JP4807072B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  In recent years, with the rapid miniaturization and diversification of consumer mobile phones, portable devices and personal digital assistants, etc., the batteries used as the power source are compact, lightweight, high energy density, and repeatedly charged for a long time. There is a strong demand for the development of secondary batteries capable of discharging. Among them, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are the most promising and active as secondary batteries that meet these requirements compared to lead batteries and nickel cadmium batteries that use aqueous electrolytes. Research has been conducted.

The positive electrode active material of the nonaqueous electrolyte secondary battery includes general formula Li such as titanium disulfide, vanadium pentoxide and molybdenum trioxide, lithium cobalt composite oxide, lithium nickel composite oxide and spinel type manganese oxide. _x MO 2 _(however, M is one or more transition metals) various compounds represented by have been studied. Especially, lithium cobalt complex oxide, lithium nickel complex oxide, spinel type lithium manganese complex oxide, etc. are 4Vvs. Since charging / discharging at an extremely noble potential of Li / Li ⁺ or higher is possible, a battery having a high discharge voltage can be realized by using it as a positive electrode.

  Various studies have been made on negative electrode active materials for non-aqueous electrolyte secondary batteries, such as metallic lithium, lithium alloys, and carbon materials capable of occluding and releasing lithium. In particular, when carbon materials are used, batteries with a long cycle life are used. Is obtained, and there is an advantage that safety is high.

The nonaqueous electrolyte of the nonaqueous electrolyte secondary battery generally includes a mixed solvent of a high dielectric constant solvent such as ethylene carbonate and propylene carbonate and a low viscosity solvent such as dimethyl carbonate and diethyl carbonate, and LiPF ₆ and LiBF _4. Although an electrolytic solution in which a salt is dissolved is used, these solvents and lithium salts can be combined innumerably depending on the target battery performance.

  Batteries for mobile vehicles such as hybrid vehicles that have been developed in recent years require not only good life performance but also excellent low-temperature discharge performance considering use in cold regions. However, it is required to have sufficient low-temperature discharge performance.

  There are various methods for improving the low-temperature discharge characteristics. In the lithium ion secondary battery as described above, for example, as shown in Patent Document 1, a low viscosity and a low freezing point such as methyl acetate is used. Methods using acid esters as solvents have been studied.

Further, as shown in Patent Document 2 and Patent Document 3, lithium bis (oxalato) borate is used as a Li salt in place of LiPF ₆ which is a general Li salt, thereby improving the thermal stability of the electrolytic solution. In addition, a method for improving the life performance by suppressing generation of hydrofluoric acid that causes elution of transition metals contained in the positive electrode active material has been studied.

Patent Document 4 discloses that in a nonaqueous electrolyte battery using a polymer gel electrolyte, the electrolyte contained in the polymer gel electrolyte includes at least one selected from lithium bis (oxide) borate, LiPF _{6 and the} like. Techniques involving lithium salts are disclosed.

Furthermore, as shown in Patent Document 5, a method for improving life characteristics by suppressing a decrease in battery capacity and gas generation by using a non-aqueous electrolyte containing an unsaturated sultone compound has been studied. .
Japanese Patent No. 2924329 Special table 2002-519352 gazette Special table 2003-536229 gazette JP 2005-050755 A JP 2002-329528 A

  However, as described in Patent Document 1, when a carboxylic acid ester such as methyl acetate is used as the solvent of the electrolytic solution, the carboxylic acid ester is more easily reduced than the chain carbonic acid ester, so that the life performance is deteriorated. There was a problem.

As described in Patent Document 2 and Patent Document 3, when lithium bis (oxalato) borate is used as the electrolyte salt, the nonaqueous electrolyte has a lower conductivity than the nonaqueous electrolyte using LiPF ₆ as the Li salt. There was a problem that the low-temperature discharge performance deteriorated.

  Patent Document 4 does not describe an example in which lithium bis (oxide) borate is used as an electrolyte salt. Therefore, the battery concentration when combined with an optimum concentration or another lithium salt has been unknown.

  In Patent Document 5, the effect of improving the life characteristics of the nonaqueous electrolyte secondary battery in a high temperature environment was recognized by including the unsaturated sultone compound in the nonaqueous electrolyte, but the low temperature discharge performance was lowered. There was a problem.

  Accordingly, an object of the present invention is to provide a non-aqueous electrolyte secondary battery having good cycle life performance and low-temperature discharge performance after cycling.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present application have included 0.1 to 1.0 mass% of lithium bis (oxalato) borate represented by Chemical Formula 1 in the non-aqueous electrolyte, By including 0.2 to 1.5 mass% of the unsaturated sultone compound represented by Chemical Formula 2, a non-aqueous electrolyte secondary battery having good cycle life performance and low-temperature discharge performance after cycling is obtained. I found out that I can. Further, it was found that by using 1,3-propene sultone represented by Chemical Formula 3 as the unsaturated sultone compound, particularly good cycle life performance and low-temperature discharge performance after cycling can be obtained.

  The invention of claim 1 is a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte. In the non-aqueous electrolyte, lithium bis (oxalato) borate represented by the chemical formula (1) 0. It contains 1 to 1.0% by mass and an unsaturated sultone compound represented by the chemical formula (2).

ただし、化学式（２）において、Ｒ１〜Ｒ４は、それぞれ独立して、水素、フッ素、または炭素数１〜４のフッ素を含んでもよい炭化水素基であり、ｎは１〜３の整数である。

However, in Chemical formula (2), R1-R4 is respectively independently the hydrocarbon group which may contain hydrogen, a fluorine, or C1-C4 fluorine, and n is an integer of 1-3.

  The invention of claim 2 is characterized in that, in the non-aqueous electrolyte secondary battery, 1,3-propene sultone represented by the chemical formula (3) is used as the unsaturated sultone compound.

請求項３の発明は、正極と、負極と、非水電解質とを備えた非水電解質二次電池の製造方法において、前記非水電解質中に、化学式（１）で示されるリチウムビス（オキサラト）ボレート０．１〜１．０質量％と、化学式（２）で示される不飽和スルトン化合物０．２〜１．５質量％とを含有することを特徴とする。

According to a third aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery manufacturing method including a positive electrode, a negative electrode, and a non-aqueous electrolyte. In the non-aqueous electrolyte, lithium bis (oxalato) represented by the chemical formula (1) is provided. It contains 0.1 to 1.0% by mass of borate and 0.2 to 1.5% by mass of an unsaturated sultone compound represented by the chemical formula (2).

ただし、式（２）において、Ｒ１〜Ｒ４は、それぞれ独立して、水素、フッ素、または炭素数１〜４のフッ素を含んでもよい炭化水素基であり、ｎは１〜３の整数である。

However, in Formula (2), R1-R4 is respectively independently the hydrocarbon group which may contain hydrogen, a fluorine, or C1-C4 fluorine, and n is an integer of 1-3.

  According to the first aspect of the present invention, in the nonaqueous electrolyte secondary battery including a positive electrode containing a substance that absorbs and releases lithium ions, a negative electrode, and a nonaqueous electrolyte, the nonaqueous electrolyte includes a chemical formula (1 ) Lithium bis (oxalato) borate represented by 0.1) to 1.0% by mass and an unsaturated sultone compound represented by chemical formula (2) at the same time, thereby reducing the discharge capacity accompanying the charge / discharge cycle Can be suppressed, and good low-temperature discharge performance can be obtained even after the charge / discharge cycle.

  The reason for this is not clearly understood, but generally, when a battery is charged and discharged, oxidation and reduction reactions of the nonaqueous electrolyte proceed on the positive electrode having a noble potential and the negative electrode having a base potential, As a result of gas generation, reduction of current collecting performance of the active material, formation of a high-resistance film on the electrode and capacity balance between the positive and negative electrodes, the battery discharge capacity decreases, that is, the cycle life performance decreases, It is believed that the low temperature discharge performance is degraded.

  When lithium bis (oxalato) borate and an unsaturated sultone compound are used in combination, the lithium bis (oxalato) borate and the unsaturated sultone can be obtained with better characteristics than when they are used alone. This is presumably because a hybrid film composed of the compound formed on the negative electrode and exhibited a synergistic effect of suppressing the reductive decomposition of the non-aqueous electrolyte, which is one of the starting points of the deterioration mechanism.

  When the lithium bis (oxalato) borate and the unsaturated sultone compound are contained at the same time, if the lithium bis (oxalato) borate content is less than 0.1% by mass relative to the total mass of the nonaqueous electrolyte, However, if the amount exceeds 1.0% by mass, the amount of gas generated by the decomposition of lithium bis (oxalato) borate increases and the battery swells significantly.

  Further, by using 1,3-propene sultone represented by chemical formula (3) as the unsaturated sultone compound, particularly excellent cycle life performance and low temperature discharge performance can be obtained. The reason for this is not clearly understood, but when 1,3-propene sultone is used, a relatively low resistance film is formed on the negative electrode surface as compared with the case of using other unsaturated sultone compounds. It is assumed that there is.

  According to invention of Claim 3, in the manufacturing method of a nonaqueous electrolyte secondary battery, 0.1 to 1.0 mass% of lithium bis (oxalato) borate represented by the chemical formula (1) is included in the nonaqueous electrolyte. By simultaneously containing 0.2 to 1.5% by mass of the unsaturated sultone compound represented by the chemical formula (2), the decrease in the discharge capacity accompanying the charge / discharge cycle is suppressed, and even after the charge / discharge cycle. Good low temperature discharge performance can be obtained.

  When the content of the unsaturated sultone compound is less than 0.2% by mass in the non-aqueous electrolyte at the time of manufacturing the non-aqueous electrolyte secondary battery, sufficient life performance cannot be obtained, and 1.5 When the content exceeds mass%, a high-resistance film resulting from the unsaturated sultone compound is formed, so that sufficient low-temperature discharge performance cannot be obtained.

  The present invention provides a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte contains 0.1 to 1.0% by mass of lithium bis (oxalato) borate, And a saturated sultone compound.

  Here, lithium bis (oxalato) borate has a structure represented by chemical formula (1), and an unsaturated sultone compound has a structure represented by chemical formula (2).

ただし、化学式（２）において、Ｒ１〜Ｒ４は、それぞれ独立して、水素、フッ素、または炭素数１〜４のフッ素を含んでもよい炭化水素基であり、ｎは１〜３の整数である。また、化学式（２）において、ｎ＝２または３の場合、各炭素に結合するＲ１およびＲ２は、それぞれ独立して、水素、フッ素、または炭素数１〜４のフッ素を含んでもよい炭化水素基である。

However, in Chemical formula (2), R1-R4 is respectively independently the hydrocarbon group which may contain hydrogen, a fluorine, or C1-C4 fluorine, and n is an integer of 1-3. In the chemical formula (2), when n = 2 or 3, R1 and R2 bonded to each carbon are each independently a hydrocarbon group that may contain hydrogen, fluorine, or fluorine having 1 to 4 carbon atoms. It is.

  Specific examples of the unsaturated sultone compound represented by the chemical formula (2) include 1,3-propene sultone, 1-methyl-1,3-propene sultone, 1-fluoro-1,3-propene sultone, 2- Methyl-1,3-propene sultone, 2-fluoro-1,3-propene sultone, 3-methyl-1,3-propene sultone, 3-fluoro-1,3-propene sultone, 1-ethyl-1,3- Examples include propene sultone, 2-ethyl-1,3-propene sultone, 3-ethyl-1,3-propene sultone, 2,3-dimethyl-1,3-propene sultone, 1,4-butene sultone, and the like.

  These can be used alone or in combination, but it is preferable to use 1,3-propene sultone represented by the chemical formula (3) from the viewpoint of suppressing an increase in resistance of the film formed on the negative electrode surface. In addition, R1 to R4 having a hydrocarbon group having 5 or more carbon atoms or unsaturated sultone compounds having n of 4 or more are not preferable because the liquid injection property is lowered due to an increase in viscosity of the nonaqueous electrolyte.

さらに本発明は、正極と、負極と、非水電解質とを備えた非水電解質二次電池の製造方法において、前記非水電解質中に、化学式（１）で示されるリチウムビス（オキサラト）ボレート０．１〜１．０質量％と、化学式（２）で示される不飽和スルトン化合物０．２〜１．５質量％とを含有することを特徴とする。

Furthermore, the present invention provides a method for producing a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein the non-aqueous electrolyte contains lithium bis (oxalato) borate 0 represented by the chemical formula (1). 0.1 to 1.0% by mass and 0.2 to 1.5% by mass of the unsaturated sultone compound represented by the chemical formula (2).

ただし、化学式（２）において、Ｒ１〜Ｒ４は、それぞれ独立して、水素、フッ素、または炭素数１〜４のフッ素を含んでもよい炭化水素基であり、ｎは１〜３の整数である。また、化学式（２）において、ｎ＝２または３の場合、各炭素に結合するＲ１およびＲ２は、それぞれ独立して、水素、フッ素、または炭素数１〜４のフッ素を含んでもよい炭化水素基である。

However, in Chemical formula (2), R1-R4 is respectively independently the hydrocarbon group which may contain hydrogen, a fluorine, or C1-C4 fluorine, and n is an integer of 1-3. In the chemical formula (2), when n = 2 or 3, R1 and R2 bonded to each carbon are each independently a hydrocarbon group that may contain hydrogen, fluorine, or fluorine having 1 to 4 carbon atoms. It is.

  As the non-aqueous electrolyte, either an electrolytic solution or a solid electrolyte can be used. When using an electrolytic solution, the electrolytic solvent may contain cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, and other solvents include γ-butyrolactone, γ-valerolactone, Sulfolane, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyl-1,3-dioxolane, halogenated dioxolane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methylpropyl Carbonate, ethylpropyl carbonate, dipropyl carbonate, methyl isopropyl carbonate, ethyl isopropyl carbonate, diisopropyl carbonate, dibutyl car Bonates, acetonitrile, halogenated acetonitrile, alkoxy and halogen-substituted cyclic phosphazenes such as ethoxypentafluorocyclotriphosphazene and chain phosphazenes, phosphate esters such as triethyl phosphate and trimethyl phosphate, N-methyloxazolidinone , N-ethyloxazolidinone and other non-aqueous solvents may be contained, and these may be used alone or in combination.

  It is preferable to use one or a mixture of ethylene carbonate and propylene carbonate as the cyclic carbonate and a mixture of dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate as the chain carbonate. Further, the cyclic carbonate in the solvent of the nonaqueous electrolytic solution is preferably 10 to 60% by volume, and more preferably 20 to 50%. The chain carbonate content is preferably 40 to 90%, more preferably 50 to 80%.

  In addition to cyclic carbonate and chain carbonate, methyl acetate, ethyl acetate, ethyl monofluoroacetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, A chain carboxylic acid ester represented by ethyl butyrate, propyl butyrate and the like may be contained, and the ratio of the nonaqueous electrolytic solution to the solvent may be appropriately determined from 0% to 80%.

The nonaqueous electrolyte is used by dissolving the supporting salt in these nonaqueous solvents. In general, lithium bis (oxalato) borate is known as a supporting salt, but lithium bis (oxalato) borate in the present invention is not used as a supporting salt because it is used as a film forming agent on the surface of the negative electrode. Examples of the supporting salt include LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ CO ₂ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiCF ₃ CF ₂ CF ₂ SO ₃ , LiN (SO ₂ CF ₃ ). ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (COCF ₃ ) ₂ , LiN (COCF ₂ CF ₃ ) ₂ , LiBF ₂ C ₂ O ₄ , LiPF ₂ (C ₂ O ₄ ) ₂ and LiPF ₃ (CF ₂ CF ₃ ) ₃ or a mixture thereof can be used, and LiPF ₆ is more preferably used, or LiPF ₆ is mainly used, and the electrolyte is preferably mixed in a small amount.

  In addition to lithium bis (oxalato) borate and unsaturated sultone compounds, a small amount of additives may be mixed in the non-aqueous electrolyte to improve battery characteristics, and unsaturated bonds such as vinylene carbonate and vinyl ethylene carbonate. Aromatic compounds such as carbonate, biphenyl, cyclohexylbenzene, tert-butylbenzene, fluorobiphenyl, fluorobenzene, anisole, and halogen-substituted alkanes such as fluorooctane may be added as appropriate according to the purpose, and ester of the solvent For the purpose of suppressing the exchange reaction, an unsaturated bond-containing carbonate such as vinylene carbonate may be mixed and used.

  When using a solid electrolyte, a porous polymer solid electrolyte membrane is used as the polymer solid electrolyte, and the polymer solid electrolyte is further added with a non-aqueous electrolyte containing a cyclic carbonate and a chain carbonate. good.

There is no restriction | limiting in particular as a positive electrode active material of the nonaqueous electrolyte secondary battery to which this invention is applied, A various material can be used suitably. For example, transition metal compounds such as manganese dioxide and vanadium pentoxide, transition metal chalcogen compounds such as iron sulfide and titanium sulfide, and composite oxides of these transition metals and lithium Li _x MO _2-δ (however, M represents Co, Ni, or Mn, and is a composite oxide in which 0.4 ≦ x ≦ 1.2 and 0 ≦ δ ≦ 0.5), or these composite oxides may include Al, Mn, Fe, Ni, A compound containing at least one element selected from Co, Cr, Ti, and Zn, or a nonmetallic element such as P and B can be used. Furthermore, a composite oxide of lithium and nickel, that is, a positive electrode active material represented by Li _x Ni _p M1 _q M2 _{rO 2-δ} (where M1 and M2 are Al, Mn, Fe, Ni, Co, Cr, Ti , Zn, or a nonmetallic element such as P or B. Further, 0.4 ≦ x ≦ 1.2, 0.8 ≦ p + q + r ≦ 1.2, 0 ≦ δ ≦ 0. 5). Examples of the organic compound include conductive polymers such as polyaniline. Furthermore, the above various active materials may be mixed and used regardless of whether they are inorganic compounds or organic compounds.

  Further, as the negative electrode material, carbonaceous materials such as graphite, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon) and the like are suitable, and together with these carbon materials, Al, Si, Sn Although it may contain an alloy-based compound such as the above and metal Li, it is particularly preferable to mainly contain non-graphitizable carbon or graphitizable carbon from the viewpoint of safety and life performance.

  Moreover, as a separator of the nonaqueous electrolyte battery according to the present invention, a woven fabric, a non-woven fabric, a synthetic resin microporous membrane, or the like can be used, and a synthetic resin microporous membrane can be particularly preferably used. Among them, polyolefin microporous membranes such as polyethylene and polypropylene microporous membranes, heat-resistant resins processed from aramid, etc., or microporous membranes that combine these are suitable in terms of thickness, membrane strength, membrane resistance, etc. Used.

  Furthermore, a separator can also be used by using a solid electrolyte such as a polymer solid electrolyte. Further, a synthetic resin microporous membrane and a polymer solid electrolyte may be used in combination. In this case, a porous polymer solid electrolyte membrane is used as the polymer solid electrolyte, and the polymer solid electrolyte further contains an electrolytic solution.

  The shape of the battery is not particularly limited, and can be applied to non-aqueous electrolyte secondary batteries having various shapes such as a rectangular shape, a long cylindrical shape, a coin shape, a button shape, a sheet shape, and a cylindrical battery.

  Hereinafter, specific embodiments to which the present invention is applied will be described. However, the present invention is not limited to the embodiments, and can be appropriately modified and implemented without departing from the scope of the present invention. .

[Examples 1 to 15 and Comparative Examples 1 to 11]
[Example 1]
FIG. 1 is a schematic cross-sectional view of a prismatic nonaqueous electrolyte secondary battery of the present example. In this rectangular nonaqueous electrolyte secondary battery 1, a positive electrode 3 formed by applying a positive electrode mixture to an aluminum current collector and a negative electrode 4 formed by applying a negative electrode mixture to a copper current collector are interposed via a separator 5. A wound flat flat electrode group 2 and a non-aqueous electrolyte are housed in a battery case 6 and have a width of 30 mm × height of 50 mm × thickness of 5 mm.

  A battery lid 7 provided with a safety valve 8 is attached to the battery case 6 by laser welding, the positive electrode 3 is connected to the battery lid 7 via the positive electrode lead 10, and the negative electrode 4 is connected to the negative electrode terminal 9 via the negative electrode lead 11. It is connected.

The positive electrode plate is a mixture of 8% by mass of polyvinylidene fluoride as a binder, 6% by mass of acetylene black as a conductive agent, and 86% by mass of a positive electrode active material as spinel type lithium manganese composite oxide (LiMn ₂ O ₄ ). N-methylpyrrolidone was added to the positive electrode mixture thus prepared to prepare a paste, which was then applied to both surfaces of a 20 μm thick aluminum foil current collector and dried.

  The negative electrode plate was prepared by adding 90% by mass of non-graphitizable carbon and 10% by mass of polyvinylidene fluoride to N-methylpyrrolidone to prepare a paste, which was then applied to both sides of a 10 μm thick copper foil current collector and dried. Made by doing.

A polyethylene microporous membrane was used for the separator. As the non-aqueous electrolyte, a solution in which 1 mol / L of LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 25: 35: 40 (volume ratio) was used. .

  Further, 0.10% by mass of lithium bis (oxalato) borate (hereinafter abbreviated as “LiBOB”) represented by the chemical formula (1) in the non-aqueous electrolyte and 1,3-propene represented by the chemical formula (3) A nonaqueous electrolyte containing 0.20% by mass of sultone (hereinafter abbreviated as “PS”) was used. The nonaqueous electrolyte secondary battery of Example 1 was produced by the above configuration / procedure.

なお、ここで「非水電解質中にＬｉＢＯＢを０．１０質量％含有させる」とは、ＥＣとＤＭＣとＥＭＣとＬｉＰＦ_６とＬｉＢＯＢとＰＳの合計質量に対するＬｉＢＯＢの質量の割合が０．１０％であることを意味し、「非水電解質中に１，３−プロペンスルトンを０．２０質量％含有させる」とは、ＥＣとＤＭＣとＥＭＣとＬｉＰＦ_６とＬｉＢＯＢとＰＳの合計質量に対するＰＳの質量の割合が０．２０％であることを意味する。

In addition, “containing 0.10% by mass of LiBOB in the nonaqueous electrolyte” here means that the ratio of the mass of LiBOB to the total mass of EC, DMC, EMC, LiPF ₆ , LiBOB, and PS is 0.10%. It means that “containing 0.20% by mass of 1,3-propene sultone in the non-aqueous electrolyte” means that the mass of PS relative to the total mass of EC, DMC, EMC, LiPF ₆ , LiBOB and PS. It means that the ratio is 0.20%.

[Example 2]
A nonaqueous electrolyte secondary battery of Example 2 was produced in the same manner as Example 1 except that 0.50% by mass of LiBOB and 0.20% by mass of PS were contained in the nonaqueous electrolyte.

[Example 3]
A nonaqueous electrolyte secondary battery of Example 3 was produced in the same manner as in Example 1 except that LiBOB was contained in 1.00% by mass and PS was contained in 0.20% by mass in the nonaqueous electrolyte.

[Example 4]
A nonaqueous electrolyte secondary battery of Example 4 was produced in the same manner as Example 1, except that LiBOB was contained in 0.10% by mass and PS in 1.00% by mass in the nonaqueous electrolyte.

[Example 5]
A nonaqueous electrolyte secondary battery of Example 5 was produced in the same manner as Example 1 except that 0.50% by mass of LiBOB and 1.00% by mass of PS were contained in the nonaqueous electrolyte.

[Example 6]
A nonaqueous electrolyte secondary battery of Example 6 was produced in the same manner as in Example 1 except that LiBOB was included in 1.00 mass% and PS in 1.00 mass% in the nonaqueous electrolyte.

[Example 7]
A nonaqueous electrolyte secondary battery of Example 7 was produced in the same manner as Example 1 except that 0.10% by mass of LiBOB and 1.50% by mass of PS were contained in the nonaqueous electrolyte.

[Example 8]
A nonaqueous electrolyte secondary battery of Example 8 was produced in the same manner as Example 1 except that 0.50% by mass of LiBOB and 1.50% by mass of PS were contained in the nonaqueous electrolyte.

[Example 9]
A nonaqueous electrolyte secondary battery of Example 9 was produced in the same manner as in Example 1 except that LiBOB was contained in 1.00% by mass and PS was contained in 1.50% by mass in the nonaqueous electrolyte.

[Example 10]
A nonaqueous electrolyte secondary battery of Comparative Example 10 was produced in the same manner as Example 1 except that 0.10 mass% LiBOB and 0.10 mass% PS were contained in the nonaqueous electrolyte.

[Example 11]
A nonaqueous electrolyte secondary battery of Comparative Example 11 was produced in the same manner as in Example 1, except that 0.50% by mass of LiBOB and 0.10% by mass of PS were contained in the nonaqueous electrolyte.

[Example 12]
A nonaqueous electrolyte secondary battery of Comparative Example 12 was produced in the same manner as in Example 1 except that LiBOB was contained in 1.00 mass% and PS was contained in 0.10 mass% in the nonaqueous electrolyte.

[Example 13]
A nonaqueous electrolyte secondary battery of Comparative Example 13 was produced in the same manner as Example 1 except that 0.10 mass% LiBOB and 2.00 mass% PS were contained in the nonaqueous electrolyte.

[Example 14]
A nonaqueous electrolyte secondary battery of Comparative Example 14 was produced in the same manner as in Example 1 except that 0.50% by mass of LiBOB and 2.00% by mass of PS were contained in the nonaqueous electrolyte.

[Example 15]
A nonaqueous electrolyte secondary battery of Comparative Example 15 was produced in the same manner as in Example 1 except that LiBOB was contained in 1.00 mass% and PS was contained in 2.00 mass% in the nonaqueous electrolyte.

[Comparative Example 1]
A nonaqueous electrolyte secondary battery of Comparative Example 1 was produced in the same manner as in Example 1, except that a nonaqueous electrolyte containing no LiBOB and PS was used.

[Comparative Example 2]
A nonaqueous electrolyte secondary battery of Comparative Example 2 was produced in the same manner as in Example 1 except that 0.01% by mass of LiBOB and 0.20% by mass of PS were contained in the nonaqueous electrolyte.

[Comparative Example 3]
A nonaqueous electrolyte secondary battery of Comparative Example 3 was produced in the same manner as in Example 1 except that 1.2% by mass of LiBOB and 0.20% by mass of PS were contained in the nonaqueous electrolyte.

[Comparative Example 4]
A nonaqueous electrolyte secondary battery of Comparative Example 4 was produced in the same manner as in Example 1 except that 0.01% by mass of LiBOB and 1.00% by mass of PS were contained in the nonaqueous electrolyte.

[Comparative Example 5]
A nonaqueous electrolyte secondary battery of Comparative Example 5 was produced in the same manner as in Example 1 except that 1.20 mass% LiBOB and 1.00 mass% PS were contained in the nonaqueous electrolyte.

[Comparative Example 6]
A nonaqueous electrolyte secondary battery of Comparative Example 6 was produced in the same manner as in Example 1 except that 0.01% by mass of LiBOB and 1.50% by mass of PS were contained in the nonaqueous electrolyte.

[Comparative Example 7]
A nonaqueous electrolyte secondary battery of Comparative Example 7 was produced in the same manner as in Example 1 except that 1.20 mass% LiBOB and 1.50 mass% PS were contained in the nonaqueous electrolyte.

[Comparative Example 8]
A nonaqueous electrolyte secondary battery of Comparative Example 8 was produced in the same manner as in Example 1 except that 0.01% by mass of LiBOB and 0.10% by mass of PS were contained in the nonaqueous electrolyte.

[Comparative Example 9]
A nonaqueous electrolyte secondary battery of Comparative Example 9 was produced in the same manner as in Example 1 except that LiBOB was contained in the nonaqueous electrolyte at 1.20 mass% and PS at 0.10 mass%.

[Comparative Example 10]
A nonaqueous electrolyte secondary battery of Comparative Example 10 was produced in the same manner as in Example 1 except that 0.01% by mass of LiBOB and 2.00% by mass of PS were contained in the nonaqueous electrolyte.

[Comparative Example 11]
A nonaqueous electrolyte secondary battery of Comparative Example 11 was produced in the same manner as in Example 1 except that LiBOB was contained in the nonaqueous electrolyte at 1.20 mass% and PS at 2.00 mass%.

[Characteristic measurement]
The square nonaqueous electrolyte secondary batteries of Examples 1 to 15 and Comparative Examples 1 to 11 were prepared for each 5 cells, and an initial discharge capacity confirmation test was performed. The initial discharge capacity was up to 4.2 V at a constant current of 250 mA at 25 ° C., and further charged at a constant voltage of 4.2 V for a total of 3 hours, and then discharged at a constant current of 250 mA and a final voltage of 2.5 V.

  Next, a charge / discharge cycle life test was conducted. Under the charge / discharge conditions during the initial discharge capacity confirmation test, 500 cycles of charge / discharge were performed in a 45 ° C. constant temperature bath, and after cooling at 25 ° C. for 5 hours, a capacity confirmation test was performed at 25 ° C.

  Thereafter, a low temperature discharge test at −20 ° C. was performed. In the low-temperature discharge test, the battery was charged at 25 ° C. under the charging conditions used in the initial discharge capacity confirmation test, and then the battery was cooled at −20 ° C. for 5 hours, in a constant temperature bath at −20 ° C., with a final current of 2 at 250 mA constant current. Discharge was performed under the condition of .5V.

  The “capacity retention ratio” at the 500th cycle in the 45 ° C. charge / discharge cycle test is a ratio of the discharge capacity at 25 ° C. after 500 cycles of 45 ° C. charge / discharge to the initial discharge capacity in terms of 100 minutes. . The “low temperature retention rate” is the percentage of the discharge capacity at −20 ° C. relative to the initial discharge capacity in 100 minutes in the battery after 500 cycles of high temperature charge / discharge.

  Table 1 shows the contents and test results of LiBOB and PS in the electrolytes of the nonaqueous electrolyte secondary batteries of Examples 1 to 9 and Comparative Examples 1 to 17. In Table 1, “capacity holding ratio” and “low temperature holding ratio” indicate average values of five cells.

  From the results of Table 1, the cycle life performance of Examples 1 to 15 containing 0.2 to 1.0% by mass of lithium bis (oxalato) borate and 1,3-propene sultone in the nonaqueous electrolyte. The low-temperature discharge performance was found to be significantly better than that of Comparative Example 1 which did not contain any additive.

  In addition, the cycle life performance and low-temperature discharge performance of Examples 1 to 15 are much higher than those of Comparative Examples 2 to 11 in which the content of lithium bis (oxalato) borate is not in the range of 0.1 to 1.0% by mass. It was good.

  In Examples 1 to 15 containing 0.2 to 1.0% by mass of lithium bis (oxalato) borate in the nonaqueous electrolyte, 1,3-propene sultone was 0.20 to 1.5% by mass. % Of Examples 1-9 containing 1% propylene sultone, cycle life performance than Examples 10-12 containing 0.10% by mass and Examples 13-15 containing 2.00% by mass It was also found that the low-temperature discharge performance was excellent.

  The cause of this is unknown at this time, but it is a hybrid film that combines the properties of excellent low-temperature discharge performance attributable to lithium bis (oxalato) borate and the property of superior cycle life performance attributable to 1,3-propene sultone. Is formed on the surface of the negative electrode, and it is presumed that this is due to its unique action.

[Examples 16 and 17 and Comparative Example 12]
[Example 16]
The same procedure as in Example 1 was performed except that 0.10% by mass of LiBOB was contained in the nonaqueous electrolyte, and 0.20% by mass of 1-fluoro-1,3-propene sultone was added instead of PS. Sixteen nonaqueous electrolyte secondary batteries were produced.

[Example 17]
The nonaqueous electrolyte of Example 17 was the same as Example 1 except that 0.10% by mass of LiBOB was contained in the nonaqueous electrolyte, and 0.20% by mass of 1,4-butene sultone was added instead of PS. A secondary battery was produced.

[Comparative Example 12]
The nonaqueous electrolyte secondary of Comparative Example 12 is the same as Example 1 except that 0.10% by mass of LiBOB is contained in the nonaqueous electrolyte and 0.20% by mass of ethylene sulfite is added instead of PS. A battery was produced.

[Characteristic measurement]
The square nonaqueous electrolyte secondary batteries of Examples 16 and 17 and Comparative Example 12 were prepared for each 5 cells, and under the same conditions as in Example 1, an initial discharge capacity confirmation test, a charge / discharge cycle life test at 45 ° C., and A low temperature discharge test at −20 ° C. was performed.

  Table 2 shows the LiBOB content, the content of the additive solvent, and the test results in the electrolytes of the nonaqueous electrolyte secondary batteries of Examples 16 and 17 and Comparative Example 12. In Table 2, “capacity retention” and “low temperature retention” are average values of five cells.

  From Table 2, as shown in Example 16 and Example 17, it was found that good cycle life performance and high low-temperature discharge performance can be obtained even when various unsaturated sultone compounds are used. However, as in Comparative Example 12, when a solvent other than the unsaturated sultone compound was added, neither cycle life performance nor low temperature discharge performance was improved.

[Examples 18 to 24]
[Example 18]
A nonaqueous electrolyte secondary battery of Example 18 was produced in the same manner as in Example 1 except that the composition of the nonaqueous electrolyte solvent was EC: DMC = 25: 75 (volume ratio).

[Example 19]
A nonaqueous electrolyte secondary battery of Example 19 was produced in the same manner as in Example 1 except that the composition of the nonaqueous electrolyte solvent was EC: EMC = 25: 75 (volume ratio).

[Example 20]
A nonaqueous electrolyte secondary battery of Example 20 was produced in the same manner as in Example 1 except that the composition of the nonaqueous electrolyte solvent was EC: DEC = 25: 75 (volume ratio).

[Example 21]
The nonaqueous electrolyte secondary battery of Example 21 was obtained in the same manner as in Example 1 except that the composition of the nonaqueous electrolyte solvent was EC: DMC: EMC: DEC = 20: 20: 30: 30 (volume ratio). Produced.

[Example 22]
A nonaqueous electrolyte secondary battery of Example 22 was fabricated in the same manner as Example 1 except that the composition of the nonaqueous electrolyte solvent was PC: DMC: EMC = 20: 40: 40 (volume ratio).

[Example 23]
A nonaqueous electrolyte secondary battery of Example 23 was fabricated in the same manner as in Example 1 except that the composition of the nonaqueous electrolyte solvent was EC: ethyl acetate = 25: 75 (volume ratio).

[Example 24]
A nonaqueous electrolyte secondary battery of Example 24 was produced in the same manner as in Example 1 except that the composition of the nonaqueous electrolyte solvent was EC: methylpropionate = 25: 75 (volume ratio).

[Characteristic measurement]
The square non-aqueous electrolyte secondary batteries of Examples 18 to 24 were prepared for each 5 cells, and under the same conditions as in Example 1, the initial discharge capacity confirmation test, the charge / discharge cycle life test at 45 ° C., and the −20 ° C. A low temperature discharge test was conducted.

  Table 3 shows the solvent composition and test results of the electrolytes of the nonaqueous electrolyte secondary batteries of Examples 18 to 24. In Table 3, “capacity holding ratio” and “low temperature holding ratio” are average values of five cells.

  From Table 3, as the solvent composition of the electrolyte, when the type and mixing ratio of the cyclic carbonate and the chain carbonate are changed, or a chain carboxylate such as ethyl acetate or methyl propionate instead of the chain carbonate It was found that the same effect can be obtained when using.

In the above example, LiPF ₆ having a concentration of 1 mol / l was used as the electrolyte salt, but the same effect was obtained when the type and concentration of the electrolyte salt were changed.

  Further, when lithium cobalt oxide or lithium nickel oxide or a mixed system thereof is used as the positive electrode active material, the same effect can be obtained. As the negative electrode active material, graphite or coke, or an alloy of a part of the negative electrode The same effect was obtained even when using.

  From the above, by containing 0.1 to 1.0% by mass of lithium bis (oxalato) borate in the nonaqueous electrolyte and containing an unsaturated sultone compound, good cycle life performance and high low temperature discharge It was found that performance was obtained.

  Further, in the method for producing a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, the non-aqueous electrolyte contains 0.1 to 1.0% by mass of lithium bis (oxalato) borate, It was found that a nonaqueous electrolyte secondary battery exhibiting good cycle life performance and high low-temperature discharge performance can be produced by containing 0.2 to 1.5 mass% of the unsaturated sultone compound.

The figure which shows the cross-section of the square battery of the Example and comparative example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Square type non-aqueous electrolyte secondary battery 2 Winding type electrode group 3 Positive electrode 4 Negative electrode 5 Separator

Claims (3)

In a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte, lithium bis (oxalato) borate represented by the chemical formula (1) is 0.1 to 1.0% by mass in the nonaqueous electrolyte. And an unsaturated sultone compound represented by the chemical formula (2).

However, in Chemical formula (2), R1-R4 is respectively independently the hydrocarbon group which may contain hydrogen, a fluorine, or C1-C4 fluorine, and n is an integer of 1-3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the unsaturated sultone compound is 1,3-propene sultone represented by the chemical formula (3).

In the method for producing a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, lithium bis (oxalato) borate represented by the chemical formula (1) 0.1 to 1. The manufacturing method of the nonaqueous electrolyte secondary battery characterized by containing 0 mass% and the unsaturated sultone compound 0.2-1.5 mass% shown by Chemical formula (2).

However, in Chemical formula (2), R1-R4 is respectively independently the hydrocarbon group which may contain hydrogen, a fluorine, or C1-C4 fluorine, and n is an integer of 1-3.

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