JP5326923B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to an additive to an electrolyte solution of a non-aqueous electrolyte secondary battery.

  Non-aqueous electrolyte secondary batteries, including lithium ion secondary batteries, have excellent features such as high energy density and high output, so they are widely used as power sources for portable electronic devices such as mobile phones, video cameras, and personal computers. In the future, it is being considered to use it for a power source such as an electric vehicle with a larger size.

Various compounds such as lithium cobalt composite oxide (LiCoO ₂ ), lithium nickel composite oxide (LiNiO ₂ ), spinel-type manganese oxide (LiMn ₂ O ₄ ) are included in the positive electrode active material of the non-aqueous electrolyte secondary battery. Since these compounds are used and can be charged and discharged at an extremely noble potential of 4 V (vs Li / Li ⁺ ) or higher, a non-aqueous electrolyte secondary battery having a high discharge voltage can be obtained.

  In addition, various negative electrode active materials such as metallic lithium, lithium alloys, and carbon materials capable of occluding and releasing lithium have been studied. Among them, when a carbon material is used, a battery having a long cycle life can be obtained. There is an advantage that it is obtained and has high safety.

Furthermore, the electrolyte includes a mixed solvent of a cyclic carbonate that is a high dielectric constant solvent such as ethylene carbonate or propylene carbonate and a chain carbonate that is a low viscosity solvent such as dimethyl carbonate or diethyl carbonate, and LiPF ₆ or LiBF. An electrolytic solution in which a lithium salt such as ₄ is dissolved is used.

  The electrode of the non-aqueous electrolyte secondary battery is a mixture of a positive electrode and a negative electrode in which a powder of an active material, a binder, a conductive additive, etc. and an organic solvent are mixed on the surface of a metal sheet current collector The paste is applied, dried, and pressed by a roll press or the like to adjust the thickness of the mixture layer. This electrode is used as a power generation element that is laminated or wound, and is housed in a container together with a non-aqueous electrolyte solution to form a non-aqueous electrolyte secondary battery.

  Recently, demand for non-aqueous electrolyte secondary batteries as a power source for mobile bodies such as electric vehicles has been increasing, and a longer life is required than for mobile phones for consumer use. As a method for improving the life characteristics of the battery, it is effective to mix a specific compound with the nonaqueous electrolytic solution. For example, addition of vinylene carbonate or 1,3-propane sultone has been proposed.

Further, as an additive to the electrolytic solution, bis (vinylsulfonyl) methane disclosed in Patent Document 1, lithium bis (oxalate) difluorophosphate disclosed in Patent Document 2 and Patent Document 3, and the like have been studied. ing.
JP 2007-173147 A JP 2005-032714 A JP 2007-335143 A

  However, when these compounds are added alone to the electrolytic solution, the internal resistance of the battery increases, the capacity decreases due to the charge / discharge cycle, sufficient characteristics cannot be obtained, and there is an additive that can be expected to further improve the characteristics. It was requested.

  Accordingly, an object of the present invention is to provide a non-aqueous electrolyte secondary battery with low internal resistance of the battery and excellent charge / discharge cycle characteristics by combining an additive to the electrolyte solution that has been used conventionally. It is in.

  The invention according to claim 1 is a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein 2.0% by weight or less of bis (vinylsulfonyl) methane and lithium are included in the non-aqueous electrolyte. It contains bis (oxalate) difluorophosphate in an amount of 1.5% by weight or less.

  According to the first aspect of the present invention, the electrolyte solution contains bis (vinylsulfonyl) methane and lithium bis (oxalate) difluorophosphate at the same time in a certain amount or less. A non-aqueous electrolyte secondary battery that does not increase the internal resistance of the battery and has a small capacity drop due to the charge / discharge cycle. Can be obtained.

  The present invention relates to a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, wherein 2.0% by weight or less of bis (vinylsulfonyl) methane and lithium bis (oxalate) are contained in the non-aqueous electrolyte. ) It contains 1.5% by weight or less of difluorophosphate.

  Bis (vinylsulfonyl) methane used in the present invention is a compound represented by the following chemical formula (1). Hereinafter, bis (vinylsulfonyl) methane is abbreviated as “BSM”.

また、本発明で用いるリチウムビス（オキサレート）ジフルオロホスフェートは次の化学式（２）で表される化合物である。なお、以下ではリチウムビス（オキサレート）ジフルオロホスフェートを［ＬｉＦＯＰ］と略す。

The lithium bis (oxalate) difluorophosphate used in the present invention is a compound represented by the following chemical formula (2). Hereinafter, lithium bis (oxalate) difluorophosphate is abbreviated as [LiFOP].

本発明において、非水電解液中のＢＳＭおよびＬｉＦＯＰの含有量は、ＢＳＭとＬｉＦＯＰとを除く電解液全体に対する重量％で表すものとする。

In the present invention, the contents of BSM and LiFOP in the nonaqueous electrolytic solution are expressed by weight% with respect to the entire electrolytic solution excluding BSM and LiFOP.

  In the present invention, by simultaneously containing BSM and LiFOP in the electrolyte, a coating composed of the decomposition products of these two types of compounds is formed on the surfaces of the positive electrode and the negative electrode, and the subsequent decomposition of the electrolyte solvent Is suppressed.

  In the present invention, the film formed on the surfaces of the positive electrode and the negative electrode is different from the film formed when BSM or LiFOP is added alone to the electrolyte, and when BSM or LiFOP is added alone. Since a special film that cannot be obtained is formed, a non-aqueous electrolyte secondary battery with excellent characteristics is obtained in which the internal resistance is small and the capacity drop due to the charge / discharge cycle is small.

  That is, when BSM alone is added to the electrolytic solution, as described in Patent Document 1, there is an effect of suppressing an increase in internal resistance associated with the life test, but a polymer film is formed on the positive and negative electrodes during initial charging. Therefore, the initial internal resistance is increased. The initial increase in internal resistance is proportional to the amount of BSM added, but for the effect of suppressing the increase in internal resistance associated with the life test, 2.0% by weight or more is added to the entire electrolyte solution excluding BSM. However, the effect is not significantly increased.

  Therefore, when BSM is added in an amount of 2.0% by weight or more, the initial internal resistance is greatly adversely affected, so that the battery characteristics are deteriorated. In addition, when the amount of BSM added is 0.1% by weight or less with respect to the entire electrolyte solution excluding BSM, the increase in the initial internal resistance is small, but the increase in the internal resistance accompanying the life test is significant, and the capacity retention rate The decrease in (ratio of the capacity after a certain number of charges / discharges with respect to the initial discharge capacity) is also large, and a sufficient protective effect cannot be obtained.

  In addition, when LiFOP is added alone to the electrolytic solution, a film is formed on the positive and negative electrodes. As described in Patent Document 2, a decrease in capacity retention and an increase in internal resistance are accompanied by a life test. Is effective, but the effect alone is not sufficient. Further, when the amount of LiFOP added is increased, a large amount of gas is generated during initial charging, battery swelling occurs, and the battery characteristics deteriorate due to a decrease in effective electrode area due to gas accumulation.

  On the other hand, when BSM and LiFOP are added to the electrolyte simultaneously, a special mixed film that cannot be obtained when added individually on the positive and negative electrodes is formed. Not only does the increase in the initial internal resistance due to this decrease, but also the subsequent increase in the internal resistance is suppressed as compared with the case where each is added alone. Furthermore, a high capacity retention can be obtained as compared with the case where each is added alone.

  Here, when the amount of LiFOP added exceeds 1.5% by weight, the film formed by LiFOP becomes dominant, and the remarkable effect of combining LiFOP and BSM disappears, similar to the case where LiFOP is added alone. Characteristics. On the other hand, when the amount of BSM added exceeds 2.0% by weight, the BSM film becomes dominant, and characteristics similar to those obtained when BSM is added alone are obtained.

  Furthermore, when the amount of BSM added exceeds 2.0% by weight and at the same time the amount of LiFOP exceeds 1.5% by weight, the adverse effects of adding these appear and the effect of the combination disappears. . However, when BSM is added in an amount of 2.0% by weight or less and LiFOP is added in an amount of 1.5% by weight or less in the electrolytic solution, an effect of suppressing an increase in internal resistance that cannot be obtained when each is added alone is Both effects of improving the capacity retention rate can be obtained.

  If BSM and LiFOP are added excessively, not only does the cost of the additive increase, but the effect is small and the battery bulge tends to increase. Therefore, the addition amount of BSM needs to be 2.0 wt% or less with respect to the whole electrolyte solution excluding BSM and LiFOP, and more preferably 0.1 wt% or more. The amount of LiFOP added needs to be 1.5% by weight or less, more preferably 0.1% by weight or more, based on the entire electrolyte solution excluding BSM and LiFOP.

  Since BSM and LiFOP are decomposed and consumed on the electrode when the battery is prepared and charged / discharged, the amount remaining in the battery when the battery is repeatedly charged / discharged is the non-aqueous electrolyte at the time of battery preparation. Less than the amount added.

  The electrode used for the non-aqueous electrolyte secondary battery of the present invention has a mixture layer on the surface of a sheet-like current collector, and the mixture layer contains an active material and a binder. In addition, when the conductivity of the active material is low, a conductive assistant made of a highly conductive material is included. Depending on the case, you may include substances other than an active material, a binder, and a conductive support agent.

  The mixing ratio of the active material / binder / conducting aid in the mixture layer may be selected according to the physical properties of the material used. The active material is about 90 wt%, and the binder and the conductive aid are several wt% each. Is suitable. Since the shape of the active material / binder / conducting aid is usually particles or powder, when mixing them into a mixture paste, an organic solvent such as N-methyl-2-pyrrolidone (NMP) is used. Mix to make a paste.

  The electrode used for the non-aqueous electrolyte secondary battery of the present invention is a mixture paste containing an active material is applied to the surface of a sheet current collector, dried, and then the density and thickness of the mixture layer are adjusted by a roll press or the like. Manufactured by doing.

In the electrode of the non-aqueous electrolyte secondary battery of the present invention, as the positive electrode active material, lithium manganate (LiMn ₂ O ₄ ), lithium cobaltate (LiCoO ₂ ), and lithium nickelate (LiNiO) capable of inserting and extracting lithium are used. Lithium composite oxides that can occlude and release lithium, such as ₂ ), lithium composite oxides in which transition metal portions of these composite oxides are substituted with other transition metals or light metals, and the like can be used.

  Further, as the negative electrode active material, carbon materials such as non-graphitizable carbon, graphitizable carbon, graphite, and vapor grown carbon fiber can be used.

  Furthermore, as the binder used in the electrode mixture layer, polyvinylidene fluoride (NMP), polyacrylonitrile (AN), styrene-butadiene rubber (SBR), etc. can be used, and acetylene black is used as the conductive auxiliary. The powder which consists of carbon materials, such as, can be used.

  As an organic solvent mixed with the mixture paste, N-methyl-2-pyrrolidone (NMP), tetrahydrofuran (THF), or the like can be used.

  As a material of the sheet-like current collector, aluminum or an aluminum alloy can be used for the positive electrode, and copper or a copper alloy can be used for the negative electrode.

  As the separator used in the non-aqueous electrolyte secondary battery of the present invention, a microporous membrane made of a polyolefin resin such as polyethylene is used, and a plurality of microporous membranes having different materials, weight average molecular weights and porosity are laminated. Or those containing a suitable amount of various plasticizers, antioxidants, flame retardants and the like in these microporous membranes.

  The solvent of the organic electrolyte used in the non-aqueous electrolyte secondary battery of the present invention includes low-viscosity chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate, and ethylene carbonate, propylene carbonate, butylene carbonate, and the like. High dielectric constant cyclic carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1-3 dioxolane, methyl acetate, methyl propionate, vinylene carbonate, dimethylformamide, sulfolane and mixtures thereof A solvent etc. can be mentioned.

Further, as the lithium salt, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiI, LiAlCl _{4 and the} like A mixture thereof may be mentioned. Preferably, a lithium salt obtained by mixing one or more of LiBF ₄ and LiPF ₆ is preferable.

  In the non-aqueous electrolyte secondary battery of the present invention, these organic solvents and lithium salts are combined and used as an electrolyte. Among these electrolytes, it is preferable to use an organic electrolyte mixed with ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate because the lithium ion conductivity is maximized.

  Further, as the shape of the power generation element, a wound oval shape or a circular shape can be used. Further, the shape of the power generation element is not limited to the winding type, and may be a shape in which flat plate plates are laminated. Other battery components include a current collector, a terminal, an insulating plate, a battery case, and the like. Conventionally, these components can be used as they are.

[Positive electrode plate]
The positive electrode plate consists of 90% by weight of LiMn ₂ O ₄ powder as a positive electrode active material, 4% by weight of acetylene black as a conductive auxiliary agent, and 6% by weight of polyvinylidene fluoride (hereinafter referred to as “PVdF”) as a binder. A positive electrode mixture paste made into a paste form by adding 150 ml of N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”) to 100 g of the mixture on both sides of a sheet-like aluminum current collector with a thickness of 20 μm. The positive electrode plate having a thickness of 150 μm was prepared by coating, drying, and then pressing with a roll press. The drying conditions were 12 hours at 150 ° C. under reduced pressure of 0.01 torr or less. The obtained positive electrode plate had a length of 650 mm and a width of 34 mm, and a 4 mm mixture layer uncoated portion was provided at one end in the width direction.

[Negative electrode plate]
The negative electrode plate was prepared by adding 180 ml of NMP to 100 g of a mixture composed of 92% by weight of graphite (Gr) as a negative electrode active material and 8% by weight of PVdF as a binder, and having a thickness of 15 μm. A negative electrode plate having a thickness of 85 μm was prepared by applying and drying both sides of the sheet-like copper current collector, followed by pressing with a roll press. The drying conditions were 12 hours at 150 ° C. under reduced pressure of 0.01 torr or less. The obtained negative electrode plate had a length of 600 mm and a width of 35 mm, and a 4 mm mixture layer uncoated portion was provided at one end in the width direction.

[Nonaqueous electrolyte secondary battery]
FIG. 1 shows the appearance of the power generation element used in the nonaqueous electrolyte secondary battery of the present invention, and FIG. 2 shows the appearance of the nonaqueous electrolyte secondary battery. 1 and 2, 11 is a nonaqueous electrolyte secondary battery, 12 is a power generation element, 13 is a positive electrode plate, 14 is a negative electrode plate, 15 is a separator, 16 is a battery case, 17 is a power generation element storage part of the battery case, Reference numeral 18 denotes a battery case lid, 19 a positive terminal, 20 a negative terminal, 21 a safety valve, and 22 an electrolyte injection port.

  In the nonaqueous electrolyte secondary battery of the present invention, a power generation element 12 in which a positive electrode plate 13 and a negative electrode plate 14 are wound in an oval shape via a separator 15 is stored in a power generation element storage portion 17 of the battery case. The power generation element storage portion 17 and the battery case lid portion 18 are sealed by laser welding, and a non-aqueous electrolyte (not shown) is injected from the electrolyte injection port 22, and then the electrolyte injection port 22. It is configured to be sealed. In addition, all processes from production of the positive electrode plate and the negative electrode plate to battery assembly were performed in a dry room having a dew point of −50 ° C. or less. The design capacity of the manufactured battery was 450 mAh.

As a basic non-aqueous electrolyte, a solution obtained by dissolving 1 mol / L of LiPF ₆ in a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (MEC) in a volume ratio of 30:40:30. Using.

[Examples 1-12 and Comparative Examples 1-7]
[Example 1]
Using the above positive electrode plate and negative electrode plate, 0.1% by weight of bis (vinylsulfonyl) methane (BSM) and 0.1% by weight of lithium bis (oxalate) difluorophosphate (LiFOP) based on the weight of the basic electrolyte A non-aqueous electrolyte secondary battery A of Example 1 having a wound electrode group was produced using the electrolyte solution simultaneously added with.

[Example 2]
A nonaqueous electrolyte secondary battery B of Example 2 was produced in the same manner as in Example 1 except that the amount of LiFOP added relative to the weight of the basic electrolyte was 0.5% by weight.

[Example 3]
A nonaqueous electrolyte secondary battery C of Example 3 was produced in the same manner as in Example 1 except that the amount of LiFOP added relative to the weight of the basic electrolyte was 1.5% by weight.

[Example 4]
A nonaqueous electrolyte secondary battery D of Example 4 was produced in the same manner as in Example 1 except that the amount of BSM added relative to the weight of the basic electrolyte was 0.5% by weight.

[Example 5]
A nonaqueous electrolyte secondary battery E of Example 5 was produced in the same manner as in Example 4 except that the amount of LiFOP added relative to the weight of the basic electrolyte was 0.5% by weight.

[Example 6]
A nonaqueous electrolyte secondary battery F of Example 6 was produced in the same manner as in Example 4 except that the amount of LiFOP added relative to the weight of the basic electrolyte was 1.5% by weight.

[Example 7]
A nonaqueous electrolyte secondary battery G of Example 7 was produced in the same manner as in Example 1 except that the amount of BSM added relative to the weight of the basic electrolyte was 1.0% by weight.

[Example 8]
A nonaqueous electrolyte secondary battery H of Example 8 was produced in the same manner as in Example 7, except that the amount of LiFOP added relative to the weight of the basic electrolyte was 0.5% by weight.

[Example 9]
A nonaqueous electrolyte secondary battery I of Example 9 was produced in the same manner as in Example 7, except that the amount of LiFOP added relative to the weight of the basic electrolyte was 1.5% by weight.

[Example 10]
A nonaqueous electrolyte secondary battery J of Example 10 was produced in the same manner as in Example 1 except that the amount of BSM added relative to the weight of the basic electrolyte was 2.0% by weight.

[Example 11]
A nonaqueous electrolyte secondary battery K of Example 11 was produced in the same manner as in Example 10 except that the amount of LiFOP added relative to the weight of the basic electrolyte was 0.5% by weight.

[Example 12]
A nonaqueous electrolyte secondary battery L of Example 12 was produced in the same manner as in Example 10 except that the amount of LiFOP added relative to the weight of the basic electrolyte was 1.5% by weight.

[Comparative Example 1]
A non-aqueous electrolyte secondary battery M of Comparative Example 1 was fabricated in the same manner as in Example 1 except that only a basic electrolytic solution not containing BSM and LiFOP was used as the electrolytic solution [Comparative Example 2]
Nonaqueous electrolyte secondary battery N of Comparative Example 2 except that 0.5% by weight of LiFOP was added to the weight of the basic electrolyte and an electrolyte containing no BSM was used. Was made.

[Comparative Example 3]
The nonaqueous electrolyte secondary battery O of Comparative Example 3 is the same as Example 1 except that 0.1% by weight of BSM is added with respect to the weight of the basic electrolyte and an electrolyte containing no LiFOP is used. Produced.

[Comparative Example 4]
A nonaqueous electrolyte secondary battery P of Comparative Example 4 was produced in the same manner as in Example 1 except that the amount of LiFOP added relative to the weight of the basic electrolyte was 2.0% by weight.

[Comparative Example 5]
Non-aqueous electrolyte secondary battery Q of Comparative Example 5 was the same as Example 1 except that 2.0% by weight of BSM was added to the weight of the basic electrolyte and an electrolyte containing no LiFOP was used. Produced.

[Comparative Example 6]
A nonaqueous electrolyte secondary battery R of Comparative Example 6 was produced in the same manner as in Example 10 except that the amount of LiFOP added relative to the weight of the basic electrolyte was 2.0% by weight.

[Comparative Example 7]
A nonaqueous electrolyte secondary battery S of Comparative Example 7 was produced in the same manner as in Example 2 except that the amount of BSM added relative to the weight of the basic electrolyte was 2.5% by weight.

  Table 1 summarizes the amounts of BSM and LiFOP added to the basic electrolyte of the batteries A to S of Examples 1 to 12 and Comparative Examples 1 to 7 prepared here.

［特性測定］
実施例１〜１２および比較例１〜７の非水電解液二次電池Ａ〜Ｓについて、次の条件で初期放電容量測定、充放電サイクル試験および内部抵抗の測定をおこなった。
（１）初期放電容量測定
試験電池を２５℃環境下で、４５０ｍＡ定電流で４．１Ｖまで充電した後、さらに４．１Ｖ定電圧で、充電時間の合計が３時間となるように定電圧充電をおこなった。その後、４５０ｍＡ定電流で２．５Ｖまで放電した。この充放電を３回繰り返し、３回目の放電容量を初期放電容量と定めた。
（２）充放電サイクル試験
試験電池を、温度を４５℃としたこと以外は、初期放電容量測定と同じ条件で３００回充放電した。その後、初期放電容量測定と同じ条件で充放電して、３００サイクル目の放電容量を求めた。そして、初期放電容量に対する３００サイクル目の放電容量の比を「容量保持率（％）」とした。
（３）内部抵抗測定
電池の内部抵抗は、試験電池を２０℃環境下で、４５０ｍＡ定電流で３．９Ｖまで充電した後、さらに３．９Ｖ定電圧で、充電時間の合計が３時間となるように定電圧充電をおこなった。そして、内部抵抗は鶴賀電機製ＤＩＧＩＴＡＬ ＤＣ ＭＥＴＥＲを用いて測定した。そして、充放電サイクル試験前の内部抵抗Ｒ_０と、３００サイクル充放電後の内部抵抗Ｒ_３００とを求め、（Ｒ_３００／Ｒ_０）を内部抵抗増加率（％）とした。

[Characteristic measurement]
For the nonaqueous electrolyte secondary batteries A to S of Examples 1 to 12 and Comparative Examples 1 to 7, initial discharge capacity measurement, charge / discharge cycle test, and internal resistance measurement were performed under the following conditions.
(1) Initial discharge capacity measurement After charging the test battery to 4.1 V at a constant current of 450 mA in an environment of 25 ° C., constant voltage charging is performed so that the total charging time is 3 hours at a further 4.1 V constant voltage. I did it. Thereafter, the battery was discharged to 2.5 V at a constant current of 450 mA. This charge / discharge was repeated three times, and the third discharge capacity was determined as the initial discharge capacity.
(2) Charging / discharging cycle test The test battery was charged and discharged 300 times under the same conditions as the initial discharge capacity measurement except that the temperature was 45 ° C. Thereafter, charging and discharging were performed under the same conditions as in the initial discharge capacity measurement, and the discharge capacity at the 300th cycle was determined. The ratio of the discharge capacity at the 300th cycle to the initial discharge capacity was defined as “capacity retention (%)”.
(3) Internal resistance measurement The internal resistance of the battery is that the test battery is charged to 3.9 V at a constant current of 450 mA in a 20 ° C. environment, and then the total charging time is 3 hours at a constant voltage of 3.9 V. A constant voltage charge was performed as shown. The internal resistance was measured using a DIGITAL DC METER manufactured by Tsuruga Electric. Then, the internal resistance R ₀ before the charge / discharge cycle test and the internal resistance R ₃₀₀ after 300 cycles of charge / discharge were determined, and (R ₃₀₀ / R ₀ ) was defined as the internal resistance increase rate (%).

  Table 2 summarizes the characteristic measurement results for the nonaqueous electrolyte secondary batteries A to S of Examples 1 to 12 and Comparative Examples 1 to 7.

表２から、非水電解液中に、基本電解液の重量に対し、ＢＳＭを２．０重量％以下を含み、同時にＬｉＦＯＰを１．５重量％以下を含む実施例１〜１２の電池Ａ〜Ｌでは、容量保持率が８０％以上で、内部抵抗増加率も４０％以下の優れた充放電サイクル特性を示したのに対し、非水電解液中にＢＳＭとＬｉＦＯＰを全く含まない比較例１の電池Ｍ、ＢＳＭとＬｉＦＯＰの一方のみを含む比較例２の電池Ｎ、比較例３の電池Ｏ、比較例５の電池Ｑ、ＢＳＭとＬｉＦＯＰの両方を含むが、ＬｉＦＯＰの含有量が２．０重量％の比較例４の電池Ｐ、比較例６の電池Ｑ、ＬｉＦＯＰを２．５重量％含む比較例７の電池Ｓでは、容量保持率は６５％以下で、内部抵抗増加率は５０％を越え、ともに悪くなることがわかった。

From Table 2, the batteries A of Examples 1 to 12 containing BSM of 2.0% by weight or less and simultaneously containing LiFOP of 1.5% by weight or less based on the weight of the basic electrolyte in the nonaqueous electrolyte L showed excellent charge / discharge cycle characteristics with a capacity retention rate of 80% or more and an internal resistance increase rate of 40% or less, whereas the nonaqueous electrolyte did not contain BSM and LiFOP at all. Battery M, Comparative Example 2 Battery N containing only one of BSM and LiFOP, Comparative Example 3 Battery O, Comparative Example Battery Q, including both BSM and LiFOP, with a LiFOP content of 2.0. In the battery P of Comparative Example 4 having a weight% of Comparative Example 4, the battery Q of Comparative Example 6 and the battery S of Comparative Example 7 containing 2.5% by weight of LiFOP, the capacity retention is 65% or less and the internal resistance increase rate is 50%. I found that both of them got worse.

The external appearance of the electric power generation element used for the nonaqueous electrolyte secondary battery of this invention. Appearance of the nonaqueous electrolyte secondary battery of the present invention.

11: Nonaqueous electrolyte secondary battery 12: Electrode group 13: Positive electrode plate 14: Negative electrode plate 15: Separator

Claims (1)

  In a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, bis (vinylsulfonyl) methane is contained in the non-aqueous electrolyte in an amount of 2.0% by weight or less and lithium bis (oxalate) difluorophosphate. A non-aqueous electrolyte secondary battery comprising 1.5% by weight or less.

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