JP4839671B2 - battery - Google Patents

Description

The present invention relates to an effective batteries in the case of using a negative electrode active material containing at least one selected from the group consisting of metal elements and metalloid elements as configuration elements.

  With the miniaturization of electronic devices, development of batteries having high energy density is required. As a battery that meets this requirement, there is a lithium metal secondary battery that utilizes a precipitation / dissolution reaction of lithium (Li). However, the lithium metal secondary battery has a problem that the cycle life is short because lithium dendrites on the negative electrode during charging and becomes inactive.

  As a battery with improved cycle life, a lithium ion secondary battery has been commercialized. The negative electrode of a lithium ion secondary battery has a negative electrode active material such as a graphite material using lithium intercalation reaction between graphite layers, or a carbonaceous material applying lithium occlusion / release action into pores. It is used. Therefore, in a lithium ion secondary battery, lithium does not deposit dendrites and the cycle life is long. In addition, since the graphite material or the carbonaceous material is stable in the air, there is a great merit in industrial production.

However, the negative electrode capacity due to intercalation has an upper limit as defined by the composition C ₆ Li of the first stage graphite intercalation compound. In addition, it is industrially difficult to control the fine pore structure of the carbonaceous material and causes a decrease in the specific gravity of the carbonaceous material, which is effective in improving the negative electrode capacity per unit volume and thus the battery capacity per unit volume. It cannot be a means. Certain low-temperature calcined carbonaceous materials are known to exhibit negative electrode discharge capacities exceeding 1000 mAh / g. However, since they have a large capacity at a noble potential of 0.8 V or more with respect to lithium metal, metal oxides or the like are used. When a battery is configured for use as the positive electrode, there are problems such as a decrease in discharge voltage.

  For these reasons, it is considered difficult for the current carbonaceous materials to cope with longer use time of electronic devices and higher energy density of the power source in the future. A negative electrode active material having a large capacity is desired.

  On the other hand, as negative electrode active materials capable of realizing higher capacities, materials that apply the electrochemical and reversible generation and decomposition of certain lithium alloys have been widely studied. For example, lithium-aluminum alloys have been extensively studied, and Patent Document 1 reports silicon alloys. However, when these alloys are used for the negative electrode of a battery, there is a problem that the cycle characteristics are deteriorated. One of the causes is that these alloys expand and contract with charging / discharging and are pulverized every time charging / discharging is repeated.

Therefore, in order to suppress the pulverization of such an alloy, for example, it has been studied to partially substitute with an element that does not participate in expansion and contraction associated with insertion and extraction of lithium. For example, LiSi _a O _b (0 ≦ a, 0 <b <2) (see Patent Document 2), Li _c Si _1-d M _d O _e (M is a metal element excluding an alkali metal or silicon (Si) is excluded. It represents a metalloid element, and 0 ≦ c, 0 <d <1, 0 <e <2 (see Patent Document 3), a lithium-aluminum-tellurium alloy (see Patent Document 4), and the like have been proposed. . In addition, a compound including at least one non-metallic element and a group 14 metal element or metalloid element in the long-period periodic table has been proposed (see Patent Document 5).
U.S. Pat. No. 4,950,566 JP-A-6-325765 JP-A-7-230800 JP 7-288130 A JP-A-11-102705

  However, even if these negative electrode active materials are used, the deterioration of cycle characteristics due to expansion and contraction is large, and the fact that the characteristics of high capacity cannot be fully utilized.

The present invention has been made in view of the above problems, its object is to provide a batteries capable of improving battery characteristics such as cycle characteristics.

A battery according to the present invention includes an electrolyte solution together with a positive electrode and a negative electrode , the negative electrode is capable of inserting and extracting an electrode reactant, and includes a negative electrode including at least one member selected from the group consisting of metal elements and metalloid elements as constituent elements The material contains a solvent, and the electrolytic solution contains a solvent containing at least one member selected from the group consisting of ethylene sulfite and derivatives thereof and a carbonate ester derivative having a halogen atom.

According to the battery of the present invention, the negative electrode is capable of occluding and releasing the electrode reactant, and contains a negative electrode material containing at least one member selected from the group consisting of a metal element and a metalloid element as a constituent element. includes at least one kind selected from the group consisting of ethylene sulfite and its derivatives. Thus contains a solvent containing a carbonic ester derivative having a halogen atom, to produce a stable coating on the negative electrode, a negative electrode The irreversible reaction occurring between the electrolyte and the electrolyte can be suppressed, and the oxidative decomposition reaction of the electrolyte that occurs at the positive electrode can be suppressed. Therefore, cycle characteristics can be improved, and low temperature characteristics and overcharge safety can be improved.

  In particular, if the content of ethylene sulfite and its derivative in the solvent is 0.05% by volume or more and 5% by volume or less, or the content of the carbonate ester derivative in the solvent is 0.1% by volume or more and 65% by volume. If it is made into% or less, a higher effect can be acquired.

Moreover, the negative electrode, can be on Let 's you containing a negative electrode material containing at least one of tin (Sn) and silicon as an element to obtain a higher effect.

  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 a so-called cylindrical type, and a wound electrode body 20 in which a strip-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. 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.

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

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

The positive electrode active material layer 21B includes, for example, any one or more of positive electrode materials capable of inserting and extracting lithium as an electrode reactant as a positive electrode active material. Materials and binders may be included. Examples of the positive electrode material capable of inserting and extracting lithium include lithium such as titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), niobium selenide (NbSe ₂ ), and vanadium oxide (V ₂ O ₅ ). Metal chalcogenides containing no lithium, or 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)) or lithium manganese composite oxide (LiMn ₂ O ₄ ) having a spinel structure. 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-v Mn _v PO ₄ (v <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 of a negative electrode current collector 22A having a pair of opposed surfaces. Although not shown, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper (Cu) foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer 22B includes, for example, a negative electrode active material, and may include a binder, a conductive material, or other materials that do not contribute to charging as necessary. As the negative electrode active material, for example, it is possible to occlude and release lithium as an electrode reactant, and one negative electrode material including at least one member selected from the group consisting of metal elements and metalloid elements as a constituent element. Or it is preferable to contain 2 or more types. Specifically, as such a negative electrode material, a simple substance, an alloy, or a compound of a metal element or a metalloid element capable of forming an alloy with lithium, an alloy, or a compound, or one or more phases thereof are at least partially included. The material which has 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.

Examples of metal elements or metalloid elements capable of forming an alloy with lithium include magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), silicon (Si), germanium (Ge), Tin, lead (Pb), antimony (Sb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr) or yttrium (Y). Among them, a group 14 metal element or metalloid element in the long-period type periodic table is preferable, and silicon or tin is particularly preferable. This is because a higher capacity can be obtained. These alloys or compounds, such as those represented by the chemical formula Ma _s Mb _t. In this chemical formula, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, and Mb represents at least one of elements other than Ma. The values of s and t are s> 0 and t ≧ 0, respectively.

  Among them, as such a 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 tin and cobalt A SnCoC-containing material having a cobalt ratio Co / (Sn + Co) of 30% by mass to 70% by mass with respect to the total is preferable. This is because a high energy density can be obtained in such a composition range, and excellent cycle characteristics can be obtained.

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

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

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

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

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

  Moreover, you may use another material for a negative electrode active material. As another negative electrode active material, for example, a carbon material capable of inserting and extracting lithium which is an electrode reactant is cited. A carbon material is preferable because excellent cycle characteristics can be obtained. Examples of the carbon material include non-graphitizable carbon, graphitizable carbon, graphite, carbon black, fibrous carbon, and pyrolytic carbon. The carbon material may be used alone as the negative electrode active material, but may be used together with the metal element or metalloid element, alloy or compound described above. When mixed and used, the carbon material also serves as a conductive material, which is preferable because high capacity can be obtained and cycle characteristics can be improved. Furthermore, other negative electrode active materials other than these may be used, and in that case, they may be used alone or mixed with other negative electrode active materials.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is composed of, for example, a porous film made of a synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene, or the like, or a porous film made of an inorganic material such as a ceramic nonwoven fabric. The porous film may be laminated.

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

Examples of the electrolyte salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiB ( Examples thereof include lithium salts such as C ₆ H ₅ ) ₄ , LiB (C ₂ O ₄ ) ₂ , LiCF ₃ SO ₃ , LiCH ₃ SO ₃ , LiCl, or LiBr. Any one electrolyte salt may be used alone, or two or more electrolyte salts may be mixed and used.

  The solvent contains at least one member selected from the group consisting of ethylene sulfite and derivatives thereof and at least one carbonate ester derivative having a halogen atom (hereinafter simply referred to as a carbonate ester derivative). A film is formed on the surface of the negative electrode 22 by ethylene sulfite and its derivative, and the reductive decomposition reaction of the electrolytic solution can be suppressed, and the oxidation potential of the electrolytic solution is increased by the carbonic acid ester derivative. This is because the oxidative decomposition reaction can be suppressed and the cycle characteristics can be improved by the synergistic effect.

FIG. 3 shows the result of current-potential measurement performed by changing the composition of the electrolytic solution. In FIG. 3, Y1 is a current-potential curve of an electrolytic solution 1 in which 1.0 mol / l LiPF ₆ is added to a mixed solvent of 75% by volume of ethylene carbonate (EC) and 25% by volume of dimethyl carbonate (DMC). Y2 is a current-potential curve of an electrolytic solution 2 in which 1.0 mol / l LiPF ₆ is added to a mixed solvent of 5% by volume of ethylene sulfite (ES), 70% by volume of ethylene carbonate, and 25% by volume of dimethyl carbonate; Y3 is the current-potential of the electrolytic solution 3 in which 1.0 mol / l LiPF ₆ is added to a mixed solvent of 75% by volume of 4-fluoro-1,3-dioxolan-2-one (FEC) and 25% by volume of dimethyl carbonate. It is a curve. In the current-potential measurement, an electrochemical measuring device manufactured by Toyo Corporation (SI1280B) was used, and platinum was used for the working electrode and lithium foil was used for the counter electrode and the reference electrode. The sweep rate of the working electrode potential was 1 mV / sec.

  As shown in FIG. 3, it can be seen that the oxidation potential is lowered when ethylene sulfite is used, and the oxidation potential is increased when 4-fluoro-1,3-dioxolan-2-one is used. That is, when ethylene sulfite or a derivative thereof is added, a cycle characteristic can be improved by forming a film on the negative electrode 22, while an oxidation potential is lowered and an oxidative decomposition reaction of the electrolytic solution occurs in the positive electrode 21. Although it is difficult to significantly improve the cycle characteristics, the addition of a carbonic acid ester derivative having a halogen atom increases the oxidation potential of the electrolytic solution, so that the oxidative decomposition reaction of the electrolytic solution in the positive electrode 21 can be suppressed. It is considered that the cycle characteristics can be drastically improved by the synergistic effect of combining the good characteristics of each other.

  Ethylene sulfite is represented by the structural formula shown in Chemical Formula 1 (1). Examples of the ethylene sulfite derivative include those shown in Chemical Formula 1 (2), specifically, 4-fluoroethylene sulfite shown in Chemical Formula 1 (3), and 4 shown in Chemical Formula 1 (4). -Chloroethylene sulfite, 4-methylethylene sulfite shown in Chemical formula 1 (5), 4-phenylethylene sulfite shown in Chemical formula 1 (6), and the like.

  Examples of the carbonic acid ester derivative include the ethylene carbonate derivatives shown in Chemical Formula 2 (1). Specifically, 4-fluoro-1,3-dioxolan-2-one shown in Chemical formula 2 (2), 4-chloro-1,3-dioxolan-2-one shown in Chemical formula 2 (3), 4-bromo-1,3-dioxolan-2-one shown in 2 (4), 4-trifluoromethyl-1,3-dioxolan-2-one shown in Chemical Formula 2 (5), etc. 4-Fluoro-1,3-dioxolan-2-one shown in Chemical Formula 2 (2) is preferred.

化２（１）において、Ｒ２１，Ｒ２２，Ｒ２３，Ｒ２４は、水素基、ハロゲン基、またはアルキル基の水素の少なくとも一部がハロゲンで置換された基を表し、それらは同一でも異なっていてもよい。但し、その少なくとも１つは水素基以外の置換基を表す。

In Chemical Formula 2 (1), R21, R22, R23, and R24 represent a hydrogen group, a halogen group, or a group in which at least a part of hydrogen of the alkyl group is substituted with halogen, and they may be the same or different. . However, at least one of them represents a substituent other than a hydrogen group.

The solvent may be composed of at least one of ethylene sulfite and its derivatives and a carbonate ester derivative, but is further mixed with a low-viscosity solvent having a boiling point of 130 ° C. or less under 1 atmosphere. It is preferable. This is because the operating temperature range of the battery can be widened and the ionic conductivity of the electrolyte can be increased. Examples of such a low viscosity solvent include dimethyl carbonate having a boiling point of 90 ° C. (CH ₃ OCOOCH ₃ ), ethyl methyl carbonate having a boiling point of 108 ° C. (CH ₃ CH ₂ OCOOCH ₃ ), or diethyl carbonate having a boiling point of 127 ° C. (C ₂ H ₅ OCOOC ₂ H ₅ ).

  Moreover, you may mix and use another 1 type, or 2 or more types of solvent for a solvent. Other solvents include, for example, vinyl ethylene carbonate, ethylene carbonate, propylene carbonate, vinylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, γ-valerolactone, tetrahydrofuran, 2-methyl Tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, anisole, acetic acid ester, butyric acid ester, propionic acid ester or fluorobenzene may be mentioned. Of these, it is preferable to use a mixture of ethylene carbonate and dimethyl carbonate because the cycle characteristics may be further improved.

  The content of ethylene sulfite and derivatives thereof in the solvent is preferably 0.05% by volume or more and 5% by volume or less, and more preferably 0.1% by volume or more and 3% by volume when two or more types are included. The following is more preferable. Further, the content of the carbonate ester derivative in the solvent is preferably 0.1% by volume or more and 65% by volume or less, and 0.2% by volume or more and 60% by volume or less in total when two or more types are included. This is more preferable. Furthermore, the content of the low-viscosity solvent in the solvent is preferably 20% by volume or more in total when two or more types are included. This is because higher characteristics can be obtained within these ranges.

  In addition, when ethylene carbonate is mixed and used, the volume ratio of ethylene carbonate to the carbonate derivative (ethylene carbonate / carbonate derivative) is preferably in the range of 1/4 or more and 4 or less. This is because higher characteristics can be obtained within this range.

  In the secondary battery, when charged, for example, lithium ions are released from the positive electrode active material layer 21B and inserted into the negative electrode active material layer 22B through the electrolytic solution. When the discharge is performed, for example, lithium ions are released from the negative electrode active material layer 22B and inserted into the positive electrode active material layer 21B through the electrolytic solution. At that time, a stable film based on ethylene sulfite or a derivative thereof is formed on the negative electrode 22, irreversible reaction occurring between the negative electrode 22 and the electrolytic solution is suppressed, and the oxidation potential of the electrolytic solution based on the carbonate derivative is reduced. By the increase, the oxidative decomposition reaction of the electrolytic solution occurring at the positive electrode 21 is suppressed.

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

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

  Next, for example, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and the negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like negative electrode mixture slurry. And Subsequently, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, and the solvent is dried. Then, the negative electrode active material layer 22B is formed by compression molding using a roll press or the like, and the negative electrode 22 is manufactured.

  Next, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through a gasket 17. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  As described above, in the present embodiment, since the electrolytic solution includes at least one member selected from the group consisting of ethylene sulfite and derivatives thereof and a carbonate ester derivative, a stable coating film is generated on the negative electrode 22. The irreversible reaction occurring between the negative electrode 22 and the electrolytic solution can be suppressed, the oxidation potential of the electrolytic solution can be improved, and the oxidative decomposition reaction of the electrolytic solution occurring at the positive electrode 21 can be suppressed. Can do. Therefore, cycle characteristics can be improved, and low temperature characteristics and overcharge safety can be improved.

  In particular, when the negative electrode 22 is capable of inserting and extracting lithium and contains a negative electrode material containing at least one member selected from the group consisting of a metal element and a metalloid element as a constituent element, a higher effect can be obtained. Obtainable.

  Further, if the content of ethylene sulfite and its derivative in the solvent is 0.05% by volume or more and 5% by volume or less, or the content of the carbonate ester derivative in the solvent is 0.1% by volume or more and 65% by volume. If it is made into% or less, a higher effect can be acquired.

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

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

  The negative electrode active material layer 22B is formed by using, for example, a vapor phase method, a liquid phase method, a firing method, or two or more of these methods. The negative electrode active material layer 22B and the negative electrode current collector It is preferable that 22A is alloyed in at least a part of the interface. Specifically, 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)
FIG. 4 shows the configuration of the secondary battery according to the third 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. 5 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 stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte 36, and the outermost peripheral portion is protected by a protective tape 37.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on 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 configuration of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 is the same as that of the positive electrode current collector 21A, the positive electrode active material in the first or second embodiment 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 36 may be composed of an electrolytic solution as in the first embodiment, but may be a so-called gel by holding the electrolytic solution in a polymer compound. 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 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 36 is formed are laminated through a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion. Thus, the wound electrode body 30 is formed. 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. 4 and 5 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 a gel electrolyte 36, and assembling the secondary battery shown in FIGS.

  Further, after forming a wound body that is a precursor of the wound electrode body 30 in the same manner, the wound body is sandwiched between the exterior members 40, and the outer peripheral edge except one side is heat-sealed into a bag shape, An electrolytic solution may be injected and sealed.

  This secondary battery acts in the same manner as the secondary battery according to the first embodiment, and can obtain the same effect.

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

(Examples 1-1 to 1-8)
A cylindrical secondary battery as shown in FIG. 1 was produced.

First, 0.5 mol of lithium carbonate and 1 mol of cobalt carbonate were mixed, and this mixture was baked at 880 ° C. for 5 hours in an air atmosphere to synthesize lithium cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material. Was made into a powder having an average particle size of 8 μm. As a result of X-ray diffraction measurement of the obtained lithium cobalt composite oxide, it was in good agreement with the spectrum of lithium cobalt composite oxide (LiCoO ₂ ) registered in the JCPDS file.

  Next, 95 parts by mass of this lithium cobalt composite oxide powder and 5 parts by mass of lithium carbonate powder are mixed, 91 parts by mass of this mixture, 6 parts by mass of graphite (KS-15 made by Lonza) as a conductive material, and binding. A positive electrode mixture was prepared by mixing 3 parts by mass of polyvinylidene fluoride as a material, and then dispersed in N-methyl-2-pyrrolidone as a solvent to prepare a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was applied to a positive electrode current collector 21A made of an aluminum foil having a thickness of 20 μm, dried, and then compression-molded to form a positive electrode active material layer 21B. Thus, a belt-like positive electrode 21 was produced.

  On the other hand, 10 g of copper powder and 90 g of tin powder were mixed, and this mixture was put into a quartz boat, heated to 1000 ° C. in an argon gas atmosphere, and allowed to cool to room temperature. The lump thus obtained was pulverized by a ball mill in an argon gas atmosphere to obtain a copper-tin (Cu-Sn) alloy powder. Then, using this copper-tin alloy powder as a negative electrode active material, 80 parts by mass of copper-tin alloy powder, 11 parts by mass of conductive material and negative electrode active material graphite (KS-15 made by Lonza), and 1 part by mass of acetylene black Then, 8 parts by mass of polyvinylidene fluoride as a binder was mixed to prepare a negative electrode mixture, and then dispersed in N-methyl-2-pyrrolidone as a solvent to prepare a negative electrode mixture slurry. Subsequently, it apply | coated to the negative electrode collector 22A which consists of copper foil with a thickness of 10 micrometers, it was made to dry, and it compression-molded and formed the negative electrode active material layer 22B, and produced the strip | belt-shaped negative electrode 22. FIG.

  The positive electrode 21 and the negative electrode 22 produced as described above are arranged in the order of the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 through the separator 23 made of a microporous polyethylene film (manufactured by Tonen Chemical; E25MMS) having a thickness of 25 μm. After the lamination, a large number of windings were performed to produce a wound electrode body 20 having an outer diameter of 18 mm. The wound electrode body 20 was fixed with an adhesive tape (not shown).

  The wound electrode body 20 was housed in an iron battery can 11 plated with nickel. Insulating plates 12 and 13 are provided on the upper and lower surfaces of the wound electrode body 20, and the positive electrode lead 25 made of aluminum is led out from the positive electrode current collector 21A to the battery lid 14, while the negative electrode lead 26 made of nickel. Was led out from the negative electrode current collector 22A and welded to the battery can 11 respectively.

Next, an electrolyte is added to a mixed solvent in which 4-fluoro-1,3-dioxolan-2-one (FEC), ethylene sulfite (ES), dimethyl carbonate (DMC), and ethylene carbonate (EC) are mixed. An electrolyte was prepared by adding 1.0 mol / l LiPF ₆ as a salt. At that time, the composition of the solvent was changed as shown in Table 1 in Examples 1-1 to 1-8. Specifically, the content of 4-fluoro-1,3-dioxolan-2-one is 10% by volume, the content of dimethyl carbonate is 50% by volume, and the ethylene sulfite content is 0.01%. The content was changed within the range of volume% to 5 volume%, and the ethylene carbonate content was adjusted accordingly.

  Subsequently, this electrolytic solution was injected into the battery can 11. After that, the battery can 11 is caulked through a gasket 17 whose surface is coated with asphalt, thereby fixing the safety valve mechanism 15 having a current interrupting mechanism, the heat sensitive resistance element 16 and the battery lid 14, and airtightness in the battery. A cylindrical secondary battery having a diameter of 18 mm and a height of 65 mm was produced.

  Further, as Comparative Examples 1-1 to 1-5 with respect to Examples 1-1 to 1-8, except that the composition of the solvent was changed as shown in Table 1, other than the same as Example 1-1 Thus, a secondary battery was produced. Comparative Example 1-1 is a mixture in which 4-fluoro-1,3-dioxolan-2-one and ethylene sulfite are not mixed, and Comparative Examples 1-2 and 1-4 are 4-fluoro-1,3-dioxolane- Only 2-one was mixed, and Comparative Examples 1-3 and 1-5 were mixed with ethylene sulfite only.

  For the fabricated secondary batteries of Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-5, cycle characteristics, low temperature characteristics, and maximum temperature outside the battery during overcharge (hereinafter referred to as overcharge temperature) ) Was evaluated as follows. The results are shown in Table 1.

<Cycle characteristics>
In a 25 ° C. environment, a constant current constant voltage charge of 1000 mA is performed up to an upper limit voltage of 4.2 V, then a constant current discharge of 1000 mA is performed up to a final voltage of 2.5 V, and charge and discharge are performed 100 cycles under the same charge and discharge conditions The capacity maintenance rate (%) at the 100th cycle when the discharge capacity at the first cycle was set to 100 was determined.

<Low temperature characteristics>
In a 25 ° C environment, a constant current constant voltage charge of 1000 mA was performed up to an upper limit voltage of 4.2 V, a constant current discharge of 1000 mA was performed up to a final voltage of 2.5 V, and then in a 25 ° C environment, After carrying out constant current and constant voltage charging up to an upper limit voltage of 4.2 V, 1000 mA constant current discharging is performed up to a final voltage of 2.5 V in an environment of −20 ° C., and the relative capacity obtained by the calculation method described later is maintained. The rate was evaluated as a low temperature characteristic. That is, the low temperature characteristics were obtained by the following formula: discharge capacity (mAh) at 1000 mA in an environment of −20 ° C. ÷ discharge capacity (mAh) at 1000 mA in an environment of 25 ° C. × 100. The discharge capacity was determined by discharge capacity (mAh) = 1000 mA × discharge time (h).

<Maximum temperature during overcharge>
In a 25 ° C. environment, 1000 mA constant current constant voltage charging was performed up to an upper limit voltage of 4.2 V, then 3000 mA constant current charging was performed for 3 hours, and the overcharge temperature was measured.

  As is apparent from Table 1, according to Examples 1-1 to 1-8 to which 4-fluoro-1,3-dioxolan-2-one and ethylene sulfite were added, Comparative Example 1-1 not containing them As compared with Comparative Examples 1-2 and 1-3 in which only one of them was added, the cycle characteristics could be improved.

  Further, as in Comparative Examples 1-4 and 1-5, only one of 4-fluoro-1,3-dioxolan-2-one or ethylene sulfite is added, and both of them are added rather than increasing the addition amount. The added Examples 1-3 to 1-8 were able to further improve the cycle characteristics. This is considered to be a synergistic effect by mixing 4-fluoro-1,3-dioxolan-2-one and ethylene sulfite.

  Furthermore, in Comparative Examples 1-2 and 1-4 in which only 4-fluoro-1,3-dioxolan-2-one was added, the temperature during overcharge was increased, whereas ethylene sulfite was also added. According to Examples 1-1 to 1-8, the overcharge temperature could be lowered. This is presumably because the oxidative decomposition potential of the electrolytic solution was lowered by the addition of ethylene sulfite, so that the electrolytic solution was decomposed and gas was generated at an early stage of overcharging, and the safety valve mechanism 15 was activated.

  In addition, in Examples 1-1 to 1-8, when the content of ethylene sulfite is increased, the cycle characteristics tend to increase to the maximum value and thereafter tend to decrease, while the overcharge temperature is increased. Tended to decrease as the concentration of ethylene sulfite increased.

  That is, if the electrolyte contains ethylene sulfite and 4-fluoro-1,3-dioxolan-2-one, cycle characteristics can be improved and the overcharge temperature can be lowered. I understood. The content of ethylene sulfite in the solvent for improving both of these characteristics is preferably 0.05% by volume or more and 5% by volume or less, more preferably 0.1% by volume or more and 3% by volume or less. I understood that.

(Examples 2-1 to 2-7)
A secondary battery was fabricated in the same manner as in Example 1-5 except that the composition of the solvent was changed as shown in Table 2. Specifically, the content of ethylene sulfite is 1% by volume, the content of 4-fluoro-1,3-dioxolan-2-one is changed within the range of 0.1% by volume to 80% by volume, Accordingly, the contents of ethylene carbonate and dimethyl carbonate were adjusted. For the secondary batteries of Examples 2-1 to 2-7, the cycle characteristics, the low temperature characteristics, and the overcharge temperature were evaluated in the same manner as in Example 1-5. The results are shown in Table 2 together with the results of Example 1-5 and Comparative Examples 1-1 and 1-3.

  As is apparent from Table 2, according to Examples 2-1 to 2-7, the cycle characteristics can be improved as compared with Comparative Examples 1-1 and 1-3 as in Example 1-5. It was. In addition, when the content of 4-fluoro-1,3-dioxolan-2-one is increased, the low-temperature characteristics are improved to the maximum value, and then tend to decrease, and the temperature during overcharge increases. There was a trend.

  That is, the content of 4-fluoro-1,3-dioxolan-2-one in the solvent is preferably 0.1% by volume or more and 65% by volume or less, and preferably 0.2% by volume or more and 60% by volume or less. It turned out to be more preferable. It was also found that it is preferable to mix 20% by volume or more of a low viscosity solvent such as dimethyl carbonate.

(Examples 3-1 and 3-2)
The low viscosity solvent was replaced with dimethyl carbonate in the same manner as in Example 1-5 except that ethyl methyl carbonate (EMC) or diethyl carbonate (DEC) was used as shown in Table 3. A battery was produced. For the secondary batteries of Examples 3-1 and 3-2, the cycle characteristics, the low temperature characteristics, and the overcharge temperature were evaluated in the same manner as in Example 1-5. The results are shown in Table 3 together with the results of Example 1-5 and Comparative Examples 1-1 to 1-3.

  As is apparent from Table 3, according to Examples 3-1 and 3-2, the cycle characteristics can be improved as compared with Comparative Examples 1-1 to 1-3 as in Example 1-5. Compared with Comparative Examples 1-1 and 1-2, the overcharge temperature could be lowered. That is, it has been found that the same effect can be obtained even when another low-viscosity solvent having a boiling point of 130 ° C. or lower is used.

(Examples 4-1 and 4-2)
Example 1 except that cobalt-tin (Co-Sn) alloy powder or cobalt-titanium-tin (Co-Ti-Sn) alloy powder was used as the negative electrode active material instead of the copper-tin alloy powder. A secondary battery was produced in the same manner as in -5. That is, the solvent used was a mixture of 4-fluoro-1,3-dioxolan-2-one 10% by volume, ethylenesulfite 1% by volume, dimethyl carbonate 50% by volume, and ethylene carbonate 39% by volume. It was.

  The cobalt-tin alloy powder is a lump obtained by mixing 10 g of cobalt powder and 90 g of tin powder, placing the mixture in a quartz boat, heating to 1000 ° C. in an argon gas atmosphere, and allowing to cool to room temperature. Was prepared by pulverizing with a ball mill in an argon gas atmosphere. The cobalt-titanium-tin alloy powder is prepared by mixing 1 g of titanium powder, 9 g of cobalt powder, and 90 g of tin powder, putting the mixture in a quartz boat, heating to 1000 ° C. in an argon gas atmosphere, and allowing to cool to room temperature. The obtained lump was produced by pulverizing with a ball mill in an argon gas atmosphere.

  In addition, as Comparative Examples 4-1 and 4-2 with respect to Examples 4-1 and 4-2, except that a mixed solvent in which 50% by volume of dimethyl carbonate and 50% by volume of ethylene carbonate were mixed was used. Secondary batteries were fabricated in the same manner as in Examples 4-1 and 4-2. For the secondary batteries of Examples 4-1 and 4-2 and Comparative Examples 4-1 and 4-2, the cycle characteristics, the low temperature characteristics, and the overcharge temperature were evaluated in the same manner as in Example 1-5. The results are shown in Tables 4 and 5.

  As apparent from Tables 4 and 5, according to Examples 4-1 and 4-2, the cycle characteristics and the low temperature characteristics can be improved as compared with Comparative Examples 4-1 and 4-2. The temperature during charging could be lowered. That is, even when other tin alloys are used, if the solvent contains ethylene sulfite and 4-fluoro-1,3-dioxolan-2-one, cycle characteristics and low-temperature characteristics can be improved. It was found that the temperature during charging can be lowered.

(Examples 5-1 to 5-8)
A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-8, except that a CoSnC-containing material was used instead of the copper-tin alloy powder as the negative electrode active material. At that time, in Examples 5-1 to 5-7, a CoSnC-containing material containing tin, cobalt, indium, titanium, and carbon was used. In Example 5-8, tin, silicon, cobalt, and carbon were used. The thing containing was used. These CoSnC-containing materials were synthesized using a mechanochemical reaction.

  When the composition of the produced CoSnC-containing material was analyzed, in Examples 5-1 to 5-7, the tin content was 48 mass%, the cobalt content was 23 mass%, and the indium content was 5 mass%. %, The content of titanium was 2% by mass, the content of carbon was 20% by mass, and the ratio Co / (Sn + Co) of cobalt to the total of tin and cobalt was 32% by mass. Moreover, in Example 5-8, content of tin is 45 mass%, content of silicon is 4 mass%, content of cobalt is 29 mass%, content of carbon is 20 mass%, tin and cobalt The ratio Co / (Sn + Co) of cobalt to the total was 39% 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-value width with a diffraction angle 2θ of 1.0 ° or more was observed between the diffraction angles 2θ = 20 ° to 50 °. Observed. Furthermore, when XPS was performed on this 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.

  In addition, the composition of the solvent was changed as shown in Tables 6 and 7 in Examples 5-1 to 5-8. Specifically, in Examples 5-1 to 5-3, the content of 4-fluoro-1,3-dioxolan-2-one was 10% by volume, and the content of ethylene sulfite was 0.5% by volume. The content was changed within the range of ˜5% by volume, and the ethylene carbonate content was adjusted accordingly. In Examples 5-4 and 5-5, the content of ethylene sulfite was changed to 1% by volume, and the content of 4-fluoro-1,3-dioxolan-2-one was changed to 1% by volume or 15% by volume. Accordingly, the ethylene carbonate content was adjusted. In Examples 5-6 and 5-7, the content of 4-fluoro-1,3-dioxolan-2-one was 10% by volume, the content of ethylene sulfite was 1% by volume, and the content of ethylene carbonate was 39%. The volume of the low-viscosity solvent was changed to ethyl methyl carbonate or diethyl carbonate. In Example 5-8, the content of 4-fluoro-1,3-dioxolan-2-one was 10% by volume, the content of ethylene sulfite was 1% by volume, and dimethyl carbonate, as in Example 1-5. The content of was 50% by volume, and the content of ethylene carbonate was 39% by volume.

  As Comparative Examples 5-1 to 5-6 with respect to the present Example, except that the composition of the solvent was changed as shown in Tables 6 and 7, it was the same as Example 5-1 to 5-8. A secondary battery was produced. Comparative Examples 5-1 and 5-6 are those in which 4-fluoro-1,3-dioxolan-2-one and ethylene sulfite are not mixed, and Comparative Example 5-2 is 4-fluoro-1,3-dioxolane- Only 2-one was mixed, and Comparative Examples 5-3 to 5-5 were prepared by mixing only ethylene sulfite.

  For the secondary batteries of Examples 5-1 to 5-8 and Comparative Examples 5-1 to 5-6, the cycle characteristics, the low temperature characteristics, and the overcharge temperature were set in the same manner as in Examples 1-1 to 1-8. evaluated. The results are shown in Tables 6 and 7.

  As is apparent from Tables 6 and 7, according to Examples 5-1 to 5-8, the cycle characteristics and the low temperature characteristics can be improved as compared with Comparative Examples 5-1 to 5-6. The temperature during charging could be lowered. That is, even when other tin-containing materials are used, if the solvent contains ethylene sulfite and 4-fluoro-1,3-dioxolan-2-one, cycle characteristics and low-temperature characteristics are improved. It was found that the temperature during overcharge can be lowered.

(Examples 6-1 and 6-2)
Other than using a copper-silicon (Cu-Si) alloy powder or a cobalt-silicon (Co-Si) alloy powder instead of the copper-tin alloy powder as the negative electrode active material, the same as in Example 1-5 Thus, a secondary battery was produced. That is, the solvent used was a mixture of 4-fluoro-1,3-dioxolan-2-one 10% by volume, ethylenesulfite 1% by volume, dimethyl carbonate 50% by volume, and ethylene carbonate 39% by volume. It was.

  The copper-silicon alloy powder was obtained by mixing 20 g of copper powder and 80 g of silicon powder, placing the mixture in a quartz boat, heating to 1000 ° C. in an argon gas atmosphere, and allowing to cool to room temperature. Was prepared by pulverizing with a ball mill in an argon gas atmosphere. The cobalt-silicon alloy powder is obtained by mixing 20 g of cobalt powder and 80 g of silicon powder, placing this mixture in a quartz boat, heating to 1000 ° C. in an argon gas atmosphere, and allowing to cool to room temperature. It was produced by grinding with a ball mill in an argon gas atmosphere.

  In addition, as Comparative Examples 6-1 and 6-2 with respect to Examples 6-1 and 6-2, except that a mixed solvent in which 50% by volume of dimethyl carbonate and 50% by volume of ethylene carbonate were mixed was used. Secondary batteries were fabricated in the same manner as in Examples 6-1 and 6-2. For the secondary batteries of Examples 6-1 and 6-2 and Comparative Examples 6-1 and 6-2, the cycle characteristics, the low temperature characteristics, and the overcharge temperature were evaluated in the same manner as in Example 1-5. The results are shown in Tables 8 and 9.

  As can be seen from Tables 8 and 9, according to Examples 6-1 and 6-2, the cycle characteristics and the low temperature characteristics can be improved as compared with Comparative Examples 6-1 and 6-2. The temperature could also be lowered. That is, even when a silicon alloy is used, if the solvent contains ethylene sulfite and 4-fluoro-1,3-dioxolan-2-one, cycle characteristics and low temperature characteristics can be improved, and overcharge can be achieved. It was found that the temperature could be lowered.

(Examples 7-1 to 7-8)
Secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-8, except that silicon was used instead of the copper-tin alloy powder as the negative electrode active material. At that time, in Examples 7-1 to 7-7, the negative electrode 22 was fabricated by forming the negative electrode active material layer 22B made of silicon on the negative electrode current collector 22A made of copper foil by the electron beam evaporation method. In Example 7-8, 90% by mass of silicon powder having an average particle diameter of 1 μm and 10% by mass of polyvinylidene fluoride as a binder were dispersed in N-methyl-2-pyrrolidone as a solvent, and from a copper foil The negative electrode current collector 22A was coated, dried, compression-molded, and then heat-treated to produce the negative electrode 22.

  In addition, the composition of the solvent was changed as shown in Tables 10 and 11 in Examples 7-1 to 7-8. Specifically, in Examples 7-1 to 7-3, the content of 4-fluoro-1,3-dioxolan-2-one was 10% by volume, and the content of ethylene sulfite was 0.5% by volume. The content was changed within the range of ˜5% by volume, and the ethylene carbonate content was adjusted accordingly. In Examples 7-4 and 7-5, the content of ethylene sulfite was changed to 1% by volume, and the content of 4-fluoro-1,3-dioxolan-2-one was changed to 1% by volume or 15% by volume. Accordingly, the ethylene carbonate content was adjusted. In Examples 7-6 and 7-7, the content of 4-fluoro-1,3-dioxolan-2-one was 10% by volume, the content of ethylene sulfite was 1% by volume, and the content of ethylene carbonate was 39%. The volume of the low-viscosity solvent was changed to ethyl methyl carbonate or diethyl carbonate. In Example 7-8, the content of 4-fluoro-1,3-dioxolan-2-one was 10% by volume, the content of ethylene sulfite was 1% by volume, and dimethyl carbonate, as in Example 1-5. The content of was 50% by volume, and the content of ethylene carbonate was 39% by volume.

  As Comparative Examples 7-1 to 7-6 with respect to the present Example, except that the composition of the solvent was changed as shown in Tables 10 and 11, other than that was the same as Example 7-1 to 7-8. A secondary battery was produced. Comparative Examples 7-1 and 7-6 are those in which 4-fluoro-1,3-dioxolan-2-one and ethylene sulfite are not mixed, and Comparative Example 7-2 is 4-fluoro-1,3-dioxolane- Only 2-one was mixed, and Comparative Examples 7-3 to 7-5 were mixed with ethylene sulfite only.

  For the secondary batteries of Examples 7-1 to 7-8 and Comparative Examples 7-1 to 7-6, the cycle characteristics, the low temperature characteristics, and the overcharge temperature were set in the same manner as in Examples 1-1 to 1-8. evaluated. The results are shown in Tables 10 and 11.

  As apparent from Tables 10 and 11, according to Examples 7-1 to 7-8, the cycle characteristics and the low temperature characteristics can be improved as compared with Comparative Examples 7-1 to 7-6. The temperature during charging could be lowered. That is, even when using a simple substance of silicon or when the negative electrode active material layer 22B is formed by a vapor phase method or a firing method, ethylene sulfite and 4-fluoro-1,3-dioxolane-2- It has been found that if ON is included, cycle characteristics and low temperature characteristics can be improved, and the overcharge temperature can be lowered.

( Reference Example 8-1)
A secondary battery was fabricated in the same manner as in Example 1-5 except that the negative electrode 22 was formed using a carbon material instead of the copper-tin alloy powder as the negative electrode active material. That is, the solvent used was a mixture of 4-fluoro-1,3-dioxolan-2-one 10% by volume, ethylenesulfite 1% by volume, dimethyl carbonate 50% by volume, and ethylene carbonate 39% by volume. It was. The negative electrode 22 is a mixture of 90 parts by mass of graphite (KS-44 manufactured by Lonza), 2 parts by weight of acetylene black, and 8 parts by weight of polyvinylidene fluoride as a binder, and dispersed in N-methyl-2-pyrrolidone. Then, the negative electrode current collector 22A made of copper foil was applied and dried, and compression molded to form the negative electrode active material layer 22B.

Further, as Comparative Examples 8-1 to 8-5 with respect to Reference Example 8-1, as shown in Table 12, except that the composition of the solvent was changed, the other two were performed in the same manner as Reference Example 8-1. A secondary battery was produced. Comparative Example 8-1 is a mixture in which 4-fluoro-1,3-dioxolan-2-one and ethylene sulfite are not mixed, and Comparative Examples 8-2 and 8-4 are 4-fluoro-1,3-dioxolane- Only 2-one was mixed, and Comparative Examples 8-3 and 8-5 were prepared by mixing only ethylene sulfite. For the secondary batteries of Reference Example 8-1 and Comparative Examples 8-1 to 8-5, the cycle characteristics, the low temperature characteristics, and the overcharge temperature were evaluated in the same manner as in Example 1-5. The results are shown in Table 12.

As is clear from Table 12, according to Reference Example 8-1 using 4-fluoro-1,3-dioxolan-2-one and ethylene sulfite, cycle characteristics and It was found that the low temperature characteristics can be improved and the temperature rise during overcharge can be suppressed. Further, compared with Comparative Examples 8-2 to 8-5, the cycle characteristics and the low temperature characteristics could be improved while suppressing the overcharge temperature to 90 ° C., so that 4-fluoro-1,3-dioxolane was obtained. A synergistic effect of 2-one and ethylene sulfite was revealed. That is, even when a carbon material is used as the negative electrode active material, if the solvent contains 4-fluoro-1,3-dioxolan-2-one and ethylene sulfite, the cycle characteristics and the low temperature characteristics are improved. It was found that the temperature during overcharge can be lowered.

(Examples 9-1 and 9-2)
Instead of 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one (ClEC) or 4-bromo-1,3-dioxolan-2-one (BrEC) A secondary battery was made in the same manner as Example 1-5 except that was used. For the secondary batteries of Examples 9-1 and 9-2, the cycle characteristics, the low temperature characteristics, and the overcharge temperature were evaluated in the same manner as in Example 1-5. The results are shown in Table 13 together with the results of Example 1-5 and Comparative Examples 1-1 to 1-3.

  As is clear from Table 13, according to Examples 9-1 and 9-2, cycle characteristics and low-temperature characteristics are improved as compared with Comparative Examples 1-1 to 1-3, as in Example 1-5. In addition, the temperature during overcharging could be lowered. That is, it was found that the same effect can be obtained even when other carbonate ester derivatives having a halogen atom are used.

(Examples 10-1 to 10-4)
Instead of ethylene sulfite, 4-fluoroethylene sulfite (F-ES), 4-chloroethylene sulfite (Cl-ES), 4-methylethylene sulfite (CH ₃ -ES), or 4-phenylethylene sulfite A secondary battery was fabricated in the same manner as in Example 1-5, except that an ethylene sulfite derivative of phyto (C ₆ H ₅ -ES) was used. For the secondary batteries of Examples 10-1 to 10-4, the cycle characteristics, the low temperature characteristics, and the overcharge temperature were evaluated in the same manner as in Example 1-5. The results are shown in Table 14 together with the results of Example 1-5 and Comparative Examples 1-1 to 1-3.

  As is apparent from Table 14, according to Examples 10-1 to 10-4, the cycle characteristics and the low temperature characteristics are improved as compared with Comparative Examples 1-1 to 1-3 as in Example 1-5. In addition, the temperature during overcharging could be lowered. That is, it was found that the same effect can be obtained even if an ethylene sulfite derivative is used.

  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 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 is, for example, as described in the above embodiment, as a negative electrode active material, a carbon material, a simple metal element, an alloy or a compound, or a simple metal element capable of inserting and extracting the light metal. Alloys or compounds can be used.

Furthermore, in the above-described embodiments and examples, a cylindrical secondary battery has been specifically described, but the present invention is a secondary battery having other shapes such as a coin type, a button type, or a square type, Alternatively, the present invention can be similarly applied to a secondary battery having another structure such as a stacked 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 characteristic view showing the electric current-potential curve by the composition of electrolyte solution. It is a disassembled perspective view showing the structure of the secondary battery which concerns on the 2nd Embodiment of this invention. It is sectional drawing showing the structure along the II line of the winding electrode body shown in FIG. 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 ... Gasket, 20, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode current collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode current collector, 22B, 34B ... Negative electrode active material layer, 23, 35 ... Separator , 24 ... Center pin, 25, 31 ... Positive electrode lead, 26, 32 ... Negative electrode lead, 36 ... Electrolyte layer, 37 ... Protective tape, 40 ... Exterior member, 41 ... Adhesion film.

Claims (6)

An electrolyte is provided together with the positive electrode and the negative electrode ,
The negative electrode is capable of occluding and releasing an electrode reactant, and contains a negative electrode material including at least one member selected from the group consisting of metal elements and metalloid elements as constituent elements,
The electrolytic solution contains a solvent containing at least one member selected from the group consisting of ethylene sulfite and derivatives thereof and a carbonate ester derivative having a halogen atom .
battery. The content of ethylene sulfite and its derivatives in the solvent is less than 5 vol% 0.05 vol%, battery according to claim 1, wherein. The content of the carbonate derivative in the solvent is less 65% by volume 0.1% by volume, battery according to claim 1, wherein. The solvent is further boiling containing 130 ° C. or less of the low viscosity solvent, battery according to claim 1, wherein. The battery according to claim 4 , wherein the content of the low-viscosity solvent in the solvent is 20% by volume or more. The negative electrode, the negative electrode material containing A battery according to claim 1 further comprising at least one of tin (Sn) and silicon (Si) as an element.

Images