JP5076283B2 - Non-aqueous secondary battery - Google Patents

Description

The present invention relates to a non-aqueous secondary battery using a material containing lithium metal, silicon (Si), tin (Sn), or the like as a negative electrode active material.

  In recent years, many portable electronic devices such as a camera-integrated VTR (Videotape Recorder), a digital still camera, a mobile phone, a portable information terminal, or a notebook personal computer have appeared, and the size and weight of the portable electronic device have been reduced. Accordingly, development of secondary batteries that are lightweight and can obtain a high energy density as a power source for these electronic devices is underway. 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 electrolyte are larger than conventional lead batteries and nickel cadmium batteries. Since energy density can be obtained, it is widely used.

  In recent years, with the improvement in performance of portable electronic devices, further improvement in capacity has been demanded, and the use of tin or silicon as a negative electrode active material in place of a carbon material has been studied. 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).

Furthermore, as a secondary battery capable of obtaining a high energy density, there is a lithium metal secondary battery that uses lithium metal for the negative electrode and uses only precipitation and dissolution reactions of lithium metal for the negative electrode reaction. Lithium metal secondary batteries have a large theoretical electrochemical equivalent of 2054 mAh / cm ^{3 of} lithium metal, which is equivalent to 2.5 times that of graphite used in lithium ion secondary batteries, so it is higher than lithium ion secondary batteries. The energy density is expected to be obtained. Until now, research and development regarding practical application of lithium metal secondary batteries has been made by many researchers and the like (for example, see Non-Patent Document 1).
Edited by Jean-Paul Gabano, "Lithium Batteries", London, New York, Academic Press, 1983 International Publication No. WO01 / 031724 Pamphlet

  However, tin alloys or silicon alloys that occlude lithium (Li) have high activity, and the reactivity of the deposited lithium metal is high, so that carbonate esters such as propylene carbonate or diethyl carbonate that have been conventionally used in electrolytes are used. However, there is a problem that these are decomposed and lithium is inactivated. Therefore, if charging / discharging is repeated, charging / discharging efficiency will fall and sufficient cycle characteristics could not be obtained.

As electrolyte salts, LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiClO _4, LiAsF _6, etc. are used. However, such as thermal stability, conductivity, storage characteristics, oxidation stability or discharge characteristics, etc. There was a problem with either of these, and in particular, there was a problem that the charge / discharge efficiency was reduced.

Furthermore, in recent years, since it exhibits relatively high conductivity and high thermal stability, LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ or LiN (C ₄ F _9). The use of imide salts such as (SO ₂ ) (CF ₃ SO ₂ ) has been studied. However, for example, aluminum (Al) was eluted from a positive electrode current collector made of an aluminum foil, and there was a problem that sufficient charge / discharge efficiency could not be obtained. Therefore, in these batteries, development of an electrolytic solution capable of improving charge / discharge efficiency has been eagerly desired.

This invention is made | formed in view of this problem, The objective is to provide the non-aqueous secondary battery which can improve charging / discharging efficiency.

The first non-aqueous secondary battery of the present invention includes an electrolyte together with a positive electrode and a negative electrode, and the negative electrode can occlude and release an electrode reactant, and includes a metal element and a metalloid element as constituent elements. A negative electrode material containing at least one kind, and an electrolyte comprising a solvent containing a halogenated carbonate and a lithium borate salt of at least one of lithium heptafluoroisopropyl trifluoroborate and lithium nonafluorobutyltrifluoroborate And an electrolyte salt containing.

The second non-aqueous secondary battery of the present invention includes an electrolyte together with a positive electrode and a negative electrode, uses lithium metal as a negative electrode active material, the electrolyte includes a solvent containing a halogenated carbonate, and boric acid shown in Chemical Formula 1 And an electrolyte salt including a lithium salt.
(Chemical formula 1)
Li [BF _m R _4-m ]
(In the formula, R represents a perfluoroalkyl group or a perfluoroaryl group. M is 0, 1, 2, or 3.)

According to the first or second non-aqueous secondary battery of the present invention, the electrolyte is a halogenated carbonate, lithium borate shown in Chemical Formula 1, lithium heptafluoroisopropyl trifluoroborate and nonafluorobutyl trichloride. Since at least one lithium borate salt of lithium fluoroborate is contained, the decomposition reaction of the electrolytic solution can be suppressed, and the charge / discharge efficiency can be improved.

  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 the first embodiment of the present invention. This secondary battery is called a so-called cylindrical type, and a winding in which a strip-like positive electrode 21 and a strip-like negative electrode 22 are laminated and wound inside a substantially hollow cylindrical battery can 11 via a separator 23. An 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. An electrolyte is injected into the battery can 11 and impregnated in the separator 23. In addition, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

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

  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 or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces or one surface of a positive electrode current collector 21A having a pair of opposed surfaces. 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, one or more of positive electrode materials capable of inserting and extracting lithium as a positive electrode active material, and a conductive material such as a carbon material and polyfluoride as necessary. A binder such as vinylidene may be included. The positive electrode material capable of inserting and extracting lithium does not contain lithium such as titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), niobium selenide (NbSe ₂ ), or vanadium oxide (V ₂ O ₅ ). Examples include chalcogenides and lithium-containing compounds containing lithium.

Among these, lithium-containing compounds are preferable because some compounds can obtain a high voltage and a high energy density. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, or a phosphate compound containing lithium and a transition metal element. In particular, cobalt (Co), nickel and manganese (Mn Among these, those containing at least one of them are preferred. This is because a higher voltage can be obtained. The chemical formula is represented by, for example, Li _x MIO ₂ or Li _y MIIPO ₄ . In the formula, MI and MII represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state of the battery, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Specific examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel composite oxide (Li _x NiO ₂ ), and lithium nickel cobalt composite oxide (Li _x Ni _1-z Co _z O ₂ (z <1)), lithium nickel cobalt manganese composite oxide (Li _x Ni _(1-vw) Co _v Mn _w O ₂ (v + w <1)), or a spinel structure Examples thereof include lithium manganese composite oxide (LiMn ₂ O ₄ ). Among these, a composite oxide containing nickel is preferable. This is because a high capacity can be obtained and excellent cycle characteristics can also be obtained. Specific examples of the phosphate compound containing lithium and a transition metal element include, for example, a lithium iron phosphate compound (LiFePO ₄ ) or a lithium iron manganese phosphate compound (LiFe _1-u Mn _u PO ₄ (u <1)). Can be mentioned.

  The negative electrode 22 has, for example, a structure in which a negative electrode active material layer 22B is provided on both surfaces or both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces, similarly to the positive electrode 21. The anode current collector 22A is made of, for example, a metal foil such as a copper foil.

  The negative electrode active material layer 22B includes, for example, any one or more of negative electrode materials capable of inserting and extracting lithium 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 a second constituent element other than tin, silicon, nickel, copper (Cu), iron, cobalt, manganese, zinc (Zn), indium (In), silver (Ag), titanium ( Examples include those containing at least one member selected from the group consisting of 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).

  Such a negative electrode active material is prepared by, for example, mixing raw materials of respective constituent elements, melting them in an electric furnace, a high frequency induction furnace or an arc melting furnace, and then solidifying them, and various atomizing methods such as gas atomization or water atomization, It can be produced by various roll methods, or methods utilizing mechanochemical reactions such as mechanical alloying methods or mechanical milling methods. Especially, it is preferable to manufacture by the method using a mechanochemical reaction. This is because the negative electrode active 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.

  The negative electrode active material layer 22B may also contain other materials such as other negative electrode active materials or conductive materials in addition to the negative electrode active materials described above. Examples of the other negative electrode active material include a carbonaceous material capable of inserting and extracting lithium. This carbonaceous material is preferable because it can improve charge / discharge cycle characteristics and also functions as a conductive material. Examples of the carbonaceous material include one or two of non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, coke, glassy carbons, organic polymer compound fired bodies, activated carbon and carbon black. More than seeds 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 such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and has a structure in which two or more kinds of porous films are laminated. It may be said.

  The electrolytic solution impregnated in the separator 23 includes a solvent and an electrolyte salt dissolved in the solvent.

  The solvent contains a halogenated carbonate. This is because the decomposition reaction of the electrolytic solution can be suppressed by forming a good film having ion conductivity on the surface of the negative electrode 22. Halogenated carbonates may be used alone or in combination of two or more.

Examples of such halogenated carbonates include 4-fluoro-1,3-dioxolan-2-one, 4-trifluoromethyl-1,3-dioxolan-2-one, 4,4-difluoro-1, 3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one, 4,4,5-trifluoro-1,3-dioxolan-2-one, 4,4,5,5 -Tetrafluoro-1,3-dioxolan-2-one, 4-fluoromethyl-1,3-dioxolan-2-one, 4-difluoromethyl-1,3-dioxolan-2-one, 4-fluoro-4- Methyl-1,3-dioxolan-2-one, 5-fluoro-4-methyl-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one or 4,5-dichloro Cyclic carbonate derivatives such as 1,3-dioxolan-2-one or fluoromethyl methyl carbonate (CH ₂ FOCOOCH _3), carbonate, bis fluoromethyl (CH ₂ FOCOOCH ₂ F) carbonate, difluoromethyl methyl carbonate (CHF ₂ OCOOCH _3, ) And the like. Among these, 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bisfluoromethyl carbonate or difluoromethyl methyl carbonate is preferable. This is because a high effect can be obtained.

  Furthermore, as a solvent, in addition to the halogenated carbonate, another solvent may be mixed and used. Examples of other solvents include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1, Non-aqueous solvents such as 3-dioxolane, 4-methyl-1,3-dioxolane, acetic acid ester, butyric acid ester, propionic acid ester, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile and the like can be mentioned. Other solvents may be used alone or in combination of two or more.

The electrolyte salt includes the lithium borate salt shown in Chemical formula 1. This is because the decomposition reaction of the electrolytic solution can be suppressed by forming a film having better ion conductivity on the surface of the negative electrode 22.
(Chemical formula 1)
Li [BF _m R _4-m ]

  In Chemical Formula 1, R represents a perfluoroalkyl group or a perfluoroaryl group, and is preferably a perfluoroalkyl group having 1 to 8 carbon atoms or a perfluoroaryl group having 1 to 8 carbon atoms. This is because when the number of carbon atoms exceeds 8, the viscosity of the electrolytic solution increases and conductivity decreases. m is 0, 1, 2 or 3.

  Examples of the perfluoroalkyl group or perfluoroaryl group include trifluoromethyl group, pentafluoroethyl group, heptafluoro-n-propyl group, heptafluoro-i-propyl group, nonafluoro-n-butyl group, and nonafluoro-i. -Butyl group, nonafluoro-t-butyl group, perfluoro-n-pentyl group, perfluoro-i-pentyl group, perfluoro-t-pentyl group, perfluoronepentyl group, perfluoro-n-hexyl group, perfluoro group A fluorocyclohexyl group or a perfluorophenyl group may be mentioned.

Specific examples of such lithium borate salts include lithium trifluoromethyl trifluoroborate (Li [BF ₃ (CF ₃ )]), lithium pentafluoroethyl trifluoroborate (Li [BF ₃ ( CF ₂ CF ₃ )]), lithium tetrakis (trifluoromethyl) borate (Li [B (CF ₃ ) ₄ ]), lithium heptafluoroisopropyl trifluoroborate (Li [BF ₃ (CF (CF ₃ ) ₂ )) ] Or lithium nonafluorobutyltrifluoroborate (Li [BF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ )]).

As the electrolyte salt, in addition to these lithium borate salts, other electrolyte salts may be mixed and used. Examples of other electrolyte salts include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), and lithium perchlorate (LiClO ₄ ). , Lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), bis [trifluoromethanesulfonyl] imido lithium ((CF ₃ SO ₂ ) ₂ NLi), tris (trifluoromethanesulfonyl) methyl lithium ((CF ₃ SO ₂ ) ₃ CLi) Or a lithium salt such as bis [pentafluoroethanesulfonyl] imide lithium ((C ₂ F ₅ SO ₂ ) ₂ NLi). Other electrolyte salts may be used alone or as a mixture of two or more.

  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 material, 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. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution. At that time, since the electrolytic solution contains the halogenated carbonate and the lithium borate salt shown in Chemical Formula 1, a good film is formed on the surface of the negative electrode 22 and the decomposition of the electrolytic solution is suppressed. .

  As described above, according to the present embodiment, the electrolytic solution contains the halogenated carbonate and the lithium borate lithium salt shown in Chemical Formula 1, so that an alloy with lithium can be formed as the negative electrode active material. When a material containing another metal element or another metalloid element as a constituent element is used, the decomposition reaction of the electrolytic solution can be suppressed, and charge / discharge efficiency can be improved.

(Second Embodiment)
The secondary battery according to the second embodiment has the same configuration and operation as the secondary battery according to the first embodiment except that the configuration of the negative electrode is different. Can be manufactured. 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.

  The negative electrode 22 has a structure in which the negative electrode active material layer 22B is provided on both surfaces or one surface of the negative electrode current collector 22A, similarly to the secondary battery according to the first embodiment. 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 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 22A are formed. Are preferably alloyed in at least 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. .

  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)
The secondary battery according to the third embodiment is a so-called lithium metal secondary battery in which the capacity of the negative electrode 22 is represented by a capacity component due to precipitation and dissolution of lithium as an electrode reactant. This secondary battery has the same configuration as the secondary battery according to the first embodiment except that the negative electrode active material layer 22B is made of lithium metal, and is manufactured in the same manner. Can do. 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.

  This secondary battery uses lithium metal as a negative electrode active material, and can thereby obtain a high energy density. The negative electrode active material layer 22B may be configured to be already provided from the time of assembly, but may be configured by lithium metal which is not present at the time of assembly and is deposited during charging. Alternatively, the negative electrode active material layer 22B may be used as a current collector, and the negative electrode current collector 22A may be deleted.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and deposited as lithium metal on the surface of the negative electrode current collector 22A through the electrolytic solution. When the discharge is performed, for example, lithium metal is eluted as lithium ions from the negative electrode active material layer 22B, and is occluded in the positive electrode 21 through the electrolytic solution. As described above, in this secondary battery, since the deposition and dissolution of lithium metal are repeated in the negative electrode 22, the activity of the negative electrode 22 is extremely high. Since the lithium borate salt shown in Chemical Formula 1 is contained, a good film is formed on the surface of the negative electrode 22 and the decomposition of the electrolytic solution is suppressed.

  As described above, according to the present embodiment, since the electrolytic solution contains the halogenated carbonate and the lithium borate salt shown in Chemical formula 1, when lithium metal is used as the negative electrode active material, The decomposition reaction of the electrolytic solution can be suppressed, and the charge / discharge efficiency can be improved.

(Fourth embodiment)
FIG. 3 shows the configuration of the secondary battery according to the fourth embodiment. 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 or one surface of a positive electrode current collector 33A. The negative electrode 34 has a structure in which the negative electrode active material layer 34B is provided on both surfaces or one surface of the negative electrode current collector 34A, and the negative electrode active material layer 34B and the positive electrode active material layer 33B are arranged to face each other. Yes. The 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 the positive electrode current collector 21A, the positive electrode active material in the first to third embodiments 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 and a polymer compound serving 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. The configuration of the electrolytic solution is the same as that of the first embodiment. 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, 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 secondary battery operates in the same manner as the secondary batteries according to the first to third embodiments, and can obtain the same effects.

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

( Experimental Examples 1-1 to 1-11)
A coin-type secondary battery as 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, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a molar ratio of Li ₂ CO ₃ : CoCO ₃ = 0.5: 1, and calcined in air at 900 ° C. for 5 hours. Lithium / cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material was obtained. Next, 91 parts by mass of this lithium / cobalt composite oxide, 6 parts by mass of graphite as a conductive material, and 3 parts by mass of polyvinylidene fluoride as a binder were prepared, and then a positive electrode mixture was prepared. A positive electrode mixture slurry was prepared by dispersing in methyl-2-pyrrolidone. Subsequently, the 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, dried, and then compression molded to form a positive electrode active material layer 51B. After that, the positive electrode 51 was produced by punching into a pellet having a diameter of 15.5 mm.

  Further, tin-cobalt-indium-titanium alloy powder and carbon powder were mixed, and a 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% by mass, the cobalt content was 23% by mass, the indium content was 5% by mass, and the titanium content was 2% by mass. The carbon content was 20% by mass, and the ratio Co / (Sn + Co) of cobalt to the total of tin and cobalt was 32.4% 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 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.

  Then, using this SnCoC-containing material as a negative electrode active material, 80 parts by mass of the SnCoC-containing material powder, 11 parts by mass of graphite (KS-15 made by Lonza) and 1 part by mass of acetylene black, and polyfluoride as a binder. 8 parts by mass of vinylidene chloride was mixed and dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry was uniformly applied to a negative electrode current collector 52A made of a copper foil having a thickness of 10 μm and dried, followed by compression molding to form a negative electrode active material layer 52B. After that, a negative electrode 52 was produced by punching into a pellet having a diameter of 16 mm. At that time, the amount of the negative electrode active material was adjusted so that the charge capacity of the negative electrode active material was larger than the charge capacity of the positive electrode 51 so that lithium metal was not deposited on the negative electrode 52 during the charge.

Next, the prepared positive electrode 51 and negative electrode 52 are placed on the outer can 54 via a separator 53 made of a microporous polypropylene film, and an electrolytic solution is injected thereon, and the outer cup 55 is covered and caulked. Was sealed. As the electrolytic solution, a solution containing a lithium borate salt shown in Chemical Formula 1 as an electrolyte salt dissolved in a solvent containing a halogenated carbonate was used. In this case, the solvent is one or two of 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bisfluoromethyl carbonate and difluoromethyl methyl carbonate, which are halogenated carbonates, Diethyl carbonate or dimethyl carbonate and, if necessary, ethylene carbonate were mixed at a ratio shown in Table 1 and used. In addition, electrolyte salts include lithium trifluoromethyl trifluoroborate (Li [BF ₃ (CF ₃ )]) and tetrakis (trifluoromethyl) lithium borate (Li [B (CF ₃ ) ₄ ]), lithium pentafluoroethyl trifluoroborate (Li [BF ₃ (CF ₂ CF ₃ )]), lithium heptafluoroisopropyl trifluoroborate (Li [BF ₃ (CF (CF ₃ ) ₂ )]), Lithium nonafluorobutyltrifluoroborate (Li [BF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ )]), and LiPF ₆ was mixed and used as necessary. The concentration of each electrolyte salt in the electrolytic solution was as shown in Table 1.

As Comparative Examples 1-1 and 1-2 for Experimental Examples 1-1 to 1-11, other than using LiPF ₆ or LiBF ₄ as the electrolyte salt without using the lithium borate salt shown in Chemical Formula 1 Were fabricated in the same manner as in Experimental Examples 1-1 to 1-11. At that time, the solvent was a mixture of 4-fluoro-1,3-dioxolan-2-one, which is a halogenated carbonate, and diethyl carbonate in a mass ratio of 50:50. The concentration of LiPF ₆ or LiBF ₄ in the electrolytic solution was 1 mol / kg.

In addition, as Comparative Example 1-3, except that a halogenated carbonate was not used and a solvent in which ethylene carbonate and diethyl carbonate were mixed at a mass ratio of 50:50 was used, the others were Experimental Example 1- Secondary batteries were fabricated in the same manner as in 1-11-1. At that time, the electrolyte salt was lithium trifluoromethyltrifluoroborate (Li [BF ₃ (CF ₃ )]), which is the lithium borate salt shown in Chemical Formula 1, and the concentration in the electrolyte was 1 mol / kg.

The cycle characteristics of the fabricated secondary batteries of Experimental Examples 1-1 to 1-11 and Comparative Examples 1-1 to 1-3 were examined. The cycle characteristics are: 50 cycles of charge / discharge at 23 ° C. 50% discharge capacity maintenance rate (50th cycle discharge capacity / first cycle discharge capacity) × 100 (%) with respect to the first cycle discharge capacity. Asked. In that case, charging, after performing a constant current density of 1 mA / cm ² until the battery voltage reached 4.2V, performed at a constant voltage of 4.2V until the current density reached 0.02 mA / cm ^2, discharge Was performed at a constant current density of 1 mA / cm ² until the battery voltage reached 2.5V. The results are shown in Table 1.

As shown in Table 1, one or two of 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bisfluoromethyl carbonate and difluoromethyl methyl carbonate and According to Experimental Examples 1-1 to 1-11 using a lithium borate salt, Comparative Examples 1-1 and 1-2 which do not use the lithium borate salt shown in Chemical Formula 1 or a halogenated carbonate The discharge capacity retention rate was improved as compared with Comparative Example 1-3 in which no was used.

  That is, when the negative electrode 52 includes a negative electrode material containing a metal element capable of inserting and extracting lithium as a constituent element, the halogenated carbonate and the lithium borate salt shown in Chemical Formula 1 are added to the electrolytic solution. It was found that the cycle characteristics can be improved by including.

( Experimental examples 2-1 to 2-11)
Secondary batteries were fabricated in the same manner as in Experimental Examples 1-1 to 1-11 except that silicon was used as the negative electrode active material and the negative electrode active material layer 52B was formed by an electron beam evaporation method. Further, as Comparative Examples 2-1 to 2-3 for Experimental Examples 2-1 to 2-11, 4-fluoro-1,3-dioxolan-2-one or lithium borate shown in Chemical Formula 1 was not used. Otherwise, secondary batteries were fabricated in the same manner as in Experimental Examples 2-1 to 2-11. At that time, the electrolytic solution was the same as in Comparative Examples 1-1 to 1-3.

Secondary batteries of Experimental Examples 2-1 to 2-11 and Comparative Examples 2-1 to 2-3 were prepared, the cycle characteristics were examined in the same manner as in Experimental Example 1-1 to 1-11. The results are shown in Table 2.

As can be seen from Table 2, as in Experimental Examples 1-1 to 1-11, among 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bisfluoromethyl carbonate and difluoromethyl methyl carbonate According to Experimental Examples 2-1 to 2-11 using one or two of the above and the lithium borate salt shown in Chemical Formula 1, Comparative Example 2 not using the lithium borate salt shown in Chemical Formula 1 The discharge capacity retention ratio was improved as compared with Comparative Example 2-3 in which -1,2-2, or halogenated carbonate was not used.

  That is, even when the negative electrode 52 includes a negative electrode material containing a metalloid capable of inserting and extracting lithium as a constituent element, the electrolytic solution contains a halogenated carbonate and the lithium borate salt shown in Chemical Formula 1 It has been found that the cycle characteristics can be improved by including.

( Experimental examples 3-1 to 3-3)
The cylindrical secondary battery shown in FIGS. The positive electrode 21 was produced in the same manner as in Experimental Examples 1-1 to 1-11, and the negative electrode 22 was produced in the same manner as in Experimental Examples 2-1 to 2-11. That is, the negative electrode active material was silicon, and the negative electrode active material layer 22B was formed by electron beam evaporation. Further, the amount of silicon was adjusted so that the charge capacity due to silicon was larger than the charge capacity of the positive electrode 21, so that lithium metal was not deposited on the negative electrode 22 during the charge.

As the separator 23, a microporous polypropylene film having a thickness of 25 μm was used, and as the electrolytic solution, a solution containing a lithium borate salt shown in Chemical Formula 1 as an electrolyte salt in a solvent containing a halogenated carbonate was used. At that time, the solvent is a halogenated carbonate 4-fluoro-1,3-dioxolan-2-one and diethyl carbonate, or a halogenated carbonate fluoromethyl methyl carbonate, ethylene carbonate, and diethyl carbonate. The mixture was used at the ratio shown in Table 1. The electrolyte salt is lithium trifluoromethyl trifluoroborate (Li [BF ₃ (CF ₃ )]) or lithium pentafluoroethyl trifluoroborate (Li [BF ₃ ], which is the lithium borate salt shown in Chemical Formula _1. (CF ₂ CF ₃ )]). The concentration of each electrolyte salt in the electrolytic solution was 1 mol / kg.

As Comparative Examples 3-1 and 3-2 for Experimental Examples 3-1 to 3-3, other than using LiPF ₆ or LiBF ₄ as the electrolyte salt without using the lithium borate salt shown in Chemical Formula 1 Produced secondary batteries in the same manner as in Experimental Examples 3-1 to 3-3. At that time, the solvent was a mixture of 4-fluoro-1,3-dioxolan-2-one, which is a halogenated carbonate, and diethyl carbonate in a mass ratio of 50:50. The concentration of LiPF ₆ or LiBF ₄ in the electrolytic solution was 1 mol / kg.

Further, as Comparative Example 3-3, except that a halogenated carbonate was not used, and a solvent in which ethylene carbonate and diethyl carbonate were mixed at a mass ratio of 50:50 was used, the others were Experimental Example 3- Secondary batteries were fabricated in the same manner as in 1-3. At that time, the electrolyte salt was lithium trifluoromethyltrifluoroborate (Li [BF ₃ (CF ₃ )]), which is the lithium borate salt shown in Chemical Formula 1, and the concentration in the electrolyte was 1 mol / kg.

For the secondary batteries of Experimental Examples 3-1 to 3-3 and Comparative Examples 3-1 through 3-3 were prepared, the cycle characteristics were examined in the same manner as in Experimental Example 1-1 to 1-11. The results are shown in Table 3.

As can be seen from Table 3, as in Experimental Examples 1-1 to 1-11, 4-fluoro-1,3-dioxolan-2-one or fluoromethyl methyl carbonate and the lithium borate salt shown in Chemical Formula 1 According to Experimental Examples 3-1 to 3-3 using and, Comparative Examples 3-1 and 3-2 that do not use the lithium borate salt shown in Chemical Formula 1, or a comparison that does not use a halogenated carbonate The discharge capacity retention rate was improved as compared with Example 3-3.

  That is, even when other exterior members were used, it was found that cycle characteristics could be improved if the electrolytic solution contained a halogenated carbonate and a lithium borate salt shown in Chemical formula 1. .

( Experimental examples 4-1 to 4-15)
A so-called lithium metal secondary battery in which the capacity of the negative electrode is represented by a capacity component due to precipitation and dissolution of lithium was produced. At that time, the cylindrical secondary battery shown in FIGS. The positive electrode 21 was produced in the same manner as in Experimental Examples 1-1 to 1-11, and the negative electrode 22 was prepared by attaching a lithium metal foil having a thickness of 30 μm to a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 8 μm. Fabricated by forming layer 22B. The separator 23 was a microporous polypropylene film having a thickness of 25 μm, as in Experimental Examples 3-1 to 3-3.

Further, as the electrolytic solution, a solution in which the lithium borate salt shown in Chemical Formula 1 was dissolved as an electrolyte salt in a solvent containing a halogenated carbonate was used. In this case, the solvent is one or two of 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bisfluoromethyl carbonate and difluoromethyl methyl carbonate, which are halogenated carbonates, Diethyl carbonate or dimethyl carbonate and, if necessary, ethylene carbonate were mixed at the ratio shown in Table 4 and used. The electrolyte salt is lithium trifluoromethyl trifluoroborate (Li [BF ₃ (CF ₃ )]) or lithium pentafluoroethyl trifluoroborate (Li [BF ₃ ], which is the lithium borate salt shown in Chemical Formula _1. (CF ₂ CF ₃ )]), lithium tetrakis (trifluoromethyl) borate (Li [B (CF ₃ ) ₄ ]), and LiPF ₆ was mixed as necessary. Table 4 shows the concentration of each electrolyte salt in the electrolytic solution.

As Comparative Example 4-1 for Experimental Examples 4-1 to 4-15, a halogenated carbonate was not used, and ethylene carbonate and diethyl carbonate were mixed as a solvent in a mass ratio of ethylene carbonate: diethyl carbonate = 30: 70. A secondary battery was fabricated in the same manner as in Experimental Examples 4-1 to 4-15, except that the above was used. At that time, the electrolyte salt is lithium pentafluoroethyl trifluoroborate (Li [BF ₃ (CF ₂ CF ₃ )]) and LiPF ₆ , which are the lithium borate salts shown in Chemical Formula 1, and the concentration in the electrolyte is respectively The amount was 0.5 mol / kg.

Moreover, as Comparative Example 4-2, the lithium borate salt shown in Chemical Formula 1 was not used, and 4-fluoro-1,3-dioxolan-2-one, which is a halogenated carbonate, and diethyl carbonate were used as solvents. 4-fluoro-1,3-dioxolan-2-one: diethyl carbonate = 30: 70, except that the mixture was used in the same manner as in Experimental Examples 4-1 to 4-15. A secondary battery was produced. At that time, the electrolyte salt was LiPF ₆ and the concentration in the electrolyte was 1 mol / kg.

Furthermore, as Comparative Examples 4-3 to 4-5, except that artificial graphite was used as the negative electrode active material and the composition of the electrolytic solution was changed, the rest was the same as in Experimental Examples 4-1 to 4-15. A secondary battery was produced. At that time, the negative electrode was made of a strip-shaped copper foil by mixing 92 parts by mass of artificial graphite powder and 8 parts by mass of polyvinylidene fluoride as a binder and adding N-methyl-2-pyrrolidone as a solvent. It was produced by uniformly applying to both sides of the current collector, drying, and compression molding with a roll press to form a negative electrode active material layer. The electrolytic solution is a solution in which LiPF ₆ is dissolved as an electrolyte salt in a solvent obtained by mixing ethylene carbonate and diethyl carbonate, or 4-fluoro-1,3-dioxolan-2-one which is a halogenated carbonate. In a solvent in which LiPF ₆ is dissolved as an electrolyte salt in a solvent in which diethyl carbonate is mixed, or in a solvent in which 4-fluoro-1,3-dioxolan-2-one, which is a halogenated carbonate, and diethyl carbonate are mixed. As the electrolyte salt, lithium pentafluoroethyl trifluoroborate (Li [BF ₃ (CF ₂ CF ₃ )]) and LiPF ₆ , which are lithium borate salts shown in Chemical Formula _1, were dissolved. The mixing ratio of each solvent and the concentration of the electrolyte salt in the electrolytic solution were as shown in Table 5. The amount of artificial graphite was adjusted so that the charge capacity of the artificial graphite was larger than the charge capacity of the positive electrode 21 so that lithium metal did not deposit on the negative electrode 22 during the charge.

The cycle characteristics of the fabricated secondary batteries of Experimental Examples 4-1 to 4-15 and Comparative Examples 4-1 to 4-5 were examined. The cycle characteristic is 100 cycles of charge / discharge at 23 ° C. The discharge capacity maintenance ratio of the 100th cycle relative to the discharge capacity of the first cycle (discharge capacity of the 100th cycle / discharge capacity of the 1st cycle) × 100 Asked. At that time, the charging is performed at a constant current of 100 mA until the battery voltage reaches 4.2 V, and then the constant voltage charging is performed until the current reaches 1 mA at a constant voltage of 4.2 V. Constant current discharge was performed until the battery voltage reached 3.0 V at a constant current of 300 mA. The results are shown in Tables 4 and 5.

As can be seen from Tables 4 and 5, as in Experimental Examples 1-1 to 1-11, 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bisfluoromethyl carbonate and difluoromethyl methyl carbonate According to Experimental Examples 4-1 to 4-15 using one or two of the above and lithium borate shown in Chemical Formula 1, 4-fluoro-1,3-dioxolan-2-one The discharge capacity retention ratio was improved as compared with Comparative Example 4-1 not used or Comparative Example 4-2 not using the lithium borate salt shown in Chemical Formula 1.

  Further, according to Comparative Examples 4-3 to 4-5 using artificial graphite as the negative electrode active material, 4-fluoro-1,3-dioxolan-2-one and lithium borate shown in Chemical Formula 1 were mixed. The improvement effect of the discharge capacity maintenance rate by doing was not seen.

  That is, even in the case of a lithium metal secondary battery using lithium metal as the negative electrode active material, if the electrolytic solution contains a halogenated carbonate and a lithium borate salt shown in Chemical Formula 1, cycle characteristics are improved. I found out that

( Experimental examples 5-1 and 5-2)
The laminate film type secondary battery shown in FIGS. First, the positive electrode 33 was produced in the same manner as in Experimental Examples 1-1 to 1-11. Moreover, the negative electrode 34 was produced by forming the negative electrode active material layer 34B which consists of silicon | silicone by the electron beam vapor deposition method similarly to Experimental example 2-1 to 2-11. At that time, the amount of silicon was adjusted so that the charge capacity of silicon was larger than the charge capacity of the positive electrode 33, so that lithium metal was not deposited on the negative electrode 34 during the charge.

Next, lithium borate shown in Chemical Formula 1 as an electrolyte salt in a solvent obtained by mixing 4-fluoro-1,3-dioxolan-2-one as a halogenated carbonate and propylene carbonate in a mass ratio of 50:50. Electrolytic solution by dissolving lithium trifluoromethyl trifluoroborate (Li [BF ₃ (CF ₃ )]) or lithium pentafluoroethyl trifluoroborate (Li [BF ₃ (CF ₂ CF ₃ )]) as a salt Was made. The concentration of each electrolyte salt in the electrolytic solution was 1 mol / kg. Subsequently, as a polymer compound, a copolymer obtained by block copolymerization of vinylidene fluoride and hexafluoropropylene at a mass ratio of vinylidene fluoride: hexafluoropropylene = 93: 7 was prepared. The prepared electrolytic solution was mixed with a mixed solvent to prepare a precursor solution. After that, the prepared precursor solution was applied to each of the positive electrode 33 and the negative electrode 34, and the mixed solvent was volatilized to form a gel electrolyte layer 36.

  Next, the positive electrode lead 31 made of aluminum is attached to the positive electrode 33, the negative electrode lead 32 made of nickel is attached to the negative electrode 34, and the positive electrode 33 and the negative electrode 34 are laminated via a separator 35 made of polyethylene having a thickness of 25 μm. After that, it was sealed under reduced pressure in an exterior member 40 made of a laminate film.

As Comparative Examples 5-1 and 5-2 with respect to Experimental Examples 5-1 and 5-2, except that the lithium borate or the halogenated carbonate shown in Chemical Formula 1 was not used, the others were Experimental Examples 5-1 and 5-2. A secondary battery was fabricated in the same manner as in 5-2. Specifically, the electrolytic solution is prepared by mixing an electrolyte with a solvent in which 4-fluoro-1,3-dioxolan-2-one, which is a halogenated carbonate, and propylene carbonate are mixed at a mass ratio of 50:50 as a solvent. A solution obtained by dissolving LiPF ₆ as a salt, or a solvent obtained by mixing ethylene carbonate and propylene carbonate in a mass ratio of 50:50 as a solvent, and trifluoromethyl trifluorolithium salt as a lithium borate shown in Chemical Formula 1 as an electrolyte salt. Lithium borate (Li [BF ₃ (CF ₃ )]) was dissolved. The concentration of each electrolyte salt in the electrolytic solution was 1 mol / kg.

Regarding the fabricated secondary batteries of Experimental Examples 5-1 and 5-2 and Comparative Examples 5-1 and 5-2, cycle characteristics were examined in the same manner as in Experimental Examples 1-1 to 1-11. The results are shown in Table 6.

As can be seen from Table 6, in the same manner as in Experimental Example 1-1 to 1-11, experimental examples 4-fluoro-1,3-dioxolan-2-one and, and using a lithium borate shown in Chemical formula 1 According to 5-1, 5-2, Comparative Example 5-1 not using the lithium borate salt shown in Chemical Formula 1 or Comparative Example not using 4-fluoro-1,3-dioxolan-2-one The discharge capacity retention rate improved compared to 5-2.

  That is, even when other exterior members are used to form a gel electrolyte, cycle characteristics can be improved by including a halogenated carbonate and lithium borate shown in Chemical Formula 1 in the electrolyte. I found out that

  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 the electrolyte solution or the gel electrolyte in which the polymer solution is held in the polymer compound is used as the electrolyte has been described, but 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 embodiment and examples, a battery using lithium as an electrode reactant has been described. However, other alkali metals such as sodium (Na) or potassium (K), or alkalis such as magnesium or calcium (Ca) are 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, one containing tin or silicon as a constituent element can be used in the same manner as 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 .

It is sectional drawing showing the structure of the secondary battery which concerns on the 1st Embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is a disassembled perspective view showing the structure of the secondary battery which concerns on the 3rd 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 SnCoC-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 (7)

With electrolyte together with positive and negative electrodes,
The negative electrode is capable of inserting and extracting 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,
The electrolyte contains a solvent containing a halogenated carbonate, and an electrolyte salt containing a lithium borate salt of at least one of lithium heptafluoroisopropyl trifluoroborate and lithium nonafluorobutyltrifluoroborate.
Non-aqueous secondary battery. The halogenated carbonate includes at least one member selected from the group consisting of 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bisfluoromethyl carbonate, and difluoromethyl methyl carbonate.
The non-aqueous secondary battery according to claim 1. The negative electrode contains a negative electrode material containing at least one of silicon (Si) and tin (Sn) as a constituent element.
The non-aqueous secondary battery according to claim 1. The content of the halogenated carbonate in the solvent is 5% by weight or more and 50% by weight or less.
The non-aqueous secondary battery according to claim 1. With electrolyte together with positive and negative electrodes,
Lithium metal is used as the negative electrode active material,
The electrolyte contains a solvent containing a halogenated carbonate and an electrolyte salt containing a lithium borate salt shown in Chemical formula 1.
Non-aqueous secondary battery.
(Chemical formula 1)
Li [BF _m R _4-m ]
(In the formula, R represents a perfluoroalkyl group or a perfluoroaryl group. M is 0, 1, 2, or 3.) The halogenated carbonate includes at least one member selected from the group consisting of 4-fluoro-1,3-dioxolan-2-one, fluoromethyl methyl carbonate, bisfluoromethyl carbonate, and difluoromethyl methyl carbonate.
The non-aqueous secondary battery according to claim 5 . The lithium borate salt includes lithium trifluoromethyl trifluoroborate, lithium pentafluoroethyl trifluoroborate, lithium tetrakis (trifluoromethyl) borate, lithium heptafluoroisopropyl trifluoroborate and nonafluorobutyl trifluoroboron. Including at least one member of the group consisting of lithium acid acid,
The non-aqueous secondary battery according to claim 5 .

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