JP2009110799A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery that obtains excellent cycle characteristics and swelling characteristics. <P>SOLUTION: The battery includes a negative electrode 21, an positive electrode 22 and an electrolyte solution as well, and the electrolyte solution is impregnated into the separator 23 which is arranged between the negative electrode 21 and the positive electrode 22. An positive electrode active material layer 22B of the positive electrode contains a plurality of positive electrode active material particles and the positive electrode active material particle contains silicon and a multilayer structure inside the particle. The electrolyte solution contains cyclic carbonic acid ester which has halogen as a solvent, tetrafluoroborate lithium as an electrolyte salt, and a unsymmetrical ester compound which, while having a methyl group at one end, has an alkyl group (carbon number =2-4) at the other end. Since the electrolyte solution becomes hard to be decomposed even if charging/discharging is repeated, a discharging capacity becomes hard to be reduced and a secondary battery becomes hard to swell. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a battery including an electrolyte solution together with a positive electrode and a negative electrode.

  In recent years, portable electronic devices such as a camera-integrated VTR (video tape recorder), a mobile phone, or a laptop computer have been widely used, and there is a strong demand for miniaturization, weight reduction, and long life. Accordingly, as a power source, development of a battery, in particular, a secondary battery that is lightweight and capable of obtaining a high energy density is in progress.

  Among them, secondary batteries (so-called lithium ion secondary batteries) that use lithium (Li) occlusion and release for charge / discharge reactions are highly expected because they can obtain higher energy density than lead batteries and nickel cadmium batteries. Yes.

  In this lithium ion secondary battery, a composite oxide containing lithium and a transition metal element is used as a positive electrode active material of a positive electrode, a carbon material is used as a negative electrode active material of a negative electrode, and a carbonate is used as a solvent of an electrolytic solution. It has been known. Since carbonate ester has better oxidation resistance and reduction resistance than water and other organic solvents, a high voltage can be obtained. Thereby, since a higher energy density is obtained than the nickel-metal hydride battery which is a water-based battery, a high capacity can be obtained.

  In recent years, there has been a demand for further improvements in battery capacity as portable electronic devices become more sophisticated and multifunctional, so as a negative electrode active material, silicon or tin is used instead of carbon materials such as graphite. Is being considered. This is because the theoretical capacity of silicon (4199 mAh / g) and the theoretical capacity of tin (994 mAh / g) are much larger than the theoretical capacity of graphite (372 mAh / g), so that a significant improvement in battery capacity can be expected.

  When silicon or the like is used as the negative electrode active material, the thickness of the negative electrode active material may be reduced in order to improve the cycle characteristics of the secondary battery. This is because the negative electrode active material is less likely to expand and contract during charge / discharge. In this case, if the thickness of the negative electrode active material is small, the capacity of the secondary battery is insufficient. Therefore, in order to increase the capacity, it is necessary to stack the negative electrode active material.

  However, when the negative electrode active material is laminated, the cycle characteristics deteriorate. This is because an interface is generated between the layers and the surface area of the negative electrode active material is increased, so that when the negative electrode active material that occludes lithium at the time of charging becomes highly active, the electrolyte is easily decomposed on the surface. In addition, when the electrolytic solution is decomposed, the secondary battery is easily swelled due to the influence of the gas generated at the time of decomposition, so that not only the cycle characteristics but also the swell characteristics are deteriorated. The swelling of the secondary battery becomes remarkable in a high temperature environment.

  In particular, since silicon is highly reactive, if highly reactive dimethyl carbonate is used as the solvent (low viscosity solvent) of the electrolyte solution, gas is easily generated during charging and discharging, leading to a decrease in swelling characteristics. Therefore, in order to suppress swelling of the secondary battery, low-reactivity diethyl carbonate is widely used as a low-viscosity solvent. However, even though it is a low-viscosity solvent, diethyl carbonate has a higher viscosity than dimethyl carbonate and the resistance of the electrolytic solution is increased, so that the swollenness characteristics are improved, while the cycle characteristics are degraded.

Various solutions have been made to solve various problems relating to these secondary batteries. Specifically, in order to improve safety without degrading various performances of the secondary battery, when using silicon as the negative electrode active material, fluoroethylene carbonate and a chain ester solvent are used as the solvent of the electrolytic solution, A technique using lithium hexafluorophosphate or lithium tetrafluoroborate as an electrolyte salt has been proposed (see, for example, Patent Document 1).
Special table 2007-504628

  In recent years, portable electronic devices have become more sophisticated and multifunctional, and their power consumption tends to increase. Therefore, charging and discharging of secondary batteries are frequently repeated, and their cycle characteristics are likely to deteriorate. . In addition, portable electronic devices are widely used in a wide range of fields, and secondary batteries can be exposed to high-temperature atmosphere during transportation, use or carrying, etc. It is in. From these things, further improvement is desired regarding the cycle characteristics and swelling characteristics of the secondary battery.

  The present invention has been made in view of such problems, and an object thereof is to provide a battery capable of obtaining excellent cycle characteristics and swelling characteristics.

  The battery of the present invention is a battery including an electrolyte solution together with a positive electrode and a negative electrode, wherein the negative electrode has a negative electrode active material layer including a plurality of negative electrode active material particles, and the negative electrode active material particles occlude an electrode reactant. And a halogen that is capable of being released and contains a material having at least one of a metal element and a metalloid element, and has a multilayer structure in the particle, wherein the electrolyte is represented by chemical formula 1 A solvent containing a cyclic carbonate having a salt, an electrolyte salt containing lithium tetrafluoroborate, and an ester compound represented by Chemical Formula 2.

（Ｒ１１〜Ｒ１４は水素基、ハロゲン基、アルキル基あるいはハロゲン化アルキル基であり、それらのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。）

(R11 to R14 are a hydrogen group, a halogen group, an alkyl group or a halogenated alkyl group, and at least one of them is a halogen group or a halogenated alkyl group.)

（Ｒ２１は炭素数が２以上４以下のアルキル基である。）

(R21 is an alkyl group having 2 to 4 carbon atoms.)

  According to the battery of the present invention, the negative electrode active material particles of the negative electrode can contain and release the electrode reactant, and contain a material having at least one of a metal element and a metalloid element, and In the case where the particles have a multilayer structure, the electrolytic solution is a solvent containing a cyclic carbonate having a halogen shown in Chemical formula 1, an electrolyte salt containing lithium tetrafluoroborate, and a chemical formula shown in Chemical formula 2 And an ester compound. In this case, as compared with the case where all the above-mentioned conditions are not satisfied, the electrolytic solution is not easily decomposed even after repeated charging and discharging, so that the discharge capacity is hardly reduced and the secondary battery is not easily swollen. . Therefore, excellent cycle characteristics and swelling characteristics can be obtained.

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

[First Embodiment]

  1 and 2 show a cross-sectional configuration of the battery according to the first embodiment, and FIG. 2 shows a cross section taken along line II-II shown in FIG. The battery described here is, for example, a lithium ion secondary battery in which the capacity of the negative electrode 22 is expressed based on insertion and extraction of lithium as an electrode reactant.

  In the secondary battery, a battery element 20 having a flat winding structure is mainly accommodated in a battery can 11. The battery can 11 is, for example, a square exterior member. As shown in FIG. 2, the square-shaped exterior member has a rectangular or substantially rectangular cross section in a longitudinal direction (including a curve in part), and is a rectangular prismatic battery. In addition to this, an oval prismatic battery is also configured. That is, the square-shaped exterior member is a bottomed rectangular type or bottomed oval shaped vessel-like member having a rectangular shape or a substantially rectangular shape (oval shape) obtained by connecting arcs with straight lines. FIG. 2 shows a case where the battery can 11 has a rectangular cross-sectional shape. The battery structure using the battery can 11 is called a square shape.

  The battery can 11 is a metal can made of, for example, a metal material containing iron, aluminum (Al), or an alloy thereof, and may have a function as an electrode terminal. In this case, iron that is harder than aluminum is preferable in order to suppress swelling of the secondary battery by utilizing the hardness (hardness of deformation) of the battery can 11 during charging and discharging. When the battery can 11 is made of iron, for example, a plating such as nickel may be applied.

  The battery can 11 has a hollow structure in which one end is closed and the other end is opened, and an insulating plate 12 and a battery lid 13 are attached to the open end to be sealed. The insulating plate 12 is disposed between the battery element 20 and the battery lid 13 so as to be perpendicular to the winding peripheral surface of the battery element 20, and is made of, for example, polypropylene. The battery lid 13 is made of, for example, the same material as that of the battery can 11 and may have a function as an electrode terminal in the same manner.

  A terminal plate 14 serving as a positive terminal is provided outside the battery lid 13, and the terminal plate 14 is electrically insulated from the battery lid 13 through an insulating case 16. The insulating case 16 is made of, for example, polybutylene terephthalate. In addition, a through hole is provided at substantially the center of the battery cover 13, and the through hole is electrically connected to the terminal plate 14 and electrically insulated from the battery cover 13 through the gasket 17. Thus, the positive electrode pin 15 is inserted. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface thereof.

  In the vicinity of the periphery of the battery lid 13, a cleavage valve 18 and an injection hole 19 are provided. The cleavage valve 18 is electrically connected to the battery lid 13 and is disconnected from the battery lid 13 to reduce the internal pressure when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. It is designed to be opened. The injection hole 19 is closed by a sealing member 19A made of, for example, a stainless steel ball.

  The battery element 20 is wound after the positive electrode 21 and the negative electrode 22 are laminated via the separator 23, and has a flat shape according to the shape of the battery can 11. A positive electrode lead 24 made of aluminum or the like is attached to an end portion (for example, an inner terminal portion) of the positive electrode 21, and a negative electrode lead 25 made of nickel or the like to an end portion (for example, the outer terminal portion) of the negative electrode 22. Is attached. The positive electrode lead 24 is welded to one end of the positive electrode pin 15 and is electrically connected to the terminal plate 14, and the negative electrode lead 25 is welded to and electrically connected to the battery can 11.

  For example, the positive electrode 21 is obtained by providing a positive electrode active material layer 21B on both surfaces of a positive electrode current collector 21A having a pair of surfaces. However, 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 a metal material such as aluminum, nickel, or stainless steel, for example. The positive electrode active material layer 21B includes one or more positive electrode materials capable of occluding and releasing lithium as a positive electrode active material, and a conductive agent, a binder, and the like as necessary. Other materials may be included.

As a positive electrode material capable of inserting and extracting lithium, for example, a lithium-containing compound is preferable. This is because a high energy density can be obtained. Examples of the 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, nickel, manganese (Mn And at least one member selected from the group consisting of iron is preferable. This is because a higher voltage can be obtained. The chemical formula is represented by, for example, Li _x M1O ₂ or Li _y M2PO ₄ . In the formula, M1 and M2 represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

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

  In addition, examples of the positive electrode material described above include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as titanium disulfide and molybdenum sulfide, chalcogenides such as niobium selenide, sulfur, Examples thereof include conductive polymers such as polyaniline and polythiophene.

  Examples of the conductive agent include carbon materials such as graphite, carbon black, and ketjen black. These may be single and multiple types may be mixed. Note that the conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

  Examples of the binder include synthetic rubbers such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene, and polymer materials such as polyvinylidene fluoride. These may be single and multiple types may be mixed. However, as shown in FIG. 2, when the positive electrode 21 and the negative electrode 22 are wound, it is preferable to use a styrene-butadiene rubber or a fluorine-based rubber having high flexibility.

  In the negative electrode 22, for example, a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of surfaces. However, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A.

  The anode current collector 22A is preferably made of a metal material having good electrochemical stability, electrical conductivity, and mechanical strength. Examples of such a metal material include copper, nickel, and stainless steel, and copper is preferable. This is because high electrical conductivity can be obtained.

  The negative electrode active material layer 22B includes a plurality of negative electrode active material particles, and may include other materials such as a conductive agent and a binder as necessary. The details of the conductive agent and the binder are the same as those described for the positive electrode 21.

  The negative electrode active material particles can store and release lithium and contain a negative electrode material having at least one of a metal element and a metalloid element. Such a negative electrode material is preferable because a high energy density is obtained. The negative electrode active material particles have a multilayer structure in the particles. Note that the charge capacity of the negative electrode material capable of inserting and extracting lithium is preferably larger than the charge capacity of the positive electrode active material.

  The negative electrode material capable of inserting and extracting lithium may be a metal element or metalloid element alone, an alloy or a compound, and may have one or two or more phases thereof at least in part. . In addition, the “alloy” in the present invention includes an alloy having one or more metal elements and one or more metalloid elements in addition to one composed of two or more metal elements. This “alloy” may have a nonmetallic element. This structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or one in which two or more of them coexist.

  Examples of the metal element or metalloid element described above include a metal element or metalloid element capable of forming an alloy with lithium. Specifically, magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), silicon, germanium, tin, lead (Pb), bismuth (Bi), cadmium (Cd), silver ( Ag), zinc, hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), or platinum (Pt). Among these, at least one of silicon and tin is preferable, and silicon is more preferable. This is because a high energy density can be obtained because the ability to occlude and release lithium is large.

  Examples of the negative electrode material having at least one of silicon and tin include, for example, a simple substance, an alloy and a compound of silicon, a simple substance, an alloy and a compound of tin, or one or two or more phases thereof. The material which has in is mentioned. These may be single and multiple types may be mixed.

Examples of the silicon alloy include, as the second constituent element other than silicon, tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony (Sb), and chromium. Those having at least one of the groups are mentioned. Examples of the silicon compound include those having oxygen or carbon (C), and may contain the second constituent element described above in addition to silicon. Examples of silicon alloys or compounds include SiB ₄ , 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 , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), Or LiSiO etc. are mentioned.

As an alloy of tin, for example, as a second constituent element other than tin, among the group consisting of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing which has at least 1 sort (s) of these is mentioned. Examples of the tin compound include those having oxygen or carbon, and may contain the above-described second constituent element in addition to tin. Examples of tin alloys or compounds include SnSiO ₃ , LiSnO, Mg ₂ Sn, and the like.

  In particular, as the negative electrode material having at least one of silicon and tin, for example, a material having tin and the second constituent element in addition to tin as the first constituent element is preferable. The second constituent elements are cobalt, iron, magnesium, titanium, vanadium (V), chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium (Nb), molybdenum, silver, indium, cerium (Ce), It is at least one selected from the group consisting of hafnium, tantalum (Ta), tungsten (W), bismuth and silicon. The third constituent element is at least one selected from the group consisting of boron, carbon, aluminum, and phosphorus (P). This is because having the second and third constituent elements improves the cycle characteristics.

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

  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, titanium, molybdenum, aluminum, phosphorus, gallium, bismuth, and the like are preferable, and two or more of them may be included. . This is because a higher effect can be obtained.

  The SnCoC-containing material has a phase containing tin, cobalt, and carbon, and the phase preferably has a low crystalline or amorphous structure. In the SnCoC-containing material, it is preferable that at least a part of carbon as a constituent element is bonded to a metal element or a metalloid element as another constituent element. This is because aggregation or crystallization of tin or the like is suppressed.

  The SnCoC-containing material can be formed by, for example, melting a mixture obtained by mixing raw materials of each constituent element in an electric furnace, a high-frequency induction furnace, an arc melting furnace, or the like and then solidifying the mixture. Also, various atomization methods such as gas atomization or water atomization, various roll methods, and methods utilizing mechanochemical reactions such as mechanical alloying or mechanical milling may be used. Among these, a method using a mechanochemical reaction is preferable. This is because the negative electrode active material has a low crystalline or amorphous structure. In the method using the mechanochemical reaction, for example, a manufacturing apparatus such as a planetary ball mill or an attritor can be used.

  An example of a measurement method for examining the bonding state of elements is X-ray photoelectron spectroscopy (XPS). In this XPS, in the apparatus calibrated so that the 4f orbit (Au4f) peak of gold atom is obtained at 84.0 eV, the peak of 1s orbit (C1s) of carbon appears at 284.5 eV in the case of 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 is high, for example, when carbon is bonded to a metal element or a metalloid element, the peak of C1s 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, for example, the peak of C1s 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 XPS, the waveform of the peak of C1s is obtained as a form including the peak of surface contamination carbon and the peak of carbon in the SnCoC-containing material. For example, by analyzing using 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).

  The negative electrode active material particles are formed by, for example, a gas phase method. As the vapor phase method, for example, physical deposition method or chemical deposition method, more specifically, vacuum evaporation method, sputtering method, ion plating method, laser ablation method, thermal chemical vapor deposition (CVD) Or plasma chemical vapor deposition. However, the negative electrode active material particles may be formed by a method other than the gas phase method.

  When the negative electrode active material particles are formed by a vapor phase method, the negative electrode material is deposited multiple times by the vapor phase method, and the deposited film is laminated, so that the negative electrode active material particles are contained in the particles. Has a multilayer structure. When negative electrode active material particles are formed by vapor deposition with high heat during deposition, the deposition process of the negative electrode material is performed by dividing the negative electrode material into a plurality of times (the negative electrode material is sequentially formed and deposited). This is because the time during which the negative electrode current collector 22A is exposed to high heat is shortened compared to the case where the process is performed once, and is less susceptible to thermal damage.

  In this case, the negative electrode active material particles preferably have a thickness of 1 μm or less and the number of the negative electrode active material particles is preferably 10 or more. This is because the thickness of the negative electrode active material particles formed in one deposition step is sufficiently thin, and thus the cycle characteristics are improved. In addition, even though the thickness of the negative electrode active material particles formed in one deposition step is thin, the total thickness of the negative electrode active material particles is sufficiently large, so that a high capacity can be obtained.

  The negative electrode active material particles are connected to the surface of the negative electrode current collector 22A that supports the negative electrode active material layer 22B, for example, and grow from the surface of the negative electrode current collector 22A in the thickness direction of the negative electrode active material layer 22B. ing. In this case, the negative electrode active material particles are preferably formed by a vapor phase method and alloyed at least at a part of the interface between the negative electrode current collector 22A and the negative electrode active material layer 22B. Specifically, the constituent element of the negative electrode current collector 22A may diffuse into the negative electrode active material layer 22B at the interface between them, or the constituent element of the negative electrode active material layer 22B diffuses into the negative electrode current collector 22A. The constituent elements of both may be diffused with each other. This is because breakage due to expansion and contraction of the negative electrode active material layer 22B during charging and discharging is suppressed, and electron conductivity between the negative electrode current collector 22A and the negative electrode active material layer 22B is improved.

  The negative electrode active material layer 22B may include an oxide-containing film that covers the surface of the negative electrode active material particles (a region in contact with the electrolytic solution) as necessary. This is because the oxide-containing film functions as a protective film against the electrolytic solution, and even when charging and discharging are repeated, the decomposition reaction of the electrolytic solution is suppressed, so that cycle characteristics are further improved. This oxide-containing film may cover a part of the surface of the negative electrode active material particles, or may cover the whole.

  The oxide-containing film contains, for example, at least one oxide selected from the group consisting of silicon, germanium, and tin, and silicon oxide is particularly preferable. This is because the entire surface of the negative electrode active material particles can be easily covered. Of course, the oxide-containing film may contain an oxide other than the above. The oxide-containing film is formed by, for example, a gas phase method or a liquid phase method, and among them, a liquid phase method such as a liquid phase deposition method, a sol-gel method, a coating method, or a dip coating method is preferable. More preferred. This is because the surface of the negative electrode active material particles can be easily covered over a wide range.

  In addition, the negative electrode active material layer 22B may include a metal material that does not alloy with lithium in the gaps between the particles of the negative electrode active material particles and the gaps in the particles as necessary. A plurality of negative electrode active material particles are bound via a metal material, and the presence and absence of the metal material in the gaps described above suppresses the expansion and contraction of the negative electrode active material layer 22B, thereby further improving cycle characteristics. Because.

  This metal material has, for example, at least one selected from the group consisting of iron, cobalt, nickel, zinc, and copper as a metal element that does not alloy with lithium, and cobalt is particularly preferable. This is because the metal material easily enters the gap. Of course, the metal material may have a metal element other than the above. However, the “metal material” mentioned here is not limited to a simple substance, but is a broad concept that includes alloys and metal compounds. This metal material is formed by, for example, a gas phase method or a liquid phase method, and among them, a liquid phase method such as an electrolytic plating method or an electroless plating method is preferable, and an electrolytic plating method is more preferable. This is because the metal material can easily enter the gap and the formation time can be shortened.

  Note that the negative electrode active material layer 22B may include only one of the above-described oxide-containing film or metal material, or may include both. However, in order to further improve the cycle characteristics, it is preferable to include both.

  Here, the detailed configuration of the negative electrode 22 will be described by taking as an example the case where the negative electrode active material layer 22B includes a metal material together with a plurality of negative electrode active material particles. 3 and 4 show an enlarged cross-sectional structure of the negative electrode. (A) is a scanning electron microscope (SEM) photograph (secondary electron image), and (B) is shown in (A). The SEM image is shown typically.

  As shown in FIG. 3, when the negative electrode active material layer 22B includes a plurality of negative electrode active material particles 221 and the negative electrode active material particles 221 have a multilayer structure in the particles, the negative electrode active material layer 22B A plurality of gaps 222 are formed inside. Specifically, a plurality of protrusions (for example, fine particles formed by electrolytic treatment) are present on the surface of the roughened negative electrode current collector 22A. In this case, when the negative electrode material is deposited a plurality of times on the surface of the negative electrode current collector 22A by a vapor phase method or the like, and the deposited film is laminated, the negative electrode active material particles 221 are formed for each of the protrusions described above. It grows stepwise in the thickness direction. Due to the dense structure, multilayer structure, and surface structure of the plurality of negative electrode active material particles 221, a plurality of gaps 222 are generated.

  The gap 222 includes two types of gaps 222A and 222B classified according to the cause of occurrence. The gap 222A is generated between the adjacent negative electrode active material particles 221 as the negative electrode active material particles 221 grow for each protrusion existing on the surface of the negative electrode current collector 22A. On the other hand, the gap 222B occurs between the layers in the negative electrode active material particles 221 as the negative electrode active material particles 221 have a multilayer structure in the particles. Of course, the gap 222 may include a gap generated due to other causes other than the gaps 222A and 222B.

  Note that a void 223 may be formed on the exposed surface (outermost surface) of the negative electrode active material particles 221. The voids 223 are generated between the protrusions as the whisker-like fine protrusions (not shown) are formed on the surface of the negative electrode active material particles 221. The void 223 may be generated over the entire exposed surface of the negative electrode active material particle 221 or may be generated only in part. However, since the above-described fine whisker-like protrusions are formed on the surface of the negative electrode active material particles 221 every time they are formed, the voids 223 are generated not only on the exposed surface of the negative electrode active material particles 221 but also on each layer. ing.

  As shown in FIG. 4, after the plurality of negative electrode active material particles 221 are formed, when the metal material 224 is formed by an electrolytic plating method or the like, the metal material 224 enters the gap 222. That is, the metal material 224 enters the gap 222 </ b> A between the negative electrode active material particles 221 and enters the gap 222 </ b> B in the negative electrode active material particles 221. In this case, the metal material 224 may also enter the gap 223 between the beard-like fine protrusions generated on the surface of the negative electrode active material particles 221. In FIG. 4, the fact that the metal material 224 is scattered on the surface of the uppermost negative electrode active material particles 221 indicates that the above-described fine protrusions exist at the scattered points.

  Here, although not specifically described with reference to the drawings, when an oxide-containing film is formed by a liquid phase deposition method or the like instead of the metal material, the oxide-containing film is formed of the negative electrode active material particles 221. Since it grows along the surface, it tends to preferentially enter the gap 222B and the gap 223. In this case, if the deposition time is increased, the oxide-containing film can easily enter the gap 222A.

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

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. The electrolytic solution includes a solvent containing a cyclic carbonate having a halogen represented by chemical formula 3 as a constituent element, an electrolyte salt containing lithium tetrafluoroborate, and an ester compound represented by chemical formula 4. It is out.

（Ｒ１１〜Ｒ１４は水素基、ハロゲン基、アルキル基あるいはハロゲン化アルキル基であり、それらのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。）

(R11 to R14 are a hydrogen group, a halogen group, an alkyl group or a halogenated alkyl group, and at least one of them is a halogen group or a halogenated alkyl group.)

（Ｒ２１は炭素数が２以上４以下のアルキル基である。）

(R21 is an alkyl group having 2 to 4 carbon atoms.)

  The reason why the electrolytic solution contains the cyclic carbonate having halogen shown in Chemical Formula 3 as a solvent is that a halogen-based film is formed on the surface of the negative electrode 22 and the decomposition reaction of the electrolytic solution is suppressed. This is because it improves.

  In addition, R11 to R14 in Chemical Formula 3 may be the same as or different from each other. The “halogenated alkyl group” described for R11 to R14 is a group in which at least a part of hydrogen in the alkyl group is substituted with halogen. The type of this halogen is not particularly limited, but at least one of the group consisting of fluorine, chlorine and bromine is preferable, and fluorine is more preferable. This is because a high effect can be obtained. Of course, halogen other than fluorine may be used.

  Examples of the cyclic carbonate having a halogen shown in Chemical formula 3 include a series of compounds represented by Chemical formulas 5 and 6. That is, 4-fluoro-1,3-dioxolan-2-one of (1) shown in Chemical formula 5, 4-chloro-1,3-dioxolan-2-one of (2), 4,5 of (3) -Difluoro-1,3-dioxolan-2-one, (4) tetrafluoro-1,3-dioxolan-2-one, (5) 4-fluoro-5-chloro-1,3-dioxolane-2-one ON, (6) 4,5-dichloro-1,3-dioxolan-2-one, (7) tetrachloro-1,3-dioxolan-2-one, (8) 4,5-bistrifluoromethyl 1,3-dioxolan-2-one, 4-trifluoromethyl-1,3-dioxolan-2-one of (9), 4,5-difluoro-4,5-dimethyl-1,3 of (10) -Dioxolan-2-one, 4-methyl-5,5 of (11) Difluoro-1,3-dioxolan-2-one, 4-ethyl-5,5-difluoro-1,3-dioxolane-2-one (12). In addition, 4-trifluoromethyl-5-fluoro-1,3-dioxolan-2-one of (1) shown in Chemical Formula 6, 4-trifluoromethyl-5-methyl-1,3-dioxolane of (2) 2-one, 4-fluoro-4,5-dimethyl-1,3-dioxolan-2-one of (3), 4,4-difluoro-5- (1,1-difluoroethyl)-of (4) 1,3-dioxolan-2-one, 4,5-dichloro-4,5-dimethyl-1,3-dioxolan-2-one in (5), 4-ethyl-5-fluoro-1, in (6) 3-dioxolan-2-one, 4-ethyl-4,5-difluoro-1,3-dioxolan-2-one of (7), 4-ethyl-4,5,5-trifluoro-1 of (8) , 3-Dioxolan-2-one, 4-fluoro-4-methyl-1 of (9) 3-dioxolan-2-one. These may be single and multiple types may be mixed.

  Among them, 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one, or 4-tri Fluoromethyl-1,3-dioxolan-2-one is preferred, and 4-fluoro-1,3-dioxolan-2-one or 4,5-difluoro-1,3-dioxolan-2-one is more preferred. This is because it is easily available and a high effect can be obtained. In particular, a higher effect is obtained with 4,5-difluoro-1,3-dioxolan-2-one than with 4-fluoro-1,3-dioxolan-2-one. 4,5-difluoro-1,3-dioxolan-2-one is preferably a trans isomer rather than a cis isomer.

  The content of the cyclic carbonate having halogen shown in Chemical Formula 3 in the electrolytic solution is not particularly limited, and can be arbitrarily set according to conditions such as the type of the cyclic carbonate having halogen. For example, when 4-fluoro-1,3-dioxolan-2-one is used, the content of 4-fluoro-1,3-dioxolan-2-one in the solvent is 30% by weight or more and 50% by weight. % Or less is preferable. When 4,5-difluoro-1,3-dioxolan-2-one is used, the content of 4,5-difluoro-1,3-dioxolan-2-one in the solvent is 10% by weight or more and 20%. It is preferable that it is less than weight%. This is because excellent cycle characteristics can be obtained.

  The solvent may contain any one kind or two or more kinds of non-aqueous solvents such as other organic solvents in addition to the cyclic carbonate having halogen shown in Chemical formula 3. The non-aqueous solvent may contain only one of a high viscosity (high dielectric constant) solvent (for example, relative dielectric constant ε ≧ 30) or a low viscosity solvent (for example, viscosity ≦ 1 mPa · s), Preferably both are included. This is because the dissociation property of the electrolyte salt and the ion mobility are improved.

  Examples of the high viscosity solvent include cyclic carbonates such as propylene carbonate and butylene carbonate, lactones such as γ-butyrolactone and γ-valerolactone, lactams such as N-methylpyrrolidone, and cyclic carbamines such as N-methyloxazolidinone. Examples include acid esters and sulfone compounds such as tetramethylene sulfone. On the other hand, examples of the low-viscosity solvent include chain carbonates such as dimethyl carbonate and dipropyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylacetate or trimethylacetic acid. Chain carboxylic acid esters such as ethyl, chain amides such as N, N′-dimethylacetamide, and chain carbamic acid esters such as methyl N, N′-diethylcarbamate or ethyl N, N′-diethylcarbamate And ethers such as 1,2-dimethoxyethane, tetrahydrofuran, tetrahydropyran, and 1,3-dioxolane. Of course, other non-aqueous solvents may be used.

  Moreover, the solvent may contain the cyclic carbonate which has an unsaturated bond. This is because the cycle characteristics are improved. Examples of the cyclic carbonate having an unsaturated bond include vinylene carbonate and vinyl ethylene carbonate. These may be single and multiple types may be mixed.

  The reason why the electrolytic solution contains lithium tetrafluoroborate as an electrolyte salt is that the swelling characteristics are improved. The concentration of lithium tetrafluoroborate in the electrolytic solution is not particularly limited, but is preferably 0.02 mol / kg or more and 0.2 mol / kg or less. This is because excellent swelling characteristics can be obtained while suppressing deterioration of cycle characteristics.

This electrolyte salt may contain any one or more of light metal salts such as other lithium salts together with lithium tetrafluoroborate. Examples of the lithium salt include lithium hexafluorophosphate, lithium hexafluoroarsenate (LiAsF _6), lithium hexafluoro antimonate (LiSbF _6), lithium perchlorate (LiClO ₄₎ or tetrachloride aluminum acid Inorganic acid lithium salts such as lithium (LiAlCl ₄ ), perfluoro such as lithium trifluoromethanesulfonate, lithium bis (trifluoromethanesulfone) imide, lithium bis (pentafluoromethanesulfone) methide or lithium tris (trifluoromethanesulfone) methide Examples include lithium salts of alkanesulfonic acid derivatives.

  Among these, lithium hexafluorophosphate is preferable. This is because the cycle resistance is improved because the electric resistance of the electrolytic solution is lowered. In particular, when the electrolyte salt contains lithium hexafluorophosphate together with lithium tetrafluoroborate, the proportion of lithium hexafluorophosphate is preferably larger than the proportion of lithium tetrafluoroborate. This is because the cycle characteristics are further improved.

  The concentration of the electrolyte salt in the electrolytic solution is preferably 0.3 mol / kg or more and 3.0 mol / kg or less. This is because, outside this range, the ion conductivity may be extremely lowered.

  The reason why the electrolytic solution contains the ester compound shown in Chemical Formula 4 (hereinafter also simply referred to as “ester compound”) is that the cycle characteristics are improved and the swollenness characteristics are also improved. This sulfone compound is an asymmetric chain compound having a methyl group at one end and an alkyl group (carbon number = 2 to 4) at the other end. In addition, the carbon number of R21 shown in Chemical formula 4 is limited to 2 or more and 4 or less because when the carbon number is 1, the secondary battery tends to swell, while when larger than 4, the viscosity of the ester compound is increased. This is because the cycle characteristics are lowered due to the increase in the value.

  Specific examples of the ester compound include a series of compounds represented by Chemical Formula 7. That is, (1) ethyl methyl carbonate, (2) methyl propyl carbonate, or (3) butyl methyl carbonate shown in Chemical formula 7.

  The content of the ester compound in the electrolytic solution is not particularly limited, but is preferably 10% by weight or more and 70% by weight or less. This is because excellent cycle characteristics and swelling characteristics can be obtained.

  In addition, the electrolyte solution may contain an acid anhydride. This is because cycle characteristics and swelling characteristics are improved. Examples of the acid anhydride include succinic anhydride, glutaric anhydride, maleic anhydride, sulfobenzoic anhydride, sulfopropionic anhydride, sulfobutyric anhydride, ethanedisulfonic anhydride, propanedisulfonic acid. An anhydride, a benzene disulfonic anhydride, etc. are mentioned, These may be individual or may be mixed. The content of the acid anhydride in the electrolytic solution is, for example, not less than 0.5% by weight and not more than 3% by weight.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution impregnated in the separator 23. On the other hand, when discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolytic solution impregnated in the separator 23.

  This secondary battery is manufactured, for example, by the following procedure.

  First, the positive electrode 21 is manufactured by forming the positive electrode active material layer 21B on both surfaces of the positive electrode current collector 21A. When forming this positive electrode active material layer 21B, a positive electrode mixture in which a positive electrode active material, a conductive agent, and a binder are mixed is dispersed in a solvent to form a paste-like positive electrode mixture slurry. The positive electrode mixture slurry is applied to the positive electrode current collector 21A by a bar coater or the like and dried, and then the coating film is compression molded by a roll press machine or the like.

  Next, the negative electrode active material layer 22B is formed on both surfaces of the negative electrode current collector 22A to produce the negative electrode 22. When forming this negative electrode active material layer 22B, a negative electrode material containing silicon is deposited on the surface of the negative electrode current collector 22A by a vapor phase method to form a plurality of negative electrode active material particles. In the case of using a vapor deposition method as the vapor phase method, the negative electrode current collector 22A is reciprocally moved relative to the vapor deposition source while the negative electrode material is deposited and laminated several times, or the vapor deposition source is laminated. Then, the anode active material particles have a multilayer structure in the particles by depositing and laminating the anode material a plurality of times while repeatedly opening and closing the shutter while the anode current collector 22A is fixed. In this case, if necessary, an oxide-containing film is formed so as to cover the surface of the negative electrode active material particles by a liquid phase deposition method or the like, or a gap between the particles of the negative electrode active material particles by an electrolytic plating method or the like. Alternatively, a metal material may be formed in the gaps in the particles.

  Next, after mixing the solvent containing the cyclic carbonate having halogen shown in Chemical Formula 3 with the ester compound shown in Chemical Formula 4, the electrolyte salt containing lithium tetrafluoroborate is dissolved, and electrolysis is performed. Prepare the solution.

  Next, the battery element 20 is produced using the positive electrode 21 and the negative electrode 22. First, the positive electrode lead 24 is attached to the positive electrode 21 by welding or the like, and the negative electrode lead 25 is attached to the negative electrode 22 by welding or the like. Subsequently, after the positive electrode 21 and the negative electrode 22 are laminated via the separator 23, they are wound in the longitudinal direction. Finally, the wound body is molded so as to have a flat shape.

  The secondary battery is assembled as follows. First, after storing the battery element 20 in the battery can 11, the insulating plate 12 is disposed on the battery element 20. Subsequently, the positive electrode lead 24 is connected to the positive electrode pin 15 by welding or the like, and the negative electrode lead 25 is connected to the battery can 11 by welding or the like, and then the battery lid is attached to the open end of the battery can 11 by laser welding or the like. 13 is fixed. Finally, after injecting the electrolyte into the battery can 11 from the injection hole 19 and impregnating the separator 23, the injection hole 19 is closed with a sealing member 19A. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  According to this secondary battery, the negative electrode active material particles of the negative electrode 22 contain a material capable of inserting and extracting lithium and containing at least one of a metal element and a metalloid element, and In the case where the particles have a multilayer structure, the electrolytic solution is a solvent containing a cyclic carbonate having a halogen shown in Chemical formula 3, an electrolyte salt containing lithium tetrafluoroborate, and a chemical formula shown in Chemical formula 4 And an ester compound. In this case, as compared with the case where all the above-mentioned conditions are not satisfied, the electrolytic solution is not easily decomposed even after repeated charging and discharging, so that the discharge capacity is hardly reduced and the secondary battery is not easily swollen. . Therefore, excellent cycle characteristics and swelling characteristics can be obtained.

  In particular, if the battery structure of the secondary battery is a rectangular shape using a metal can (battery can 11), swelling tends to be manifested in the flat portion of the battery can 11 during charging and discharging. Therefore, the swelling characteristic can be more effectively improved.

  Moreover, if the electrolyte salt contains lithium hexafluoroborate together with lithium tetrafluoroborate, cycle characteristics can be further improved.

  In addition, when the cyclic carbonate having a halogen shown in Chemical formula 3 is 4-fluoro-1,3-dioxolan-2-one, 4-fluoro-1,3-dioxolan-2-one in the electrolyte solution 4,5-difluoro-1,3-dioxolane in the electrolytic solution when the content is 30% by weight or more and 50% by weight or less, or 4,5-difluoro-1,3-dioxolan-2-one When the content of 2-one is 10% by weight or more and 20% by weight or less, excellent cycle characteristics can be obtained.

  Moreover, if the concentration of lithium tetrafluoroborate in the electrolytic solution is 0.02 mol / kg or more and 0.2 mol / kg or less, excellent swelling characteristics can be obtained.

  Moreover, if the content of the ester compound shown in Chemical Formula 4 in the electrolytic solution is 10 wt% or more and 70 wt% or less, excellent cycle characteristics and swelling characteristics can be obtained.

  Moreover, if the thickness per layer of the negative electrode active material particles is 1 μm or less and the number of the negative electrode active material particles is 10 or more, high capacity can be obtained with excellent cycle characteristics.

  Further, the negative electrode active material layer 22B includes an oxide-containing film that covers the surface of the negative electrode active material particles, or a metal material that does not alloy with the electrode reactant in the gaps between the negative electrode active material particles and the gaps in the particles. If it contains, cycling characteristics and a swelling characteristic can be improved more. In this case, if both the oxide-containing film and the metal material are included, both characteristics can be further improved.

[Second Embodiment]
FIG. 5 shows an exploded perspective configuration of a battery according to the second embodiment of the present invention, and FIG. 6 shows an enlarged cross section taken along line VI-VI shown in FIG. The battery described here is, for example, a lithium ion secondary battery as in the first embodiment described above.

  In this secondary battery, a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is mainly housed in a film-like exterior member 40. The battery structure using the film-shaped exterior member 40 is called a laminate film type.

  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 metal material such as aluminum, and the negative electrode lead 32 is made of, for example, a metal material such as copper, nickel, or stainless steel. These metal materials are, for example, in a thin plate shape or a mesh shape.

  The exterior member 40 is made of, for example, a rectangular aluminum laminate film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. In the exterior member 40, for example, a polyethylene film faces the wound electrode body 30, and each outer edge portion is in close contact with each other by fusion or an adhesive.

  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 made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32. Examples of such a material include polyolefin resins such as polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

  The exterior member 40 may be constituted by a laminate film having another laminated structure instead of the above-described three-layer aluminum laminated film, or may be constituted by a polymer film such as polypropylene or a metal film. It may be.

  The wound electrode body 30 is wound after the positive electrode 33 and the negative electrode 34 are laminated via the separator 35 and the electrolyte 36, and the outermost peripheral portion thereof is protected by a protective tape 37.

  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 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 layer in the first embodiment described above. The configurations of 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23 are the same.

  The electrolyte 36 includes an electrolytic solution and a polymer compound that holds the electrolytic solution, and is a so-called gel electrolyte. The gel electrolyte is preferable because high ion conductivity (for example, 1 mS / cm or more at room temperature) is obtained and liquid leakage is prevented.

  The composition of the electrolytic solution is the same as the composition of the electrolytic solution in the first embodiment. However, the solvent in this case is not only a liquid solvent but also a broad concept including those having ion conductivity capable of dissociating the electrolyte salt. Accordingly, when a polymer compound having ion conductivity is used, the polymer compound is also included in the solvent.

  Examples of the polymer compound that holds the electrolytic solution include polymers of vinylidene fluoride such as polyvinylidene fluoride having a structural unit represented by Chemical Formula 8 and a copolymer of vinylidene fluoride and hexafluoropropylene. It is done. This is because the redox stability is high.

  Examples of the polymer compound include those formed by polymerizing a polymerizable compound. Examples of the polymerizable compound include those having a vinyl group or a group obtained by substituting a part of hydrogen with a substituent such as a methyl group. Specifically, monofunctional acrylates such as acrylic acid esters, monofunctional methacrylates such as methacrylic acid esters, polyfunctional acrylates such as diacrylic acid esters or triacrylic acid esters, dimethacrylic acid esters or trimethacrylic acid esters, etc. Polyfunctional methacrylates, acrylonitrile, methacrylonitrile, and the like. Among them, esters having an acrylate group or a methacrylate group are preferable. This is because the polymerization proceeds easily and the reaction rate of the polymerizable compound is high. Moreover, as a polymeric compound, what does not have an ether group is preferable. This is because when an ether group is present, lithium ions are coordinated to the ether group, and the ionic conductivity is lowered. Examples of such a polymer compound include polyacrylic acid ester having a structural unit represented by Chemical formula 9.

（ＲはＣ_g Ｈ_2h-1Ｏ_h である。ただし、ｇは１以上８以下の整数であり、ｈは０以上４以下の整数である。）

(R is C _g H _2h-1 O _h . However, g is an integer of 1-8, and h is an integer of 0-4.)

  Any one of the polymerizable compounds may be used alone, but a mixture of a monofunctional substance and a polyfunctional substance is preferred, and a polyfunctional substance alone or a mixture of two or more kinds is preferred. This is because it becomes easy to achieve both the mechanical strength and the electrolyte solution retention of the polymer compound formed by polymerization.

  Furthermore, as a high molecular compound, what has polyvinyl formal which has a structural unit represented by Chemical formula 10 is also preferable. Polyvinyl formal is a polymer compound having an acetal group as a structural unit.

  The ratio of the acetal group in the polyvinyl formal is preferably in the range of 60 mol% to 80 mol%. This is because the solubility with the solvent is improved and the stability of the electrolyte 16 is further increased. Moreover, it is preferable that the weight average molecular weights of polyvinyl formal are 10,000 or more and 500,000 or less. This is because if the molecular weight is too low, the polymerization reaction may be difficult to proceed, while if the molecular weight is too high, the viscosity of the electrolytic solution may increase too much.

  The above polymer compounds may be used singly, a plurality of types may be mixed, or two or more types of copolymers may be used. Further, it may be polymerized with a crosslinking agent.

  Instead of the gel electrolyte 36 in which the electrolytic solution is held by the polymer compound, the electrolytic solution may be used as it is. In this case, the separator 35 is impregnated with the electrolytic solution.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 33 and inserted in the negative electrode 34 through the electrolyte 36. On the other hand, when discharging is performed, for example, lithium ions are extracted from the negative electrode 34 and inserted into the positive electrode 33 through the electrolyte 36.

  This secondary battery is manufactured by the following three types of manufacturing methods, for example.

  In the first manufacturing method, first, the positive electrode active material layer 33B is formed on both surfaces of the positive electrode current collector 33A by the same procedure as in the first embodiment to produce the positive electrode 33, and the negative electrode current collector 34A. The negative electrode active material layer 34B is formed on both surfaces of the negative electrode 34 to produce the negative electrode 34.

  Next, after mixing the solvent containing the cyclic carbonate having halogen shown in Chemical Formula 3 with the ester compound shown in Chemical Formula 4, the electrolyte salt containing lithium tetrafluoroborate is dissolved, and electrolysis is performed. Prepare the solution.

  Next, a precursor solution containing an electrolytic solution, a polymer compound, and a solvent is prepared and applied to the positive electrode 33 and the negative electrode 34, and then the solvent is volatilized to form a gel electrolyte 36. Subsequently, the positive electrode lead 31 is attached to the positive electrode 33 by welding or the like, and the negative electrode lead 32 is attached to the negative electrode 34 by welding or the like. Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte 36 is formed are stacked via the separator 35 and then wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion thereof to produce the wound electrode body 30. To do.

  Finally, for example, after the wound electrode body 30 is sandwiched between two film-shaped exterior members 40, the outer edge portions of the exterior member 40 are bonded together by heat-sealing or the like. Enclose. At this 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. 5 and 6 is completed.

  In the second manufacturing method, first, the positive electrode lead 31 is attached to the positive electrode 33 and the negative electrode lead 32 is attached to the negative electrode 34, and then the positive electrode 33 and the negative electrode 34 are stacked and wound via the separator 35. A protective tape 37 is adhered to the outer peripheral portion to produce a wound body that is a precursor of the wound electrode body 30. 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 bonded by heat sealing or the like, 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 opening part of the exterior member 40 is sealed by heat sealing or the like. Finally, the gel electrolyte 36 is formed by thermally polymerizing the monomer to obtain a polymer compound. Thereby, the secondary battery is completed.

  In the third production method, a wound body is produced by manufacturing a wound body in the same manner as in the second production method described above, except that the separator 35 coated with the polymer compound on both sides is used first. 40 is housed inside. Examples of the polymer compound applied to the separator 35 include a polymer containing vinylidene fluoride as a component, that is, a homopolymer, a copolymer, or a multi-component copolymer. Specifically, polyvinylidene fluoride, binary copolymers containing vinylidene fluoride and hexafluoropropylene as components, and ternary copolymers containing vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Such as coalescence. In addition, the high molecular compound may contain the other 1 type, or 2 or more types of high molecular compound with the polymer which uses the above-mentioned vinylidene fluoride as a component. Subsequently, after injecting the electrolyte into the exterior member 40, the opening of the exterior member 40 is sealed by heat fusion or the like. Finally, 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. As a result, the electrolytic solution is impregnated into the polymer compound, and the polymer compound is gelled to form the electrolyte 36. Thus, the secondary battery is completed.

  In the third manufacturing method, the swollenness of the secondary battery is suppressed as compared with the first manufacturing method. Further, in the third manufacturing method, compared with the second manufacturing method, there are hardly any monomers or solvents that are raw materials for the polymer compound remaining in the electrolyte 36, and the formation process of the polymer compound is well controlled. Therefore, sufficient adhesion is obtained between the positive electrode 33, the negative electrode 34, the separator 35, and the electrolyte 36.

  According to this secondary battery, the negative electrode active material particles and the electrolyte solution of the negative electrode 34 have the same configuration as the negative electrode active material particles and the electrolyte solution of the negative electrode 21 in the first embodiment described above, respectively. Excellent cycle characteristics and swelling characteristics can be obtained.

  In particular, if the battery structure of the secondary battery is a laminate film type, the swelling characteristics during charging / discharging tend to become obvious, so that the swelling characteristics can be improved more effectively.

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

(Example 1-1)
The square secondary battery shown in FIGS. 1 and 2 was fabricated using silicon as the negative electrode active material. At this time, a lithium ion secondary battery in which the capacity of the negative electrode 22 was expressed based on insertion and extraction of lithium was made.

First, the positive electrode 21 was produced. First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a molar ratio of 0.5: 1, and then calcined in air at 900 ° C. for 5 hours to form a lithium cobalt composite. An oxide (LiCoO ₂ ) was obtained. Subsequently, 94 parts by mass of lithium cobalt composite oxide as a positive electrode active material, 3 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to form a positive electrode mixture. Dispersed in methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was uniformly applied to both surfaces of the positive electrode current collector 21A made of an aluminum foil (thickness = 20 μm) by a bar coater and dried, and then the coating film was compression-molded by a roll press machine. An active material layer 21B was formed. At this time, the weight per unit area of the positive electrode active material layer 21B on one side of the positive electrode current collector 21A was set to 20 mg / cm ² . Finally, the positive electrode current collector 21A on which the positive electrode active material layer 21B was formed was cut into a strip shape having a width of 50 mm and a length of 300 mm.

  Next, the negative electrode 22 was produced. First, a negative electrode active material layer 22B is formed by depositing silicon on both surfaces of a negative electrode current collector 22A made of an electrolytic copper foil (thickness = 12 μm) by electron beam evaporation to form a plurality of negative electrode active material particles. Formed. In the case of forming this negative electrode active material layer 22B, negative electrode active material particles are formed by depositing and laminating silicon multiple times while the negative electrode current collector 22A is reciprocally moved relative to the vapor deposition source. Had a multilayer structure in the particles. At this time, the deposition thickness per silicon layer was 0.3 μm, and the vapor deposition step and the cooling step were repeated 25 times, so that the number of negative electrode active material particles was 25 (total thickness = 7.5 μm). Finally, the negative electrode current collector 22A on which the negative electrode active material layer 22B was formed was cut into a strip shape having a width of 50 mm and a length of 300 mm.

Next, 4-fluoro-1,3-dioxolan-2-one (FEC) which is a cyclic carbonate having a halogen shown in Chemical Formula 3 as a solvent and ethyl methyl carbonate (EMC) which is a sulfone compound shown in Chemical Formula 4 And lithium hexafluorophosphate (LiPF ₆ ) and lithium tetrafluoroborate (LiBF ₄ ) were dissolved as an electrolyte salt to prepare an electrolytic solution. At this time, the mixing ratio (FEC: EMC: LiPF ₆ : LiBF ₄ ) in the electrolytic solution was set to 43.52: 43.52: 12.03: 0.93 by weight. In this case, the mixing ratio of FEC and EMC (FEC: EMC) is 50:50 by weight, in other words, the contents of FEC and EMC in the electrolytic solution are both 50% by weight. Further, the concentrations of LiPF ₆ and LiBF ₄ in the electrolytic solution are 0.9 mol / kg and 0.1 mol / kg, respectively.

  Next, a secondary battery was assembled using the electrolyte together with the positive electrode 21 and the negative electrode 22. First, the positive electrode lead 24 made of aluminum was welded to the positive electrode current collector 21A, and the negative electrode lead 25 made of nickel was welded to the negative electrode current collector 22A. Subsequently, the positive electrode 21 and the negative electrode 22 are laminated through a separator 23 made of a microporous polyethylene film (thickness = 9 μm), wound in the longitudinal direction, and then formed into a flat shape to form a battery element 20. Was made. Subsequently, after the battery element 20 was accommodated in the iron battery can 11, the insulating plate 12 was disposed on the battery element 20. Subsequently, the positive electrode lead 24 was welded to the positive electrode pin 15 and the negative electrode lead 25 was welded to the battery can 11, and then the battery lid 13 was fixed to the open end of the battery can 11 by laser welding. Finally, after the electrolyte was injected into the battery can 11 through the injection hole 19, the injection hole 19 was closed with a sealing member 19A. Thereby, a square secondary battery was completed. The capacity of this secondary battery is 800 mAh.

(Example 1-2)
A procedure similar to that of Example 1-1 was performed except that the mixing ratio of FEC and EMC (FEC: EMC) was changed to 30:70 by weight.

(Examples 1-3 and 1-4)
Diethyl carbonate (DEC), which is a symmetric chain compound, is added as a solvent, and the mixing ratio of FEC, DEC, and EMC (FEC: DEC: EMC) is 50:40:10 (Example 1-3) by weight or A procedure similar to that of Example 1-1 was performed except that the ratio was changed to 30:60:10 (Example 1-4).

(Examples 1-5, 1-6)
The concentrations of LiPF ₆ and LiBF ₄ were changed to 0.8 mol / kg and 0.2 mol / kg (Example 1-5) or 0.98 mol / kg and 0.02 mol / kg (Example 1-6), respectively. Except for, the same procedure as in Example 1-1 was performed.

(Examples 1-7, 1-8)
As a solvent, trans-4,5-difluoro-1,3-dioxolan-2-one (DFEC) is used in place of FEC, and ethylene carbonate (EC) is added, and a mixing ratio of DFEC, EC and EMC (DFEC). : EC: EMC), except that the weight ratio was changed to 10:40:50 (Example 1-7) or 20:30:50 (Example 1-8). It went through.

(Example 1-9)
A procedure similar to that of Example 1-1 was performed, except that part of the EMC was replaced with anhydrous methyl sulfopropionate (SPAH), which is an acid anhydride. At this time, the mixing ratio (FEC: EMC: SPAH) of FEC, EMC, and SPAH was set to 50: 49: 1.

(Comparative Example 1-1)
The same procedure as in Example 1-1 was performed, except that LIBF ₄ was not added and the concentration of LiPF ₆ was 1.0 mol / kg.

(Comparative Example 1-2)
A procedure similar to that of Example 1-1 was performed except that DEC was used instead of EMC.

(Comparative Example 1-3)
A procedure similar to that of Example 1-1 was performed except that dimethyl carbonate (DMC), which is a symmetric chain compound, was used instead of EMC.

(Comparative Example 1-4)
A procedure similar to that of Example 1-1 was performed except that EC was used instead of FEC.

  When the cycle characteristics and the swollenness characteristics of the secondary batteries of Examples 1-1 to 1-9 and Comparative Examples 1-1 to 1-4 were examined, the results shown in Table 1 were obtained.

  When investigating cycle characteristics, charge and discharge for one cycle in an atmosphere at 23 ° C. to measure the discharge capacity, and then repeatedly charge and discharge in the same atmosphere until the total number of cycles reaches 300 cycles to measure the discharge capacity. After that, the discharge capacity retention ratio (%) = (discharge capacity at the 300th cycle / discharge capacity at the first cycle) × 100 was calculated. As charging / discharging conditions for one cycle, the battery is charged at a constant current of 800 mA to an upper limit voltage of 4.2 V, and further charged at a constant voltage of 4.2 V until the total time from the start of charging is 3 hours, and then 800 mA. The battery was discharged at a constant current to a final voltage of 3.0V.

  When investigating the swelling characteristics, charge in an atmosphere of 23 ° C., measure the thickness of the secondary battery, and continue to store in a constant temperature bath at 90 ° C. for 4 hours in the charged state. After measuring the thickness, the swelling (mm) = (thickness after storage−thickness before storage) was calculated. At this time, the charging conditions were the same as those for examining the cycle characteristics.

  The procedures and conditions for examining the cycle characteristics and the swollenness characteristics described above are the same for the series of examples and comparative examples that follow.

As shown in Table 1, when the battery structure is square, Examples 1-1 to 1-9 in which the electrolytic solution contains FEC or DFEC as a solvent, LiBF ₄ as an electrolyte salt, and EMC. In comparison with Comparative Examples 1-1 to 1-4, which did not satisfy all of these conditions, swelling was suppressed to a small level while obtaining a high discharge capacity retention rate.

In this case, when the content of FEC in the electrolytic solution is 30% by weight or more and 50% by weight or less, or when the content of DFEC in the electrolytic solution is 10% by weight or more and 20% by weight or less, a high discharge capacity. A retention rate was obtained. Further, when the concentration of LiBF ₄ in the electrolytic solution was 0.02 mol / kg or more and 0.2 mol / kg or less, a high discharge capacity retention rate was obtained while suppressing an increase in swelling. Furthermore, when the content of EMC in the electrolytic solution was 10% by weight or more and 70% by weight or less, a high discharge capacity retention rate was obtained while an increase in swelling was suppressed.

  In addition, when the electrolytic solution contained SPAH, the discharge capacity retention rate was higher and the swelling was smaller. In addition, although the result at the time of using acid anhydrides other than SPAH is not shown here, the acid anhydride represented by SPAH has a role to increase the discharge capacity maintenance rate and reduce swelling in common. Therefore, it is clear that similar results can be obtained even when other acid anhydrides other than SPAH are used.

Therefore, in the prismatic secondary battery of the present invention, when the negative electrode active material particles of the negative electrode 22 contain silicon and have a multilayer structure, the electrolytic solution is FEC or DFEC and LiBF ₄ as the electrolyte salt as a solvent. It was confirmed that excellent cycle characteristics and swollenness characteristics can be obtained by including C and EMC. In this case, it was also confirmed that both characteristics were further improved if the electrolytic solution contained an acid anhydride such as SPAH.

(Examples 2-1 and 2-2)
A procedure similar to that of Example 1-1 was performed except that methylpropyl carbonate (MPC: Example 2-1) or butylmethyl carbonate (BMC: Example 2-2) was used instead of EMC as the ester compound.

  When the cycle characteristics and the swollenness characteristics of the secondary batteries of Examples 2-1 and 2-2 were examined, the results shown in Table 2 were obtained.

  As shown in Table 2, in Examples 2-1 and 2-2 in which the electrolytic solution contains MPC or the like, as compared with Example 1-1 containing EMC, compared with Comparative Examples 1-1 to 1-4. Thus, swelling was suppressed to a small level while obtaining a high discharge capacity retention rate. In this case, when an asymmetrical EMC having 2 to 4 carbon atoms of R21 shown in Chemical Formula 4 was used, the discharge capacity retention rate was increased and the swelling was reduced. On the other hand, when a symmetric DMC having 1 carbon is used, the discharge capacity retention rate is increased but the swelling is increased, and when a symmetric DEC is used, the swelling is reduced but the discharge capacity maintenance rate is lowered. It was.

  From these facts, it was confirmed that in the square secondary battery of the present invention, excellent cycle characteristics and swelling characteristics can be obtained even when the electrolyte contains MPC or the like, as in the case of containing EMC. .

(Example 3-1)
A procedure similar to that of Example 1-1 was performed, except that the number of layers of the negative electrode active material particles was changed to 10 instead of 25. At this time, the deposition thickness per silicon layer was set to 0.75 μm, and the vapor deposition step and the cooling step were repeated 10 times to set the total thickness of the negative electrode active material particles to 7.5 μm.

(Example 3-2)
In forming the negative electrode active material layer 22B, after forming a plurality of negative electrode active material particles, a silicon oxide (SiO ₂ ) is deposited as an oxide-containing film on the surface of the negative electrode active material particles by a liquid phase deposition method. Except that, the same procedure as in Example 1-1 was performed. In the case of forming this oxide-containing film, the negative electrode current collector 22A on which the negative electrode active material particles are formed is immersed for 3 hours in a solution obtained by dissolving boron as an anion scavenger in hydrofluoric acid. After depositing silicon oxide on the surface of the negative electrode active material particles, it was washed with water and dried under reduced pressure.

(Example 3-3)
When forming the negative electrode active material layer 22B, after forming a plurality of negative electrode active material particles, a plating film of cobalt (Co) as a metal material was grown by an electrolytic plating method, and Example 1-1 A similar procedure was followed. In the case of forming this metal material, electricity was supplied while supplying air to the plating bath, and cobalt was deposited on both surfaces of the negative electrode current collector 22A. At this time, a cobalt plating solution manufactured by Japan High Purity Chemical Co., Ltd. was used as the plating solution, the current density was 2 A / dm ^{2 to} 5 A / dm ² , and the plating rate was 10 nm / second.

(Example 3-4)
Except that after depositing an oxide of silicon as an oxide-containing film according to the procedure described in Examples 3-2 and 3-3, a cobalt plating film was further grown as a metal material. 1 was followed.

(Comparative Example 2)
A procedure similar to that of Example 1-1 was performed except that the number of layers of the negative electrode active material particles was changed to one instead of 25. At this time, the deposition thickness of silicon (the thickness of the negative electrode active material particles) was set to 7.5 μm.

  When the cycle characteristics and the swollenness characteristics of the secondary batteries of Examples 3-1 to 3-4 and Comparative Example 2 were examined, the results shown in Table 3 were obtained.

  As shown in Table 3, assuming that the thickness of the negative electrode active material particles is constant (7.5 μm), Examples 1-1 and 3-1 in which the negative electrode active material particles have a multilayer structure have a single layer structure. Compared to Comparative Example 2, the discharge capacity retention rate was increased while the swelling was maintained substantially the same. In this case, the discharge capacity retention rate increased as the number of layers of the negative electrode active material particles increased, and the discharge capacity retention rate increased sufficiently when the number of layers was 10 or more.

  Further, in Examples 3-2 to 3-4 in which the oxide-containing film and the metal material were formed, the discharge capacity was maintained while the swelling was maintained substantially the same as in Example 1-1 in which they were not formed. The rate has increased. In this case, the discharge capacity retention rate was higher when the metal material was formed, and the discharge capacity retention rate was further increased when both the oxide-containing film and the metal material were formed.

  Here, only the result in the case where the deposition thickness of silicon deposited in one vapor deposition process is 0.3 μm or 0.75 μm is shown, but the deposition thickness of silicon necessary for obtaining sufficient cycle characteristics is shown. When the upper limit of the thickness was examined, the upper limit was 1 μm.

  For these reasons, in the prismatic secondary battery of the present invention, when the negative electrode active material particles have a multilayer structure, the cycle characteristics are improved and the thickness of one layer of the negative electrode active material particles is 1 μm or less. It was confirmed that sufficient characteristics could be obtained if the number of layers was 10 or more. It was also confirmed that the cycle characteristics were further improved when an oxide-containing film or a metal material was formed, and the characteristics were significantly improved when a metal material or both were formed as compared with the oxide-containing film.

(Examples 4-1 to 4-7)
The same procedure as in Examples 1-1 to 1-7 was performed except that the laminate film type secondary battery shown in FIG. 5 and FIG. 6 was produced by the following procedure. When producing this laminated film type secondary battery, first, 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 on both surfaces of the negative electrode current collector 34A. After forming the negative electrode active material layer 34B and producing the negative electrode 34, the positive electrode lead 31 made of aluminum is welded to one end of the positive electrode current collector 33A, and the negative electrode lead 32 made of nickel is attached to one end of the negative electrode current collector 34A. Welded. Subsequently, the positive electrode 33, the separator 35, the negative electrode 34, and the separator 35 described above are laminated in this order and then wound many times in the longitudinal direction, and then the winding end portion is covered with a protective tape 37 made of an adhesive tape. It fixed and the winding body which is the precursor of the winding electrode body 30 was formed. Subsequently, an exterior made of a laminate film having a three-layer structure in which a nylon film (thickness = 30 μm), an aluminum foil (thickness = 40 μm), and an unstretched polypropylene film (thickness = 30 μm) are laminated from the outside. After the wound body was sandwiched between the members 40, the outer edge portions except for one side were heat-sealed, and the wound body was stored inside the bag-shaped exterior member 40. Subsequently, 2 g of an electrolytic solution was injected into the inside from the opening of the exterior member 40, and the separator 35 was impregnated with the electrolytic solution to produce a wound electrode body 30. Finally, the laminated film type secondary battery was completed by thermally sealing and sealing the opening of the exterior member 40 in a vacuum atmosphere.

(Examples 4-8 and 4-9)
A procedure similar to that in Example 4-1 was performed except that MPC (Example 4-8) or BMC (Example 4-9) was used instead of EMC.

(Comparative Examples 3-1 to 3-3)
A procedure similar to those of Comparative Examples 1-1 to 1-3 was performed, except that laminate film type secondary batteries were produced in the same manner as in Examples 4-1 to 4-9.

  When the cycle characteristics and the swollenness characteristics of the secondary batteries of Examples 4-1 to 4-9 and Comparative Examples 3-1 to 3-3 were examined, the results shown in Table 4 were obtained.

As shown in Table 4, when the battery structure was a laminate film type, the same results as in the case of the square type (Tables 1 and 2) were obtained. That is, in Examples 4-1 to 4-9 in which the electrolytic solution contains FEC or DFEC as a solvent, LiBF ₄ as an electrolyte salt, EMC, and the like, Comparative Example 3-1 that does not satisfy all of these conditions As compared with ˜3-3, swelling was suppressed to a small level while obtaining a high discharge capacity retention rate.

Accordingly, in the laminated film type secondary battery of the present invention, when the negative electrode active material particles of the negative electrode 34 contain silicon and have a multilayer structure, the electrolytic solution is FEC as a solvent or DFEC and LiBF as an electrolyte salt. By including ₄ and EMC or the like, it was confirmed that excellent cycle characteristics and swollenness characteristics can be obtained as in the case of the square secondary battery.

  From the results of Tables 1 to 4 above, in the secondary battery of the present invention, the negative electrode active material particles of the negative electrode can occlude and release the electrode reactant, and among the metal elements and metalloid elements, When the material contains at least one material and has a multilayer structure in the particles, the electrolytic solution contains a solvent containing a cyclic carbonate having a halogen shown in Chemical Formula 3 and lithium tetrafluoroborate. By including the electrolyte salt contained and the ester compound shown in Chemical formula 4, excellent cycle characteristics and the dependence on the battery structure, the composition of the solvent, the concentration of the electrolyte salt, and the content of the ester compound It was confirmed that the swollenness characteristics can be obtained.

  The present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the embodiments described in the above embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, the case where the electrolytic solution or the gel electrolyte in which the electrolytic solution is held in a polymer compound is used as the electrolyte of the battery of the present invention has been described. 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 electrolyte, or a mixture of another inorganic compound and an electrolyte. Or a mixture of these inorganic compounds and a gel electrolyte.

  In the above-described embodiments and examples, the lithium ion secondary battery in which the capacity of the negative electrode is expressed based on insertion and extraction of lithium is described as the battery of the present invention. However, the present invention is not necessarily limited to this. Absent. In the battery of the present invention, the negative electrode material capable of occluding and releasing lithium has a smaller charge capacity than that of the positive electrode, so that the negative electrode capacity is based on the storage and release of lithium and the deposition of lithium and The present invention can be similarly applied to a secondary battery including a capacity based on melting and represented by the sum of the capacities.

  In the above-described embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, the group 1A element in other short-period periodic tables such as sodium (Na) or potassium (K), magnesium, and the like Or 2A group elements, such as calcium (Ca), and other light metals, such as aluminum, may be used. Also in this case, the negative electrode material described in the above embodiment can be used.

  In the above-described embodiments or examples, the battery of the present invention has been described by taking the case where the battery structure is a square type and a laminate film type, and the case where the battery element has a winding structure as an example, The battery of the present invention can be similarly applied to a case where the battery has another battery structure such as a cylindrical shape, a coin shape or a button shape, and a case where the battery element has another structure such as a laminated structure.

  Further, in the above-described embodiments and examples, regarding the battery of the present invention, the content of the ester compound in the electrolytic solution is described in an appropriate range derived from the results of the examples. The possibility that the content is outside the above range is not completely denied. In other words, the appropriate range described above is a particularly preferable range for obtaining the effect of the present invention, and the content may be slightly deviated from the above range as long as the effect of the present invention is obtained. The same applies to the content of halogenated cyclic carbonate and the concentration of lithium tetrafluoroborate.

It is sectional drawing showing the structure of the battery which concerns on the 1st Embodiment of this invention. It is sectional drawing along the II-II line of the battery shown in FIG. FIG. 3 is an SEM photograph showing a cross-sectional structure of the negative electrode shown in FIG. 2 and a schematic diagram thereof. FIG. 3 is an SEM photograph showing another cross-sectional structure of the negative electrode shown in FIG. 2 and a schematic diagram thereof. It is a disassembled perspective view showing the structure of the battery which concerns on the 2nd Embodiment of this invention. It is sectional drawing showing the structure along the VI-VI line of the wound electrode body shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12 ... Insulation board, 13 ... Battery cover, 14 ... Terminal board, 15 ... Positive electrode pin, 16 ... Insulation case, 17 ... Gasket, 18 ... Cleavage valve, 19 ... Injection hole, 19A ... Sealing member, DESCRIPTION OF SYMBOLS 20 ... Battery element, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode collector, 22B, 34B ... Negative electrode active Material layer, 23, 35 ... separator, 24, 31 ... positive electrode lead, 25, 32 ... negative electrode lead, 30 ... wound electrode body, 36 ... electrolyte, 37 ... protective tape, 40 ... exterior member, 41 ... adhesion film, 221 ... negative electrode active material particles, 222 (222A, 222B) ... gaps, 223 ... gaps, 224 ... metal materials.

Claims (14)

A battery comprising an electrolyte solution together with a positive electrode and a negative electrode,
The negative electrode has a negative electrode active material layer including a plurality of negative electrode active material particles,
The negative electrode active material particles can contain and release electrode reactants, contain a material having at least one of a metal element and a metalloid element, and have a multilayer structure in the particles. ,
The electrolytic solution includes a solvent containing a cyclic carbonate having a halogen represented by Chemical Formula 1, an electrolyte salt containing lithium tetrafluoroborate (LiBF ₄ ), and an ester compound represented by Chemical Formula 2. A battery characterized by including.

(R11 to R14 are a hydrogen group, a halogen group, an alkyl group or a halogenated alkyl group, and at least one of them is a halogen group or a halogenated alkyl group.)

(R21 is an alkyl group having 2 to 4 carbon atoms.)   The battery according to claim 1, wherein the negative electrode active material particles contain silicon (Si).   The battery according to claim 1, wherein the negative electrode has a negative electrode current collector that supports the negative electrode active material layer, and the negative electrode active material particles are connected to a surface of the negative electrode current collector. .   The cyclic carbonate having a halogen shown in Chemical Formula 1 is 4-fluoro-1,3-dioxolan-2-one, and the inclusion of 4-fluoro-1,3-dioxolan-2-one in the electrolyte solution The battery according to claim 1, wherein the amount is 30% by weight or more and 50% by weight or less.   The cyclic carbonate having a halogen shown in Chemical Formula 1 is 4,5-difluoro-1,3-dioxolan-2-one, and 4,5-difluoro-1,3-dioxolane-2 in the electrolytic solution is used. The battery according to claim 1, wherein the content of -on is 10 wt% or more and 20 wt% or less.   The battery according to claim 1, wherein the concentration of lithium tetrafluoroborate in the electrolytic solution is 0.02 mol / kg or more and 0.2 mol / kg or less. The battery according to claim 1, wherein the electrolyte salt contains lithium hexafluorophosphate (LiPF ₆ ).   2. The battery according to claim 1, wherein the content of the ester compound represented by Formula 2 in the electrolytic solution is 10 wt% or more and 70 wt% or less.   The battery according to claim 1, wherein the negative electrode active material layer includes an oxide-containing film that covers a surface of the negative electrode active material particles.   The battery according to claim 9, wherein the oxide-containing film contains at least one oxide selected from the group consisting of silicon, germanium (Ge), and tin (Sn).   2. The battery according to claim 1, wherein the negative electrode active material layer includes a metal material that is not alloyed with an electrode reactant in a gap between particles of the negative electrode active material particles and a gap in the particles.   12. The metal material according to claim 11, wherein the metal material has at least one selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), and copper (Cu). battery.   The battery according to claim 1, wherein the positive electrode, the negative electrode, and the electrolytic solution are accommodated in a rectangular metal can.   The battery according to claim 1, wherein the positive electrode, the negative electrode, and the electrolytic solution are housed in a film-shaped exterior member.

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