JP2012234767A - Electrolytic solution for secondary battery, secondary battery, electronic device, electric power tool, electric vehicle, and power storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery capable of achieving increase in a high battery capacity while inhibiting the swelling of the battery.SOLUTION: The secondary battery comprises a positive electrode, a negative electrode, and an electrolytic solution. The electrolytic solution contains a cyclic carboxylic acid imide, and at least one of a halogenated cyclic carbonic ester and an unsaturated carbon bond cyclic carbonic ester.

Description

  The present technology relates to an electrolyte for a secondary battery, a secondary battery using the electrolyte for the secondary battery, and an electronic device, an electric tool, an electric vehicle, and an electric power storage system using the secondary battery.

  In recent years, electronic devices typified by mobile phones or personal digital assistants (PDAs) have become widespread, and further downsizing, weight reduction, and long life have been strongly demanded. Accordingly, as a power source, development of a battery, in particular, a secondary battery that is small and lightweight and capable of obtaining a high energy density is in progress. In recent years, this secondary battery is not limited to the above-described electronic devices, but can be applied to various uses represented by power storage systems such as electric tools such as electric drills, electric vehicles such as electric vehicles, and household electric power servers. Has also been considered.

  As secondary batteries, those using various charge / discharge principles have been widely proposed. Among them, lithium ion secondary batteries using lithium ions as electrode reactants are promising. This is because higher energy density can be obtained than lead batteries and nickel cadmium batteries.

  The secondary battery includes an electrolytic solution together with a positive electrode and a negative electrode. Each of the positive electrode and the negative electrode includes a positive electrode active material and a negative electrode active material capable of taking in and out the electrode reactant. In order to obtain a high battery capacity, a composite oxide (lithium composite oxide) containing lithium and a transition metal as a constituent element is used as the positive electrode active material, and a carbon material or the like is used as the negative electrode active material. It is used. Further, as the solvent of the electrolytic solution, a carbonate-based mixed solvent or the like is used.

  As a form of the secondary battery, a laminate film type using a film such as an aluminum laminate film is adopted in addition to a cylindrical type using a metal can as an exterior member for housing a positive electrode, a negative electrode and an electrolyte solution. Yes. This is because the secondary battery can be reduced in weight. In this laminated film type secondary battery, in addition to a liquid electrolyte (electrolytic solution), a gel electrolyte in which the electrolytic solution is held by a polymer compound is also used.

  Since the composition of the electrolytic solution greatly affects the performance of the secondary battery, various studies have been made on the composition of the electrolytic solution. Specifically, in order to improve battery capacity characteristics, cycle characteristics, storage characteristics, load characteristics, and the like, it has been proposed to contain an imide compound in the electrolytic solution (see, for example, Patent Documents 1 to 7). As the imide compound, succinimide, a metal salt thereof, or a partially substituted material thereof is used. The metal salt of succinimide is an alkali metal salt or the like, and the partially substituted material of succinimide is N-alkyl succinimide or the like.

JP 2005-093293 A JP 2003-151622 A Japanese Patent Laid-Open No. 11-273726 Japanese Patent Laid-Open No. 11-045724 JP 2002-270181 A JP 2007-257959 A JP 2007-257958 A

  In recent years, electronic devices and the like have become higher performance and multifunctional, and their power consumption tends to increase more and more. Therefore, further improvements regarding the battery capacity of secondary batteries are desired. In this case, gas is generated in the battery due to the decomposition reaction of the electrolyte during charging and discharging, and the battery tends to swell. However, the increase in battery capacity increases the swelling of the secondary battery. I will let you. Therefore, conventionally, since increase in battery capacity and suppression of battery swelling are in a trade-off relationship, it has been difficult to achieve both.

  The present technology has been made in view of such problems, and the purpose thereof is an electrolyte solution for a secondary battery, a secondary battery, an electronic device, an electric motor capable of achieving both an increase in battery capacity and suppression of battery swelling. It is to provide a tool, an electric vehicle, and an electric power storage system.

  The electrolyte solution for a secondary battery according to the present technology includes at least one cyclic carboxylic imide represented by the following formulas (1) to (4) and a halogenation represented by the following formula (5). It contains at least one of a cyclic carbonate and an unsaturated carbon bond cyclic carbonate represented by the formula (6).

（Ｒ１〜Ｒ１６は水素基、または炭素数＝１〜４のアルキル基である。）

(R1 to R16 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)

（Ｒ２１〜Ｒ２４は水素基、ハロゲン基、炭素数＝１〜４のアルキル基、または炭素数＝１〜４のハロゲン化アルキル基であり、Ｒ２１〜Ｒ２４のうちの少なくとも１つはハロゲン基またはハロゲン化アルキル基である。Ｒ２５およびＲ２６は水素基、または炭素数＝１〜４のアルキル基である。）

(R21 to R24 are a hydrogen group, a halogen group, an alkyl group having 1 to 4 carbon atoms, or a halogenated alkyl group having 1 to 4 carbon atoms, and at least one of R21 to R24 is a halogen group or a halogen atom. R25 and R26 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)

  The secondary battery of the present technology includes the above-described electrolyte for the secondary battery of the present technology together with the positive electrode and the negative electrode. The electronic device, the electric tool, the electric vehicle, or the power storage system of the present technology is described above. The secondary battery of the present technology is used.

  According to the secondary battery electrolyte, secondary battery, electronic device, electric tool, electric vehicle, or power storage system of the present technology, the electrolyte is a cyclic carboxylic imide, a halogenated cyclic carbonate, and an unsaturated carbon-bonded cyclic carbonate. And at least one of the esters. Therefore, both increase in battery capacity and suppression of battery swelling can be achieved.

It is sectional drawing showing the structure of the secondary battery (cylindrical type) of one Embodiment of this technique. It is sectional drawing which expands and represents a part of winding electrode body shown in FIG. It is sectional drawing showing the structure of a separator. It is a perspective view showing the structure of the other secondary battery (laminate film type) of one Embodiment of this technique. FIG. 5 is a cross-sectional view taken along line VV of the spirally wound electrode body illustrated in FIG. 4.

Hereinafter, embodiments of the present technology will be described in detail with reference to the drawings. The order of explanation is as follows.

1. Secondary battery 1-1. Cylindrical type 1-2. Laminated film type Applications of secondary batteries

<1. Secondary battery / 1-1. Cylindrical type>
1 and 2 show a cross-sectional configuration of a secondary battery according to an embodiment of the present technology. In FIG. 2, a part of the wound electrode body 20 shown in FIG. 1 is enlarged.

[Overall structure of secondary battery]
The secondary battery described here is, for example, a lithium ion secondary battery in which battery capacity is obtained by occlusion and release of lithium ions, and is a so-called cylindrical type. In this secondary battery, a spirally wound electrode body 20 and a pair of insulating plates 12 and 13 are housed in a substantially hollow cylindrical battery can 11. In the wound electrode body 20, for example, a positive electrode 21 and a negative electrode 22 are stacked and wound via a separator 23.

  The battery can 11 has a hollow structure in which one end is closed and the other end is opened, and is formed of, for example, Fe, Al, or an alloy thereof. Note that a metal material such as Ni may be plated on the surface of the battery can 11. The pair of insulating plates 12 and 13 are disposed so as to sandwich the wound electrode body 20 from above and below and to extend perpendicularly to the wound peripheral surface.

  A battery lid 14, a safety valve mechanism 15, and a heat sensitive resistance element (positive temperature coefficient: PTC element) 16 are caulked through a gasket 17 at the open end of the battery can 11. Thereby, the battery can 11 is sealed. The battery lid 14 is formed of the same material as the battery can 11, for example. The safety valve mechanism 15 and the thermal resistance element 16 are provided inside the battery lid 14, and the safety valve mechanism 15 is electrically connected to the battery lid 14 via the thermal resistance element 16. In the safety valve mechanism 15, when the internal pressure becomes a certain level or more due to an internal short circuit or external heating, the disk plate 15A is reversed and the electrical connection between the battery lid 14 and the wound electrode body 20 is established. It is designed to cut. The heat sensitive resistance element 16 prevents abnormal heat generation caused by a large current. In the heat sensitive resistance element 16, the resistance increases as the temperature rises. The gasket 17 is made of, for example, an insulating material, and asphalt may be applied to the surface thereof.

  A center pin 24 may be inserted in the center of the wound electrode body 20. For example, a positive electrode lead 25 formed of a conductive material such as Al is connected to the positive electrode 21. For example, a negative electrode lead 26 formed of a conductive material such as Ni is connected to the negative electrode 22. The positive electrode lead 25 is welded to the safety valve mechanism 15 and is electrically connected to the battery lid 14. The negative electrode lead 26 is welded to the battery can 11 and is electrically connected to the battery can 11.

[Positive electrode]
The positive electrode 21 is, for example, one in which a positive electrode active material layer 21B is provided on one side or both sides of a positive electrode current collector 21A. The positive electrode current collector 21A is formed of a conductive material such as Al, Ni, or stainless steel, for example.

  The positive electrode active material layer 21 </ b> B includes one or more positive electrode materials that occlude and release lithium ions as the positive electrode active material, and other positive electrode binders or positive electrode conductive agents as necessary. It may contain material.

The positive electrode material is preferably a lithium-containing compound. This is because a high energy density can be obtained. Examples of the lithium-containing compound include a composite oxide containing Li and a transition metal element as constituent elements, and a phosphate compound containing Li and a transition metal element as constituent elements. Among them, the transition metal element is preferably one or more of Co, Ni, Mn, and Fe. 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, but are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10. However, M1 may contain any one kind or two kinds or more of M in the formula (10) described later together with Co described above.

The composite oxide containing Li and a transition metal element is, for example, Li _x CoO ₂ , Li _x NiO ₂ , LiMn ₂ O _4, or a LiNi-based composite oxide represented by the following formula (10). The phosphate compound containing Li and a transition metal element is, for example, LiFePO ₄ or LiFe _1-u Mn _u PO ₄ (u <1). This is because high battery capacity is obtained and excellent cycle characteristics are also obtained. The positive electrode material may be a material other than the above.

LiNi _1-x M _x O ₂ (10)
(M is Co, Mn, Fe, Al, V, Sn, Mg, Ti, Sr, Ca, Zr, Mo, Tc, Ru, Ta, W, Re, Yb, Cu, Zn, Ba, B, Cr, Si , Ga, P, Sb and Nb, and x is 0.005 <x <0.5.)

  In addition, the positive electrode material may be, for example, an oxide, disulfide, chalcogenide, or conductive polymer. Examples of the oxide include titanium oxide, vanadium oxide, and manganese dioxide. Examples of the disulfide include titanium disulfide and molybdenum sulfide. An example of the chalcogenide is niobium selenide. Examples of the conductive polymer include sulfur, polyaniline, and polythiophene.

  The positive electrode binder includes, for example, any one kind or two kinds or more of synthetic rubber or polymer material. Examples of the synthetic rubber include styrene butadiene rubber, fluorine rubber, and ethylene propylene diene. The polymer material is, for example, polyvinylidene fluoride or polyimide.

  The positive electrode conductive agent includes, for example, any one type or two or more types of carbon materials. Examples of the carbon material include graphite, carbon black, acetylene black, and ketjen black. The positive electrode conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

[Negative electrode]
In the negative electrode 22, for example, a negative electrode active material layer 22B is provided on one or both surfaces of a negative electrode current collector 22A.

  The negative electrode current collector 22A is formed of, for example, a conductive material such as Cu, Ni, or stainless steel. The surface of the negative electrode current collector 22A is preferably roughened. This is because the so-called anchor effect improves the adhesion of the negative electrode active material layer 22B to the negative electrode current collector 22A. In this case, the surface of the negative electrode current collector 22A may be roughened at least in a region facing the negative electrode active material layer 22B. Examples of the roughening method include a method of forming fine particles by electrolytic treatment. This electrolytic treatment is a method of providing irregularities by forming fine particles on the surface of the anode current collector 22A by an electrolytic method in an electrolytic bath. A copper foil produced by an electrolytic method is generally called an electrolytic copper foil.

  The negative electrode active material layer 22B includes one or more negative electrode materials that occlude and release lithium ions as the negative electrode active material, and other negative electrode binders or negative electrode conductive agents as necessary. It may contain material. Note that details regarding the negative electrode binder and the negative electrode conductive agent are the same as, for example, the positive electrode binder and the positive electrode conductive agent, respectively. In this negative electrode active material layer 22B, for example, the chargeable capacity of the negative electrode material is larger than the discharge capacity of the positive electrode 21 in order to prevent unintentional deposition of Li metal during charging and discharging. Is preferred.

  The negative electrode material is, for example, a carbon material. This is because the change in crystal structure at the time of occlusion and release of lithium ions is very small, so that high energy density and excellent cycle characteristics can be obtained. In addition, it also functions as a negative electrode conductive agent. This carbon material is, for example, graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, or graphite having a (002) plane spacing of 0.34 nm or less. . More specifically, pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon or carbon blacks. Among these, the cokes include pitch coke, needle coke, petroleum coke and the like. The organic polymer compound fired body is obtained by firing (carbonizing) a polymer compound such as a phenol resin or a furan resin at an appropriate temperature. In addition, the carbon material may be low crystalline carbon or amorphous carbon heat-treated at about 1000 ° C. or less. The shape of the carbon material may be any of a fibrous shape, a spherical shape, a granular shape, and a scale shape.

  The negative electrode material is, for example, a material (metal material) containing any one or two of metal elements and metalloid elements as constituent elements. This is because a high energy density can be obtained. The metal-based material may be a single element, alloy or compound of a metal element or a metalloid element, or may be two or more kinds thereof, or may have at least a part of one or two or more phases thereof. . The alloy includes a material including one or more metal elements and one or more metalloid elements in addition to a material composed of two or more metal elements. The alloy may contain a nonmetallic element. The structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a coexistence of two or more kinds thereof.

  The metal element or metalloid element described above is, for example, a metal element or metalloid element capable of forming an alloy with Li, and specifically, one or more of the following elements. Mg, B, Al, Ga, In, Si, Ge, Sn, Pb, Bi, Cd, Ag, Zn, Hf, Zr, Y, Pd, or Pt. Among these, at least one of Si and Sn is preferable. This is because the ability to occlude and release lithium ions is excellent, and a high energy density can be obtained.

  The material containing at least one of Si and Sn may be a simple substance, an alloy, or a compound of Si or Sn, or may be two or more of them, or at least a part of one or more of those phases. You may have. The simple substance is a simple substance in a general sense (may contain a small amount of impurities), and does not necessarily mean 100% purity.

  An alloy of Si is, for example, a material containing one or more of the following elements as a constituent element other than Si. Sn, Ni, Cu, Fe, Co, Mn, Zn, In, Ag, Ti, Ge, Bi, Sb or Cr. Examples of the Si compound include those containing C or O as a constituent element other than Si. Note that the Si compound may include, for example, one or more of the elements described for the Si alloy as a constituent element other than Si.

Examples of the Si alloy or compound include the following materials. SiB _4, a _{SiB 6, Mg 2 Si, Ni} 2 Si, TiSi 2, MoSi 2, CoSi 2, NiSi 2, CaSi 2, CrSi 2, Cu 5 Si, FeSi 2, MnSi 2, NbSi 2 or TaSi _2. VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2) or LiSiO. Note that _v in SiO _v may be 0.2 <v <1.4.

The Sn alloy is, for example, a material containing one or more of the following elements as a constituent element other than Sn. Si, Ni, Cu, Fe, Co, Mn, Zn, In, Ag, Ti, Ge, Bi, Sb or Cr. Examples of the Sn compound include a material containing C or O as a constituent element. The Sn compound may contain, for example, one or more of the elements described for the Sn alloy as a constituent element other than Sn. Examples of the alloy or compound of Sn include SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSnO, or Mg ₂ Sn.

  Moreover, as a material containing Sn, for example, a material containing Sn as the first constituent element and the second and third constituent elements in addition thereto is preferable. The second constituent element is, for example, one or more of the following elements. Co, Fe, Mg, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, In, Ce, Hf, Ta, W, Bi, or Si. The third constituent element is, for example, one type or two or more types of B, C, Al, and P. This is because when the second and third constituent elements are included, a high battery capacity and excellent cycle characteristics can be obtained.

  Among these, a material containing Sn, Co and C (SnCoC-containing material) is preferable. As the composition of the SnCoC-containing material, for example, the C content is 9.9 mass% to 29.7 mass%, and the Sn and Co content ratio (Co / (Sn + Co)) is 20 mass% to 70 mass%. % By mass. This is because a high energy density can be obtained in such a composition range.

  This SnCoC-containing material has a phase containing Sn, Co, and C, and the phase is preferably low crystalline or amorphous. This phase is a reaction phase capable of reacting with Li, and excellent characteristics can be obtained due to the presence of the reaction phase. The full width at half maximum of the diffraction peak obtained by X-ray diffraction of this phase is 1.0 ° or more at a diffraction angle 2θ when CuKα ray is used as the specific X-ray and the drawing speed is 1 ° / min. Is preferred. This is because lithium ions are occluded and released more smoothly, and the reactivity with the electrolytic solution is reduced. Note that the SnCoC-containing material may include a phase containing a simple substance or a part of each constituent element in addition to the low crystalline or amorphous phase.

  Whether a diffraction peak obtained by X-ray diffraction corresponds to a reaction phase capable of reacting with Li can be easily determined by comparing X-ray diffraction charts before and after electrochemical reaction with Li. . For example, if the position of the diffraction peak changes before and after the electrochemical reaction with Li, it corresponds to a reaction phase capable of reacting with Li. In this case, for example, a diffraction peak of a low crystalline or amorphous reaction phase is observed between 2θ = 20 ° and 50 °. Such a reaction phase has, for example, each of the above-described constituent elements, and is considered to be low crystallization or amorphous mainly due to the presence of C.

  In the SnCoC-containing material, it is preferable that at least a part of C that is a constituent element is bonded to a metal element or a metalloid element that is another constituent element. This is because aggregation or crystallization of Sn or the like is suppressed. The bonding state of the elements can be confirmed by, for example, X-ray photoelectron spectroscopy (XPS). In a commercially available apparatus, for example, Al—Kα ray or Mg—Kα ray is used as the soft X-ray. When at least a part of C is bonded to a metal element, a metalloid element, or the like, the peak of the synthesized wave of C 1s orbital (C1s) appears in a region lower than 284.5 eV. It is assumed that energy calibration is performed so that a peak of 4f orbit (Au4f) of Au atoms is obtained at 84.0 eV. At this time, since the surface contamination carbon usually exists on the surface of the substance, the C1s peak of the surface contamination carbon is set to 284.8 eV, which is used as the energy standard. In XPS measurement, the waveform of the C1s peak is obtained in a form that includes the surface contamination carbon peak and the C peak in the SnCoC-containing material. For example, the two peaks are analyzed by analysis with commercially available software. To do. 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).

  In addition, as long as SnCoC containing material contains Sn, Co, and C, it may contain other structural elements as needed. Examples of such other constituent elements include one or more of Si, Fe, Ni, Cr, In, Nb, Ge, Ti, Mo, Al, P, Ga, and Bi.

  In addition to this SnCoC-containing material, a material containing Sn, Co, Fe and C (SnCoFeC-containing material) is also preferable. The composition of the SnCoFeC-containing material can be arbitrarily set. For example, the composition when the Fe content is set to be small is as follows. The content of C is 9.9 mass% to 29.7 mass%, the content of Fe is 0.3 mass% to 5.9 mass%, and the ratio of the content of Sn and Co (Co / (Sn + Co)) is 30% by mass to 70% by mass. For example, the composition in the case where the Fe content is set to be large is as follows. The content of C is 11.9 mass% to 29.7 mass%, and the ratio of the content of Sn, Co and Fe ((Co + Fe) / (Sn + Co + Fe)) is 26.4 mass% to 48.5 mass%, Co The ratio of the Fe content (Co / (Co + Fe)) is 9.9 mass% to 79.5 mass%. This is because a high energy density can be obtained in such a composition range. The physical properties (half width, etc.) of this SnCoFeC-containing material are the same as those of the above-described SnCoC-containing material.

  The other negative electrode material may be, for example, a metal oxide or a polymer compound. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.

  The negative electrode active material layer 22B is formed by, for example, a coating method, a gas phase method, a liquid phase method, a thermal spraying method, a firing method (sintering method), or two or more kinds thereof. The coating method is, for example, a method in which a particulate negative electrode active material is mixed with a binder and then dispersed in a solvent such as an organic solvent. Examples of the vapor phase method include a physical deposition method and a chemical deposition method. Specific examples include vacuum deposition, sputtering, ion plating, laser ablation, thermal chemical vapor deposition, chemical vapor deposition (CVD), and plasma chemical vapor deposition. Examples of the liquid phase method include an electrolytic plating method and an electroless plating method. The thermal spraying method is a method in which the negative electrode active material is sprayed in a molten state or a semi-molten state. The baking method is, for example, a method in which heat treatment is performed at a temperature higher than the melting point of a binder or the like after being applied in the same procedure as the application method. A known method can be used for the firing method. As an example, an atmosphere firing method, a reaction firing method, a hot press firing method, or the like can be given.

  In this lithium ion secondary battery, as described above, in order to prevent Li metal from unintentionally depositing on the negative electrode 22 during charging, the electrochemical equivalent of the negative electrode material capable of occluding and releasing lithium ions is positive. It is larger than the electrochemical equivalent. Further, when the open circuit voltage (that is, the battery voltage) at the time of full charge is 4.30 V or more, even when the same positive electrode active material is used, the amount of released lithium ions per unit mass is large compared to the case of 4.20 V. Therefore, the amount of the positive electrode active material and the negative electrode active material is adjusted accordingly. Thereby, a high energy density can be obtained.

[Separator]
The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes. The separator 23 includes a liquid electrolyte (electrolyte). Is impregnated. The separator 23 is, for example, a porous film made of synthetic resin or ceramic, and may be a laminate of two or more kinds of porous films. The synthetic resin is, for example, polytetrafluoroethylene, polypropylene, or polyethylene.

  In particular, the separator 23 preferably has a multilayer structure. FIG. 3 shows a cross-sectional configuration of the separator 23 and corresponds to FIG. For example, as shown in FIG. 3, the separator 23 having the multilayer structure includes a base material layer 23A made of the porous film described above and a polymer compound layer provided on at least one surface of the base material layer 23A. 23B. This is because the adhesion of the separator 23 to the positive electrode 21 and the negative electrode 22 is improved and distortion of the wound electrode body 20 is suppressed, so that the decomposition reaction of the electrolytic solution is further suppressed. Moreover, it is because the leakage of the electrolyte solution impregnated in the base material layer 23A is suppressed. Thereby, even if it repeats charging / discharging, while the resistance of a secondary battery becomes difficult to rise, battery swelling is suppressed.

  The polymer compound layer 23 includes, for example, a polymer material such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable. However, the polymer material may be a material other than polyvinylidene fluoride. For example, after preparing a solution in which a polymer material is dissolved, the polymer compound layer 23 is applied to the surface of the base material layer 23A, or the base material layer 23A is immersed in the solution and then dried. It is formed by letting.

[Electrolyte]
The electrolytic solution contains a cyclic carboxylic imide and at least one of a halogenated cyclic carbonate and an unsaturated carbon bond cyclic carbonate together with an electrolyte salt. The cyclic carboxylic acid imide is one or more of compounds represented by the following formulas (1) to (4). The halogenated cyclic carbonate is a compound represented by the following formula (5), and the unsaturated carbon bond cyclic carbonate is a compound represented by the following formula (6).

（Ｒ１〜Ｒ１６は水素基、または炭素数＝１〜４のアルキル基である。）

(R1 to R16 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)

（Ｒ２１〜Ｒ２４は水素基、ハロゲン基、炭素数＝１〜４のアルキル基、または炭素数＝１〜４のハロゲン化アルキル基であり、Ｒ２１〜Ｒ２４のうちの少なくとも１つはハロゲン基またはハロゲン化アルキル基である。Ｒ２５およびＲ２６は水素基、または炭素数＝１〜４のアルキル基である。）

(R21 to R24 are a hydrogen group, a halogen group, an alkyl group having 1 to 4 carbon atoms, or a halogenated alkyl group having 1 to 4 carbon atoms, and at least one of R21 to R24 is a halogen group or a halogen atom. R25 and R26 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)

[Cyclic carboxylic acid imide]
The cyclic carboxylic imide is a cyclic compound having —C (═O) —NH—C (═O) —. The electrolyte solution contains the cyclic carboxylic imide and the halogenated cyclic carbonate together because a strong and stable protective film is formed on the surface of the negative electrode 22 by the synergistic action of both, This is because the decomposition reaction of the electrolytic solution is remarkably suppressed.

  Specifically, the cyclic carboxylic acid imide has a property of preferentially decomposing before reaching the potential (decomposition potential) at which the main component of the electrolytic solution reacts with the negative electrode active material. This main component is a non-aqueous solvent containing ethylene carbonate or diethyl carbonate, as will be described later. For this reason, a coating derived from the cyclic carboxylic imide is formed on the surface of the negative electrode 22 at an early stage during the first charge / discharge.

  Further, the halogenated cyclic carbonate and the like have a property of forming a film on the surface of the negative electrode 22 by being decomposed during charging and discharging. For this reason, at the time of charging / discharging, in addition to the film derived from the cyclic carboxylic imide described above, a film derived from a halogenated cyclic carbonate or the like is also formed.

  Thereby, compared with the case where electrolyte solution contains only any one of cyclic carboxylic imide, halogenated cyclic carbonate, etc., battery swelling is suppressed, maintaining the first charge / discharge efficiency high.

  Note that the cyclic carboxylic acid imide has a nitrogen-hydrogen bond (N—H), as is clear from having —C (═O) —NH—C (═O) —. The reason why this cyclic carboxylic acid imide has a nitrogen-hydrogen bond is that the above-described film can be formed more easily than when the hydrogen group is substituted with an alkyl group such as a methyl group. Such a tendency is the same when the hydrogen group is substituted with a group other than an alkyl group.

  Specifically, in a substituted cyclic carboxylic acid imide having an alkyl group or the like, the decomposability is reduced due to the difficulty of detachment of the alkyl group and the like, so that a coating is formed on the surface of the negative electrode 22 during the first charge / discharge. Is difficult to form. On the other hand, in an unsubstituted cyclic carboxylic imide having a hydrogen group, the decomposability is improved due to the easy elimination of the hydrogen group and the like. A film is easily formed.

  Each kind of R1 to R16 in the formulas (1) to (4) may be arbitrary as long as it is a hydrogen group or an alkyl group. That is, R1 to R16 may be the same type of group or different types of groups. In this case, any two or more of R1 to R16 may be bonded to each other to form a ring. The “alkyl group having 1 to 4 carbon atoms” is a methyl group, an ethyl group, a propyl group, or a butyl group, and the propyl group and the butyl group may be linear or branched. The reason why R1 to R16 have 1 to 4 carbon atoms is that excellent solubility and compatibility can be obtained.

  Specific examples of the cyclic carboxylic acid imide are as follows. A specific example of the cyclic carboxylic acid imide represented by the formula (1) is succinimide in which R1 to R4 are hydrogen groups. A specific example of the cyclic carboxylic imide represented by the formula (2) is glutarimide in which R5 to R10 are hydrogen groups. A specific example of the cyclic carboxylic imide represented by the formula (3) is maleimide in which R11 and R12 are hydrogen groups. A specific example of the cyclic carboxylic imide represented by the formula (4) is phthalimide in which R13 to R16 are hydrogen groups. This is because a stable film can be formed and excellent solubility and compatibility can be obtained. However, the cyclic carboxylic imide may be other compounds as long as the conditions of the chemical formulas shown in the formulas (1) to (4) are satisfied. That is, as an example, the cyclic carboxylic acid imide may be a compound in which at least one hydrogen group in the succinimide described above is substituted with an alkyl group.

  For confirmation, a specific example of the substituted cyclic carboxylic imide is N-methylsuccinimide in which a hydrogen group in a nitrogen-hydrogen bond is substituted with a methyl group.

  Although content of cyclic carboxylic imide in electrolyte solution is not specifically limited, It is preferable that they are 0.1 weight%-1 weight% especially. This is because a higher effect can be obtained.

[Halogenated cyclic carbonate]
The halogenated cyclic carbonate is a cyclic carbonate containing one or more halogens as constituent elements. The type of halogen is not particularly limited, but among them, F, Cl or Br is preferable, and F is more preferable. This is because a higher effect can be obtained. However, the number of halogens is preferably two rather than one, and may be three or more. This is because a stronger and more stable coating is formed, so that the decomposition reaction of the electrolytic solution is further suppressed.

  Each kind of R21-R24 in Formula (5) may be arbitrary as long as it is an above-described hydrogen group, a halogen group, an alkyl group, or a halogenated alkyl group. That is, R21 to R24 may be the same type of group or different types of groups. In this case, any two of R21 to R24 may be bonded to each other to form a ring. However, since the halogenated cyclic carbonate contains one or more halogens as a constituent element, at least one of R21 to R24 is a halogen group or a halogenated alkyl group. The halogenated alkyl group is a group in which at least one hydrogen group in an alkyl group is substituted with a halogen group. The details regarding the “alkyl group having 1 to 4 carbon atoms” are the same as those described for the alkylated cyclic carbonate.

  Specific examples of the halogenated cyclic carbonate include 4-fluoro-1,3-dioxolan-2-one or 4,5-difluoro-1,3-dioxolan-2-one, and any one of them can be used. It may be a mixture of two or more. This is because the film-forming ability is excellent. However, the halogenated cyclic carbonate may be another compound as long as the condition of the chemical formula shown in Formula (5) is satisfied.

  The content of the halogenated cyclic carbonate in the electrolytic solution is not particularly limited, but is preferably 0.5% by weight to 5% by weight. This is because a higher effect can be obtained. In addition, when electrolyte solution contains both halogenated cyclic carbonate and unsaturated carbon bond cyclic carbonate, the total amount should just be in the above-mentioned range.

[Unsaturated carbon bond cyclic carbonate]
An unsaturated carbon bond cyclic ester carbonate is a cyclic ester carbonate having one or more unsaturated carbon bonds (carbon-carbon double bonds). The details regarding the respective types of R25 and R26 in Formula (6) are the same as R21 to R24 in Formula (5).

  Specific examples of the unsaturated carbon bond cyclic ester carbonate include vinylene carbonate and vinyl ethylene carbonate, and one of them may be used, or a mixture of two or more thereof may be used. This is because the film-forming ability is excellent. However, as long as the conditions of the chemical formula shown in Formula (6) are satisfied, the unsaturated carbon bond cyclic carbonate may be another compound.

  The content of the unsaturated carbon bond cyclic carbonate in the electrolytic solution is not particularly limited, but is the same as the content of the halogenated cyclic carbonate, for example.

[Alkylated cyclic carbonate]
In addition, it is preferable that electrolyte solution contains the alkylated cyclic carbonate represented by following formula (7). Since this alkylated cyclic carbonate is less reactive than non-alkylated cyclic carbonates such as ethylene carbonate described later, the decomposition reaction of the electrolytic solution due to the reaction with the negative electrode active material or the like is suppressed. is there.

（Ｒ３１〜Ｒ３６は水素基、または炭素数＝１〜４のアルキル基である。）

(R31 to R36 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)

  The details regarding each type of R31 to R36 in Formula (7) are the same as R21 to R24 in Formula (5). Specific examples of the alkylated cyclic carbonate are propylene carbonate and butylene carbonate described above, and one of them may be used, or two or more of them may be used. However, the alkylated cyclic carbonate may be another compound as long as the condition of the chemical formula shown in Formula (7) is satisfied.

  The content of the alkylated cyclic carbonate in the electrolytic solution is arbitrary. However, when the electrolyte contains highly reactive ethylene carbonate, the content (wt%) of the alkylated cyclic carbonate in the electrolyte must be equal to or greater than the content (wt%) of ethylene carbonate. Is preferred. This is because even when the electrolytic solution contains ethylene carbonate, the decomposition reaction of the electrolytic solution is suppressed.

[Nonaqueous solvent]
The electrolytic solution contains any one kind or two or more kinds of non-aqueous solvents such as organic solvents in addition to the electrolyte salt, cyclic carboxylic acid imide, halogenated cyclic carbonate and unsaturated carbon bond cyclic carbonate. May be. Here, the cyclic carboxylic acid imide, the halogenated cyclic carbonate and the unsaturated carbon-bonded cyclic carbonate are excluded from the non-aqueous solvent.

  Nonaqueous solvents include, for example, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, trimethyl Methyl acetate, ethyl trimethyl acetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N′-dimethyl Tyrimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate or dimethyl sulfoxide. This is because excellent battery capacity, cycle characteristics, storage characteristics, and the like can be obtained.

  In particular, at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate is preferable. This is because more excellent characteristics can be obtained. In this case, a high-viscosity (high dielectric constant) solvent such as ethylene carbonate that is a cyclic carbonate (for example, a relative dielectric constant ε ≧ 30) and a low-viscosity solvent such as dimethyl carbonate that is a chain carbonate (for example, viscosity ≦ 1 mPa · s) is more preferable. This is because the dissociation property of the electrolyte salt and the ion mobility are improved.

  In addition, the non-aqueous solvent may contain a halogenated chain carbonate. This is because, like the halogenated cyclic carbonate, the decomposition reaction of the electrolytic solution is suppressed by the protective film formed on the surface of the negative electrode 22 during charging and discharging. This halogenated chain carbonate is a chain carbonate containing one or more halogens as a constituent element, and the type and number of the halogens are the same as those of the halogenated cyclic carbonate. Specific examples of the halogenated chain carbonate ester include fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, difluoromethyl methyl carbonate, and the like, and may be used alone or as a mixture of two or more. The content of the halogenated chain carbonate in the solvent is not particularly limited, but is, for example, 0.01 wt% to 50 wt%, preferably 0.5 wt% to 5 wt%. This is because the decomposition reaction of the electrolytic solution is suppressed without excessively reducing the battery capacity.

  The non-aqueous solvent may contain sultone (cyclic sulfonic acid ester). This is because the chemical stability of the electrolytic solution is improved. The sultone is, for example, propane sultone or propene sultone. In addition, content of sultone in a non-aqueous solvent is 0.5 weight%-5 weight%, for example. This is because the decomposition reaction of the electrolytic solution is suppressed without excessively reducing the battery capacity.

  Furthermore, the non-aqueous solvent may contain an acid anhydride. This is because the chemical stability of the electrolytic solution is further improved. Examples of the acid anhydride include dicarboxylic acid anhydride, disulfonic acid anhydride, and carboxylic acid sulfonic acid anhydride. Examples of the dicarboxylic acid anhydride include succinic anhydride, glutaric anhydride, and maleic anhydride. Examples of the disulfonic anhydride include ethanedisulfonic anhydride and propanedisulfonic anhydride. Examples of the carboxylic acid sulfonic acid anhydride include anhydrous sulfobenzoic acid, anhydrous sulfopropionic acid, and anhydrous sulfobutyric acid. In addition, content of the acid anhydride in a nonaqueous solvent is 0.5 weight%-5 weight%, for example. This is because the decomposition reaction of the electrolytic solution is suppressed without excessively reducing the battery capacity.

[Electrolyte salt]
The electrolyte salt includes, for example, any one or more of lithium salts. However, the electrolyte salt may be a salt other than the lithium salt (for example, a light metal salt other than the lithium salt).

The lithium salt is, for example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiAlCl ₄ , Li ₂ SiF ₆ , LiCl or LiBr. . This is because excellent battery capacity, cycle characteristics, storage characteristics, and the like can be obtained.

Among these, at least one of LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ is preferable, and LiPF ₆ is more preferable. This is because a higher effect can be obtained because the internal resistance is lowered.

  The content of the electrolyte salt is preferably 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent. This is because high ionic conductivity is obtained.

[Operation of secondary battery]
In this secondary battery, for example, during charging, lithium ions released from the positive electrode 21 are occluded in the negative electrode 22 through the electrolytic solution, and during discharging, lithium ions released from the negative electrode 22 are used as the electrolytic solution. And inserted in the positive electrode 21.

[Method for producing secondary battery]
This secondary battery is manufactured by the following procedure, for example.

  First, the positive electrode 21 is produced. A positive electrode active material and, if necessary, a positive electrode binder and a positive electrode conductive agent are mixed to obtain a positive electrode mixture. Subsequently, the positive electrode mixture is dispersed in an organic solvent or the like to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is applied to both surfaces of the positive electrode current collector 21A and then dried to form the positive electrode active material layer 21B. Subsequently, the positive electrode active material layer 21 </ b> B is compression-molded with a roll press or the like while being heated as necessary. In this case, compression molding may be repeated a plurality of times.

  In addition, the negative electrode 22 is prepared by the same procedure as that of the positive electrode 21 described above. Specifically, a negative electrode mixture in which a negative electrode active material and, if necessary, a negative electrode binder and a negative electrode conductive agent are mixed is dispersed in an organic solvent or the like to obtain a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 22A and then dried to form the negative electrode active material layer 22B, and then the negative electrode active material layer 22B is compression molded as necessary.

  Next, after mixing a cyclic carboxylic acid imide, at least one of a halogenated cyclic carbonate and an unsaturated carbon-bonded cyclic carbonate, and a non-aqueous solvent and an alkylated cyclic carbonate as necessary, an electrolyte salt Is dissolved to prepare an electrolytic solution.

  Finally, a secondary battery is assembled using the positive electrode 21 and the negative electrode 22. First, the positive electrode lead 25 is attached to the positive electrode current collector 21A and the negative electrode lead 26 is attached to the negative electrode current collector 22A by a welding method or the like. Subsequently, after the positive electrode 21 and the negative electrode 22 are laminated via the separator 23 and wound to produce the wound electrode body 20, the center pin 24 is inserted into the winding center. When this separator 23 is prepared, the porous film may be used as it is, or the polymer compound layer 23B may be formed on the surface of the base material layer 23A that is a porous film. Subsequently, the wound electrode body 20 is accommodated in the battery can 11 while being sandwiched between the pair of insulating plates 12 and 13. In this case, the tip of the positive electrode lead 25 is attached to the safety valve mechanism 15 and the tip of the negative electrode lead 26 is attached to the battery can 11 by a welding method or the like. Subsequently, an electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. Subsequently, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are caulked to the opening end of the battery can 11 through the gasket 17.

[Operation and effect of secondary battery]
According to this cylindrical secondary battery, the electrolytic solution contains a cyclic carboxylic imide and at least one of a halogenated cyclic carbonate and an unsaturated carbon bond cyclic carbonate. In this case, as described above, a strong and stable protective film is formed on the surface of the negative electrode 22 by the synergistic action of both. As a result, the decomposition reaction of the electrolytic solution is suppressed during the first charge / discharge, so that the first charge / discharge efficiency is maintained high, and the amount of gas generated during the charge / discharge is reduced, so that battery swelling is suppressed. . Therefore, both increase in battery capacity and suppression of battery swelling can be achieved.

  In particular, if the cyclic carboxylic acid imide is at least one of succinimide, glutarimide, maleimide, and phthalimide, or the content of the cyclic carboxylic acid imide in the electrolytic solution is 0.1 wt% to 1 wt%, A higher effect can be obtained.

  Further, if the halogenated cyclic carbonate is 4-fluoro-1,3-dioxolan-2-one or the unsaturated carbon-bonded cyclic carbonate is vinylene carbonate, a higher effect can be obtained. The same applies even if the content of the halogenated cyclic carbonate and unsaturated carbon bond cyclic carbonate in the electrolyte is 0.5 wt% to 5 wt%.

  Moreover, since the reactivity of the electrolyte solution itself will fall if the electrolyte solution contains the alkylated cyclic carbonate, the battery swelling can be further suppressed. In this case, if the content (% by weight) of the alkylated cyclic carbonate in the electrolytic solution is equal to or higher than the content (% by weight) of ethylene carbonate, a higher effect can be obtained.

  In addition, if the separator 23 includes the polymer compound layer 23B on the surface of the base material layer 23A that is a porous film, the decomposition reaction of the electrolytic solution is further suppressed, so that a higher effect can be obtained.

<1-2. Laminate film type>
FIG. 4 illustrates an exploded perspective configuration of another secondary battery according to an embodiment of the present technology, and FIG. 5 is an enlarged cross-sectional view taken along line VV of the spirally wound electrode body 30 illustrated in FIG. As shown. In the following, the components of the cylindrical secondary battery already described will be referred to as needed.

[Overall structure of secondary battery]
The secondary battery described here is, for example, a so-called laminate film type lithium ion secondary battery, in which a wound electrode body 30 is accommodated in a film-shaped exterior member 40. In the wound electrode body 30, the positive electrode 33 and the negative electrode 34 are laminated and wound via the separator 35 and the electrolyte layer 36. A positive electrode lead 31 is attached to the positive electrode 33, and a negative electrode lead 32 is attached to the negative electrode 34. The outermost periphery of the wound electrode body 30 is protected by a protective tape 37.

  For example, the positive electrode lead 31 and the negative electrode lead 32 are led out in the same direction from the inside of the exterior member 40 toward the outside. The positive electrode lead 31 is made of, for example, a conductive material such as Al, and the negative electrode lead 32 is made of, for example, a conductive material such as Cu, Ni, or stainless steel. These materials have, for example, a thin plate shape or a mesh shape.

  The exterior member 40 is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protective layer are laminated in this order. In this laminate film, for example, the outer peripheral edge portions of the two layers of the fusion layers are bonded together with an adhesive or the like so that the fusion layer faces the wound electrode body 30. The fusing layer is, for example, a film of polyethylene or polypropylene. The metal layer is, for example, an Al foil. The surface protective layer is, for example, a film such as nylon or polyethylene terephthalate.

  Among these, as the exterior member 40, an aluminum laminated film in which a polyethylene film, an aluminum foil, and a nylon film are laminated in this order is preferable. However, the exterior member 40 may be a laminate film having another laminated structure, a polymer film such as polypropylene, or a metal film.

  An adhesion film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 in order to prevent intrusion of outside air. The adhesion film 41 is formed of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32. Such a material is, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  In the positive electrode 33, for example, a positive electrode active material layer 33B is provided on both surfaces of a positive electrode current collector 33A. In the negative electrode 34, for example, a negative electrode active material layer 34B is provided on both surfaces of a negative electrode current collector 34A. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, and the negative electrode active material layer 34B are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, the negative electrode current collector 22A, and the negative electrode active material layer. The configuration is the same as 22B. The configuration of the separator 35 is the same as the configuration of the separator 23.

  The electrolyte layer 36 is one in which an electrolytic solution is held by a polymer compound, and may contain other materials such as additives as necessary. The electrolyte layer 36 is a so-called gel electrolyte. This is because high ionic conductivity (for example, 1 mS / cm or more at room temperature) is obtained and leakage of the electrolytic solution is prevented.

  Examples of the polymer compound include one or more of the following polymer materials. Polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, polyvinyl fluoride, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, Examples thereof include polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, and polycarbonate. In addition, a copolymer of vinylidene fluoride and hexafluoropyrene may be used. Among these, polyvinylidene fluoride or a copolymer of vinylidene fluoride and hexafluoropyrene is preferable, and polyvinylidene fluoride is more preferable. This is because it is electrochemically stable.

  The composition of the electrolytic solution is the same as that of the cylindrical type, and includes a cyclic carboxylic imide and at least one of a halogenated cyclic carbonate and an unsaturated carbon bond cyclic carbonate together with an electrolyte salt. However, in the electrolyte layer 36 which is a gel electrolyte, the solvent of the electrolytic solution is a wide concept including not only a liquid solvent but also a material having ion conductivity capable of dissociating the electrolyte salt. Therefore, when using a polymer compound having ion conductivity, the polymer compound is also included in the solvent.

  Instead of the gel electrolyte layer 36, the electrolytic solution may be used as it is. In this case, the separator 35 is impregnated with the electrolytic solution.

[Operation of secondary battery]
In this secondary battery, for example, at the time of charging, lithium ions released from the positive electrode 33 are occluded by the negative electrode 34 through the electrolyte layer 36, and at the time of discharging, lithium ions released from the negative electrode 34 are absorbed by the electrolyte layer. It is occluded in the positive electrode 53 through 36.

[Method for producing secondary battery]
The secondary battery provided with the gel electrolyte layer 36 is manufactured by, for example, the following three types of procedures.

  In the first procedure, the positive electrode 33 and the negative electrode 34 are manufactured by the same manufacturing procedure as that of the positive electrode 21 and the negative electrode 22. In this case, the positive electrode active material layer 33B is formed on both surfaces of the positive electrode current collector 33A to produce the positive electrode 33, and the negative electrode active material layer 34B is formed on both surfaces of the negative electrode current collector 34A to produce the negative electrode 34. To do. Subsequently, after preparing a precursor solution containing an electrolytic solution, a polymer compound, an organic solvent, and the like, the precursor solution is applied to the positive electrode 33 and the negative electrode 34 to form a gel electrolyte layer 36. Subsequently, 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 by a welding method or the like. Subsequently, after the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are stacked via the separator 35 and wound to produce the wound electrode body 30, a protective tape 37 is attached to the outermost peripheral portion thereof. wear. Subsequently, the wound electrode body 30 is sandwiched between two film-shaped exterior members 40, and then the outer peripheral edge portions of the exterior member 40 are bonded to each other by a heat fusion method or the like to enclose the wound electrode body 30. To do. In this case, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40.

  In the second procedure, the positive electrode lead 31 is attached to the positive electrode 33 and the negative electrode lead 52 is attached to the negative electrode 34. Subsequently, after the positive electrode 33 and the negative electrode 34 are laminated via the separator 35 and wound to produce a wound body that is a precursor of the wound electrode body 30, a protective tape 37 is attached to the outermost peripheral portion thereof. wear. Subsequently, after sandwiching the wound body between the two film-like exterior members 40, the remaining outer peripheral edge portion excluding the outer peripheral edge portion on one side is adhered by a heat fusion method or the like, and the bag-shaped outer member 40 is bonded. The wound body is accommodated in the exterior member 40. Subsequently, an electrolyte composition containing 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 to form a bag-shaped exterior member. After injecting into the inside of 40, the exterior member 40 is sealed by a heat sealing method or the like. Subsequently, the monomer is thermally polymerized. Thereby, since a high molecular compound is formed, the gel electrolyte layer 36 is formed.

  In the third procedure, a wound body is produced and stored in the bag-shaped exterior member 40 in the same manner as in the second procedure described above except that the separator 35 coated with the polymer compound on both sides is used. Examples of the polymer compound applied to the separator 35 include a polymer (such as a homopolymer, a copolymer, or a multi-component copolymer) containing vinylidene fluoride as a component. Specifically, a binary copolymer comprising polyvinylidene fluoride, vinylidene fluoride and hexafluoropropylene as components, or a ternary copolymer comprising vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Etc. One or two or more other polymer compounds may be used together with the polymer containing vinylidene fluoride as a component. Subsequently, an electrolyte solution is prepared and injected into the exterior member 40, and then the opening of the exterior member 40 is sealed by a thermal fusion method or the like. Subsequently, the exterior member 40 is heated while applying a load, and the separator 35 is brought into close contact with the positive electrode 33 and the negative electrode 34 through the polymer compound. Thereby, since the electrolytic solution impregnates the polymer compound, the polymer compound is gelled to form the electrolyte layer 36.

  In the third procedure, the swelling of the secondary battery is suppressed more than in the first procedure. In the third procedure, since the monomer or solvent that is a raw material of the polymer compound hardly remains in the electrolyte layer 36 than in the second procedure, the formation process of the polymer compound is controlled well. For this reason, sufficient adhesion is obtained between the positive electrode 33, the negative electrode 34 and the separator 35 and the electrolyte layer 36.

[Operation and effect of secondary battery]
According to this laminated film type secondary battery, the electrolytic solution contains a cyclic carboxylic imide and at least one of a halogenated cyclic carbonate and an unsaturated carbon bond cyclic carbonate. Therefore, for the same reason as the above-described cylindrical secondary battery, it is possible to achieve both increase in battery capacity and suppression of battery swelling. In particular, in the laminate film type, battery swelling is likely to occur due to the influence of gas generation, so that the battery swelling can be effectively suppressed. Other operations and effects are the same as those of the cylindrical type.

<2. Applications of secondary batteries>
Next, application examples of the above-described secondary battery will be described.

  This secondary battery can be used as a machine, device, instrument, device, or system (an assembly of multiple devices) that can be used as a power source for driving or a power storage source for storing power. There is no particular limitation. When a secondary battery is used as a power source, it may be a main power source (a power source used preferentially) or an auxiliary power source (a power source used in place of or switched from the main power source). In the latter case, the main power source is not limited to the secondary battery.

  Examples of uses of the secondary battery include the following uses. It is an electronic device such as a video camera, a digital still camera, a mobile phone, a notebook computer, a cordless phone, a headphone stereo, a portable radio, a portable television, or a personal digital assistant (PDA). Note that the electronic device includes a household electric appliance such as an electric shaver, a storage device such as a backup power source or a memory card, and a medical electronic device such as a pacemaker or a hearing aid. An electric tool such as an electric drill or an electric saw. Electric vehicles (including hybrid vehicles) such as electric vehicles. It is an electric power storage system such as a home battery system that stores electric power in case of an emergency.

  Especially, it is effective that a secondary battery is applied to an electronic device, an electric tool, an electric vehicle, or an electric power storage system. This is because excellent characteristics are required for the secondary battery, and the characteristics can be effectively improved by using the secondary battery of the present technology. The electronic device performs various functions (music reproduction, etc.) using a secondary battery as an operating power source. An electric tool moves a movable part (for example, drill etc.) by using a secondary battery as a driving power source. The electric vehicle travels using a secondary battery as a driving power source, and may be an automobile (such as a hybrid automobile) provided with a driving source other than the secondary battery as described above. The power storage system is a system that uses a secondary battery as a power storage source. For example, in a power storage system for home use, electric power is stored in a secondary battery as a power storage source, and the electric power stored in the secondary battery is consumed as necessary, so that the home electric product is used. Various devices such as can be used.

  Specific examples of the present technology will be described in detail.

(Experimental Examples 1-1 to 1-25)
The laminated film type secondary battery shown in FIG. 4 and FIG. 5 was produced by the following procedure, and then the characteristics of the secondary battery were examined. The results shown in Table 1 and Table 2 were obtained. .

In the case of producing the positive electrode 33, 94 parts by mass of a positive electrode active material (LiCo _0.99 Al _0.01 O ₂ ), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride: PVDF), and 3 parts by mass of a positive electrode conductive agent (graphite) Were mixed to obtain a positive electrode mixture. Subsequently, the positive electrode mixture was dispersed in an organic solvent (N-methyl-2-pyrrolidone: NMP) to obtain a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was applied to both surfaces of the positive electrode current collector 33A (Al foil: thickness = 20 μm) and then dried to form a positive electrode active material layer 33B (thickness on one side = 40 μm). . After that, the positive electrode current collector 33A on which the positive electrode active material layer 33B was formed was cut into a strip shape (width 30 mm × length 550 mm).

  When producing the negative electrode 34, 97 mass parts of negative electrode active materials (graphite or amorphous carbon) and 3 mass parts of negative electrode binder (PVDF) were mixed, and it was set as the negative electrode mixture. Subsequently, the negative electrode mixture was dispersed in an organic solvent (NMP) to obtain a negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry was applied to both surfaces of the negative electrode current collector 34A (Cu foil: thickness = 15 μm) and then dried to form a negative electrode active material layer 34B (thickness on one side = 40 μm). After that, the negative electrode current collector 34A on which the negative electrode active material layer 34B was formed was cut into a strip shape (width 30 mm × length 550 mm).

When preparing an electrolytic solution, after mixing a non-aqueous solvent and, if necessary, a cyclic carboxylic imide, a halogenated cyclic carbonate, an unsaturated carbon bond cyclic carbonate and an alkylated cyclic carbonate, an electrolyte salt (LiPF ₆ ) was dissolved. As the non-aqueous solvent, ethylene carbonate (EC) and diethyl carbonate (DEC) were used. 4-Fluoro-1,3-dioxolan-2-one (FEC) was used as the halogenated cyclic carbonate, and vinylene carbonate (VC) was used as the unsaturated carbon-bonded cyclic carbonate. As the alkylated cyclic carbonate, propylene carbonate (PC) or butylene carbonate (BC) was used. As the cyclic carboxylic acid imide, succinimide (SCI), glutarimide (GLI), maleimide (MLI) or phthalimide (PHI) was used, and N-methylsuccinimide (NSCI) was also used as a comparative object. The composition of the electrolyte is based on EC: DEC: LiPF ₆ = 52: 34: 14 (weight ratio), part of EC is an alkylated cyclic carbonate, part of DEC is a cyclic carboxylic imide, A portion was replaced with a halogenated cyclic carbonate or an unsaturated carbon-bonded cyclic carbonate. The details of the composition of the electrolytic solution are as shown in Tables 1 and 2. The “ratio (%)” of the alkylated cyclic carbonate is the weight ratio of the alkylated cyclic carbonate (PC, etc.) to the non-alkylated cyclic carbonate (EC). This ratio is calculated by the ratio (%) = [content of alkylated cyclic carbonate (% by weight) / content of non-alkylated cyclic carbonate (% by weight)] × 100.

  When assembling the secondary battery, the positive electrode lead 51 made of Al was welded to one end of the positive electrode current collector 33A, and the negative electrode lead 52 made of Ni was welded to one end of the negative electrode current collector 34A. Subsequently, the positive electrode 33, the separator 35 (a microporous polyethylene film as a porous film: thickness = 12 μm), the negative electrode 34, and the separator 35 were laminated in this order. Subsequently, the laminate was wound in the longitudinal direction to form a wound body which is a precursor of the wound electrode body 30, and then the winding end portion was fixed with a protective tape 57 (adhesive tape). Subsequently, after sandwiching the wound body between the exterior members 60, the outer peripheral edge portions except for one side were heat-sealed, and the wound body was housed inside the bag-shaped exterior member 60. As the exterior member 60, an aluminum laminated film in which a nylon film (thickness = 30 μm), an aluminum foil (thickness = 40 μm) and an unstretched polypropylene film (thickness = 30 μm) were laminated from the outside was used. Subsequently, 2 g of the electrolyte solution was injected from the opening of the exterior member 60 and impregnated in the separator 55, thereby manufacturing the wound electrode body 50. Finally, the opening of the exterior member 60 was heat-sealed and sealed in a vacuum atmosphere. Thereby, the secondary battery was completed. The battery capacity of this secondary battery is 900 mAh.

  In order to examine the initial charge / discharge characteristics, the secondary battery was charged in a normal temperature environment (23 ° C.), the charge capacity was measured, and then discharged in the same environment to measure the discharge capacity. From this result, the initial efficiency (%) = (discharge capacity / charge capacity) × 100 was calculated. At the time of charging / discharging, after charging for 3 hours with an upper limit voltage of 4.2 V with a current of 900 mA, the battery was discharged with a final voltage of 3.0 V with a current of 900 mA.

  In order to examine the initial swelling characteristics, when examining the above-mentioned initial charge / discharge characteristics, the thickness of the secondary battery was measured before charging, and then the thickness was measured again after charging. From this result, the initial swelling rate (%) = [(thickness after charging−thickness before charging) / thickness before charging] × 100 was calculated.

  In order to examine the swelling characteristics after storage, the thickness of the secondary battery is measured, the secondary battery is charged in a normal temperature environment (23 ° C.), and then in a high temperature environment (85 ° C. with the charged state). ) For 24 hours, and then the thickness was measured again. From this result, the swelling ratio after storage (%) = [(thickness after storage−thickness before storage) / thickness before storage] × 100 was calculated. The charging conditions are the same as when the initial charge / discharge characteristics were examined.

  When the electrolytic solution contains a cyclic carboxylic acid imide, a halogenated cyclic carbonate and the like together (Experimental Examples 1-1 to 1-16), it does not contain them together (Experimental Examples 1-17 to 1- 1). Good results were obtained compared to 25).

  Specifically, when neither a cyclic carboxylic acid imide nor a halogenated cyclic carbonate is used (Experimental Examples 1-17 and 1-20), only one of them is used (Experimental Example 1-18). , 1-19, 1-21, 1-22), the initial efficiency increased and the initial swelling rate tended to decrease. In contrast, when both were used (Experimental Example 1-3), the initial swelling rate was significantly reduced while maintaining high initial efficiency as compared with the case where only one was used.

  This difference in tendency is specifically described as numerical values as follows. When only the cyclic carboxylic acid imide was used (Experimental Example 1-21), the initial efficiency increased by about 7.35% and the initial blistering ratio was about It decreased by 9.87%. In addition, when only a halogenated cyclic carbonate or the like was used (Experimental Example 1-22), the initial efficiency increased by about 1.03% and the initial swelling rate was about 37.22 compared to the above standard. %Diminished. Therefore, when both are used, the initial efficiency increases by about 8.38% (= 7.35% + 1.03%) and the initial swelling rate is 47.09% (= 9.87% + 37.22%). Expected to decrease. However, in practice, when both were used (Experimental Example 1-3), the initial efficiency increased by approximately 7.81%, which is almost equivalent to the expected value, whereas the initial swelling rate far exceeded the expected value. It was reduced by about 72.20%. This result indicates that when both are combined, a specific action (advantage) that cannot be expected from the result obtained when used alone is obtained. In other words, when both are combined, it tends to decrease not only to the initial expansion rate but also to the initial efficiency, in which case only the initial expansion rate is significantly reduced while the decrease in the initial efficiency is sufficiently suppressed. .

  In particular, when the electrolytic solution contains both, when the content of the cyclic carboxylic imide in the electrolytic solution is 0.1% by weight to 1% by weight, high initial efficiency is obtained and the initial swelling rate is sufficient. It was suppressed. Similarly, good results were obtained when the content of halogenated cyclic carbonate and the like in the electrolytic solution was 0.5 wt% to 5 wt%. Furthermore, when the electrolytic solution contains an alkylated cyclic carbonate, and the content of the alkylated cyclic carbonate is equal to or higher than the content of the non-alkylated cyclic carbonate, the initial efficiency and the initial swelling rate are almost maintained. As a result, the swelling rate after storage decreased significantly.

  Note that, when amorphous carbon (battery capacity = 700 mAh) is used as the negative electrode active material, good initial efficiency and initial expansion rate can be obtained, but it is secondary compared to the case of using graphite (battery capacity = 900 mAh). The battery capacity of the battery is reduced.

  In addition, when NSCI (Experimental Example 1-25), which is a substituted cyclic carboxylic acid imide, is used instead of SCI (Experimental Example 1-3), which is an unsubstituted cyclic carboxylic acid imide, the initial efficiency is negligible. And the initial swelling rate is only slightly reduced. As described above, as described above, when the hydrogen group in the nitrogen-hydrogen bond (N—H) is substituted with an alkyl group, the decomposability of the cyclic carboxylic acid imide is lowered. This indicates that it is difficult to form a film.

(Experimental examples 2-1 to 2-25)
Except that the configuration of the separator 35 was changed, secondary batteries were produced in the same procedure as in Experimental Examples 1-1 to 1-25, and various characteristics were examined. The results shown in Table 3 and Table 4 were obtained. It was.

  As the separator 35, a material in which a polymer compound layer (PVDF: thickness on one side = 2 μm) is formed on both sides of a base material layer (a microporous polyethylene film as a porous film: thickness = 7 μm) is used. It was. In the case of forming this polymer compound layer, a solution in which PVDF was dissolved in NMP was prepared, and the solution was applied to both surfaces of the base material layer and then dried.

  Even when the configuration of the separator 35 was changed, the same results as in Tables 1 and 2 were obtained. That is, when the electrolytic solution contains a cyclic carboxylic acid imide, a halogenated cyclic carbonate and the like together (Experimental Examples 2-1 to 2-16), it does not contain them together (Experimental Examples 2-17 to Compared with 2-25), the initial swelling rate was remarkably reduced while maintaining a high initial efficiency. In addition, when the electrolytic solution contained an alkylated cyclic carbonate, the swelling rate after storage was also reduced.

  From the results of Tables 1 to 4, when the electrolytic solution contains a cyclic carboxylic imide and at least one of a halogenated cyclic carbonate and an unsaturated carbon bond cyclic carbonate, the battery capacity increases and the battery swells. It was confirmed that both suppression can be achieved.

  The present technology has been described with reference to the embodiments and examples. However, the present technology is not limited to the aspects described in the embodiments and examples, and various modifications are possible. For example, the positive electrode active material of the present technology includes a lithium ion secondary battery in which the capacity of the negative electrode includes a capacity due to insertion and extraction of lithium ions and a capacity due to precipitation and dissolution of lithium metal, and is expressed by the sum of these capacities. , As well as applicable. In this case, the chargeable capacity of the negative electrode material is set to be smaller than the discharge capacity of the positive electrode.

  In the embodiments and examples, the case where the battery structure is a cylindrical type or a laminate film type or the case where the battery element has a winding structure has been described as an example, but the present invention is not limited thereto. The lithium ion secondary battery of the present technology can be similarly applied to a case where it has another battery structure such as a coin type, a square type or a button type, or a case where the battery element has another structure such as a laminated structure. is there.

  Moreover, embodiment and the Example demonstrate the appropriate range derived | led-out from the result of the Example about content of cyclic carboxylic imide. However, the explanation does not completely deny the possibility that the content will be outside the above range. In other words, the appropriate range described above is a particularly preferable range in obtaining the effects of the present technology to the end, and therefore the content may be slightly deviated from the above ranges as long as the effects of the present technology can be obtained. The same applies to the contents of the halogenated cyclic carbonate, unsaturated carbon bond cyclic carbonate and alkylated cyclic carbonate.

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 20, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode collection Electrical body, 22B, 34B ... negative electrode active material layer, 23, 35 ... separator, 23A ... base material layer, 23B ... polymer compound layer, 36 ... electrolyte layer, 40 ... exterior member.

Claims (15)

An electrolyte is provided together with the positive electrode and the negative electrode,
The electrolytic solution includes at least one of cyclic carboxylic imides represented by the following formulas (1) to (4), a halogenated cyclic carbonate represented by the following formula (5), and a formula ( 6) at least one of unsaturated carbon bond cyclic carbonate represented by
Secondary battery.

(R1 to R16 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)

(R21 to R24 are a hydrogen group, a halogen group, an alkyl group having 1 to 4 carbon atoms, or a halogenated alkyl group having 1 to 4 carbon atoms, and at least one of R21 to R24 is a halogen group or a halogen atom. R25 and R26 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)   The cyclic carboxylic imide is at least one of succinimide, glutarimide, maleimide and phthalimide, the halogenated cyclic carbonate is 4-fluoro-1,3-dioxolan-2-one, and the unsaturated carbon The secondary battery according to claim 1, wherein the bonded cyclic carbonate is vinylene carbonate.   The content of the cyclic carboxylic imide in the electrolytic solution is 0.1% by weight to 1% by weight, and the content of the halogenated cyclic carbonate and the unsaturated carbon bond cyclic carbonate in the electrolytic solution is The secondary battery according to claim 1, wherein the content is 0.5 wt% to 5 wt%. The secondary battery according to claim 1, wherein the electrolytic solution includes an alkylated cyclic carbonate represented by the following formula (7).

(R31 to R36 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)   The secondary battery according to claim 4, wherein the alkylated cyclic carbonate is at least one of propylene carbonate and butylene carbonate.   5. The electrolyte according to claim 4, wherein the electrolytic solution contains ethylene carbonate, and the content (% by weight) of the alkylated cyclic carbonate in the electrolytic solution is equal to or greater than the content (% by weight) of the ethylene carbonate. Next battery.   The positive electrode and the negative electrode are stacked via a separator, and the separator includes a base material layer that is a porous film and a polymer compound layer provided on at least one surface of the base material layer. The secondary battery according to 1.   The secondary battery according to claim 7, wherein the polymer compound layer includes polyvinylidene fluoride.   The secondary battery according to claim 1, wherein the positive electrode, the negative electrode, and the electrolytic solution are housed inside a film-shaped exterior member.   The secondary battery according to claim 1, which is a lithium ion secondary battery. At least one of cyclic carboxylic imides represented by the following formulas (1) to (4), a halogenated cyclic carbonate represented by the following formula (5), and a formula (6) An electrolyte solution for a secondary battery, comprising at least one of unsaturated carbon-bonded cyclic carbonates.

(R1 to R16 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)

(R21 to R24 are a hydrogen group, a halogen group, an alkyl group having 1 to 4 carbon atoms, or a halogenated alkyl group having 1 to 4 carbon atoms, and at least one of R21 to R24 is a halogen group or a halogen atom. R25 and R26 are a hydrogen group or an alkyl group having 1 to 4 carbon atoms.)   An electronic device using the secondary battery according to any one of claims 1 to 10.   The electric tool using the secondary battery of any one of Claim 1 thru | or 10.   The electric vehicle using the secondary battery of any one of Claim 1 thru | or 10.   The power storage system using the secondary battery of any one of Claims 1 thru | or 10.

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