JP2006302757A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of enhancing cycle characteristics even if charge voltage is set higher than 4.2 V. <P>SOLUTION: The battery is equipped with a wound electrode body 20 formed by winding a positive electrode 1, and a negative electrode 22 through a separator 23. Open circuit voltage in full charge is 4.25-6.00 V. The separator is impregnated with an electrolyte in which an electrolyte salt is dissolved in a solvent. The solvent contains a compound having a sulfite structure such as ethylene sulfite. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a battery using an electrolyte containing a compound having a specific structure.

  With the remarkable development of portable electronic technology in recent years, electronic devices such as mobile phones and notebook computers have begun to be recognized as fundamental technologies that support an advanced information society. In addition, research and development related to the enhancement of the functions of these electronic devices have been energetically advanced, and the power consumption of these electronic devices has been increasing proportionally. On the other hand, these electronic devices are required to be driven for a long time, and a high energy density of a secondary battery as a driving power source has been inevitably desired.

  From the viewpoint of the occupied volume and mass of the battery built in the electronic device, the higher the energy density of the battery, the better. At present, since lithium ion secondary batteries have an excellent energy density, they have been built into most devices.

  Usually, in lithium ion secondary batteries, lithium cobaltate is used for the positive electrode and a carbon material is used for the negative electrode, and the operating voltage is used in the range of 4.2V to 2.5V. In the unit cell, the terminal voltage can be increased to 4.2 V largely due to excellent electrochemical stability such as a non-aqueous electrolyte material or a separator.

By the way, in the conventional lithium ion secondary battery that operates at a maximum of 4.2 V, the positive electrode active material such as lithium cobaltate used for the positive electrode only uses about 60% of its theoretical capacity. Absent. For this reason, it is possible in principle to utilize the remaining capacity by further increasing the charging pressure. In fact, it is known that high energy density is manifested by setting the voltage during charging to 4.25 V or more (see Patent Document 1).
International Publication No. WO03 / 019713 Pamphlet

  However, in a battery in which the charging voltage is set to exceed 4.2 V, the oxidizing atmosphere is particularly strong in the vicinity of the surface of the positive electrode. As a result, the non-aqueous electrolyte and the separator in physical contact with the positive electrode are oxidized and decomposed. There is a problem that the increase is induced, and the cycle characteristics are deteriorated.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a battery capable of improving cycle characteristics even when the charging voltage is higher than 4.2V.

  The battery according to the present invention includes a positive electrode and a negative electrode together with an electrolyte containing a solvent, and the open circuit voltage in a fully charged state per pair of the positive electrode and the negative electrode is in the range of 4.25 V to 6.00 V. Yes, the solvent contains the compound having the sulfite structure shown in Chemical Formula 1.

  According to the battery of the present invention, since the open circuit voltage at the time of full charge per pair of positive electrode and negative electrode is in the range of 4.25V to 6.00V, a high energy density can be obtained. Further, since the solvent contains the compound having the sulfite structure shown in Chemical Formula 1, a film can be formed on the surface of the positive electrode, and the electrochemical stability of the surface of the positive electrode can be improved. Therefore, the energy density can be increased and the cycle characteristics can be improved.

  In particular, if the content of the compound having the sulfite structure shown in Chemical Formula 1 is within the range of 0.01% by mass or more and 20% by mass or less with respect to the solvent, the cycle characteristics can be further improved. it can.

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

(First embodiment)
FIG. 1 shows a cross-sectional structure of the secondary battery according to the first embodiment. This secondary battery is a so-called lithium ion secondary battery in which (Li) is used as an electrode reactant and the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium. This secondary battery is called a so-called cylindrical type, and is a winding in which a pair of strip-like positive electrode 21 and strip-like negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. A rotating electrode body 20 is provided. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

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

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

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. Although not shown, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode active material layer 21B includes, for example, one or more positive electrode materials capable of inserting and extracting lithium, which is an electrode reactant, as a positive electrode active material. A conductive agent and a binder such as polyvinylidene fluoride are included.

As the positive electrode material capable of inserting and extracting lithium, for example, lithium-containing compounds such as lithium oxide, lithium phosphorus oxide, lithium sulfide, or an intercalation compound containing lithium are suitable. May be used in combination. In order to increase the energy density, a lithium-containing compound containing lithium, a transition metal element, and oxygen (O) is preferable. Among them, the transition metal element includes cobalt (Co), nickel, manganese (Mn), and iron. It is more preferable if it contains at least one of them. As such a lithium-containing compound, for example, the layered rock salt type lithium composite oxide shown in Chemical Formula 2, Chemical Formula 3 or Chemical Formula 4, the spinel type lithium composite oxide shown in Chemical Formula 5, or the chemical formula 6 is shown. Examples include olivine-type lithium composite phosphates, and specifically LiNi _0.50 Co _0.20 Mn _0.30 O ₂ , Li _a CoO ₂ (a≈1), Li _b NiO ₂ (b≈1), Li _c1 Ni _{c 2} Co ₁ -c ₂ O ₂ (c 1 ≈ 1, 0 <c 2 <1), Li _d Mn ₂ O ₄ (d ≈ 1), Li _e FePO ₄ (e ≈ 1), or the like.

（式中、Ｍ１は、コバルト，マグネシウム（Ｍｇ），アルミニウム，ホウ素（Ｂ），チタン（Ｔｉ），バナジウム（Ｖ），クロム（Ｃｒ），鉄，銅（Ｃｕ），亜鉛（Ｚｎ），ジルコニウム（Ｚｒ），モリブデン（Ｍｏ），スズ（Ｓｎ），カルシウム（Ｃａ），ストロンチウム（Ｓｒ）およびタングステン（Ｗ）からなる群のうちの少なくとも１種を表す。ｆ，ｇ，ｈ，ｊおよびｋは、０．８≦ｆ≦１．２、０＜ｇ＜０. ５、０≦ｈ≦０. ５、ｇ＋ｈ＜１、−０. １≦ｊ≦０. ２、０≦ｋ≦０．１の範囲内の値である。なお、リチウムの組成は充放電の状態によって異なり、ｆの値は完全放電状態における値を表している。）

(In the formula, M1 is cobalt, magnesium (Mg), aluminum, boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron, copper (Cu), zinc (Zn), zirconium ( Zr), Molybdenum (Mo), Tin (Sn), Calcium (Ca), Strontium (Sr) and Tungsten (W) are represented by at least one of f, g, h, j and k, 0.8 ≦ f ≦ 1.2, 0 <g <0.5, 0 ≦ h ≦ 0.5, g + h <1, −0.1 ≦ j ≦ 0.2, 0 ≦ k ≦ 0.1 (Note that the composition of lithium varies depending on the state of charge and discharge, and the value of f represents a value in a fully discharged state.)

（式中、Ｍ２は、コバルト，マンガン，マグネシウム，アルミニウム，ホウ素，チタン，バナジウム，クロム，鉄，銅，亜鉛，モリブデン，スズ，カルシウム，ストロンチウムおよびタングステンからなる群のうちの少なくとも１種を表す。ｍ，ｎ，ｐおよびｑは、０．８≦ｍ≦１．２、０. ００５≦ｎ≦０. ５、−０. １≦ｐ≦０. ２、０≦ｑ≦０. １の範囲内の値である。なお、リチウムの組成は充放電の状態によって異なり、ｍの値は完全放電状態における値を表している。）

(In the formula, M2 represents at least one selected from the group consisting of cobalt, manganese, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, calcium, strontium, and tungsten. m, n, p and q are within the range of 0.8 ≦ m ≦ 1.2, 0.005 ≦ n ≦ 0.5, −0.1 ≦ p ≦ 0.2, 0 ≦ q ≦ 0.1. (Note that the composition of lithium varies depending on the state of charge and discharge, and the value of m represents a value in a fully discharged state.)

（式中、Ｍ３は、ニッケル，マンガン，マグネシウム，アルミニウム，ホウ素，チタン，バナジウム，クロム，鉄，銅，亜鉛，モリブデン，スズ，カルシウム，ストロンチウムおよびタングステンからなる群のうちの少なくとも１種を表す。ｒ，ｓ，ｔおよびｕは、０．８≦ｒ≦１．２、０≦ｓ＜０．５、−０．１≦ｔ≦０．２、０≦ｕ≦０．１の範囲内の値である。なお、リチウムの組成は充放電の状態によって異なり、ｒの値は完全放電状態における値を表している。）

(In the formula, M3 represents at least one selected from the group consisting of nickel, manganese, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, calcium, strontium, and tungsten. r, s, t, and u are values within the range of 0.8 ≦ r ≦ 1.2, 0 ≦ s <0.5, −0.1 ≦ t ≦ 0.2, and 0 ≦ u ≦ 0.1. Note that the composition of lithium varies depending on the state of charge and discharge, and the value of r represents the value in a fully discharged state.)

（式中、Ｍ４は、コバルト，ニッケル，マグネシウム，アルミニウム，ホウ素，チタン，バナジウム，クロム，鉄，銅，亜鉛，モリブデン，スズ，カルシウム，ストロンチウムおよびタングステンからなる群のうちの少なくとも１種を表す。ｖ，ｗ，ｘおよびｙは、０．９≦ｖ≦１．１、０≦ｗ≦０．６、３．７≦ｘ≦４．１、０≦ｙ≦０．１の範囲内の値である。なお、リチウムの組成は充放電の状態によって異なり、ｖの値は完全放電状態における値を表している）

(In the formula, M4 represents at least one selected from the group consisting of cobalt, nickel, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, calcium, strontium, and tungsten. v, w, x and y are values in the range of 0.9 ≦ v ≦ 1.1, 0 ≦ w ≦ 0.6, 3.7 ≦ x ≦ 4.1, 0 ≦ y ≦ 0.1. (Note that the composition of lithium varies depending on the state of charge and discharge, and the value of v represents the value in a fully discharged state.)

（式中、Ｍ５は、コバルト，マンガン，鉄，ニッケル，マグネシウム，アルミニウム，ホウ素，チタン，バナジウム，ニオブ，銅，亜鉛，モリブデン，カルシウム，ストロンチウム，タングステンおよびジルコニウムからなる群のうちの少なくとも１種を表す。ｚは、０．９≦ｚ≦１．１の範囲内の値である。なお、リチウムの組成は充放電の状態によって異なり、ｚの値は完全放電状態における値を表している）

(In the formula, M5 represents at least one selected from the group consisting of cobalt, manganese, iron, nickel, magnesium, aluminum, boron, titanium, vanadium, niobium, copper, zinc, molybdenum, calcium, strontium, tungsten and zirconium. Z is a value in the range of 0.9 ≦ z ≦ 1.1 (the composition of lithium varies depending on the state of charge and discharge, and the value of z represents a value in a fully discharged state)

In addition to these, examples of the positive electrode material capable of inserting and extracting lithium include inorganic compounds not containing lithium, such as MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , NiS, and MoS.

  The negative electrode 22 has, for example, a structure in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces. Although not shown, the negative electrode active material layer 22B may be provided only on one surface of the negative electrode current collector 22A. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil having good electrochemical stability, electrical conductivity, and mechanical strength. In particular, copper foil is most preferable because it has high electrical conductivity.

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of inserting and extracting lithium as the negative electrode active material, and the positive electrode active material layer 21B as necessary. It is comprised including the binder similar to.

  In this secondary battery, the electrochemical equivalent of the negative electrode material capable of inserting and extracting lithium is larger than the electrochemical equivalent of the positive electrode 21, and lithium metal is deposited on the negative electrode 22 during charging. It is supposed not to.

  In addition, this secondary battery is designed so that the open circuit voltage (that is, the battery voltage) at the time of full charge is in the range of 4.25V to 6.00V. Therefore, even when the positive electrode active material is the same as that of the battery having an open circuit voltage of 4.20 V at the time of full charge, the amount of lithium released per unit mass is increased. And the amount has been adjusted. As a result, a high energy density can be obtained.

  Examples of negative electrode materials capable of inserting and extracting lithium include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, and fired organic polymer compounds , Carbon materials such as carbon fiber or activated carbon. Among these, examples of coke include pitch coke, needle coke, and petroleum coke. An organic polymer compound fired body is a carbonized material obtained by firing a polymer material such as a phenol resin or a furan resin at an appropriate temperature, and part of it is non-graphitizable carbon or graphitizable carbon. Some are classified as: These carbon materials are preferable because the change in crystal structure that occurs during charge and discharge is very small, a high charge and discharge capacity can be obtained, and good cycle characteristics can be obtained. In particular, graphite is preferable because it has a high electrochemical equivalent and can provide a high energy density. Further, non-graphitizable carbon is preferable because excellent cycle characteristics can be obtained. Furthermore, those having a low charge / discharge potential, specifically, those having a charge / discharge potential close to that of lithium metal are preferable because a high energy density of the battery can be easily realized.

  Examples of the negative electrode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and including at least one of a metal element and a metalloid element as a constituent element. . This is because a high energy density can be obtained by using such a material. In particular, the use with a carbon material is more preferable because a high energy density can be obtained and excellent cycle characteristics can be obtained. The negative electrode material may be a single element, alloy or compound of a metal element or metalloid element, or may have at least a part of one or more of these phases. In the present invention, alloys include those containing one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of the metal element or metalloid element constituting the negative electrode material include magnesium, boron, aluminum, gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin, lead (Pb), Bismuth (Bi), cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium, yttrium (Y), palladium (Pd), or platinum (Pt) can be used. These may be crystalline or amorphous.

  Among these, as the negative electrode material, a material containing a 4B group metal element or a semimetal element in the short-period type periodic table as a constituent element is preferable, and at least one of silicon and tin is particularly preferable as a constituent element. This is because silicon and tin have a large ability to occlude and release lithium, and a high energy density can be obtained.

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

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

Examples of the negative electrode material capable of inserting and extracting lithium further include other metal compounds or polymer materials. Examples of other metal compounds include oxides such as MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ ), sulfides such as NiS and MoS, and lithium nitrides such as LiN _3. Examples include polyacetylene and polypyrrole.

  The separator 23 is made of, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and has a structure in which two or more kinds of porous films are laminated. May be. Among these, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve the safety of the battery due to the shutdown effect. In particular, polyethylene is preferable as a material constituting the separator 23 because a shutdown effect can be obtained within a range of 100 ° C. or higher and 160 ° C. or lower and the electrochemical stability is excellent. Polypropylene is also preferable, and any other resin having chemical stability can be used by copolymerizing or blending with polyethylene or polypropylene.

  This polyolefin porous film is formed, for example, by kneading a molten low-volatile solvent in a molten polyolefin composition into a high-concentration solution of a uniform polyolefin composition, and then molding this with a die. It is obtained by cooling to a gel-like sheet and stretching.

  As the low volatility solvent, for example, low volatility aliphatic or cyclic hydrocarbon such as nonane, decane, decalin, p-xylene, undecane or liquid paraffin can be used. The blending ratio of the polyolefin composition and the low-volatile solvent may be 10% by mass or more and 80% by mass or less, and further 15% by mass or more and 70% by mass or less, with the total of both being 100% by mass. preferable. This is because if the polyolefin composition is too small, swelling or neck-in becomes large at the die outlet during molding, and sheet molding becomes difficult. On the other hand, when there are too many polyolefin compositions, it is difficult to prepare a uniform solution.

  When molding a high-concentration solution of a polyolefin composition with a die, in the case of a sheet die, the gap is preferably, for example, 0.1 mm or more and 5 mm or less. The extrusion temperature is preferably 140 ° C. or more and 250 ° C. or less, and the extrusion rate is preferably 2 cm / min or more and 30 cm / min or less.

  Cooling is performed to at least the gelation temperature or lower. As a cooling method, a method of directly contacting cold air, cooling water, or another cooling medium, a method of contacting a roll cooled by a refrigerant, or the like can be used. Note that the high-concentration solution of the polyolefin composition extruded from the die may be taken up at a take-up ratio of 1 to 10 and preferably 1 to 5 before cooling or during cooling. If the take-up ratio is too large, the neck-in becomes large, and breakage tends to occur during stretching, which is not preferable.

  The gel-like sheet is preferably stretched by biaxial stretching, for example, by heating the gel-like sheet and using a tenter method, a roll method, a rolling method, or a method combining these. At that time, either longitudinal or transverse simultaneous stretching or sequential stretching may be used, but simultaneous secondary stretching is particularly preferable. The stretching temperature is preferably not more than the temperature obtained by adding 10 ° C. to the melting point of the polyolefin composition, and more preferably not less than the crystal dispersion temperature and less than the melting point. If the stretching temperature is too high, effective molecular chain orientation due to stretching cannot be achieved due to melting of the resin, which is not preferable. If the stretching temperature is too low, the resin becomes insufficiently softened and breaks during stretching. This is because it is easy to stretch at a high magnification.

  In addition, after extending | stretching a gel-like sheet | seat, it is preferable to wash | clean the extended film | membrane with a volatile solvent, and to remove the remaining low-volatile solvent. After washing, the stretched film is dried by heating or blowing to volatilize the washing solvent. Examples of the cleaning solvent include hydrocarbons such as pentane, hexane and hebutane, chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride, fluorocarbons such as ethane trifluoride, and ethers such as diethyl ether and dioxane. Easily volatile materials are used. The cleaning solvent is selected according to the low-volatile solvent used, and is used alone or in combination. Washing can be performed by a method of extracting by immersing in a volatile solvent, a method of sprinkling a volatile solvent, or a method combining these. This washing is performed until the residual low-volatile solvent in the stretched film is less than 1 part by mass with respect to 100 parts by mass of the polyolefin composition.

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. This electrolytic solution contains a solvent and an electrolyte salt dissolved in the solvent.

  As the solvent, cyclic carbonates such as ethylene carbonate or propylene carbonate can be used, and it is preferable to use one of ethylene carbonate and propylene carbonate, particularly a mixture of both. This is because the cycle characteristics can be improved.

  As the solvent, in addition to these cyclic carbonates, it is preferable to use a mixture of chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate or methylpropyl carbonate. This is because high ionic conductivity can be obtained.

  It is preferable that the solvent further contains 2,4-difluoroanisole or vinylene carbonate. This is because 2,4-difluoroanisole can improve discharge capacity, and vinylene carbonate can improve cycle characteristics. Therefore, it is preferable to use a mixture of these because the discharge capacity and cycle characteristics can be improved.

  In addition to these, examples of the solvent include butylene carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3- Dioxolane, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropironitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N-dimethyl Examples include imidazolidinone, nitromethane, nitroethane, sulfolane, dimethyl sulfoxide, and trimethyl phosphate.

  A compound obtained by substituting at least a part of hydrogen in these non-aqueous solvents with fluorine may be preferable because the reversibility of the electrode reaction may be improved depending on the type of electrode to be combined.

  In addition, the solvent preferably contains a compound having a sulfite structure shown in Chemical Formula 7 (sulfite ester compound). This is because by including a compound having a sulfite structure, a film can be formed on the surface of the positive electrode 21 and the electrochemical stability of the surface of the positive electrode 21 can be improved.

  Examples of the compound having the sulfite structure shown in Chemical formula 7 include the cyclic sulfite shown in Chemical formula 8 or the chain sulfite shown in Chemical formula 9.

（式中、Ｒ１は炭化水素基、または任意の１以上の原子よりなる分子構造を表す。）

(In the formula, R1 represents a hydrocarbon group or a molecular structure composed of any one or more atoms.)

（式中、Ｒ２，Ｒ３は、炭化水素基、または任意の１以上の原子よりなる分子構造を表す。Ｒ２，Ｒ３は同一であっても、異なっていてもよい。）

(In the formula, R2 and R3 represent a hydrocarbon group or a molecular structure composed of any one or more atoms. R2 and R3 may be the same or different.)

  Examples of the cyclic sulfite include the cyclic compound shown in Chemical Formula 12 represented by ethylene sulfite shown in Chemical Formula 10 or erythritan sulfite (II) shown in Chemical Formula 11.

（式中、Ｒ４，Ｒ５は炭化水素基、または任意の１以上の原子よりなる分子構造を表し、ＸはＯ，Ｎ，Ｐ，またはＰ＝Ｏを含む分子構造を表す。Ｒ４，Ｒ５は同一であっても、異なっていてもよい。）

(In the formula, R 4 and R 5 represent a hydrocarbon group or a molecular structure composed of any one or more atoms, X represents a molecular structure containing O, N, P, or P═O. R 4 and R 5 are the same. Or it may be different.)

Examples of the chain sulfite include dimethyl sulfite (CH ₃ OSOOCH ₃ ), diethyl sulfite (C ₂ H ₅ OSOOC ₂ H ₅ ), dipropyl sulfite (C ₃ H ₇ OSOOC ₃ H ₇ ), and dibutyl. Sulfite (C ₄ H ₉ OSOOC ₄ H ₉ ), methyl ethyl sulfite (CH ₃ OSOOC ₂ H ₅ ), methyl propyl sulfite (CH ₃ OSOOC ₃ H ₇ ), methyl butyl sulfite (CH ₃ OSOOOC ₄ H ₉₎ ), Ethylpropyl sulfite (C ₂ H ₅ OSOOC ₃ H ₇ ) and ethyl butyl sulfite (C ₂ H ₅ OSOOC ₄ H ₉ ).

  The content of the compound having a sulfite structure is preferably in the range of 0.01% by mass to 20% by mass with respect to the entire solvent. If the amount is less than 0.01% by mass, the chemical stability of the electrolyte cannot be sufficiently improved. If the amount exceeds 20% by mass, the decomposition reaction of the compound having a sulfite structure has a great influence on the electrode characteristics. This is because the battery characteristics are deteriorated.

As electrolyte salt, lithium salt is mentioned, for example, 1 type may be used independently, and 2 or more types may be mixed and used for it. Lithium salts include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, difluoro [oxolato-O, O ′] lithium borate, lithium bisoxalate borate, or LiBr. Among them, LiPF ₆ is preferable because it can obtain high ion conductivity and can improve cycle characteristics.

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

  First, for example, the positive electrode active material layer 21B is formed on the positive electrode current collector 21A to produce the positive electrode 21. The positive electrode active material layer 21B is prepared, for example, by mixing a positive electrode material capable of inserting and extracting lithium, a conductive agent, and a binder to prepare a positive electrode mixture. By dispersing in a solvent such as methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture slurry, applying this positive electrode mixture slurry to the positive electrode current collector 21A, drying the solvent, and then compression molding with a roll press or the like Form.

  Further, for example, the negative electrode active material layer 22B is formed on the negative electrode current collector 22A to produce the negative electrode 22. The negative electrode active material layer 22B may be formed by, for example, any one of a vapor phase method, a liquid phase method, a baking method, and coating, or a combination of two or more thereof. When formed by a vapor phase method, a liquid phase method, or a firing method, the negative electrode active material layer 22B and the negative electrode current collector 22A may be alloyed at least at a part of the interface at the time of formation. An alloy may be formed by heat treatment under a non-oxidizing atmosphere.

  As the vapor phase method, for example, a physical deposition method or a chemical deposition method can be used. Specifically, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a thermal CVD (Chemical Vapor Deposition) A chemical vapor deposition method) or a plasma CVD method can be used. As the liquid phase method, a known method such as electrolytic plating or electroless plating can be used. As for the firing method, a known method can be used. For example, an atmosphere firing method, a reaction firing method, or a hot press firing method can be used. In the case of application, it can be formed in the same manner as the positive electrode 21.

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

  In this secondary battery, when charged, lithium ions are released from the positive electrode active material layer 21B, and the negative electrode material that can occlude and release lithium contained in the negative electrode active material layer 22B via the electrolytic solution. Occluded. Next, when discharging is performed, lithium ions stored in the negative electrode material capable of inserting and extracting lithium in the negative electrode active material layer 22B are released, and are inserted into the positive electrode active material layer 21B through the electrolytic solution. . Here, since the solvent includes the compound having the sulfite structure shown in Chemical Formula 7, a film is formed on the surface of the positive electrode 21, and even if the open circuit voltage during full charge is increased, Electrochemical stability is improved.

  As described above, in this embodiment, the open circuit voltage at the time of full charge per pair of the positive electrode 21 and the negative electrode 22 is set in the range of 4.25 V or more and 6.00 V or less, so that a high energy density can be obtained. In addition, since the solvent includes the compound having the sulfite structure shown in Chemical Formula 7, a film can be formed on the surface of the positive electrode 21, and the electrochemical stability of the surface of the positive electrode 21 can be improved. it can. Therefore, the energy density can be increased and the cycle characteristics can be improved.

  In particular, if the content of the compound having a sulfite structure shown in Chemical formula 7 is within the range of 0.01% by mass or more and 20% by mass or less with respect to the solvent, cycle characteristics can be further improved. it can.

(Second Embodiment)
The secondary battery according to the second embodiment of the present invention is a so-called lithium metal secondary battery in which the capacity of the negative electrode is represented by a capacity component due to precipitation and dissolution of lithium as an electrode reactant.

  This secondary battery has the same configuration and effects as those of the secondary battery according to the first embodiment except that the configuration of the negative electrode active material layer 22B is different. Therefore, with reference to FIG. 1 and FIG. 2, the same code | symbol is attached | subjected to a corresponding component and description of the same part is abbreviate | omitted.

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

  This secondary battery is different from the secondary battery except that the negative electrode 22 is made of only the negative electrode current collector 22A, lithium metal alone, or lithium metal is attached to the negative electrode current collector 22A to form the negative electrode active material layer 22B. Can be manufactured in the same manner as the secondary battery according to the first embodiment.

  In this secondary battery, when charged, for example, lithium ions are released from the positive electrode 21 and deposited as lithium metal on the surface of the negative electrode current collector 22A via the electrolytic solution, as shown in FIG. Then, the negative electrode active material layer 22B is formed. When the discharge is performed, for example, lithium metal is eluted as lithium ions from the negative electrode active material layer 22B, and is occluded in the positive electrode 21 through the electrolytic solution. Here, since the solvent includes the compound having the sulfite structure shown in Chemical Formula 7, a film is formed on the surface of the positive electrode 21, and even if the open circuit voltage during full charge is increased, Electrochemical stability is improved.

(Third embodiment)
In the secondary battery according to the third embodiment of the present invention, the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is expressed by the sum thereof It is.

  This secondary battery has the same configuration and effect as the first or second secondary battery except that the configuration of the negative electrode active material layer is different, and can be manufactured in the same manner. Therefore, here, description will be made with reference to FIGS. 1 and 2 using the same reference numerals. Detailed descriptions of the same parts are omitted.

  For example, the negative electrode active material layer 22B has an open circuit voltage (that is, a battery voltage) in the charging process by making the charge capacity of the negative electrode material capable of occluding and releasing lithium smaller than the charge capacity of the positive electrode 21. When lithium is lower than the overcharge voltage, lithium metal begins to deposit on the negative electrode 22. Therefore, in this secondary battery, both the negative electrode material capable of inserting and extracting lithium and lithium metal function as a negative electrode active material, and the negative electrode material capable of inserting and extracting lithium is lithium metal. It is a base material for precipitation.

  In addition, this secondary battery has the same positive electrode active material at the time of full charge when the open circuit voltage (that is, battery voltage) at the time of full charge is in the range of 4.25V to 6.00V. Since the amount of lithium released per unit mass in the positive electrode active material is larger than in a battery having an open circuit voltage of 4.20 V, the amount of lithium occluded and deposited in the released negative electrode 22 is optimized. Further, the amounts of the positive electrode active material and the negative electrode active material are adjusted. As a result, a high energy density can be obtained.

  In the present specification, occlusion and release of the electrode reactant means that the ions of the electrode reactant are electrochemically occluded and released without losing its ionicity. This includes not only the case where the occluded electrode reactant is present in a complete ionic state, but also the case where it is present in a state that is not a complete ionic state. As a case corresponding to these, for example, occlusion by an electrochemical intercalation reaction of ions of an electrode reactant to graphite. Further, occlusion of the electrode reactant into the alloy containing the intermetallic compound, or occlusion of the electrode reactant due to the formation of the alloy can also be mentioned.

  The overcharge voltage refers to the open circuit voltage when the battery is overcharged. For example, the “lithium secondary battery” is one of the guidelines established by the Japan Storage Battery Industry Association (Battery Industry Association). Refers to a voltage that is higher than the open circuit voltage of a “fully charged” battery as defined and defined in the “Safety Evaluation Criteria Guidelines” (SBA G1101). In other words, it refers to a voltage higher than the open circuit voltage after charging using the charging method, standard charging method, or recommended charging method used when determining the nominal capacity of each battery.

  Thereby, in this secondary battery, it is possible to obtain a high energy density and to improve cycle characteristics and quick charge characteristics. This secondary battery is the same as the conventional lithium ion secondary battery in that a negative electrode material capable of inserting and extracting lithium is used for the negative electrode 22, and lithium metal is deposited on the negative electrode 22. However, although it is the same as that of a conventional lithium metal secondary battery, the following advantages are obtained by depositing lithium metal on a negative electrode material capable of inserting and extracting lithium.

  First, in the conventional lithium metal secondary battery, it was difficult to deposit lithium metal uniformly, which was a cause of deterioration of cycle characteristics. However, negative electrode materials capable of inserting and extracting lithium are as follows. Since the surface area is generally large, this secondary battery can deposit lithium metal uniformly. Secondly, in the conventional lithium metal secondary battery, the volume change accompanying the precipitation and dissolution of lithium metal is large, which has also caused the cycle characteristics to deteriorate, but in this secondary battery, lithium is occluded and released. This is because the volumetric change is small because lithium metal is deposited also in the gaps between the particles of the negative electrode material. Thirdly, the larger the amount of lithium metal deposited / dissolved in a conventional lithium metal secondary battery, the greater the above problem. In this secondary battery, however, it depends on the negative electrode material capable of inserting and extracting lithium. Since insertion and extraction of lithium also contribute to the charge / discharge capacity, the amount of lithium metal deposited / dissolved is small although the battery capacity is large. Fourthly, in a conventional lithium metal secondary battery, if rapid charging is performed, lithium metal is deposited more unevenly, resulting in further deterioration in cycle characteristics. Lithium is occluded in the anode material that can be occluded and released, so that rapid charging becomes possible.

  In order to obtain these advantages more effectively, for example, the maximum deposition capacity of lithium metal deposited on the negative electrode 22 at the maximum voltage before the open circuit voltage becomes the overcharge voltage is to occlude and release lithium. It is preferable that it is 0.05 times or more and 3.0 times or less of the charge capacity capacity of the negative electrode material which can carry out. This is because when the amount of deposited lithium metal is too large, the same problem as that of the conventional lithium secondary battery occurs, and when the amount is too small, the charge / discharge capacity cannot be sufficiently increased. Further, for example, the discharge capacity capability of the negative electrode material capable of inserting and extracting lithium is preferably 150 mAh / g or more. This is because the amount of lithium metal deposited becomes relatively smaller as the ability to occlude and release lithium increases. The charge capacity capability of the negative electrode material can be obtained, for example, from the amount of electricity when a negative electrode using lithium metal as a counter electrode and the negative electrode material as a negative electrode active material is charged to 0 V by a constant current / constant voltage method. The discharge capacity capability of the negative electrode material is obtained, for example, from the amount of electricity when the current is discharged to 2.5 V over 10 hours or more by the constant current method.

  In this secondary battery, when charged, lithium ions are released from the positive electrode 21 and are first inserted into the negative electrode material capable of inserting and extracting lithium contained in the negative electrode 22 through the electrolytic solution. When charging is further continued, lithium metal begins to deposit on the surface of the negative electrode material capable of inserting and extracting lithium in a state where the open circuit voltage is lower than the overcharge voltage. After that, lithium metal continues to deposit on the negative electrode 22 until charging is completed. Next, when discharging is performed, first, lithium metal deposited on the negative electrode 22 is eluted as ions, and is occluded in the positive electrode 21 through the electrolytic solution. When the discharge is further continued, lithium ions occluded in the negative electrode material capable of occluding and releasing lithium in the negative electrode 22 are released and inserted in the positive electrode 21 through the electrolytic solution. Here, since the solvent contains the compound having the sulfite structure shown in Chemical Formula 7, a film is formed on the surface of the positive electrode 21, and even if the open circuit voltage at the time of full charge is high, Chemical stability is improved.

(Fourth embodiment)
FIG. 3 shows a configuration of a secondary battery according to the fourth embodiment of the present invention. 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 housed in a film-like exterior member 40, and can be reduced in size, weight, and thickness. ing.

  The positive electrode lead 31 and the negative electrode lead 32 are led out from the inside of the exterior member 40 to the outside, for example, in the same direction. The positive electrode lead 31 and the negative electrode lead 32 are each made of a metal material such as aluminum, copper, nickel, or stainless steel, and each have a thin plate shape or a mesh shape.

  The exterior member 40 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. For example, the exterior member 40 is disposed so that the polyethylene film side and the wound electrode body 30 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 40 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 4 shows a cross-sectional structure taken along line II of the spirally wound electrode body 30 shown in FIG. The wound electrode body 30 is obtained by stacking and winding a positive electrode 33 and a negative electrode 34 with a separator 35 and an electrolyte layer 36 interposed therebetween, and the outermost peripheral portion is protected by a protective tape 37.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on one or both surfaces of a positive electrode current collector 33A. The negative electrode 34 has a structure in which a negative electrode active material layer 34B is provided on one surface or both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B side is disposed so as to face the positive electrode active material layer 33B. Yes. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, and the negative electrode current collector 22A. The same as the negative electrode active material layer 22B and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. The gel electrolyte layer 36 is preferable because high ion conductivity can be obtained and battery leakage can be prevented. The configuration of the electrolytic solution (that is, the solvent, the electrolyte salt, and the like) is the same as that of the secondary battery according to the first to third embodiments. Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, and polysiloxane. , Polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene or polycarbonate. In particular, from the viewpoint of electrochemical stability, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, or polyethylene oxide is preferable.

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

  First, a precursor solution containing a solvent, an electrolyte salt, a polymer compound, and a mixed solvent is applied to each of the positive electrode 33 and the negative electrode 34, and the mixed solvent is volatilized to form the electrolyte layer 36. After that, the positive electrode lead 31 is attached to the end of the positive electrode current collector 33A by welding, and the negative electrode lead 32 is attached to the end of the negative electrode current collector 34A by welding. Next, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are laminated via a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion. Thus, the wound electrode body 30 is formed. Finally, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edges of the exterior members 40 are sealed and sealed by heat fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  Further, this secondary battery may be manufactured as follows. First, the positive electrode 33 and the negative electrode 34 are prepared as described above, and after the positive electrode lead 31 and the negative electrode lead 32 are attached to the positive electrode 33 and the negative electrode 34, the positive electrode 33 and the negative electrode 34 are stacked via the separator 35 and wound. Rotate and adhere the protective tape 37 to the outermost periphery to form a wound body that is a precursor of the wound electrode body 30. Next, the wound body is sandwiched between the exterior members 40, and the outer peripheral edge portion excluding one side is heat-sealed to form a bag shape, and is stored inside the exterior member 40. Subsequently, an electrolyte composition including a solvent, an electrolyte salt, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared, and the exterior member Inject into 40.

  After injecting the electrolyte composition, the opening of the exterior member 40 is heat-sealed and sealed in a vacuum atmosphere. Next, heat is applied to polymerize the monomer to obtain a polymer compound, thereby forming a gel electrolyte layer 36, and assembling the secondary battery shown in FIGS.

  The operation and effect of the secondary battery are the same as those of the secondary battery according to the first to third embodiments.

  Furthermore, specific examples of the present invention will be described in detail.

(Examples 1-1 to 1-7)
A battery in which the capacity of the negative electrode 22 is represented by a capacity component due to insertion and extraction of lithium, that is, a lithium ion secondary battery was manufactured. At that time, the battery was as shown in FIG.

First, a positive electrode active material was prepared. After mixing commercially available nickel nitrate, cobalt nitrate, and manganese nitrate as aqueous solutions so that the molar ratios of Ni, Co, and Mn are 0.50, 0.20, and 0.30, respectively, sufficiently stirring Ammonia water was added dropwise to the mixed solution to obtain a composite hydroxide. The composite hydroxide and lithium hydroxide were mixed, calcined at 850 ° C. for 10 hours in an oxygen stream, and then pulverized to obtain a lithium composite oxide powder as a positive electrode active material. When the obtained lithium composite oxide powder was analyzed by atomic absorption spectrometry (ASS), the composition of LiNi _0.50 Co _0.20 Mn _0.30 O ₂ was confirmed. Further, when the particle diameter was measured by a laser diffraction method, the average particle diameter was 13 μm. Furthermore, when X-ray diffraction measurement was performed, it was similar to the pattern of LiNiO ₂ described in 09-0063 of the ICDD (International Center for Diffraction Data) card, and a layered rock salt structure similar to LiNiO ₂ was formed. It was confirmed that Furthermore, when observed with a scanning electron microscope (SEM), spherical particles in which primary particles of 0.1 μm to 5 μm aggregated were observed.

The obtained LiNi _0.50 Co _0.20 Mn _0.30 O ₂ powder and lithium carbonate powder were mixed at a mass ratio of LiNi _0.50 Co _0.20 Mn _0.30 O ₂ powder: lithium carbonate powder = 95: 5. Amorphous carbon powder (Ketjen Black) and polyvinylidene fluoride as a binder are mixed at a mass ratio of mixture: amorphous carbon powder: polyvinylidene fluoride = 94: 3: 3 to form a positive electrode mixture Was prepared. Subsequently, this positive electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, which is uniformly applied to both surfaces of a positive electrode current collector 21A made of a strip-shaped aluminum foil having a thickness of 20 μm and dried. Then, the cathode active material layer 21B was formed by compression molding with a roll press machine, and the cathode 21 was produced. The thickness of the positive electrode 21 was set to 150 μm. After that, an aluminum positive electrode lead 25 was attached to one end of the positive electrode current collector 21A.

Further, spherical graphite powder having an average particle size of 30 μm and a specific surface area of 0.8 g / cm ³ as a negative electrode active material, and polyvinylidene fluoride as a binder, spherical graphite powder: polyvinylidene fluoride = 90: 10 The negative electrode mixture was prepared by mixing at a mass ratio of Subsequently, the negative electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a negative electrode mixture slurry, which is uniformly applied to both surfaces of the negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 15 μm, and heated. The negative electrode 22 was fabricated by press molding to form the negative electrode active material layer 22B. The thickness of the negative electrode 22 was set to 160 μm. After that, a negative electrode lead 26 made of nickel was attached to one end of the negative electrode current collector 22A. In addition, the electrochemical equivalent ratio of the positive electrode 21 and the negative electrode 22 was designed so that the capacity | capacitance of the negative electrode 22 was represented by the capacity | capacitance component by occlusion and discharge | release of lithium.

  After preparing the positive electrode 21 and the negative electrode 22, a microporous separator 23 is prepared, the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 are laminated in this order, and this laminate is wound many times in a spiral shape to form a jelly roll A spirally wound electrode body 20 was produced.

  After producing the wound electrode body 20, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. The wound electrode body 20 was housed inside a nickel-plated iron battery can 11. Thereafter, 4.0 g of electrolyte solution was injected into the battery can 11 by a reduced pressure method.

To the electrolytic solution, ethylene sulfite is added as a compound having a sulfite structure shown in Chemical Formula 7 to a solvent in which ethylene carbonate and dimethyl carbonate are mixed in a mass ratio of ethylene carbonate: dimethyl carbonate = 35: 60 as a solvent. Further, an electrolyte salt in which LiPF ₆ was dissolved to 1.5 mol / kg was used. At that time, the content of ethylene sulfite was set to 5% by mass with respect to the solvent.

  After injecting the electrolyte into the battery can 11, the battery lid 14 was caulked to the battery can 11 through the gasket 17 having the surface coated with asphalt, whereby Examples 1-1 to 1-7 had a diameter of 14 mm. A cylindrical secondary battery having a height of 65 mm was obtained.

  With respect to the obtained secondary batteries of Examples 1-1 to 1-7, the rated capacity and the cycle characteristics were measured as follows.

  First, at a constant current of 500 mA, the battery voltage is constant until it reaches 4.25V, 4.30V, 4.35V, 4.40V, 4.45V, 4.50V, or 4.55V as shown in Table 1. After charging, perform full voltage charging for 5 hours at a constant voltage of 4.25V, 4.30V, 4.35V, 4.40V, 4.45V, 4.50V, or 4.55V. It was in a state. Subsequently, constant current discharge was performed at a constant current of 300 mA until the battery voltage reached 2.75 V to obtain a complete discharge state. This charge / discharge was repeated, and the discharge capacity at the second cycle was defined as the rated capacity. In addition, the cycle characteristics were obtained by setting the discharge capacity maintenance ratio at the 500th cycle (discharge capacity at the 500th cycle / rated capacity) × 100 (%) with respect to the rated capacity (the discharge capacity at the second cycle). The results are shown in Table 1.

  As Comparative Example 1-1 with respect to Examples 1-1 to 1-7, a secondary battery was fabricated in the same manner as in Examples 1-1 to 1-7, and the open circuit voltage during full charge was 4.20V. As described above, the rated capacity and cycle characteristics were measured in the same manner as in Examples 1-1 to 1-7. In addition, as Comparative Examples 1-2 to 1-4, except that ethylene sulfite, which is a compound having a sulfite structure shown in Chemical Formula 7, was not added, the others were as Examples 1-1 to 1-7. In the same manner, a secondary battery was produced, and the rated capacity and the capacity were changed in the same manner as in Examples 1-1 to 1-7 so that the open circuit voltage during full charge was 4.20 V, 4.25 V, or 4.40 V Cycle characteristics were measured. At that time, charging is performed at a constant current of 500 mA until the battery voltage reaches 4.20V, 4.25V or 4.40V, and then remains at 4.20V, 4.25V or 4.40V. The battery was charged at a constant voltage for 5 hours. The results are shown in Table 1.

  As can be seen from Table 1, according to Examples 1-1 and 1-4 in which the solvent contains ethylene sulfite, the discharge capacity retention ratio is improved as compared with Comparative Examples 1-3 and 1-4 that do not contain ethylene sulfite. did. Moreover, the high capacity | capacitance maintenance factor was obtained similarly to Examples 1-1 and 1-4 also about Examples 1-2, 1-3, 1-5-1-7 which contain ethylene sulfite in a solvent. Furthermore, according to Comparative Examples 1-1 and 1-2 in which the open circuit voltage at the time of full charge was 4.20 V, there was no effect of improving the discharge capacity retention rate by including ethylene sulfite in the solvent.

  That is, in a battery having an open circuit voltage of 4.25 V or more and 6.00 V or less when fully charged, if the solvent contains a compound having the sulfite structure shown in Chemical Formula 7, cycle characteristics are improved. I found out that I could do it.

(Examples 2-1 to 2-5)
A secondary battery was fabricated in the same manner as in Example 1-4, except that the content of ethylene sulfite was changed within the range of 0.01% by mass to 20% by mass with respect to the solvent.

  For the obtained secondary batteries of Examples 2-1 to 2-5, the rated capacity and the cycle characteristics were measured in the same manner as in Example 1-4. The results are shown in Table 2.

  As can be seen from Table 2, the discharge capacity retention rate increased as the content of ethylene sulfite increased, and decreased after showing a maximum value. That is, it was found that the content of the compound having a sulfite structure shown in Chemical Formula 7 is preferably in the range of 0.01% by mass to 20% by mass with respect to the solvent.

(Examples 3-1 to 3-6)
As compounds having the sulfite structure shown in Chemical Formula 7, dimethyl sulfite (CH ₃ OSOOCH ₃ ), diethyl sulfite (C ₂ H ₅ OSOOC ₂ H ₅ ), ethyl propyl sulfite (C ₂ H ₅ OSOOC ₃ H ₇₎ ), Dipropyl sulfite (C ₃ H ₇ OSOOC ₃ H ₇ ), dibutyl sulfite (C ₄ H ₉ OSOOC ₄ H ₉ ), or erythritan sulfite (II). A secondary battery was fabricated in the same manner as in 1-4.

  For the obtained secondary batteries of Examples 3-1 to 3-6, the rated capacity and the cycle characteristics were measured in the same manner as in Example 1-4. The results are shown in Table 3.

  As can be seen from Table 3, the same results as in Example 1-4 were obtained. That is, it was found that the cycle characteristics can be improved even when the solvent contains another compound having the sulfite structure shown in Chemical Formula 7.

(Example 4-1)
A battery in which the capacity of the negative electrode 22 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof, was produced. At that time, a secondary battery was fabricated in the same manner as in Example 1-4 except that the thickness of the negative electrode 22 was set to 100 μm. The charge capacity of the positive electrode 21 and the negative electrode 22 was designed so that the capacity of the negative electrode 22 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. . Further, the amounts of the positive electrode active material and the negative electrode active material were adjusted so that the open circuit voltage at the time of full charge was 4.40V.

  As Comparative Example 4-1 with respect to Example 4-1, except that ethylene sulfite, which is a compound having the sulfite structure shown in Chemical Formula 7, was not added, the same procedure was performed as in Example 4-1, except that A secondary battery was produced.

  For the obtained secondary batteries of Example 4-1 and Comparative example 4-1, the rated capacity and cycle characteristics were measured in the same manner as in Example 1-4. The results are shown in Table 4.

  Separately, two secondary batteries of Example 4-1 and Comparative Example 4-1 produced in the same manner were prepared, and it was disassembled to examine whether lithium metal was deposited. It was confirmed that lithium metal was deposited on the surface of the negative electrode 22 during full charge. In addition, lithium metal disappeared from the surface of the negative electrode 22 during complete discharge. That is, it was confirmed that the capacity of the negative electrode 22 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is expressed by the sum thereof.

  As can be seen from Table 4, if the solvent contains the compound having the sulfite structure shown in Chemical Formula 7, the capacity of the negative electrode 22 is determined by the capacity component due to insertion and extraction of lithium and the capacity due to precipitation and dissolution of lithium. In addition, the cycle characteristics can be improved even in the case of a secondary battery that includes a component and is expressed by the sum thereof and has an open circuit voltage in the range of 4.25 V to 6.00 V during full charge. I understood that I could do it.

(Examples 5-1 and 5-2)
A secondary battery of Example 5-1 was produced in the same manner as in Example 1-4, except that the negative electrode 22 was produced using silicon powder having an average particle diameter of 3 μm as the negative electrode active material. Further, tin is used as the negative electrode active material, a precursor layer made of tin is formed on the negative electrode current collector 22A made of copper foil by an electroless plating method, and heat treatment is performed in vacuum at 200 ° C. for 1 hour. A secondary battery of Example 5-2 was produced in the same manner as in Example 1-4 except that the negative electrode active material layer 22B was formed by the above and the negative electrode 22 was produced. At that time, in Example 5-2, the thickness of the negative electrode 22 was set to 100 μm. In addition, the electrochemical equivalent ratio of the positive electrode 21 and the negative electrode 22 was designed so that the capacity | capacitance of the negative electrode 22 was represented by the capacity | capacitance component by occlusion and discharge | release of lithium.

  As Comparative Examples 5-1 and 5-2 with respect to Examples 5-1 and 5-2, except that ethylene sulfite, which is a compound having an ethylene sulfite structure shown in Chemical Formula 7, was not added, the others were carried out. Secondary batteries were fabricated in the same manner as in Examples 5-1 and 5-2.

  For the obtained secondary batteries of Examples 5-1 and 5-2 and Comparative examples 5-1 and 5-2, the rated capacity and the cycle characteristics were measured in the same manner as in Example 1-4. The results are shown in Table 5.

  As can be seen from Table 5, if the solvent contains the compound having the sulfite structure shown in Chemical Formula 7, the other anode active material is used for the anode 22, and the open circuit voltage during full charge is 4.25V. It has been found that the cycle characteristics can be improved also in the case of a secondary battery having a range of 6.00 V or less.

(Examples 6-1 and 6-2)
A secondary battery of Example 6-1 was produced in the same manner as in Example 1-4, except that lithium cobaltate (LiCoO ₂ ) having an average particle diameter of 10 μm was used as the positive electrode active material. In addition, Example 6 was carried out in the same manner as in Example 1-4, except that as the positive electrode active material, half of LiNi _0.50 Co _0.20 Mn _0.30 O ₂ was replaced with lithium cobaltate (LiCoO ₂ ). A secondary battery of 2 was produced.

  As Comparative Examples 6-1 and 6-2 with respect to Examples 6-1 and 6-2, except that ethylene sulfite, which is a compound having the sulfite structure shown in Chemical Formula 7, was not added, the other examples Secondary batteries were fabricated in the same manner as in 6-1 and 6-2.

  For the obtained secondary batteries of Examples 6-1 and 6-2 and Comparative examples 6-1 and 6-2, the rated capacity and the cycle characteristics were measured in the same manner as in Example 1-4. The results are shown in Table 6.

  As can be seen from Table 6, if the solvent contains the compound having the sulfite structure shown in Chemical Formula 7, the open circuit voltage during full charge is 4.25 V or more and 6.00 V using another positive electrode active material. It was found that the cycle characteristics can be improved also in the case of a secondary battery within the following range.

(Example 7-1)
The secondary battery shown in FIGS. 3 and 4 was produced. First, the positive electrode 33 and the negative electrode 34 were produced in the same manner as in Example 1-4. After that, the positive electrode lead 31 and the negative electrode lead 32 were attached to one end of the positive electrode 33 and the negative electrode 34.

Next, an electrolytic solution and a copolymer of polyvinylidene fluoride and hexafluoropropylene, which are polymer compounds, were dissolved in a mixed solvent to prepare a precursor solution. At that time, the mass ratio of the electrolytic solution to the polymer compound was set to electrolyte solution: polymer compound = 92: 8. In addition, the electrolytic solution is a sulfite structure shown in Chemical Formula 7 in a solvent in which ethylene carbonate, propylene carbonate, and vinylene carbonate are mixed as a solvent in a mass ratio of ethylene carbonate: propylene carbonate: vinylene carbonate = 46: 46: 4. A compound in which ethylene sulfite was added as a compound having an amount of LiPF ₆ and LiPF ₆ was dissolved to 1.0 mol / kg as an electrolyte salt was used. The content of ethylene sulfite was set to 5% by mass with respect to the solvent.

  Subsequently, the obtained precursor solution was applied to the positive electrode 33 and the negative electrode 34 using a coating apparatus, and the mixed solvent was volatilized to form an electrolyte layer 36 having a thickness of 5 μm.

  After that, the positive electrode 33 and the negative electrode 34 were laminated through a separator 35 made of polyethylene having a thickness of 9 μm so that the surface on which the electrolyte layer 36 was formed was opposed, and wound to form the wound electrode body 30. .

  The obtained wound electrode body 30 was vacuum-sealed in an exterior member 40 made of a moisture-proof aluminum laminate film to produce a secondary battery having a thickness of 3.8 mm, a width of 3.4 cm, and a height of 5 cm.

  As Comparative Example 7-1 with respect to Example 7-1, except that ethylene sulfite, which is a compound having the sulfite structure shown in Chemical Formula 7, was not added, the others were the same as in Example 7-1. A secondary battery was produced.

  For the obtained secondary batteries of Example 7-1 and Comparative Example 7-1, the rated capacity and the cycle characteristics were measured in the same manner as in Example 1-4. The results are shown in Table 7.

  As can be seen from Table 7, if the solvent contains a compound having the sulfite structure shown in Chemical Formula 7, a gel electrolyte is used, and the open circuit voltage during full charge is 4.25 V or higher. It was found that the cycle characteristics can be improved even in the case of a secondary battery in the range of 00 V or less.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, other Group 1A elements such as sodium (Na) or potassium (K), or magnesium or calcium (Ca), etc. The present invention can also be applied to the case of using the 2A group element, other light metals such as aluminum, lithium, or alloys thereof, and the same effects can be obtained. At that time, as the negative electrode active material, the negative electrode material described in the above embodiment can be used in the same manner.

  In the above embodiments and examples, the secondary battery having a winding structure has been described. However, the present invention is similarly applied to a secondary battery having a structure in which a positive electrode and a negative electrode are folded or stacked. be able to. In addition, the present invention can also be applied to a so-called coin type, button type, or square type secondary battery. Moreover, not only a secondary battery but a primary battery is applicable.

It is sectional drawing showing the structure of the secondary battery which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is a disassembled perspective view showing the structure of the secondary battery which concerns on other embodiment of this invention. It is sectional drawing along the II line | wire of the winding electrode body shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17 ... Gasket, 20, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode current collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode current collector, 22B, 34B ... Negative electrode active material layer, 23, 35 ... Separator , 24 ... Center pin, 25, 31 ... Positive electrode lead, 26, 32 ... Negative electrode lead, 36 ... Electrolyte layer, 37 ... Protective tape, 40 ... Exterior member, 41 ... Adhesion film.

Claims (12)

A battery including an electrolyte containing a solvent together with a positive electrode and a negative electrode,
The open circuit voltage in a fully charged state per pair of positive electrode and negative electrode is in the range of 4.25V to 6.00V,
The battery includes a compound having a sulfite structure shown in Chemical Formula 1.

The battery according to claim 1, wherein the content of the compound having a sulfite structure is in a range of 0.01% by mass to 20% by mass with respect to the solvent. The compound having a sulfite structure includes at least one selected from the group consisting of a cyclic sulfite shown in Chemical Formula 2 and a chain sulfite shown in Chemical Formula 3. battery.

(In the formula, R1 represents a hydrocarbon group or a molecular structure composed of any one or more atoms.)

(In the formula, R2 and R3 each represent a hydrocarbon group or a molecular structure composed of any one or more atoms.) The battery according to claim 1, wherein the compound having a sulfite structure includes ethylene sulfite represented by Chemical Formula 4.

The battery according to claim 1, wherein the compound having a sulfite structure includes the cyclic sulfite shown in Chemical formula 5.

(In the formula, R 4 and R 5 represent a hydrocarbon group or a molecular structure composed of any one or more atoms, and X represents a molecular structure containing O, N, P, or P═O.) The battery according to claim 1, wherein the compound having a sulfite structure includes erythritan sulfite (II) shown in Chemical Formula 6.

The battery according to claim 1, wherein the positive electrode includes a lithium composite oxide represented by Chemical Formula 7.

(In the formula, M1 is cobalt (Co), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu ), Zinc (Zn), zirconium (Zr), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), and tungsten (W). g, h, j and k are 0.8 ≦ f ≦ 1.2, 0 <g <0.5, 0 ≦ h ≦ 0.5, g + h <1, −0.1 ≦ j ≦ 0.2, (It is a value within the range of 0 ≦ k ≦ 0.1.)   The battery according to claim 1, wherein the negative electrode includes a carbon material.   The battery according to claim 1, wherein the negative electrode contains graphite.   The negative electrode is capable of inserting and extracting an electrode reactant, and contains a negative electrode material containing at least one of a metal element and a metalloid element as a constituent element. battery.   The battery according to claim 1, wherein the negative electrode contains a material containing at least one of silicon (Si) and tin as a constituent element. 2. The battery according to claim 1, wherein the capacity of the negative electrode includes a capacity component due to occlusion and release of the electrode reactant and a capacity component due to precipitation and dissolution of the electrode reactant, and is expressed as a sum thereof. .

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