolytic solution according to an embodiment of the present invention includes, for example, a solvent and an electrolyte salt dissolved in the solvent.

  The solvent contains a high dielectric constant solvent having a relative dielectric constant of 30 or more. This is because the number of lithium ions can be increased.

  The high dielectric constant solvent contains a cyclic carbonate derivative having a halogen atom. This is because the decomposition reaction of the electrolytic solution can be suppressed and the stability can be improved. Specific examples of such cyclic carbonate derivatives include 4-fluoro-1,3-dioxolan-2-one and 4-difluoro-1,3-dioxolane-2 shown in Chemical Formula 1 (1). -One, 4,5-difluoro-1,3-dioxolan-2-one, 4-difluoro-5-fluoro-1,3-dioxolan-2-one, 4-fluoromethyl-1,3-dioxolane-2- ON, 4-trifluoromethyl-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one shown in Chemical formula 2 (2) or 4,5-dichloro-1,3- Examples include dioxolan-2-one, among which 4-fluoro-1,3-dioxolan-2-one or 4-chloro-1,3-dioxolan-2-one is preferable, and 4-fluoro-1,3 is particularly preferable. Dioxolan-2-one is desirable. This is because a higher effect can be obtained. One kind of cyclic carbonate derivative may be used alone, or a plurality of kinds may be mixed and used.

  In addition to these cyclic carbonate derivatives, other high dielectric constant solvents may be mixed and used as the high dielectric constant solvent. Other high dielectric constant solvents include, for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate or vinyl ethylene carbonate, lactams such as N-methyl-2-pyrrolidone, N-methyl-2- Examples thereof include cyclic carbamates such as oxazolidinone and sulfone compounds such as tetramethylene sulfone. As other high dielectric constant solvents, one kind may be used alone, or a plurality of kinds may be mixed and used.

  Moreover, it is preferable to mix and use a low-viscosity solvent having a viscosity of 1 mPa · s or less as the high dielectric constant solvent. This is because high ion conductivity can be obtained. Examples of the low viscosity solvent include chain carbonate esters such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate or trimethyl. A chain carboxylic acid ester such as ethyl acetate; a chain amide such as N, N-dimethylacetamide; a chain carbamic acid ester such as methyl N, N-diethylcarbamate or ethyl N, N-diethylcarbamate; -Ethers such as dimethoxyethane, tetrahydrofuran, tetrahydropyran or 1,3-dioxolane. One low viscosity solvent may be used alone, or a plurality of low viscosity solvents may be mixed and used.

As the electrolyte salt, e.g., lithium hexafluorophosphate (LiPF _6), lithium tetrafluoroborate (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium hexafluoro antimonate (LiSbF ₆₎ , Inorganic lithium salts such as lithium perchlorate (LiClO ₄ ), lithium tetrachloroaluminate (LiAlCl ₄ ), lithium trifluoromethanesulfonate (CF ₃ SO ₃ Li), lithium bis (trifluoromethanesulfone) imide ((CF ₃ SO ₂ ) ₂ NLi), lithium bis (pentafluoroethanesulfone) imide ((C ₂ F ₅ SO ₂ ) ₂ NLi), lithium tris (trifluoromethanesulfone) methide ((CF ₃ SO ₂ ) ₃ CLi), etc. Examples thereof include lithium lithium salts of fluoroalkanesulfonic acid derivatives. One electrolyte salt may be used alone, or a plurality of electrolyte salts may be mixed and used.

  This electrolytic solution further contains a lactone as an additive. This is because the decomposition reaction of the electrolytic solution can be further suppressed, and the stability can be further improved.

  Examples of such a lactone include the compound shown in Chemical Formula 2 or the compound shown in Chemical Formula 3.

（式中、Ｒ１は、Ｃ_m Ｈ_2m-nＦ_n 、Ｃ_p Ｈ_2p-q-2Ｆ_q 、またはＣ_r Ｈ_2r-s-4Ｆ_s を表す。ｍ，ｎ，ｐ，ｑ，ｒ，ｓは、１≦ｍ≦５，０≦ｎ≦２ｍ，２≦ｐ≦５，０≦ｑ≦２ｐ−２，３≦ｒ≦５，０≦ｓ≦２ｒ−４の範囲内の整数を表す。）

(Wherein, R1 _{is, C m H 2m-n F} n, C p H 2p-q-2 F q or .m representing the _{C r H 2r-s-4} F s,, n, p, q, r , S represents an integer in the range of 1≤m≤5, 0≤n≤2m, 2≤p≤5, 0≤q≤2p-2, 3≤r≤5, 0≤s≤2r-4. .)

（式中、Ｒ２は、Ｃ_t Ｈ_2t-uＦ_u 、Ｃ_v Ｈ_2v-w-2Ｆ_w 、またはＣ_x Ｈ_2x-y-4Ｆ_y を表す。ｔ，ｕ，ｖ，ｗ，ｘ，ｙは、０≦ｔ≦４，０≦ｕ≦２ｔ，１≦ｖ≦４，０≦ｗ≦２ｖ−２，２≦ｘ≦４，０≦ｙ≦２ｘ−４の範囲内の整数を表す。）

(Wherein, R2 _{is, C t H 2t-u F} u, C v H 2v-w-2 F w or .t representing the _{C x H 2x-y-4} F y,, u, v, w, x , Y represents an integer in the range of 0≤t≤4, 0≤u≤2t, 1≤v≤4, 0≤w≤2v-2, 2≤x≤4, 0≤y≤2x-4. .)

  For example, β-propiolactone shown in Chemical formula 4 (1), β-butyrolactone shown in Chemical formula 4 (2), diketene shown in Chemical formula 4 (3), Chemical formula 4 (4) Γ-butyrolactone shown, γ-valerolactone shown in chemical formula 4 (5), γ-crotonolactone shown in chemical formula 4 (6), 2-coumaranone shown in chemical formula 4 (7), chemical formula 4 (8) Phthalide shown in Chemical Formula 4 (9), δ-valerolactone shown in Chemical Formula 4 (9), δ-caprolactone shown in Chemical Formula 4 (10), α-pyrone shown in Chemical Formula 4 (11), chemical formula 4 (12) There are derivatives such as coumarin, 3,4-dihydrocoumarin shown in Chemical formula 4 (13), ε-caprolactone shown in Chemical formula 4 (14), or alkyl-substituted products thereof.

  Among them, compounds having a 4-membered lactone ring such as β-propiolactone, β-butyrolactone or diketene (β-lactone), δ-valerolactone, δ-caprolactone, α-pyrone, coumarin or 3,4- A compound having a 6-membered lactone ring such as dihydrocoumarin (δ-lactone), a compound having a 7-membered lactone ring such as ε-caprolactone (ε-lactone), or a double such as γ-crotonolactone A compound having a bond in the lactone ring is preferred. This is because the stability of the electrolytic solution can be further improved. Note that the lactone ring refers to a ring having —CO—O—.

  The content of these lactones is preferably in the range of 0.1% by mass to 2% by mass. This is because the stability of the electrolytic solution is particularly improved within this range.

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

(First secondary battery)
FIG. 1 shows a cross-sectional configuration of a first secondary battery using the electrolytic solution according to the present embodiment. This secondary battery is a so-called cylindrical type, and a wound electrode body 20 in which a belt-like positive electrode 21 and a negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. have. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12, 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 of the positive electrode current collector 21A. The positive electrode current collector 21A is made of a metal material such as aluminum, nickel, or stainless steel, for example. The positive electrode active material layer 21B includes, for example, any one or more of positive electrode materials capable of occluding and releasing lithium, which is an electrode reactant, as a positive electrode active material. A conductive agent and a binder such as polyvinylidene fluoride may be included.

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 f Co g Mn} h) O 2)) (f, g and h Is 0 <f <1, 0 <g <1, 0 <h <1, f + g + h = 1), or manganese spinel (LiMn ₂ O ₄ ) or its solid solution (Li (Mn _2−z Ni _z). Lithium composite oxides such as) O ₄ ) (the value of z is z <2) or phosphate compounds having an olivine structure such as lithium iron phosphate (LiFePO ₄ ) are preferred. This is because a high energy density can be obtained. Examples of positive electrode materials capable of occluding and releasing lithium include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as iron disulfide, titanium disulfide and molybdenum sulfide, sulfur, Examples thereof include conductive polymers such as polyaniline and polythiophene.

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

  The negative electrode active material layer 22B includes, for example, one or more negative electrode materials capable of inserting and extracting lithium as an electrode reactant as a negative electrode active material. Examples of the negative electrode material capable of inserting and extracting lithium include a material containing tin or silicon as a constituent element. This is because tin and silicon have a large ability to occlude and release lithium, and a high energy density can be obtained.

  As such a negative electrode material, specifically, a simple substance, an alloy, or a compound of tin, a simple substance, an alloy, or a compound of silicon, or a material having one or more phases thereof at least in part. Is mentioned. 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.

  As an alloy of tin, for example, as the second constituent element other than tin, silicon, nickel, copper, iron, cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver (Ag) , Titanium (Ti), germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr). As an alloy of silicon, for example, as a second constituent element other than silicon, among the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing containing at least 1 sort (s) of these is mentioned.

  Examples of the tin compound or silicon compound include those containing oxygen (O) or carbon (C), and may contain the second constituent element described above in addition to tin or silicon.

  Among these, 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 CoSnC-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 CoSnC-containing material may further contain other constituent elements as necessary. As other constituent elements, for example, silicon, iron, nickel, chromium, indium, niobium (Nb), germanium, titanium, molybdenum (Mo), aluminum, phosphorus (P), gallium (Ga) or bismuth is preferable. It may contain more than seeds. This is because the capacity or cycle characteristics can be further improved.

  This CoSnC-containing material has a phase containing tin, cobalt, and carbon, and this phase preferably has a low crystallinity or an amorphous structure. 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 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 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).

  As a negative electrode material capable of inserting and extracting lithium, for example, a material containing another metal element or other metalloid element capable of forming an alloy with lithium as a constituent element can also be used. Such metal elements or metalloid elements include magnesium (Mg), boron (B), aluminum, gallium, indium, germanium, lead (Pb), bismuth, cadmium (Cd), silver, zinc, hafnium (Hf). , Zirconium (Zr), yttrium (Y), palladium (Pd), or platinum (Pt).

  As a negative electrode material capable of inserting and extracting lithium, for example, a carbon material such as graphite, non-graphitizable carbon, or graphitizable carbon may be used. The negative electrode material may be used together. The carbon material has very little change in crystal structure due to insertion and extraction of lithium. For example, when used together with the negative electrode material described above, a high energy density and excellent cycle characteristics can be obtained. It is also preferable because it functions as a conductive agent.

  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.

  The separator 23 is impregnated with the electrolytic solution according to the present embodiment. Thereby, a favorable film is formed on the surface of the electrode, and decomposition of the electrolytic solution is suppressed. In particular, a compound having a 4-membered lactone ring, a compound having a 6-membered lactone ring, a compound having a 7-membered lactone ring or a compound having a double bond in the lactone ring has high reactivity. Furthermore, since a favorable film can be formed, it is preferable.

  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 active material powder, a conductive agent, and a binder to prepare a positive electrode mixture, and then using the positive electrode mixture in a solvent such as N-methyl-2-pyrrolidone. The positive electrode mixture slurry is dispersed to form a positive electrode mixture slurry, and the positive electrode mixture slurry is applied to the positive electrode current collector 21A, dried, and compression molded. Further, for example, in the same manner as the positive electrode 21, the negative electrode active material layer 22 </ b> B is formed on the negative electrode current collector 22 </ b> A to produce the negative electrode 22.

  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 FIGS. 1 and 2 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 contains a cyclic carbonate derivative having a halogen atom and a lactone, a good film is formed on the surface of the electrode, and the decomposition reaction of the electrolytic solution is suppressed.

  As described above, according to the present embodiment, since the electrolytic solution includes the cyclic carbonate derivative having a halogen atom and the lactone, the charge / discharge efficiency can be improved and the cycle characteristics can be improved. Can do.

  In particular, as a lactone, a compound having a 4-membered lactone ring, a compound having a 6-membered lactone ring, a compound having a 7-membered lactone ring, or a compound having a double bond in the lactone ring may be used. High effects can be obtained.

  Further, if the lactone content in the electrolytic solution is in the range of 0.1% by mass or more and 2% by mass or less, a higher effect can be obtained.

  Furthermore, it is possible to occlude and release the electrode reactant in the negative electrode 22, and when containing a material containing at least one of a metal element and a metalloid element as a constituent element, or as a constituent element, tin and A particularly high effect can be obtained when a negative electrode material containing at least one of silicon is contained.

(Secondary secondary battery)
The second secondary battery has the same configuration and operation as the first secondary battery except that the configuration of the negative electrode is different, and can be manufactured in the same manner. 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.

  Similar to the first secondary battery, 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 contains, for example, a negative electrode active material containing tin or silicon as a constituent element. Specifically, for example, it contains a simple substance, an alloy, or a compound of tin, or a simple substance, an alloy, or a compound of silicon, 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 thermal spraying method, a firing method, or two or more of these methods. The electrical conductor 22A is preferably alloyed at least at a part of the interface. 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. . The firing method is, for example, a method in which a particulate negative electrode active material is mixed with a binder or the like, dispersed in a solvent, applied, and then heat-treated at a temperature higher than the melting point of the binder or the like. .

(Third secondary battery)
FIG. 3 shows the configuration of the third secondary battery. This secondary battery is a so-called laminate film type, and has a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached accommodated in a film-shaped exterior member 40.

  The positive electrode lead 31 and the negative electrode lead 32 are led out 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 electrode winding body 30 is obtained by laminating a positive electrode 33 and a negative electrode 34 via a separator 35 and an electrolyte layer 36 and winding them, and the outermost periphery 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 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 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. 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 the same as those in the first or second secondary battery described above. This is the same as the material layer 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution according to the present embodiment and a polymer compound that serves as a holding body that holds the electrolytic solution, and has a so-called gel shape. A gel electrolyte is preferable because high ion conductivity can be obtained and battery leakage can be prevented. Examples of the polymer compound include polyethylene polymer or an ether polymer compound such as 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, a precursor solution containing an electrolytic solution, 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 the electrolyte layer 36. Next, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A. Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are laminated via a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and the protective tape 37 is attached to the outermost peripheral portion. The wound electrode body 30 is formed by bonding. After that, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edge portions of the exterior members 40 are sealed and sealed by thermal fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  Further, 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 Then, the opening of the exterior member 40 is heat-sealed and sealed. Thereafter, heat is applied to polymerize the monomer to obtain a polymer compound, thereby forming the gel electrolyte layer 36, and assembling the secondary battery shown in FIGS.

  The operation and effect of this secondary battery are the same as those of the first or second secondary battery described above.

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

(Examples 1-1 to 1-15)
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, 94 parts by mass of lithium cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 3 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed, and then N-methyl as a solvent. -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.

  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. The electrolytic solution includes a cyclic carbonate derivative having a halogen atom as a high dielectric constant solvent, dimethyl carbonate as a low viscosity solvent, lithium hexafluorophosphate as an electrolyte salt, and a cyclic carbonate derivative: dimethyl carbonate: six Lithium fluorophosphate was mixed at a mass ratio of 42:42:16, and lactone was further added as an additive. At that time, the content of lactone in the electrolytic solution was set to 1% by mass. Further, the cyclic carbonate derivative is 4-chloro-1,3-dioxolan-2-one in Example 1-1, and 4-fluoro-1,3-diene in Examples 1-2 to 1-15. Dioxolan-2-one was used. Further, in Examples 1-1 and 1-2, the lactone is ε-caprolactone shown in Chemical Formula 4 (14), and in Example 1-3, δ-valerolactone shown in Chemical Formula 4 (9) is used. -4 is δ-caprolactone shown in Chemical Formula 4 (10), Example 1-5 is β-propiolactone shown in Chemical Formula 4 (1), and Example 1-6 is shown in Chemical Formula 4 (2). Β-butyrolactone, diketene represented by Chemical Formula 4 (3) in Example 1-7, γ-crotonolactone represented by Chemical Formula 4 (6) in Example 1-8, and in Example 1-9 2-coumaranone shown in Chemical formula 4 (7), phthalide shown in Chemical formula 4 (8) in Example 1-10, and α-pyrone shown in Chemical formula 4 (11) in Example 1-11 In Example 1-12, the coumarin shown in Chemical Formula 4 (12) was used. In Example 1-13, Chemical Formula 4 (13) was used. And was 3,4-dihydro coumarin, and γ- butyrolactone shown in Example 1-14 In Chemical formula 4 (4), and a γ- valerolactone shown in Examples 1-15 in of 4 (5).

  As Comparative Example 1-1 with respect to Examples 1-1 to 1-15, except that the high dielectric constant solvent was ethylene carbonate and the additive was ε-caprolactone, the others were the same as those of Examples 1-1 to 1-15. Similarly, a secondary battery was produced. Further, as Comparative Example 1-2, a secondary battery was fabricated in the same manner as in Examples 1-1 to 1-15 except that the high dielectric constant solvent was ethylene carbonate and the additive was not added. . Furthermore, as Comparative Examples 1-3 and 1-4, the high dielectric constant solvent was 4-chloro-1,3-dioxolan-2-one or 4-fluoro-1,3-dioxolan-2-one, and the additive was A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-15, except that the addition was not performed.

  For the obtained secondary batteries of Examples 1-1 to 1-15 and Comparative examples 1-1 to 1-4, the battery was charged at 1.77 mA with 4.2 V as the upper limit for 12 hours, and then rested 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 results are shown in Table 1.

  As can be seen from Table 1, Examples 1-1 and 1 using 4-chloro-1,3-dioxolan-2-one or 4-fluoro-1,3-dioxolan-2-one and ε-caprolactone were used. -2 improves the discharge capacity retention rate over Comparative Example 1-1 in which 4-chloro-1,3-dioxolan-2-one or 4-fluoro-1,3-dioxolan-2-one was not used. did. In addition, the discharge capacity retention ratio was improved as compared with Comparative Examples 1-3 and 1-4 in which ε-caprolactone was not used. Furthermore, the discharge capacity retention rate was dramatically improved over Comparative Example 1-2 in which neither of these was used. In addition, in Examples 1-3 to 1-15 using other lactones, the discharge capacity retention rate was improved similarly to Example 1-2, and in particular, ε-caprolactone, δ-valerolactone, δ- High values were obtained when caprolactone, β-propiolactone, β-butyrolactone, diketene, γ-crotonolactone, α-pyrone, coumarin or 3,4-dihydrocoumarin were used.

  That is, if the electrolytic solution contains a cyclic carbonate derivative having a halogen atom and a lactone, the cycle characteristics can be improved. Particularly, a compound having a 4-membered lactone ring as the lactone, 6-membered It has been found that it is preferable to use a compound having a ring lactone ring, a compound having a 7-membered lactone ring, or a compound having a double bond in the lactone ring.

(Examples 2-1 to 2-15, 3-1 to 3-15)
As Examples 2-1 to 2-15, tin is used as the negative electrode active material, and the negative electrode active material layer 52B made of tin having a thickness of 5 μm is formed on the negative electrode current collector 52A made of copper foil having a thickness of 15 μm by vapor deposition. Otherwise, coin-type secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-15.

  As Examples 3-1 to 3-15, using a CoSnC-containing material powder containing indium and titanium as a negative electrode active material, 94 parts by mass of this CoSnC-containing material powder, 3 parts by mass of graphite as a conductive agent, and a binder 3 parts by weight of polyvinylidene fluoride as a solvent is dispersed in N-methyl-2-pyrrolidone as a solvent, and then uniformly applied to a negative electrode current collector 52A made of a copper foil having a thickness of 15 μm and dried to obtain a negative electrode active having a thickness of 70 μm. A coin-type secondary battery was fabricated in the same manner as in Examples 1-1 to 1-15 except that the material layer 52B was formed.

  At that time, the CoSnC-containing material powder was synthesized by mixing a tin-cobalt-indium-titanium alloy powder and a carbon powder and utilizing a mechanochemical reaction. When the composition of the obtained CoSnC-containing material was analyzed, the tin content was 48.0% by mass, the cobalt content was 23.0% by mass, the indium content was 5.0% by mass, The content was 2.0% by mass, the carbon content was 20.0% by mass, and the ratio Co / (Sn + Co) of cobalt to the total of tin and cobalt was 32% by mass. The carbon content was measured by a carbon / sulfur analyzer, and the contents of tin, cobalt, indium and titanium were measured by ICP (Inductively Coupled Plasma) emission analysis. Further, when X-ray diffraction was performed on the obtained CoSnC-containing material, a diffraction peak having a wide half-width with a diffraction angle 2θ of 1.0 ° or more was observed between diffraction angles 2θ = 20 ° to 50 °. It was. Further, when XPS was performed on the CoSnC-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 CoSnC-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 CoSnC-containing material was bonded to other elements.

  As Comparative Examples 2-1 to 2-4 and 3-1 to 3-4 with respect to these Examples, Example 2 was otherwise used except that the same electrolytic solution as Comparative Examples 1-1 to 1-4 was used. Secondary batteries were fabricated in the same manner as -1 to 2-15 and 3-1 to 3-15.

  Regarding the obtained secondary batteries of Examples 2-1 to 2-15, 3-1 to 3-15 and Comparative Examples 2-1 to 2-4 and 3-1 to 3-4, Example 1-1 was also performed. The discharge capacity retention ratio at the 50th cycle was determined in the same manner as ˜1-15. The results are shown in Tables 2 and 3.

  As can be seen from Tables 2 and 3, as in Examples 1-1 to 1-15, 4-chloro-1,3-dioxolan-2-one or 4-fluoro-1,3-dioxolan-2-one and According to Examples 2-1, 2-2, 3-1, 3-2 using ε-caprolactone, 4-chloro-1,3-dioxolan-2-one or 4-fluoro-1,3 -The discharge capacity retention ratio was improved as compared with Comparative Examples 2-1 and 3-1, which did not use dioxolan-2-one. In addition, the discharge capacity retention rate was improved as compared with Comparative Examples 2-3, 2-4, 3-3, 3-4 in which ε-caprolactone was not used. Furthermore, the discharge capacity retention rate was dramatically improved over Comparative Examples 2-2 and 3-2 which did not use both of them. In addition, in Examples 2-3 to 2-15 and 3-3 to 3-15 using other lactones, the discharge capacity retention rate was improved similarly to Examples 2-2 and 3-2. , Ε-caprolactone, δ-valerolactone, δ-caprolactone, β-propiolactone, β-butyrolactone, diketene, γ-crotonolactone, α-pyrone, coumarin or 3,4-dihydrocoumarin. A value was obtained.

  That is, even when other negative electrode active materials are used, if the electrolytic solution contains a cyclic carbonate derivative having a halogen atom and a lactone, the cycle characteristics can be improved. It has been found that it is preferable to use a compound having a ring lactone ring, a compound having a 6-membered lactone ring, a compound having a 7-membered lactone ring, or a compound having a double bond in the lactone ring. .

(Examples 4-1, 4-2, 5-1, 5-2, 6-1, 6-2)
A secondary battery was fabricated in the same manner as in Examples 1-2, 2-2, and 3-2 except that the content of ε-caprolactone in the electrolytic solution was 2% by mass or 0.1% by mass.

  For the secondary batteries of these examples, the discharge capacity retention ratio at the 50th cycle was determined in the same manner as in Examples 1-1 to 1-15. The results are shown in Tables 4 to 6 together with the results of Comparative Examples 1-4, 2-4, and 3-4.

  As can be seen from Tables 4 to 6, a high discharge capacity retention rate was obtained in the range where the content of ε-caprolactone in the electrolytic solution was 0.1% by mass or more and 2% by mass or less.

  That is, it was found that the lactone content in the electrolytic solution is preferably in the range of 0.1% by mass to 2% by mass.

  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, the case where an electrolytic solution is used as the electrolyte is described. In the above-described embodiment, the case where a gel electrolyte in which the electrolytic solution is held in a polymer compound is used is also described. Other electrolytes may be used. Other electrolytes include, for example, a mixture of an ion conductive inorganic compound such as ion conductive ceramics, ion conductive glass or ionic crystal and an electrolytic solution, or a mixture of another inorganic compound and an electrolytic solution. Or a mixture of these inorganic compounds and a gel electrolyte.

  In the above embodiments and examples, a battery using lithium as an electrode reactant has been described. However, another alkali metal such as sodium (Na) or potassium (K), or an alkali such as magnesium or calcium (Ca) is used. The present invention can also be applied to the case of using an earth metal or another light metal such as aluminum. At that time, the negative electrode active material described in the above embodiment, for example, a material containing tin or silicon as a constituent element can be used in the same manner for the negative electrode.

  Further, in the above-described embodiment or example, a cylindrical type, laminated film type, or coin type secondary battery has been specifically described, but the present invention has other shapes such as a button type or a square type. The present invention can be similarly applied to a secondary battery or a secondary battery having another structure such as a laminated structure. Further, the present invention is not limited to the secondary battery, and can be similarly applied to other batteries such as a primary battery.

It is sectional drawing showing the structure of the 1st secondary battery using the electrolyte solution 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 3rd secondary battery using the electrolyte solution which concerns on one embodiment of this invention. It is sectional drawing showing the structure along the II line 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 CoSnC-containing material produced in an example.

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 (10)

An electrolytic solution comprising a cyclic carbonate derivative having a halogen atom and a lactone.   The lactone is selected from the group consisting of a compound having a 4-membered lactone ring, a compound having a 6-membered lactone ring, a compound having a 7-membered lactone ring, and a compound having a double bond in the lactone ring. The electrolytic solution according to claim 1, comprising at least one kind.   2. The electrolytic solution according to claim 1, wherein a content of the lactone is in a range of 0.1% by mass to 2% by mass.   2. The cyclic carbonate derivative comprises at least one of 4-fluoro-1,3-dioxolan-2-one and 4-chloro-1,3-dioxolan-2-one. The electrolytic solution described. A battery comprising an electrolyte solution together with a positive electrode and a negative electrode,
The battery includes a cyclic carbonate derivative having a halogen atom and a lactone.   The lactone is selected from the group consisting of a compound having a 4-membered lactone ring, a compound having a 6-membered lactone ring, a compound having a 7-membered lactone ring, and a compound having a double bond in the lactone ring. The battery according to claim 5, comprising at least one kind.   The battery according to claim 5, wherein the content of the lactone in the electrolytic solution is in a range of 0.1% by mass to 2% by mass.   6. The cyclic carbonate derivative includes at least one of 4-fluoro-1,3-dioxolan-2-one and 4-chloro-1,3-dioxolan-2-one. The battery described.   6. The battery according to claim 5, wherein the negative electrode is capable of inserting and extracting an electrode reactant, and contains a material containing at least one of a metal element and a metalloid element as a constituent element. . The battery according to claim 5, wherein the negative electrode contains a negative electrode material containing at least one of tin (Sn) and silicon (Si) as a constituent element.

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