Secondary battery, battery pack, and vehicle

Abstract

To provide a secondary battery having excellent lifetime performance at high temperatures, a battery pack including the secondary battery, and a vehicle including the battery pack.SOLUTION: According to an embodiment, a secondary battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte is provided. The positive electrode includes a positive electrode active material-containing layer containing sulfur atoms. The nonaqueous electrolyte includes a sultone compound and a cyclic carbonate. In a total ion chromatogram obtained by gas chromatography mass spectrometry (GC-MS) of the nonaqueous electrolyte, a ratio B / A of an area B in a retention time range of 13.5 minutes or more and 14.5 minutes or less to an area A in a retention time range of 15 minutes or more and 18 minutes or less is within a range of 0 or more and 0.000944 or less. A mass M (g / m3) of sulfur atoms per unit volume of the positive electrode active material-containing layer and a concentration E (mol / L) of the sultone compound in the nonaqueous electrolyte satisfy the following expression (1): 1×10-6≤ E / M≤9×10-4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments relate to a secondary battery, a battery pack, and a vehicle. [Background technology]

[0002] Secondary batteries containing non-aqueous electrolytes have problems with high-temperature durability. One reason for this is that the non-aqueous electrolyte reacts with the electrodes to generate gas. When gas is generated, bubbles form inside the electrodes, which can easily cause the active material to peel off, increasing resistance and reducing output performance. Secondary batteries containing non-aqueous electrolytes are particularly prone to gas generation in high-temperature environments. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2020-512676 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the embodiments is to provide a secondary battery having a long life performance at high temperatures, a battery pack including the secondary battery, and a vehicle including the battery pack. [Means for solving the problem]

[0005] According to an embodiment, a secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte is provided. The positive electrode includes a positive electrode active material-containing layer containing sulfur atoms. The non-aqueous electrolyte includes a sultone compound and a cyclic carbonate. In gas chromatography mass spectrometry of the non-aqueous electrolyte, in a total ion chromatogram in which the vertical axis represents detection intensity and the horizontal axis represents retention time, the ratio B / A of the area B within the retention time range of 13.5 to 14.5 minutes to the area A within the retention time range of 15 to 18 minutes is 0 to 0.000944. The following formula (1) is satisfied:

[0006] Formula (1): 1×10 -6 ≦E / M≦9×10 -4 In formula (1), M is the mass of sulfur atoms per unit volume of the positive electrode active material-containing layer (g / m 3 ) where E is the concentration (mol / L) of the sultone compound in the non-aqueous electrolyte.

[0007] According to another embodiment, a battery pack including the secondary battery of the embodiment is provided.

[0008] According to another embodiment, a vehicle including the battery pack of the embodiment is provided. [Brief explanation of the drawings]

[0009] [Figure 1] 2 is a cross-sectional view of the secondary battery according to the embodiment, taken along a direction perpendicular to the terminal extending direction. FIG. [Figure 2] FIG. 2 is an enlarged cross-sectional view of part A in FIG. 1. [Figure 3] FIG. 2 is a partially cutaway cross-sectional view of the secondary battery according to the embodiment. [Figure 4] FIG. 4 is a side view of the battery of FIG. 3. [Figure 5] FIG. 10 is a partially cutaway perspective view schematically showing another example of a secondary battery according to an embodiment. [Figure 6] FIG. 6 is an enlarged cross-sectional view of part B of the secondary battery shown in FIG. 5. [Figure 7] 5A to 5C are schematic plan views showing an example of a method for manufacturing a secondary battery according to an embodiment. [Figure 8] FIG. 2 is an exploded perspective view of the battery pack according to the embodiment. [Figure 9] FIG. 9 is a block diagram showing the electrical circuit of the battery pack of FIG. 8. [Figure 10] 1 is a schematic diagram showing an example of a vehicle equipped with a secondary battery according to an embodiment; [Figure 11] FIG. 10 is a diagram schematically illustrating another example of a vehicle according to an embodiment. [Figure 12] Total ion chromatogram showing the results of gas chromatography-mass spectrometry. [Figure 13] An enlarged view of the total ion chromatogram shown in Figure 12. DETAILED DESCRIPTION OF THE INVENTION

[0010] (First embodiment) According to a first embodiment, a secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte is provided. The positive electrode includes a positive electrode active material-containing layer containing sulfur atoms. The non-aqueous electrolyte includes a sultone compound and a cyclic carbonate. In gas chromatography mass spectrometry of the non-aqueous electrolyte, in a total ion chromatogram in which the vertical axis represents detection intensity and the horizontal axis represents retention time, the ratio B / A of the area B within the retention time range of 13.5 to 14.5 minutes to the area A within the retention time range of 15 to 18 minutes is 0 to 0.000944. The following formula (1) is satisfied:

[0011] Formula (1): 1×10 -6 ≦E / M≦9×10 -4 In formula (1), M is the mass of sulfur atoms per unit volume of the positive electrode active material-containing layer (g / m 3 ) where E is the concentration (mol / L) of the sultone compound in the non-aqueous electrolyte.

[0012] As a result of extensive research, the present inventors have found that the presence of a sultone compound in a non-aqueous electrolyte can improve the high-temperature durability of a secondary battery. The mechanism behind this is presumed to be as follows.

[0013] When the non-aqueous electrolyte comes into contact with the positive electrode under high-temperature conditions, the non-aqueous electrolyte may be oxidized and decomposed to generate gas, which may result in the generation of bubbles in the positive electrode and an increase in resistance, thereby reducing the lifespan of the secondary battery.

[0014] The secondary battery according to the embodiment includes a sultone compound in a non-aqueous electrolyte. When a sultone compound is present in the non-aqueous electrolyte, the reaction in which the sultone compound reacts with the positive electrode active material in the positive electrode and decomposes proceeds more easily than the reaction between the positive electrode active material and components other than the sultone compound in the non-aqueous electrolyte. Furthermore, no gas is generated during the decomposition reaction of the sultone compound. In other words, the sultone compound, acting as a sacrificial material, decomposes preferentially over other non-aqueous electrolyte components, thereby suppressing gas generation due to oxidative decomposition of the non-aqueous electrolyte. Therefore, even at high temperatures, gas generation due to oxidative decomposition of the non-aqueous electrolyte can be suppressed. This suppresses the generation of bubbles in the positive electrode, which increases resistance. Consequently, the battery's life performance at high temperatures can be improved.

[0015] The positive electrode includes a positive electrode active material containing layer containing sulfur atoms. The positive electrode active material containing layer containing sulfur atoms can suppress oxidative decomposition of the non-aqueous electrolyte when it comes into contact with the non-aqueous electrolyte, thereby suppressing gas generation.

[0016] However, sulfur atoms contained in the positive electrode active material-containing layer may be consumed by reacting with the non-aqueous electrolyte. As a result, the effect of suppressing oxidative decomposition of the non-aqueous electrolyte when the positive electrode active material-containing layer comes into contact with the non-aqueous electrolyte is reduced. Furthermore, the reaction consuming sulfur atoms contained in the positive electrode active material-containing layer consumes electrons, which may cause a potential difference between the positive and negative electrodes. As a result, the life performance of the secondary battery at high temperatures may ultimately be reduced.

[0017] As a result of extensive research, the present inventors have found that when sulfur atoms contained in the positive electrode active material-containing layer are consumed, the area B in the retention time range of 13.5 minutes or more and 14.5 minutes or less in a total ion chromatogram obtained by gas chromatography-mass spectrometry of a non-aqueous electrolyte, in which the detection intensity is plotted on the vertical axis and the retention time is plotted on the horizontal axis, increases. In other words, in a secondary battery in which the area B is relatively small, the reaction in which sulfur atoms contained in the positive electrode active material-containing layer are consumed is suppressed. From this, the present inventors have found that the life performance of a secondary battery at high temperatures can be improved by maintaining the area B relatively small.

[0018] In the secondary battery according to the embodiment, in the total ion chromatogram of the nonaqueous electrolyte, the ratio B / A of the area A within the retention time range of 15 to 18 minutes to the area B within the retention time range of 13.5 to 14.5 minutes is in the range of 0 to 0.000944. When the ratio is within this range, the area B is kept relatively small. Therefore, the life performance of the secondary battery at high temperatures can be improved.

[0019] The secondary battery according to this embodiment further satisfies the following formula (1).

[0020] Formula (1): 1×10 -6 ≦E / M≦9×10 -4 In formula (1), M is the mass of sulfur atoms per unit volume of the positive electrode active material-containing layer (g / m 3 ) where E is the concentration (mol / L) of the sultone compound in the non-aqueous electrolyte.

[0021] In order for the sultone compound to be decomposed as a sacrificial material preferentially over other non-aqueous electrolyte components, the sultone compound must be present in the non-aqueous electrolyte. -6 In this case, the sultone compound is present in the non-aqueous electrolyte to an extent that it can function sufficiently as a sacrificial material, thereby suppressing gas generation due to oxidative decomposition of the non-aqueous electrolyte.

[0022] In addition, the secondary battery has an E / M of 9×10 -4 or less, the mass of sulfur atoms per unit volume of the positive electrode active material-containing layer is large, and therefore, even when the positive electrode active material-containing layer comes into contact with the non-aqueous electrolyte, gas generation due to oxidative decomposition of the non-aqueous electrolyte can be suppressed.

[0023] Therefore, according to the embodiment, a secondary battery having a long life performance at high temperatures can be provided.

[0024] The secondary battery according to the embodiment will be described in further detail with reference to the drawings.

[0025] The secondary battery may be, for example, a secondary battery that uses alkali metal ions as carrier ions, such as a lithium battery (lithium ion battery).

[0026] The positive electrode may include a positive electrode active material-containing layer, the negative electrode may include a negative electrode active material-containing layer, and the negative electrode active material-containing layer may include a negative electrode active material.

[0027] As a result of decomposition of the sultone compound, the positive electrode active material-containing layer contained in the positive electrode contains sulfur atoms. In addition, the negative electrode active material-containing layer that may be contained in the negative electrode may contain sulfur atoms.

[0028] The positive electrode active material-containing layer included in the positive electrode and the negative electrode active material-containing layer that may be included in the negative electrode (active material-containing layer) may each contain a sulfur-containing phase containing sulfur atoms. The sulfur atoms may be derived from decomposition products of the non-aqueous electrolyte. Furthermore, the sulfur atoms may be derived from decomposition products of a sultone compound contained in the non-aqueous electrolyte. The sulfur-containing phase may be, for example, a phase containing decomposition products of the sultone compound.

[0029] The sulfur-containing phase may be formed on the active material of the active material-containing layer. The sulfur-containing phase may be a layer formed on the active material, or may be a film that covers at least a portion of the surface of the active material particles. The sulfur-containing phase may be, for example, a layer located on the surface of the active material-containing layer and interposed between the active material and the separator. The sulfur-containing phase may contain other types of atoms in addition to sulfur atoms (S). Examples of other types of atoms include oxygen atoms (O) and carbon atoms (C).

[0030] The sulfur-containing phases that the positive electrode active material-containing layer and the negative electrode active material-containing layer may contain may be referred to as a positive electrode sulfur-containing phase and a negative electrode sulfur-containing phase, respectively.

[0031] The non-aqueous electrolyte may generate gas when it comes into contact with the positive electrode active material in the positive electrode active material-containing layer. When the positive electrode sulfur-containing phase is larger than the positive electrode active material-containing layer, the mass M (g / m) of sulfur atoms per unit volume of the positive electrode active material-containing layer 3) may become large. Therefore, when the mass M of sulfur atoms per unit volume of the positive electrode active material-containing layer is large, the positive electrode active material contained in the positive electrode active material-containing layer is unlikely to come into contact with the non-aqueous electrolyte. Therefore, gas generation can be suppressed.

[0032] Examples of the sultone compound contained in the non-aqueous electrolyte include propane sultone (PS; 1,3-propane sultone), 1,4-butane sultone, 1,3-propene sultone, and 2,4-butane sultone. One or more types of sultone compounds may be used. The sultone compound preferably contains propane sultone.

[0033] 12 is a total ion chromatogram showing the results of gas chromatography mass spectrometry, where the vertical axis represents the detection intensity and the horizontal axis represents the retention time.

[0034] Chromatogram a shows the results of gas chromatography mass spectrometry of an example of a non-aqueous electrolyte that can be contained in the secondary battery according to the embodiment. Chromatogram b shows the results of gas chromatography mass spectrometry of a non-aqueous electrolyte that can be contained in a secondary battery according to another example. Chromatograms a and b are both total ion chromatograms obtained by the method described below.

[0035] Fig. 13 is an enlarged view of the total ion chromatogram shown in Fig. 12. Fig. 13 shows an enlarged view of the total ion chromatogram shown in Fig. 12, with the range of detection intensity on the vertical axis from 0 to 200,000 and the range of retention time from 11 to 17 minutes.

[0036] In the total ion chromatogram of the non-aqueous electrolyte, the area A within the retention time range of 15 minutes or more and 18 minutes or less, the area B within the retention time range of 13.5 minutes or more and 14.5 minutes or less, and the area C within the retention time range of 11.5 minutes or more and 12.5 minutes or less can be calculated as follows.

[0037] A baseline is drawn in the background of the chromatogram. The area below the baseline is subtracted from the chromatogram. The chart obtained by the subtraction process is integrated over a predetermined retention time range. For example, to calculate area A, the chart obtained by the subtraction process is integrated over the range from 15 minutes to 18 minutes. The integrated value thus obtained is defined as area A.

[0038] When calculating area B, the integration range is from 13.5 minutes to 14.5 minutes. When calculating area C, the integration range is from 11.5 minutes to 12.5 minutes. Otherwise, areas B and C can be calculated in the same way as area A.

[0039] Chromatogram b has peak Pb1 in the retention time range of 15 to 18 minutes, as well as peak Pb2 in the retention time range of 13.5 to 14.5 minutes. Therefore, the ratio B / A of the area B in the retention time range of 13.5 to 14.5 minutes to the area A in the retention time range of 15 to 18 minutes is greater than 0.000944.

[0040] A peak in a chromatogram is, for example, a signal in the chromatogram having a signal / noise ratio (S / N ratio) of 3 or more.

[0041] In contrast, chromatogram a has peak Pa1 within the retention time range of 15 to 18 minutes, but does not have a peak at the retention time where chromatogram b has Pb2. In other words, chromatogram a may have low detection intensity throughout the retention time range of 15 to 18 minutes. Therefore, the ratio B / A of area B within the retention time range of 13.5 to 14.5 minutes to area A within the retention time range of 15 to 18 minutes in chromatogram a is 0 to 0.000944.

[0042] Both chromatograms a and b have multiple peaks within the retention time range of 11.5 minutes to 12.5 minutes, and therefore, the ratio C / A of the area C within the retention time range of 11.5 minutes to the area A is 0.0003 or greater.

[0043] In gas chromatography mass spectrometry of a non-aqueous electrolyte, the components contained in the non-aqueous electrolyte can be qualitatively analyzed from the positions of peaks in a total ion chromatogram, and the components can be quantitatively analyzed from the areas of the peaks.

[0044] For example, in a total ion chromatogram obtained by gas chromatography-mass spectrometry of a non-aqueous electrolyte, a peak of, for example, a cyclic carbonate may appear within a retention time range of 15 minutes to 18 minutes. In other words, if the total ion chromatogram of a non-aqueous electrolyte has a peak within this range, a qualitative analysis result can be obtained that the non-aqueous electrolyte contains a cyclic carbonate. Furthermore, the content of the cyclic carbonate in the non-aqueous electrolyte can be quantified from the area of ​​this peak.

[0045] The range in which the cyclic carbonate peak appears may be, for example, within the range of 15.0 minutes to 18.0 minutes.

[0046] The area of ​​the peak appearing within the retention time range of 15 minutes to 18 minutes can account for a large portion of the area within the retention time range of 15 minutes to 18 minutes. The area of ​​this peak is less susceptible to the effects of charge / discharge cycles. Therefore, the area A within the retention time range of 15 minutes to 18 minutes can be used as a reference value when evaluating the relative amount of the area within a specific range in the total ion chromatogram. The area A can be, for example, 557,761,000 to 559,899,000.

[0047] For example, a peak of propanesulfonate ester may appear within the retention time range of 13.5 minutes to 14.5 minutes. The propanesulfonate ester may be a substance produced by a reaction in which sulfur atoms contained in the positive electrode active material-containing layer are consumed. For example, the propanesulfonate ester may be a substance produced by a reaction between the positive electrode sulfur-containing phase and a component in the non-aqueous electrolyte. The propanesulfonate ester may be produced, for example, when the non-aqueous electrolyte contains propane sultone as a sultone compound. The area B within the range of 13.5 minutes to 14.5 minutes may be, for example, 11,787.726 to 527,376.928.

[0048] In other words, when the ratio B / A of the area A within the retention time range of 15 minutes to 18 minutes in the total ion chromatogram of the nonaqueous electrolyte to the area B within the retention time range of 13.5 minutes to 14.5 minutes is 0 or more and 0.000944 or less, the amount of propanesulfonic acid ester relative to the amount of cyclic carbonate contained in the nonaqueous electrolyte may be sufficiently small. Therefore, when B / A is within the above range, the positive electrode sulfur-containing phase may remain in a large amount without being consumed. Therefore, gas generation can be suppressed. The lower limit of B / A may be 0.000000. B / A may be, for example, within the range of 0.00028 to 0.000944.

[0049] In a total ion chromatogram of the non-aqueous electrolyte, the ratio C / A of the area C within the retention time range of 11.5 minutes or more and 12.5 minutes or less to the area A can be 0.0003 or more.

[0050] After the secondary battery is assembled, when the secondary battery is subjected to initial charge / discharge and aging, the non-aqueous electrolyte may be partially decomposed, for example, the cyclic carbonate contained in the non-aqueous electrolyte may be partially decomposed.

[0051] In the total ion chromatogram of the nonaqueous electrolyte, a peak of a decomposition product of a cyclic carbonate may appear within the retention time range of 11.5 minutes to 12.5 minutes. An example of a decomposition product of a cyclic carbonate is 3,5-dimethyldihydrofuran-2-one. The area C within the range of 11.5 minutes to 12.5 minutes may be, for example, 1,281,000 to 1,394,000.

[0052] That is, in a total ion chromatogram of the nonaqueous electrolyte contained in a secondary battery, when the ratio C / A of the area C within the retention time range of 11.5 minutes to 12.5 minutes to the area A is 0.0003 or more, this means that the secondary battery has undergone initial charge / discharge and aging. C / A may be 0.0024 or more. The upper limit of C / A is not particularly limited, but may be, for example, 0.0247.

[0053] The non-aqueous electrolyte may further contain a chain carbonate in addition to the cyclic carbonate. A non-aqueous electrolyte containing a chain carbonate can increase the mobility of lithium ions, thereby improving the output performance of the secondary battery. The chain carbonate is preferably an ester compound represented by the following chemical formula (2): In chemical formula (2), R is a first hydrocarbon group, and R' is a second hydrocarbon group containing 3 or more carbon atoms.

[0054] Chemical formula (2):

[0055] [ka]

[0056] Even when the ester compound comes into contact with the positive electrode, it is unlikely to undergo a reaction that consumes sulfur atoms contained in the positive electrode active material-containing layer (e.g., a reaction with the positive electrode sulfur-containing phase). This is thought to be because, compared with an ester compound in which R' in chemical formula (2) contains three or more carbon atoms, decomposition initiated by elimination of an alkyl group is unlikely to occur compared to an ester compound in which R' in chemical formula (2) contains two or fewer carbon atoms (e.g., diethyl carbonate). Therefore, when the nonaqueous electrolyte contains an ester compound represented by chemical formula (2) in which R is a first hydrocarbon group and R' is a second hydrocarbon group containing three or more carbon atoms, a reaction that consumes sulfur atoms contained in the positive electrode active material-containing layer is unlikely to occur. Therefore, gas generation can be suppressed.

[0057] When the non-aqueous electrolyte contains the ester compound, for example, it can reduce the reaction between the non-aqueous electrolyte and the positive electrode sulfur-containing phase. Furthermore, for example, it can reduce the generation of propanesulfonic acid ester. Therefore, when the non-aqueous electrolyte contains the ester compound, the area B in the retention time range of 13.5 minutes to 14.5 minutes in the total ion chromatogram of the non-aqueous electrolyte can be kept small. Therefore, the ratio B / A can be set to a range of 0 to 0.000944.

[0058] In a total ion chromatogram of a non-aqueous electrolyte, a peak of an ester compound represented by chemical formula (2), where R is a first hydrocarbon group and R' is a second hydrocarbon group containing 3 or more carbon atoms, may appear within a retention time range of 15 minutes to 18 minutes. That is, in a total ion chromatogram of a non-aqueous electrolyte, a peak of the ester compound may appear in addition to a peak of a cyclic carbonate within a retention time range of 15 minutes to 18 minutes. Alternatively, a single peak may appear in which the peak of the ester compound and the peak of the cyclic carbonate overlap.

[0059] Examples of ester compounds represented by chemical formula (2), in which R is a first hydrocarbon group and R' is a second hydrocarbon group containing 3 or more carbon atoms, include propyl propionate (PP), ethyl butyrate (EB), and pentyl propionate. The type of the ester compound can be one or more types.

[0060] The number of carbon atoms contained in the second hydrocarbon group R' may be, for example, within the range of 3 to 5. The number of carbon atoms contained in the first hydrocarbon group R is not particularly limited, but may be, for example, 3 or 4. The first hydrocarbon group and the second hydrocarbon group may be the same type or different types.

[0061] The higher the content of the ester compound in the non-aqueous electrolyte, represented by chemical formula (2), where R is a first hydrocarbon group and R' is a second hydrocarbon group containing three or more carbon atoms, the more likely it is that the reaction between the non-aqueous electrolyte and the positive electrode sulfur-containing phase and the generation of propanesulfonic acid ester can be suppressed. The content of the ester compound can be, for example, 10% by mass or more. The lower the content of the ester compound, the greater the proportion of cyclic carbonate in the non-aqueous electrolyte, which tends to facilitate dissociation of the electrolyte salt. The content of the ester compound can be, for example, 90% by mass or less.

[0062] Hereinafter, an ester compound represented by chemical formula (2), in which R is a first hydrocarbon group and R' is a second hydrocarbon group containing 3 or more carbon atoms, may be referred to as an ester compound represented by chemical formula (2).

[0063] 1 and 2 show an example of a secondary battery using an exterior member made of a laminate film.

[0064] As shown in FIGS. 1 and 2, the electrode group 1 is a flat wound electrode group. The wound electrode group 1 is housed in a bag-shaped exterior member 12 made of a laminate film with a metal layer sandwiched between two resin films. The flat wound electrode group 1 is formed by spirally winding a laminate, in order from the outside, of a negative electrode 4, a separator 5, a positive electrode 3, and a separator 5 around an axis parallel to the short side direction, and then press-molding the laminate. The outermost negative electrode 4, as shown in FIG. 2, has a configuration in which a negative electrode active material-containing layer 4b containing a negative electrode active material is formed on one side of the inner surface of a negative electrode current collector 4a. The other negative electrodes 4 have a negative electrode active material-containing layer 4b formed on both sides of the negative electrode current collector 4a. The positive electrode 3 has a positive electrode active material-containing layer 3b formed on both sides of a positive electrode current collector 3a.

[0065] Near the outer peripheral edge of the wound electrode group 1, the negative electrode terminal 13 is connected to the negative electrode current collector 4a of the outermost negative electrode 4, and the positive electrode terminal 14 is connected to the positive electrode current collector 3a of the inner positive electrode 3. These negative electrode terminal 13 and positive electrode terminal 14 extend to the outside from an opening of the bag-shaped exterior member 12. The opening of the bag-shaped exterior member 12 is heat-sealed to hermetically seal the wound electrode group 1. When heat-sealing, the negative electrode terminal 13 and positive electrode terminal 14 are sandwiched by the bag-shaped exterior member 12 at this opening.

[0066] 3 and 4 show an example of a secondary battery using a metal container.

[0067] The electrode group 1 is housed in a rectangular cylindrical metal container 2. The electrode group 1 is formed, for example, by winding a positive electrode 3 and a negative electrode 4, with a separator 5 interposed therebetween, into a flat spiral shape around an axis parallel to the short side direction. As shown in FIG. 4 , strip-shaped positive electrode leads 6 are electrically connected to multiple locations on the end of the positive electrode 3 located on the end face of the electrode group 1 that intersects the electrode stacking direction. Strip-shaped negative electrode leads 7 are electrically connected to multiple locations on the end of the negative electrode 4 located on this end face. The multiple positive electrode leads 6 are bundled together and electrically connected to a positive electrode current collector tab 8. The positive electrode lead 6 and the positive electrode current collector tab 8 form a positive electrode terminal. The negative electrode leads 7 are bundled together and connected to a negative electrode current collector tab 9. The negative electrode lead 7 and the negative electrode current collector tab 9 form a negative electrode terminal. A metal sealing plate 10 is fixed to the opening of the metal container 2 by welding or the like. The positive electrode current collecting tab 8 and the negative electrode current collecting tab 9 are each pulled out to the outside through an extraction hole provided in the sealing plate 10. The inner circumferential surface of each extraction hole in the sealing plate 10 is covered with an insulating member 11 to prevent short circuits due to contact with the positive electrode current collecting tab 8 and the negative electrode current collecting tab 9.

[0068] The secondary battery according to the embodiment is not limited to the secondary battery having the configuration shown in FIGS. 1 and 2 and the secondary battery having the configuration shown in FIGS. 3 and 4, but may also be, for example, a battery having the configuration shown in FIGS. 5 and 6.

[0069] Fig. 5 is a partially cutaway perspective view schematically showing another example of a secondary battery, and Fig. 6 is an enlarged cross-sectional view of part B of the secondary battery shown in Fig. 5.

[0070] The secondary battery shown in Figures 5 and 6 includes an electrode group 1 shown in Figures 5 and 6, an exterior member 12 shown in Figure 5, and an electrolyte (not shown). The electrode group 1 and the electrolyte are housed in the exterior member 12. The electrolyte is held in the electrode group 1.

[0071] The exterior member 12 is made of a laminate film including two resin layers and a metal layer interposed between them.

[0072] The electrode group 1 is a laminated electrode group, as shown in Fig. 6. The laminated electrode group 1 has a structure in which negative electrodes 4 and positive electrodes 3 are alternately laminated with separators 5 interposed therebetween.

[0073] The electrode group 1 includes a plurality of negative electrodes 4. Each of the plurality of negative electrodes 4 includes a negative electrode current collector 4a and a negative electrode active material-containing layer 4b supported on both sides of the negative electrode current collector 4a. The electrode group 1 also includes a plurality of positive electrodes 3. Each of the plurality of positive electrodes 3 includes a positive electrode current collector 3a and a positive electrode active material-containing layer 3b supported on both sides of the positive electrode current collector 3a.

[0074] The negative electrode current collector 4a of each negative electrode 4 includes a portion on one side where no negative electrode active material-containing layer 4b is supported on any surface. This portion serves as a negative electrode current collector tab 4c. As shown in FIG. 6 , the negative electrode current collector tab 4c does not overlap with the positive electrode 3. The multiple negative electrode current collector tabs 4c are electrically connected to a strip-shaped negative electrode terminal 13. The tip of the strip-shaped negative electrode terminal 13 is extended to the outside of the exterior member 12.

[0075] Although not shown, the positive electrode current collector 3a of each positive electrode 3 includes a portion on one side where the positive electrode active material-containing layer 3b is not supported on any surface. This portion functions as a positive electrode current collector tab. Like the negative electrode current collector tab 4c, the positive electrode current collector tab does not overlap with the negative electrode 4. The positive electrode current collector tab is located on the opposite side of the electrode group 1 from the negative electrode current collector tab 4c. The positive electrode current collector tab is electrically connected to a strip-shaped positive electrode terminal 14. The tip of the strip-shaped positive electrode terminal 14 is located on the opposite side from the negative electrode terminal 13 and is drawn out to the outside of the exterior member 12.

[0076] As an example of a secondary battery according to an embodiment, a method for manufacturing a secondary battery including a wound electrode group will be described with reference to Fig. 7. Fig. 7 is a schematic diagram illustrating an outline of a method for manufacturing a secondary battery using a bag-shaped exterior member made of a laminate film.

[0077] First, the positive electrode 3 and the negative electrode 4 are prepared.

[0078] For example, a positive electrode is prepared by suspending a positive electrode active material, a conductive agent, and a binder in a solvent to prepare a slurry. This slurry is then applied to one or both sides of a current collector. The applied slurry is then dried to obtain a laminate of a positive electrode active material-containing layer and a current collector. This laminate is then pressed. In this manner, a positive electrode is produced. Alternatively, the positive electrode may be produced by the following method. First, the active material, the conductive agent, and the binder are mixed to obtain a mixture. Next, this mixture is formed into pellets. Next, these pellets are placed on a current collector to obtain a positive electrode.

[0079] The negative electrode can be produced, for example, by the following method. First, a negative electrode active material, a conductive agent, and a binder are suspended in a solvent to prepare a slurry. This slurry is applied to one or both sides of a current collector. Next, the applied slurry is dried to obtain a laminate of a negative electrode active material-containing layer and a current collector. Then, this laminate is pressed. In this manner, the negative electrode is produced. Alternatively, the negative electrode may be produced by the following method. First, the negative electrode active material, the conductive agent, and the binder are mixed to obtain a mixture. Next, this mixture is formed into pellets. Next, these pellets are placed on a current collector to obtain a negative electrode.

[0080] An electrode group 1 is produced by disposing a separator 5 between a positive electrode 3 and a negative electrode 4. A positive electrode terminal 14 is electrically connected to the positive electrode 3 of the electrode group 1, and a negative electrode terminal 13 is electrically connected to the negative electrode 4 of the electrode group 1.

[0081] The electrode group 1 having the positive and negative electrode terminals 13, 14 is housed in a bag-shaped exterior member 12 made of a laminate film, and then the other end 21b, excluding the first end 21a, is sealed by heat sealing. Next, a nonaqueous electrolyte is injected into the bag-shaped exterior member 12 from the first end 21a, and the first end 21a is sealed by heat sealing. The heat sealing may be performed under reduced pressure. This results in a secondary battery 30 that has been subjected to a first seal.

[0082] Next, the secondary battery 30 after the first sealing is subjected to an initial charge / discharge cycle at room temperature (e.g., 25°C), followed by aging at a temperature above room temperature. Through the initial charge / discharge cycle and aging, a reaction occurs between the sultone compound and the positive electrode active material, resulting in the incorporation of sulfur atoms into the positive electrode active material-containing layer. Specifically, a decomposition product of the nonaqueous electrolyte containing the sultone compound may be formed on the surface of the positive electrode active material contained in the positive electrode active material-containing layer. As a result, a layered sulfur-containing phase may be formed on the surface of the positive electrode active material. In this way, a positive electrode active material-containing layer 3b containing sulfur atoms can be obtained. At this time, sulfur atoms may also be incorporated into the negative electrode active material-containing layer. As a result, a negative electrode active material-containing layer 4b containing sulfur atoms can be obtained.

[0083] After aging, the temperature of the secondary battery 30 is returned to room temperature, and then in an argon atmosphere, the bag-shaped exterior member 12 is cut along the unsealed cutting line 22 inside the first end 21a and opened to release the gas inside the bag-shaped exterior member 12 to the outside. The portion cut from the bag-shaped exterior member 12 along the cutting line 22 is indicated by reference numeral 23.

[0084] After bag-shaped exterior member 12 is cut and opened, a sultone compound or a solution containing a sultone compound may be supplied into bag-shaped exterior member 12. The sultone compound contained in the non-aqueous electrolyte injected into bag-shaped exterior member 12 before the first sealing is consumed through the initial charge / discharge and aging, but the concentration of the sultone compound in the non-aqueous electrolyte can be adjusted thereafter by adding the sultone compound or a solution containing a sultone compound.

[0085] The edges 24 along the cut lines 22 are then sealed under reduced pressure (eg, -90 kPa).

[0086] By adjusting the manufacturing conditions of the manufacturing method described above, the mass of sulfur atoms per unit volume of the positive electrode active material-containing layer and the concentration of the sultone compound in the non-aqueous electrolyte can be set within the target range, thereby obtaining the secondary battery 31 of the embodiment.

[0087] The manufacturing conditions are described in detail below.

[0088] The positive and negative electrodes used in the preparation of the electrode assembly are preferably dried beforehand before the preparation of the electrode assembly. The higher the temperature and the longer the drying time, the less moisture remains in the electrodes. From the viewpoint of reducing the moisture in the electrodes, drying is preferably performed under reduced pressure. For example, vacuum drying at 120°C for 24 hours is preferred.

[0089] When the positive electrode and the negative electrode are produced by applying the slurry to one or both surfaces of the current collector and then drying the coating film of the applied slurry, it is preferable to further perform the above-mentioned drying after the coating film drying step.

[0090] Drying the positive and negative electrodes used to prepare the electrode assembly reduces the amount of moisture introduced into the secondary battery. Moisture introduced into a secondary battery can electrolyze water itself, generating gas, and also facilitate side reactions at the negative electrode. Therefore, during the battery reaction, lithium ions released from the positive electrode are consumed in side reactions at the negative electrode, making it difficult for the lithium ions to be absorbed into the negative electrode. This can result in a deviation in SOC or a shift in the positive electrode potential toward a higher potential. If the positive electrode potential becomes too high and deviates from the potential range in which the nonaqueous electrolyte can stably exist, the nonaqueous electrolyte is more likely to decompose at the positive electrode, resulting in gas generation. Furthermore, moisture introduced into a secondary battery can cause the nonaqueous electrolyte to react with water to generate hydrofluoric acid, which can lead to electrode degradation.

[0091] Therefore, if the positive electrode and negative electrode used to prepare the electrode group are dry, side reactions can be suppressed, and as a result, gas generation in the secondary battery of the embodiment can be suppressed, which is preferable.

[0092] 7, when the first sealed secondary battery 30 is subjected to initial charge / discharge and aging, gas is generated in the first sealed secondary battery 30. The gas generating reaction may be, for example, a reaction in which water brought into the secondary battery 30 decomposes.

[0093] As described with reference to Fig. 7, the gas generated during the initial charge / discharge and aging is released to the outside after aging. Therefore, by allowing the gas generating reaction to proceed during aging, the amount of substances that cause gas generation remaining in the secondary battery 31 of the embodiment obtained after aging can be reduced. Therefore, gas generation in the secondary battery 31 of the embodiment can be suppressed.

[0094] Lowering the aging temperature or shortening the aging time can suppress decomposition and consumption of the sultone compound during aging, thereby increasing the amount of the sultone compound remaining in the nonaqueous electrolyte of the secondary battery 31 of this embodiment. Increasing the aging temperature or lengthening the aging time tends to facilitate the reaction between the sultone compound and the positive electrode active material and the gas generation reaction during aging.

[0095] To allow the sultone compound to remain in the nonaqueous electrolyte contained in the secondary battery 31 of this embodiment, aging can be performed, for example, on a secondary battery having an SOC of 50% to 80% at a low temperature of 30°C to 60°C for a short period of time, such as 3 hours to 12 hours. Aging is preferably performed on a secondary battery having an SOC of 50% to 70%. The aging temperature can be, for example, 45°C. The aging time can be, for example, 7 hours.

[0096] Mass M (g / m) of sulfur atoms per unit volume of the positive electrode active material-containing layer 3 ), and the concentration E (mol / L) of the sultone compound in the non-aqueous electrolyte is 1 × 10 -6 ≦E / M≦9×10 -4 A secondary battery that satisfies the above condition can be obtained, for example, by carrying out the aging process as described above. It is more preferable to carry out the aging process as described above after adjusting the composition of the non-aqueous electrolyte.

[0097] Hereinafter, the positive electrode, negative electrode, and non-aqueous electrolyte will be described. The separator and the exterior member that the secondary battery of the embodiment can include in addition to these members will also be described below.

[0098] 1) Positive electrode The positive electrode can include a positive electrode current collector and a positive electrode active material-containing layer. The positive electrode active material-containing layer can be formed on one or both sides of the positive electrode current collector. The positive electrode active material-containing layer can include a positive electrode active material, a sulfur atom, and optionally a conductive agent and a binder. The positive electrode active material-containing layer can include the positive electrode sulfur-containing phase described above. The sulfur atom can be included in the positive electrode sulfur-containing phase. The positive electrode sulfur-containing phase may be present on at least a part of the positive electrode surface, or may cover at least a part of the surface of the positive electrode active material particles. The positive electrode sulfur-containing phase may be in the form of a film or a layer.

[0099] E and M are 1×10 -6 ≦E / M≦9×10 -4 In the secondary battery of the embodiment that satisfies, the mass M of sulfur atoms per unit volume of the positive electrode active material-containing layer is, for example, 389 g / m 3 or more and 3000 g / m 3 or less.

[0100] As the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain a single compound as the positive electrode active material, or may contain a combination of two or more compounds. Examples of the oxide and sulfide include compounds into which Li or Li ions can be inserted and desorbed.

[0101] Such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li x Mn2O4 or Li x MnO2; 0 <x ≦ 1), lithium nickel composite oxide (for example, Li x NiO2; 0 <x ≦ 1), lithium cobalt composite oxide (for example, Li xCoO2; 0 < x ≤ 1), lithium nickel cobalt composite oxide (e.g., Li x Ni 1-y Co y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn y Co 1-y O2; 0 < x ≤ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≤ 1, Li x Fe 1-y Mn y PO4; 0 < x ≤ 1, 0 < y ≤ 1, Li x CoPO4; 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), lithium nickel cobalt-containing oxide (LiNi x Co y M z O2; x + y + z = 1, x ≥ 0.8, M consists of Mn and Al), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) are included.

[0102] Among the above, examples of more preferred compounds as the positive electrode active material include lithium manganese composite oxide having a spinel structure, lithium nickel cobalt manganese composite oxide, lithium phosphate having an olivine structure, lithium nickel cobalt-containing oxide, lithium manganese nickel composite oxide having a spinel structure, lithium nickel cobalt manganese composite oxide, and lithium cobalt composite oxide. More specific examples include lithium manganese composite oxide having a spinel structure (e.g., Li x Mn2O4; 0 < x ≤ 1, Li x Mn 2-y Ni yO4; 0 < x ≤ 1, 0 < y < 2), lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1), lithium phosphate having an olivine structure (e.g., Li x FePO4; 0 < x ≤ 1, Li x Fe 1-y Mn y PO4; 0 < x ≤ 1, 0 < y ≤ 1, Li x CoPO4; 0 < x ≤ 1), lithium nickel cobalt-containing oxide (LiNi x Co y M z O2; x + y + z = 1, x ≥ 0.8, M consists of Mn and Al), lithium manganese nickel composite oxide having a spinel structure (e.g., Li x Mn 2-y Ni y O4; 0 < x ≤ 1, 0 < y < 2), lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, y + z < 1) and lithium cobalt composite oxide (e.g., Li x CoO2; 0 < x ≤ 1) can be mentioned. When these compounds are used as the positive electrode active material, the battery voltage can be increased. In the lithium nickel cobalt manganese composite oxide represented by Li x Ni 1-y-z Co y Mn z O2, those in which y and z satisfy 0 < y + z ≤ 0.2 can achieve a high energy density.

[0103] The positive electrode active material can be in the form of particles. The primary particle size of the positive electrode active material is preferably 100 nm or more and 1 μm or less. A positive electrode active material with a primary particle size of 100 nm or more is easy to handle in industrial production. A positive electrode active material with a primary particle size of 1 μm or less can allow the solid-state diffusion of lithium ions to proceed smoothly.

[0104] The specific surface area of ​​the positive electrode active material is 0.1 m 2 / g or more 10m 2 / g or less is preferable. 2 A positive electrode active material with a specific surface area of ​​10m / g or more can secure sufficient sites for absorbing and releasing Li ions. 2 A positive electrode active material having a specific surface area of ​​0.15g / g or less is easy to handle in industrial production and can ensure good charge-discharge cycle performance.

[0105] The binder is blended to fill gaps between the dispersed positive electrode active material and to bind the positive electrode active material and the positive electrode current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0106] The conductive agent is blended to improve current collection performance and reduce contact resistance between the positive electrode active material and the positive electrode current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as the conductive agent, or two or more may be used in combination as the conductive agent. The conductive agent may also be omitted.

[0107] When the conductive agent is omitted, the positive electrode active material and the binder are preferably blended in the positive electrode active material-containing layer in proportions of 80% by mass or more and 98% by mass or less and 2% by mass or more and 20% by mass or less, respectively, so that the total is 100% by mass.

[0108] By using a binder amount of 2% by mass or more, sufficient electrode strength can be obtained. Furthermore, the binder can function as an insulator. Therefore, by using a binder amount of 20% by mass or less, the amount of insulator contained in the electrode is reduced, thereby reducing internal resistance.

[0109] When a conductive agent is added, the positive electrode active material, binder, and conductive agent are preferably blended in proportions of 77% by mass or more and 95% by mass or less, 2% by mass or more and 20% by mass or less, and 3% by mass or more and 15% by mass or less, respectively, so that the total is 100% by mass.

[0110] By setting the amount of conductive agent to 3% by mass or more, the above-mentioned effects can be achieved. Furthermore, by setting the amount of conductive agent to 15% by mass or less, the proportion of conductive agent in contact with the electrolyte can be reduced. This low proportion can reduce decomposition of the electrolyte during high-temperature storage.

[0111] The positive electrode current collector is preferably an aluminum foil or an aluminum alloy foil containing one or more elements selected from Mg, Ti, Zn, Ni, Cr, Mn, Fe, Cu, and Si.

[0112] The thickness of the aluminum foil or aluminum alloy foil is preferably 5 μm or more and 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% by mass or more. The content of transition metals such as iron, copper, nickel, and chromium contained in the aluminum foil or aluminum alloy foil is preferably 1% by mass or less.

[0113] The positive electrode current collector may also include a portion on the surface of which the positive electrode active material-containing layer is not formed, and this portion can function as a positive electrode current collecting tab.

[0114] 2) Negative electrode The negative electrode may include a current collector and a negative electrode active material-containing layer. The negative electrode active material-containing layer may be formed on one or both sides of the current collector. The negative electrode active material-containing layer may include a negative electrode active material, and optionally a conductive agent and a binder. The negative electrode active material-containing layer preferably contains sulfur atoms. The negative electrode active material-containing layer may include the negative electrode sulfur-containing phase described above. The sulfur atoms may be contained in the negative electrode sulfur-containing phase. The negative electrode sulfur-containing phase may be present on at least a portion of the negative electrode surface, or may cover at least a portion of the surface of the negative electrode active material particles. The negative electrode sulfur-containing phase may be in the form of a film or a layer.

[0115] The negative electrode active material is not particularly limited as long as it can absorb and release lithium or lithium ions. One or more types of negative electrode active material can be used. Examples of negative electrode active materials include titanium-containing oxides, niobium-containing oxides, and carbon materials.

[0116] Examples of the titanium-containing oxide include lithium titanium-containing oxide and titanium oxide. Examples of the niobium-containing oxide include niobium titanium oxide, niobium tungsten-containing oxide and niobium titanium molybdenum-containing oxide.

[0117] Examples of titanium-containing oxides include lithium titanate (e.g., Li) with a ramsdellite structure. 2+y Ti3O7, 0≦y≦3), lithium titanates with spinel structure (e.g., Li 4+x Ti5O 12 , 0≦x≦3), monoclinic titanium dioxide (TiO2), anatase titanium dioxide, rutile titanium dioxide, hollandite titanium composite oxide, and orthorhombic titanium composite oxide. The lithium ion absorption / desorption potential of titanium-containing oxides is 0.4V (vs. Li / Li + )That's all.

[0118] As an example of the above orthorhombic titanium-containing composite oxide, Li 2+a M I 2-b Ti 6-c M IId O 14+σ In this case, M I is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb and K. II is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦a≦6, 0≦b<2, 0≦c<6, 0≦d<6, and -0.5≦σ≦0.5. Specific examples of orthorhombic titanium-containing composite oxides include Li 2+a Na2Ti6O 14 (0≦a≦6).

[0119] Examples of the niobium-containing oxide include niobium oxide, niobium titanium oxide, niobium tungsten-containing oxide, and niobium titanium molybdenum-containing oxide.

[0120] An example of niobium titanium oxide is monoclinic niobium titanium oxide. An example of monoclinic niobium titanium oxide is Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3. Specific examples of monoclinic niobium titanium oxide include Li x Examples include Nb2TiO7 (0≦x≦5).

[0121] Another example of monoclinic niobium titanium oxide is Li x Ti 1-y M3 y+z Nb 2-z O 7-δHere, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3.

[0122] Examples of carbon materials include graphite, hard carbon, etc. When a carbon material is used for the negative electrode, a copper foil is used for the negative electrode current collector.

[0123] Among the negative electrode active materials, monoclinic niobium titanium oxide has a lithium ion absorption / desorption potential of 1.0 V (vs. Li / Li + ), which allows the decomposition reaction of the sultone compound at the negative electrode to occur appropriately. The lithium ion absorption / desorption potential of lithium titanate is 1.4 V (vs. Li / Li + ), and the lithium ion absorption / desorption potential of the carbon material is around 0 V (vs. Li / Li + ) near

[0124] The negative electrode active material can be in particulate form.

[0125] A conductive agent can be blended to improve current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon nanotubes, carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as the conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, the surfaces of the active material particles may be coated with carbon or an electronically conductive inorganic material.

[0126] The binder is blended to fill gaps between the dispersed active materials and to bind the active materials and the current collector. Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing rubber, styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and CMC salts. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0127] The negative electrode active material and binder in the negative electrode active material-containing layer are preferably blended in proportions of 68% by mass to 98% by mass and 2% by mass to 32% by mass, respectively, so that the total is 100% by mass. By using a binder amount of 2% by mass or more, sufficient binding strength between the negative electrode active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, a binder amount of 32% by mass or less is preferred for achieving high capacity.

[0128] When a conductive agent is blended into the negative electrode active material-containing layer, the blending ratios of the negative electrode active material, conductive agent, and binder in the negative electrode active material-containing layer are, for example, preferably 68% by mass to 96% by mass, 2% by mass to 30% by mass, and 2% by mass to 30% by mass, respectively, so that the total is 100% by mass. By adjusting the amount of conductive agent to 2% by mass or more, the current collection performance of the negative electrode active material-containing layer can be improved. Furthermore, by adjusting the amount of binder to 2% by mass or more, sufficient binding between the negative electrode active material-containing layer and the current collector can be achieved, and excellent cycle performance can be expected. On the other hand, it is preferable to adjust the amount of conductive agent and binder to 30% by mass or less, respectively, in order to achieve high capacity.

[0129] The current collector is made of a material that is electrochemically stable at the potential at which lithium (Li) is inserted and extracted from the negative electrode active material.+ ) or more is used, examples of the current collector include copper, nickel, stainless steel, aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the current collector is preferably 5 μm or more and 20 μm or less. A current collector with such a thickness can achieve a balance between the strength and weight of the electrode.

[0130] The current collector may also include a portion on the surface of which the negative electrode active material-containing layer is not formed, and this portion can function as a negative electrode current collecting tab.

[0131] 3) Nonaqueous electrolyte The nonaqueous electrolyte may be, for example, a liquid nonaqueous electrolyte or a gel nonaqueous electrolyte. The liquid nonaqueous electrolyte includes an electrolyte salt, a sultone compound, and a cyclic carbonate. The liquid nonaqueous electrolyte may further include an ester compound represented by chemical formula (2), in which R is a first hydrocarbon group and R' is a second hydrocarbon group containing 3 or more carbon atoms.

[0132] [ka]

[0133] The liquid nonaqueous electrolyte contains a solvent capable of dissolving the electrolyte salt. The solvent may be an organic solvent.

[0134] The sultone compound, the cyclic carbonate, and the ester compound represented by chemical formula (2) may each function as a solvent. The sultone compound may function as an electrolyte salt, or may serve as both an electrolyte salt and a solvent. The liquid nonaqueous electrolyte may further contain a solvent other than the sultone compound, the cyclic carbonate, and the ester compound represented by chemical formula (2).

[0135] E and M are 1×10 -6 ≦E / M≦9×10 -4In a secondary battery according to an embodiment that satisfies the above, the concentration E of the sultone compound in the non-aqueous electrolyte may be, for example, 0.001 mol / L or more and 0.082 mol / L or less.

[0136] In the composition of the non-aqueous electrolyte contained in the secondary battery of the embodiment, the concentration of the sultone compound may have changed from the composition (initial composition) of the non-aqueous electrolyte before the secondary battery is manufactured. This is because, for example, after the secondary battery is assembled in which the non-aqueous electrolyte is injected and the first sealing is performed, the sultone compound may be consumed during initial charge / discharge, aging, etc.

[0137] In the secondary battery of the embodiment, the concentration E of the sultone compound in the non-aqueous electrolyte is 1×10 -6 ≦E / M≦9×10 -4 In order to satisfy the above, for example, the concentration (initial concentration) of the sultone compound in the non-aqueous electrolyte before the secondary battery is manufactured can be set in the range of 1.0 mass % to 5.0 mass %.

[0138] The higher the initial concentration of the sultone compound, the more likely the sultone compound will remain in the non-aqueous electrolyte in the secondary battery of the embodiment.The lower the initial concentration of the sultone compound, the less decomposition products will be generated by the reaction of the sultone compound with the electrode active material, and the more likely an increase in electrode resistance will be suppressed.

[0139] After the initial charge / discharge and aging, the concentration of the sultone compound in the non-aqueous electrolyte of the secondary battery of the embodiment may be adjusted to fall within the above range by adding a sultone compound or a solution containing a sultone compound to the non-aqueous electrolyte.

[0140] Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO), lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoroarsenic (LiAsF), lithium trifluoromethanesulfonate (LiCFSO), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, LiN(CFSO)), and lithium bis(fluorosulfonyl)imide (LiFSI, LiN(FSO)), and mixtures thereof. The electrolyte salt is preferably one that is resistant to oxidation even at high potentials, with LiPF being most preferred. The concentration of the electrolyte salt in the nonaqueous electrolyte is preferably 0.5 mol / L or more and 2.5 mol / L or less.

[0141] Cyclic carbonates are preferred because they have a high dielectric constant and therefore make it easier for the electrolyte salt to dissociate in the non-aqueous electrolyte.

[0142] Examples of cyclic carbonates include propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC). The type of cyclic carbonate can be one or more. These cyclic carbonates have 3 to 5 carbon atoms. Cyclic carbonates having 3 to 5 carbon atoms are detected within a retention time range of 15 to 18 minutes in a total ion chromatogram obtained by gas chromatography-mass spectrometry. That is, the area within a retention time range of 15 to 18 minutes in a total ion chromatogram obtained by gas chromatography-mass spectrometry of a non-aqueous electrolyte can be an indicator of the content of cyclic carbonates having 3 to 5 carbon atoms in the non-aqueous electrolyte.

[0143] Examples of organic solvents other than the sultone compound, cyclic carbonate, and ester compound represented by chemical formula (2) include chain carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC); cyclic ethers such as tetrahydrofuran (THF), 2-methyl tetrahydrofuran (2MeTHF), and dioxolane (DOX); chain ethers such as dimethoxyethane (DME) and diethoxyethane (DEE); γ-butyrolactone (GBL), acetonitrile (AN), ethyl propionate (EP), and sulfolane (SL). The nonaqueous electrolyte may contain one or more of these organic solvents.

[0144] The gel-like non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte with a polymeric material, such as polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), or a mixture thereof.

[0145] Alternatively, the nonaqueous electrolyte may include, in addition to a liquid nonaqueous electrolyte and a gel nonaqueous electrolyte, a room temperature molten salt (ionic melt) containing lithium ions, a polymer solid electrolyte, an inorganic solid electrolyte, and the like. 4) Separator The separator is formed, for example, from a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin nonwoven fabric. From the viewpoint of safety, it is preferable to use a porous film formed from polyethylene or polypropylene. This is because these porous films melt at a certain temperature and can interrupt current.

[0146] An electrolyte layer containing an inorganic solid electrolyte may be used as the separator. Examples of the lithium ion conductive inorganic solid electrolyte include a lithium ion conductive oxide-based solid electrolyte and a lithium ion conductive sulfide-based solid electrolyte. Examples of the lithium ion conductive oxide-based solid electrolyte include a NASICON-type structure lithium phosphate solid electrolyte and an amorphous LIPON (Li 2.9 PO 3.3 N 0.46 ), or garnet-type structure LLZ (Li7La3Zr2O 12 ) can be mentioned.

[0147] 5) Exterior materials The exterior member may be, for example, a container made of a laminate film or a metal container.

[0148] The thickness of the laminate film is, for example, 0.5 mm or less, preferably 0.2 mm or less.

[0149] The laminate film is a multilayer film containing multiple resin layers and metal layers interposed between the resin layers. The resin layers include polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layers are preferably made of aluminum foil or aluminum alloy foil to reduce weight. The laminate film can be molded into the shape of the exterior component by sealing it by heat fusion.

[0150] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0151] The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. If the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of these metals is preferably 100 mass ppm or less.

[0152] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior member can be appropriately selected depending on the battery dimensions and the intended use of the battery.

[0153] <Measurement method> (Gas Chromatography Mass Spectrometry) A method for obtaining a total ion chromatogram of a non-aqueous electrolyte by gas chromatography mass spectrometry (GC-MS), a method for calculating the area within a specific retention time range in the total ion chromatogram, and a method for measuring the concentration (mol / L) of a sultone compound in a non-aqueous electrolyte will be described below.

[0154] (Preparation of GC-MS measurement sample) In a glove box, the exterior packaging of the secondary battery is opened and the nonaqueous electrolyte is sampled. For example, if the exterior packaging is a bag-shaped packaging made of laminate film, an end is cut off and the nonaqueous electrolyte is sampled from the opening. The nonaqueous electrolyte is diluted 20 times with acetonitrile to prepare a measurement sample.

[0155] (Acquisition of total ion chromatogram) The measurement sample is subjected to gas chromatography mass spectrometry under the instrument conditions shown in Table 1 below.

[0156] [Table 1]

[0157] The time elapsed after the sample was injected into the gas chromatography mass spectrometer was taken as the retention time. The total ion chromatogram was obtained by plotting the detection intensity on the vertical axis and the retention time on the horizontal axis.

[0158] (Calculation method for area within a specific retention time range) First, a baseline is drawn in the background of the obtained total ion chromatogram. The area below the baseline is subtracted from the total ion chromatogram. The chart obtained by the subtraction process is integrated over a predetermined retention time range. The integral value thus obtained is used as the area within the predetermined retention time range of the total ion chromatogram. For example, when calculating area A, the integral value obtained by integrating the chart obtained by the subtraction process over the integration range of 15 minutes to 18 minutes is used as area A within the retention time range of 15 minutes to 18 minutes.

[0159] (Calculation of the concentration of sultone compound in non-aqueous electrolyte) The concentration (mol / L) of the sultone compound in the non-aqueous electrolyte is measured as follows.

[0160] First, a standard sample is diluted with acetonitrile for HPLC (manufactured by Merck) to prepare a standard sample solution with a known concentration. When measuring the concentration of a sultone compound, 1,3-propane sultone (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) can be used as the standard sample. A calibration curve is created by subjecting the standard sample solution to gas chromatography-mass spectrometry. Next, gas chromatography-mass spectrometry is performed on the measurement sample, and the obtained data is plotted on the calibration curve to determine the concentration of the sultone compound in the non-aqueous electrolyte.

[0161] (ICP optical emission spectrometry) The type of ester compound contained in the non-aqueous electrolyte, the concentration (mass%) of the ester compound in the non-aqueous electrolyte, and the mass (g / m) of sulfur atoms per unit volume of the positive electrode active material-containing layer 3 ) is measured by inductively coupled plasma (ICP) optical emission spectrometry.

[0162] (Preparation of sample for ICP optical emission spectrometry) The exterior packaging of a secondary battery with a 50% SOC (State of Charge) is opened and the electrode group is removed. The jig (such as tape) holding the electrode group together is removed, and if the outermost layer is a separator, the separator is peeled back to remove the first layer of electrode (e.g., negative electrode). The separator is then peeled back to remove the first layer of electrode (e.g., positive electrode). The process of peeling back the separator and removing the electrodes is repeated until all positive and negative electrodes that make up the electrode group are removed. The removed electrodes and separator are then placed in a centrifuge to extract the non-aqueous electrolyte and separate the electrodes from the separator.

[0163] (ICP optical emission analysis of non-aqueous electrolytes) The non-aqueous electrolyte separated by the centrifuge is analyzed by ICP to determine the type of ester compound contained in the non-aqueous electrolyte and the concentration (mass %) of the ester compound in the non-aqueous electrolyte.

[0164] (ICP optical emission spectroscopy of electrodes) The electrodes separated by the centrifuge are washed with methyl ethyl carbonate (MEC) and dried in vacuum. The electrode to be measured (e.g., the positive electrode) is placed in a fixed area (2 × 2 cm 2 The thickness of the active material-containing layer of the punched electrode was measured with a film thickness meter, and the area (2 × 2 cm) was 2 ) to obtain the volume of the active material-containing layer in the punched electrode. A certain amount of pure water (10 cc) is added to the punched electrode and ultrasonic irradiation is performed for 30 minutes or more. The extracted solution is analyzed by ICP to measure the mass of sulfur atoms in the extract, thereby obtaining the mass of sulfur atoms per unit volume of the active material-containing layer.

[0165] According to the first embodiment described above, a secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte is provided. The positive electrode includes a positive electrode active material-containing layer containing sulfur atoms. The non-aqueous electrolyte includes a sultone compound and a cyclic carbonate. In gas chromatography mass spectrometry of the non-aqueous electrolyte, in a total ion chromatogram in which the vertical axis represents detection intensity and the horizontal axis represents retention time, the ratio B / A of the area B within the retention time range of 13.5 to 14.5 minutes to the area A within the retention time range of 15 to 18 minutes is 0 to 0.000944. The following formula (1) is satisfied:

[0166] Formula (1): 1×10 -6 ≦E / M≦9×10 -4 In formula (1), M is the mass of sulfur atoms per unit volume of the positive electrode active material-containing layer (g / m 3 ) where E is the concentration (mol / L) of the sultone compound in the non-aqueous electrolyte. Therefore, a secondary battery with long life performance at high temperatures can be realized.

[0167] (Second embodiment) The battery pack according to the second embodiment can include one or more secondary batteries (single cells) according to the embodiment. A plurality of secondary batteries can be electrically connected in series, in parallel, or in a combination of series and parallel to form a battery assembly. The battery pack according to the embodiment may include a plurality of battery assemblies.

[0168] The battery pack according to the embodiment may further include a protection circuit. The protection circuit has a function of controlling the charging and discharging of the secondary battery. Alternatively, a circuit included in a device (e.g., electronic device, automobile, etc.) that uses the battery pack as a power source may also be used as the protection circuit for the battery pack.

[0169] The battery pack according to the embodiment may further include external terminals for current flow. The external terminals for current flow are for outputting current from the secondary battery to the outside and inputting current to the secondary battery. In other words, when the battery pack is used as a power source, current is supplied to the outside through the external terminals for current flow. When charging the battery pack, charging current (including regenerative energy from the power of a vehicle such as an automobile) is supplied to the battery pack through the external terminals for current flow.

[0170] Figures 8 and 9 show an example of a battery pack 50. This battery pack 50 includes a plurality of flat batteries having the structure shown in Figure 8. Figure 8 is an exploded perspective view of the battery pack 50, and Figure 9 is a block diagram showing the electrical circuit of the battery pack 50 of Figure 8.

[0171] A plurality of cells 51 are stacked so that the negative electrode terminals 13 and positive electrode terminals 14 extending outward are aligned in the same direction, and are fastened together with adhesive tape 52 to form a battery pack 53. These cells 51 are electrically connected in series as shown in FIG.

[0172] The printed wiring board 54 is disposed opposite the side surface of the battery cell 51 from which the negative electrode terminal 13 and the positive electrode terminal 14 extend. As shown in Fig. 9, the printed wiring board 54 is mounted with a thermistor 55, a protective circuit 56, and an external terminal 57 for supplying electricity to an external device as an external terminal for supplying electricity. An insulating plate (not shown) is attached to the surface of the printed wiring board 54 facing the battery pack 53 to prevent unnecessary connection with the wiring of the battery pack 53.

[0173] The positive electrode lead 58 is connected to the positive electrode terminal 14 located on the bottom layer of the battery pack 53, and its tip is inserted into and electrically connected to a positive electrode connector 59 on the printed wiring board 54. The negative electrode lead 60 is connected to the negative electrode terminal 13 located on the top layer of the battery pack 53, and its tip is inserted into and electrically connected to a negative electrode connector 61 on the printed wiring board 54. These connectors 59, 61 are connected to the protection circuit 56 through wires 62, 63 formed on the printed wiring board 54.

[0174] The thermistor 55 detects the temperature of the cell 51 and transmits the detection signal to the protection circuit 56. The protection circuit 56 can interrupt the positive wiring 64a and the negative wiring 64b between the protection circuit 56 and a terminal 57 for supplying current to an external device under predetermined conditions. The predetermined condition is, for example, when the temperature detected by the thermistor 55 exceeds a predetermined temperature. Another predetermined condition is when an overcharge, overdischarge, overcurrent, or the like of a cell 51 is detected. This overcharge detection is performed for each cell 51 or for all cells 51. When detecting an individual cell 51, the battery voltage or the positive or negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each cell 51. In the case of FIGS. 8 and 9, voltage detection wiring 65 is connected to each cell 51, and a detection signal is transmitted to the protection circuit 56 through these wirings 65.

[0175] Protective sheets 66 made of rubber or resin are disposed on the three sides of the battery pack 53, excluding the sides from which the positive electrode terminal 14 and the negative electrode terminal 13 protrude.

[0176] The battery pack 53 is housed in a storage container 67 together with the protective sheets 66 and the printed wiring board 54. That is, the protective sheets 66 are arranged on both inner surfaces along the long sides and the inner surface along the short sides of the storage container 67, and the printed wiring board 54 is arranged on the inner surface on the opposite side along the short sides. The battery pack 53 is located in a space surrounded by the protective sheets 66 and the printed wiring board 54. A lid 68 is attached to the top surface of the storage container 67.

[0177] Heat-shrinkable tape may be used to secure the battery pack 53 instead of the adhesive tape 52. In this case, protective sheets are placed on both sides of the battery pack, and the heat-shrinkable tape is wrapped around the battery pack, and then the heat-shrinkable tape is thermally shrunk to bind the battery pack.

[0178] 8 and 9 show a configuration in which the cells 51 are connected in series, but they may be connected in parallel to increase battery capacity. Alternatively, a combination of series and parallel connections may be used. The assembled battery pack may also be connected in series or parallel.

[0179] 8 and 9 include one battery pack, the battery pack according to the embodiment may include multiple battery packs. The multiple battery packs are electrically connected in series, in parallel, or in a combination of series and parallel connections.

[0180] The battery pack configuration may be modified as appropriate depending on the intended use. The battery pack according to the embodiment is suitable for use in applications requiring excellent cycle performance when drawing a large current. Specifically, it is used as a power source for digital cameras, or as a vehicle battery for, for example, two- to four-wheeled hybrid electric vehicles, two- to four-wheeled electric vehicles, power-assisted bicycles, or railway vehicles (e.g., electric trains), or as a stationary battery. In particular, it is suitable for use as an on-board battery mounted in a vehicle.

[0181] The battery pack of the second embodiment described above includes the secondary battery of the embodiment, and therefore can improve the life performance at high temperatures.

[0182] (Third embodiment) A vehicle of the third embodiment includes one or more secondary batteries of the embodiment, or includes a battery pack of the embodiment.

[0183] In a vehicle such as an automobile equipped with a battery pack according to the third embodiment, the battery pack may, for example, recover regenerative energy from the vehicle's power. The vehicle may also include a mechanism for converting the vehicle's kinetic energy into regenerative energy.

[0184] FIG. 10 shows an example of a car equipped with an example battery pack according to the embodiment.

[0185] An automobile 71 shown in Fig. 10 is equipped with a battery pack 72 according to an embodiment in an engine compartment at the front of the automobile. The location of the battery pack in an automobile is not limited to the engine compartment. For example, the battery pack can also be installed at the rear of the automobile or under the seat.

[0186] Fig. 11 is a diagram illustrating a schematic configuration of an example of a vehicle according to the embodiment. The vehicle 300 illustrated in Fig. 11 is an electric vehicle.

[0187] The vehicle 300 shown in FIG. 11 includes a vehicle power supply 301, a vehicle ECU (ECU: Electric Control Unit) 380 which is a higher-level control means for the vehicle power supply 301, an external terminal 370, an inverter 340, and a drive motor 345.

[0188] Vehicle 300 has vehicle power supply 301 mounted, for example, in the engine compartment, the rear of the vehicle body, or under a seat. However, in Fig. 11, the location where the secondary battery is mounted in vehicle 300 is shown only schematically.

[0189] The vehicle power supply 301 includes a plurality of (for example, three) battery packs 312 a , 312 b , and 312 c , a battery management unit (BMU) 311 , and a communication bus 310 .

[0190] The three battery packs 312a, 312b, and 312c are electrically connected in series. Battery pack 312a includes an assembled battery 314a and an assembled battery monitoring device (VTM: Voltage Temperature Monitoring) 313a. Battery pack 312b includes an assembled battery 314b and an assembled battery monitoring device 313b. Battery pack 312c includes an assembled battery 314c and an assembled battery monitoring device 313c. Battery packs 312a, 312b, and 312c can each be removed independently and replaced with another battery pack.

[0191] Each of the assembled batteries 314a to 314c includes a plurality of secondary batteries connected in series. Each secondary battery is a secondary battery according to the embodiment. Each of the assembled batteries 314a to 314c is charged and discharged via a positive terminal 316 and a negative terminal 317.

[0192] In order to collect information related to the maintenance of the vehicle power supply 301, the battery management device 311 communicates with the battery pack monitoring devices 313a to 313c and collects information such as the voltage and temperature of the secondary batteries of the battery packs 314a to 314c included in the vehicle power supply 301.

[0193] A communication bus 310 is connected between the battery management unit 311 and the assembled battery monitoring units 313a to 313c. The communication bus 310 is configured so that one set of communication lines is shared by multiple nodes (a battery management unit and one or more assembled battery monitoring units). The communication bus 310 is configured based on, for example, the CAN (Control Area Network) standard.

[0194] The assembled battery monitoring devices 313a to 313c measure the voltage and temperature of each of the secondary batteries constituting the assembled batteries 314a to 314c based on commands communicated from the battery management device 311. However, the temperature can be measured at only a few points per assembled battery, and it is not necessary to measure the temperatures of all the secondary batteries.

[0195] Vehicle power supply 301 may also have an electromagnetic contactor (for example, switch device 333 shown in FIG. 11) for connecting and disconnecting the positive and negative terminals. Switch device 333 includes a pre-charge switch (not shown) that is turned on when battery packs 314a to 314c are being charged, and a main switch (not shown) that is turned on when battery output is being supplied to a load. The pre-charge switch and main switch include relay circuits (not shown) that are turned on and off by signals supplied to coils located near the switch elements.

[0196] Inverter 340 converts the input DC voltage into a three-phase AC high voltage for driving the motor. The output voltage of inverter 340 is controlled based on a control signal from battery management unit 311 or vehicle ECU 380, which controls the overall operation of the vehicle. The three-phase output terminals of inverter 340 are connected to the three-phase input terminals of drive motor 345, respectively.

[0197] The drive motor 345 rotates using the power supplied from the inverter 340, and transmits the rotation to the axles and drive wheels W via, for example, a differential gear unit.

[0198] Although not shown, vehicle 300 is also equipped with a regenerative braking mechanism that rotates drive motor 345 when braking vehicle 300, and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to inverter 340 and converted into direct current. The direct current is input to vehicle power supply 301.

[0199] One terminal of a connection line L1 is connected to the negative terminal 317 of the vehicle power supply 301 via a current detection unit (not shown) in the battery management device 311. The other terminal of the connection line L1 is connected to the negative input terminal of the inverter 340.

[0200] One terminal of a connection line L2 is connected to the positive terminal 316 of the vehicle power supply 301 via a switch device 333. The other terminal of the connection line L2 is connected to the positive input terminal of the inverter 340.

[0201] The external terminal 370 is connected to the battery management unit 311. The external terminal 370 can be connected to, for example, an external power source.

[0202] Vehicle ECU 380 manages the entire vehicle by controlling battery management device 311 in cooperation with other devices in response to operational inputs from the driver, etc. Data relating to the maintenance of vehicle power supply 301, such as the remaining capacity of vehicle power supply 301, is transferred between battery management device 311 and vehicle ECU 380 via a communication line.

[0203] The vehicle of the embodiment includes a battery pack including the secondary battery of the embodiment, and the battery pack (e.g., battery packs 312a, 312b, and 312c) has a long life at high temperatures, resulting in a highly reliable vehicle. Furthermore, each battery pack is inexpensive and highly safe, which reduces the cost of the vehicle and improves safety. [Example]

[0204] A secondary battery was fabricated in the following manner.

[0205] Example 1 <Preparation of positive electrode> The positive electrode active material is lithium nickel cobalt manganese composite oxide (LiNi 0.8 Co 0.1 Mn 0.1O2) powder was prepared. Acetylene black was prepared as a conductive agent. Polyvinylidene fluoride (PVdF) was prepared as a binder. Next, the positive electrode active material, conductive agent, and binder were added to N-methylpyrrolidone (NMP) as a solvent in proportions of 82 mass%, 9 mass%, and 9 mass%, and mixed to prepare a positive electrode slurry. This positive electrode slurry was applied to both sides of a current collector made of aluminum foil with a thickness of 15 μm. Next, the coating was dried in a thermostatic oven at 120°C to form a positive electrode active material-containing layer, and the positive electrode active material-containing layer was pressed to obtain a positive electrode.

[0206] <Preparation of negative electrode> Niobium titanium oxide (Nb2TiO7) powder was prepared as a negative electrode active material. The average secondary particle diameter of the niobium titanium oxide was 7.5 μm. The specific surface area of ​​the niobium titanium oxide was 4.0 m 2 / g. In addition, acetylene black was prepared as a conductive agent, and polyvinylidene fluoride (PVdF) was prepared as a binder. Next, the negative electrode active material, conductive agent, and binder were added to N-methylpyrrolidone (NMP) as a solvent in proportions of 82 mass%, 9 mass%, and 9 mass%, and mixed to prepare a negative electrode slurry. This negative electrode slurry was applied to both sides of a current collector made of aluminum foil with a thickness of 15 μm. Next, the coating was dried in a thermostatic oven at 120°C to form a negative electrode active material-containing layer, and the negative electrode active material-containing layer was pressed to obtain a negative electrode.

[0207] <Preparation of electrode groups> Two 25 μm thick polyethylene nonwoven fabrics were prepared as separators. Next, a positive electrode, a separator, a negative electrode, and a separator were stacked in this order to obtain a laminate. This laminate was then spirally wound. This was then hot-pressed at 80°C to produce a flat electrode assembly. A positive electrode terminal was electrically connected to the positive electrode of the electrode assembly. A negative electrode terminal was also electrically connected to the negative electrode of the electrode assembly.

[0208] <Storage of electrode group> A container was prepared, consisting of a 0.1 mm-thick laminate film with a three-layer structure of nylon, aluminum, and polyethylene. The electrode assembly prepared above was placed in this container. Next, with a portion of the periphery of the container open, the inside of the container was dried in a vacuum at 80°C for 16 hours.

[0209] <Preparation of Liquid Non-Aqueous Electrolyte> A mixed solvent (volume ratio 1:2) of propylene carbonate (PC) as a cyclic carbonate and propyl propionate (PP) as an ester compound represented by chemical formula (2) was prepared as a solvent. LiPF6 as an electrolyte salt was dissolved in the solvent at a concentration of 1 mol / L. 1,3-propane sultone (PS) as a sultone compound was added and dissolved therein so that its concentration in the nonaqueous electrolyte was 1.0 mass%. Thus, a liquid nonaqueous electrolyte (nonaqueous electrolyte solution) was obtained in which the concentrations of propylene carbonate (PC), propyl propionate (PP), LiPF6, and 1,3-propane sultone in the liquid nonaqueous electrolyte were 29 mass%, 60 mass%, 10 mass%, and 1.0 mass%, respectively. The liquid nonaqueous electrolyte was prepared in an argon box.

[0210] <Battery construction> A nonaqueous electrolyte was poured into the container housing the electrode group. The open peripheral edges of the container were then heat-sealed to hermetically seal the container. This resulted in a battery with external dimensions of 11 cm × 8 cm × 0.3 cm, excluding the positive and negative electrode terminals (also referred to as positive and negative electrode tabs), and internal dimensions (dimensions of the sealed portion) of 9 cm × 7 cm × 0.25 cm. This battery is referred to as the first sealed battery.

[0211] <First charge> The initial charge and discharge were carried out by carrying out the following initial charge and initial discharge. The first sealed battery was subjected to the initial charge in an environment of 25°C according to the following procedure. First, the first sealed battery was charged at a constant current (CC) of 0.2 C until a voltage of 3 V was reached. Next, the first sealed battery was charged at a constant voltage (CV) of 3 V. The constant voltage charge was terminated when the total time of the constant current charge and constant voltage charge reached 10 hours.

[0212] <First discharge> Next, the first sealed battery was discharged at a constant current (CC) of 0.2 C in an environment of 25°C until the voltage reached 1.5 V.

[0213] <Post-processing> Next, the first sealed battery after the initial charge / discharge was charged at a constant current (CC) of 0.2 C in an environment of 25°C until a voltage of 2.31 V was reached. The first sealed battery was then charged at a constant voltage (CV) of 2.31 V until the current value reached 1 / 20 C. That is, the first sealed battery was subjected to constant current / constant voltage (CCCV) charging. As a result, the SOC of the first sealed battery was 60%. This first sealed battery was subjected to aging. The aging was performed by holding the battery in a thermostatic chamber at 50°C for 6 hours. Thereafter, the first sealed battery was placed in an argon box, and one location of the sealed portion of the exterior member was cut to release the gas inside the exterior member. The end opened by cutting was sealed with a heat seal. In this way, a secondary battery according to Example 1 was produced.

[0214] (Examples 2 to 7, 9, and 10) A secondary battery was fabricated in the same manner as in Example 1, except that the positive electrode active material was changed as shown in Table 2.

[0215] Example 8 The positive electrode active material Li(Ni 0.5 Mn 1.5 )O4 is a 5V-based positive electrode active material with a spinel-type crystal structure.

[0216] The secondary battery of Example 8 contains Li(Ni 0.5 Mn 1.5 )O4, the charge and discharge conditions from the initial charge to post-treatment were as follows:

[0217] <First charge> The first sealed battery was subjected to initial charging in an environment of 25°C according to the following procedure. First, the first sealed battery was charged at a constant current (CC) of 0.2 C until a voltage of 3.7 V was reached. Next, the first sealed battery was charged at a constant voltage (CV) of 3.7 V. The constant voltage charging was terminated when the total time of the constant current charging and constant voltage charging reached 10 hours.

[0218] <First discharge> Next, the first sealed battery was discharged at a constant current (CC) of 0.2 C in an environment of 25°C until the voltage reached 2.5V.

[0219] <Post-processing> Next, the first sealed battery was charged at a constant current (CC) of 0.2 C in an environment of 25°C until a voltage of 3.7 V was reached. The first sealed battery was then charged at a constant voltage (CV) of 3.7 V until the current value reached 1 / 20 C. That is, the first sealed battery was subjected to constant current / constant voltage (CCCV) charging. As a result, the SOC of the first sealed battery was 60%. This first sealed battery was placed in a thermostatic chamber at 80°C and held for 24 hours for aging. The subsequent steps were the same as in Example 1, and a secondary battery according to Example 8 was fabricated.

[0220] (Examples 11, 13, and 14) A secondary battery was fabricated in the same manner as in Example 1, except that the negative electrode active material was changed as shown in Table 2.

[0221] Example 12 The negative electrode active material was changed to graphite (C) as shown in Table 2. Graphite powder and polyvinylidene fluoride (PVdF) were mixed in a ratio of 90% by mass and 10% by mass, and the resulting mixture was kneaded in the presence of an organic solvent (N-methylpyrrolidone) to prepare a slurry. The resulting slurry was applied to a current collector made of copper foil with a thickness of 15 μm, dried, and pressed to obtain a negative electrode. When a negative electrode containing graphite was used, the steps from initial charging to post-treatment were carried out as follows to prepare a secondary battery.

[0222] <First charge> The first sealed battery was subjected to initial charging in an environment of 25°C according to the following procedure. First, the first sealed battery was charged at a constant current (CC) of 0.2 C until a voltage of 4.15 V was reached. Next, the first sealed battery was charged at a constant voltage (CV) of 4.15 V. The constant voltage charging was terminated when the total time of the constant current charging and constant voltage charging reached 10 hours.

[0223] <First discharge> Next, the first sealed battery was discharged at a constant current (CC) of 0.2 C in an environment of 25°C until the voltage reached 2V.

[0224] <Post-processing> Next, the first sealed battery after the initial charge / discharge was charged at a constant current (CC) of 0.2 C in an environment of 25°C until a voltage of 3.46 V was reached. The first sealed battery was then charged at a constant voltage (CV) of 3.46 V until the current value reached 1 / 20 C. That is, the first sealed battery was subjected to constant current / constant voltage (CCCV) charging. As a result, the SOC of the first sealed battery was 60%. This first sealed battery was subjected to aging. The aging was performed by holding the battery in a thermostatic chamber at 50°C for 6 hours. Thereafter, the first sealed battery was placed in an argon box, and one location of the sealed portion of the exterior member was cut to release the gas inside the exterior member. The end opened by the cut was sealed with a heat seal. In this way, a secondary battery according to Example 12 was produced.

[0225] Example 15 A secondary battery according to Example 15 was fabricated in the same manner as in Example 1, except that the following changes were made in the post-treatment.

[0226] First, a sultone compound solution was prepared in the same manner as in the liquid nonaqueous electrolyte described in Example 1, except that the concentration of 1,3-propane sultone as the sultone compound was 5 mass %.

[0227] In post-treatment, the first sealed battery after aging was placed in an argon box, and one location of the sealing portion of the exterior member was cut to release the gas inside the exterior member.

[0228] After degassing, a sultone compound solution was added to the first sealed battery so that the concentration of 1,3-propane sultone (PS) in the non-aqueous electrolyte in the first sealed battery was 5.0 mass %. The cut end was sealed with a heat seal.

[0229] Example 16 A secondary battery was fabricated in the same manner as in Example 1, except that ethyl butyrate (EB) was used instead of propyl propionate (PP) in preparing the non-aqueous electrolyte.

[0230] Example 17 A secondary battery was fabricated in the same manner as in Example 1, except that pentyl propionate was used instead of propyl propionate (PP) in preparing the non-aqueous electrolyte.

[0231] (Examples 18 and 19) A secondary battery was fabricated in the same manner as in Example 1, except that the aging temperature in the post-treatment was set as shown in Table 7.

[0232] (Examples 20 and 21) A secondary battery was fabricated in the same manner as in Example 1, except that the aging time in the post-treatment was set as shown in Table 7.

[0233] Example 22 In the post-treatment, the first sealed battery after the initial charge / discharge was charged at a constant current (CC) of 0.2 C in an environment of 25°C until a voltage of 2.25 V was reached. Next, the first sealed battery was charged at a constant voltage (CV) of 2.25 V until the current value became 1 / 20 C. That is, the first sealed battery was subjected to constant current constant voltage (CCCV) charging. As a result, the SOC of the first sealed battery was 50%. A secondary battery was fabricated in the same manner as in Example 1 except for the above.

[0234] Example 23 In the post-treatment, the first sealed battery after the initial charge / discharge was charged at a constant current (CC) of 0.2 C in an environment of 25°C until a voltage of 2.43 V was reached. Next, the first sealed battery was charged at a constant voltage (CV) of 2.43 V until the current value became 1 / 20 C. That is, the first sealed battery was subjected to constant current / constant voltage (CCCV) charging. As a result, the SOC of the first sealed battery was 70%. A secondary battery was fabricated in the same manner as in Example 1 except for the above.

[0235] Example 24 A secondary battery was fabricated in the same manner as in Example 1, except that in the preparation of the nonaqueous electrolyte, the concentrations of propylene carbonate (PC), propyl propionate (PP), LiPF, and 1,3-propane sultone in the liquid nonaqueous electrolyte were changed to 77 mass%, 12 mass%, 10 mass%, and 1.0 mass%, respectively.

[0236] Example 25 A secondary battery was fabricated in the same manner as in Example 23, except that the aging temperature and time in the post-treatment were set as shown in Table 7.

[0237] Example 26 In preparing the non-aqueous electrolyte, the concentrations of propylene carbonate (PC), propyl propionate (PP), LiPF6, and 1,3-propane sultone in the liquid non-aqueous electrolyte were changed to 25 mass%, 60 mass%, 10 mass%, and 5.0 mass%, respectively. In the post-treatment, the aging temperature and time were set as shown in Table 7. Except for the above, a secondary battery was fabricated in the same manner as in Example 22.

[0238] Example 27 In preparing the non-aqueous electrolyte, the concentrations of propylene carbonate (PC), propyl propionate (PP), LiPF6, and 1,3-propane sultone in the liquid non-aqueous electrolyte were changed to 3 mass %, 90 mass %, 6 mass %, and 1.0 mass %, respectively.

[0239] In the post-treatment, the first sealed battery after the initial charge / discharge was charged at a constant current (CC) of 0.2 C in an environment of 25°C until a voltage of 2.28 V was reached. Next, the first sealed battery was charged at a constant voltage (CV) of 2.28 V until the current value became 1 / 20 C. In other words, the first sealed battery was subjected to constant current / constant voltage (CCCV) charging. As a result, the SOC of the first sealed battery was 55%. The aging temperature and time were as shown in Table 7. A secondary battery was fabricated in the same manner as in Example 1, except for the above.

[0240] Example 28 In preparing the non-aqueous electrolyte, the concentrations of propylene carbonate (PC), propyl propionate (PP), LiPF6, and 1,3-propane sultone in the liquid non-aqueous electrolyte were changed to 1 mass%, 95 mass%, 3 mass%, and 1.0 mass%, respectively. Except for the above, a secondary battery was fabricated in the same manner as in Example 1.

[0241] (Comparative Example 1) A secondary battery was fabricated in the same manner as in Example 1, except that diethyl carbonate (DEC) was used instead of propyl propionate (PP) in preparing the non-aqueous electrolyte.

[0242] (Comparative Example 2) A secondary battery was fabricated in the same manner as in Example 1, except that the aging temperature in the post-treatment was set as shown in Table 7.

[0243] (Comparative Example 3) In preparing the non-aqueous electrolyte, the concentrations of propylene carbonate (PC), propyl propionate (PP), LiPF6, and 1,3-propane sultone in the liquid non-aqueous electrolyte were changed to 29.5 mass%, 60 mass%, 10 mass%, and 0.5 mass%, respectively. The aging time in the post-treatment was set as shown in Table 7. Except for the above, secondary batteries were fabricated in the same manner as in Example 1.

[0244] Comparative Example 4 In the post-treatment, the first sealed battery after the initial charge / discharge was charged at a constant current (CC) of 0.2 C in an environment of 25°C until a voltage of 3 V was reached. Next, the first sealed battery was charged at a constant voltage (CV) of 3 V until the current value became 1 / 20 C. In other words, the first sealed battery was subjected to constant current / constant voltage (CCCV) charging. As a result, the SOC of the first sealed battery was 100%. A secondary battery was fabricated in the same manner as in Example 1 except for the above.

[0245] (Comparative Example 5) A secondary battery was fabricated in the same manner as in Example 1, except that aging was not performed in the post-treatment.

[0246] <Gas chromatography mass spectrometry> The nonaqueous electrolytes contained in the secondary batteries of each Example and Comparative Example were subjected to the gas chromatography mass spectrometry described above. Tables 8 and 9 show the area A within the retention time range of 15 to 18 minutes, the area B within the retention time range of 13.5 to 14.5 minutes, the area C within the retention time range of 11.5 to 12.5 minutes, the values ​​of B / A and C / A, and the concentration E (mol / L) of the sultone compound in the nonaqueous electrolyte.

[0247] <Measurement of the mass of sulfur atoms per unit volume of the active material-containing layer> For each of the secondary batteries of the Examples and Comparative Examples, the mass M of sulfur atoms per unit volume of the positive electrode active material-containing layer was measured by the ICP optical emission spectrometry described above. The previously measured concentration E of the sultone compound in the non-aqueous electrolyte was divided by M to calculate the value of E / M. The mass M of sulfur atoms per unit volume of the positive electrode active material-containing layer and the values ​​of E / M are shown in Tables 8 and 9.

[0248] <High temperature cycle performance test> The secondary batteries of the examples and comparative examples were subjected to a high-temperature cycle performance test as follows.

[0249] First, the secondary battery was charged at a constant current (CC) of 0.2 C in an environment of 70°C until a voltage of 3 V was reached. Next, the secondary battery was charged at a constant voltage (CV) of 3 V until the current value became 1 / 20 C. That is, the secondary battery was subjected to constant current / constant voltage (CCCV) charging to bring its SOC to 100%. Thereafter, it was discharged at a constant current (CC) of 1 C, and the discharge capacity was measured. The above constant current / constant voltage (CCCV) charging and constant current (CC) discharging constitute one cycle, and this cycle was repeated 400 times. The discharge capacity at the first cycle and the discharge capacity at the 400th cycle were measured.

[0250] The discharge capacity at the 400th cycle was divided by the discharge capacity at the 1st cycle, and the result was multiplied by 100 to calculate the 400 cycle retention rate (%).

[0251] The 400 cycle retention rate obtained from the high temperature cycle performance test described above is an index of life performance at high temperatures.

[0252] Tables 2 to 5 show the type of positive electrode active material, the type of negative electrode active material, the sultone compound concentration (% by mass) in the non-aqueous electrolyte before secondary battery production, the type of ester compound, and the ester compound concentration (% by mass) for each Example and Comparative Example. In the tables, "PP" in the "Type of Ester Compound" column stands for propyl propionate. For Example 15, the sultone compound concentration (% by mass) in the non-aqueous electrolyte after aging and the addition of the sultone compound solution is also shown.

[0253] Tables 6 and 7 show the aging temperature, aging time, and SOC (%) during aging in the post-treatment for each example and comparative example. Note that for comparative example 5, in which aging was not performed, the columns for aging temperature (°C) and SOC (%) during aging are indicated by "-".

[0254] Tables 8 and 9 show the area A within the retention time range of 15 minutes or more and 18 minutes or less, the area B within the retention time range of 13.5 minutes or more and 14.5 minutes or less, B / A, and the mass M (g / m) of sulfur atoms per unit volume of the positive electrode active material-containing layer in the secondary batteries after post-treatment in each of the Examples and Comparative Examples.3 ), the concentration E (mol / L) of the sultone compound in the non-aqueous electrolyte, and E / M.

[0255] Tables 10 and 11 show the area C, C / A, ester compound concentration (mass%) in the electrolyte, and 400 cycle retention rate (%) for each example and comparative example within the retention time range of 11.5 minutes or more and 12.5 minutes or less.

[0256] [Table 2]

[0257] [Table 3]

[0258] [Table 4]

[0259] [Table 5]

[0260] [Table 6]

[0261] [Table 7]

[0262] [Table 8]

[0263] [Table 9]

[0264] [Table 10]

[0265] [Table 11]

[0266] The following became clear from Tables 2 to 11.

[0267] All of Examples 1 to 28 were superior in 400 cycle retention rate compared to Comparative Examples 1 to 5. This demonstrates that the secondary battery according to the embodiment can improve the life performance at high temperatures.

[0268] Examples 1 to 10 reveal that the life performance at high temperatures can be improved even if the type of positive electrode active material is changed. Examples 1 and 11 to 14 reveal that the life performance at high temperatures can be improved even if the type of negative electrode active material is changed.

[0269] Example 15 revealed that the life performance at high temperatures can be improved even when a solution containing a sultone compound is added to the non-aqueous electrolyte after the initial charge / discharge and aging.

[0270] From Examples 1, 16, and 17, it became clear that the life performance at high temperatures can be improved even if the type of ester compound represented by chemical formula (2) is changed.

[0271] Even when the aging conditions were changed in various ways as in Examples 1, 18 to 23, B / A was within the range of 0 to 0.000944 and E / M was 1×10 -6 Over 9x10 -4 It was revealed that the following secondary batteries could be obtained and that the life performance at high temperatures could be improved. From the comparison of Examples 1, 18, and 19, it was revealed that the lower the aging temperature, the lower the B / A value tends to be.

[0272] According to at least one of these embodiments or examples, a secondary battery is provided that includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The positive electrode includes a positive electrode active material-containing layer that includes sulfur atoms. The non-aqueous electrolyte includes a sultone compound and a cyclic carbonate. In gas chromatography mass spectrometry of the non-aqueous electrolyte, in a total ion chromatogram in which the vertical axis represents detection intensity and the horizontal axis represents retention time, the ratio B / A of the area B within the retention time range of 13.5 to 14.5 minutes to the area A within the retention time range of 15 to 18 minutes is 0 to 0.000944. The following formula (1) is satisfied:

[0273] Formula (1): 1×10 -6 ≦E / M≦9×10 -4 In formula (1), M is the mass of sulfur atoms per unit volume of the positive electrode active material-containing layer (g / m 3 ) where E is the concentration (mol / L) of the sultone compound in the non-aqueous electrolyte. Therefore, a secondary battery with long life performance at high temperatures can be provided.

[0274] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims.

[0275] The invention according to the embodiment will be described below.

[0276] [1] A battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, the positive electrode includes a positive electrode active material-containing layer that includes sulfur atoms, the non-aqueous electrolyte contains a sultone compound and a cyclic carbonate, In gas chromatography mass spectrometry of the non-aqueous electrolyte, in a total ion chromatogram in which the vertical axis represents detection intensity and the horizontal axis represents retention time, the ratio B / A of the area B within the retention time range of 13.5 minutes or more and 14.5 minutes or less to the area A within the retention time range of 15 minutes or more and 18 minutes or less is 0 or more and 0.000944 or less, A secondary battery that satisfies the following formula (1). Formula (1): 1×10 -6 ≦E / M≦9×10 -4 In formula (1), M is the mass (g / m) of the sulfur atoms per unit volume of the positive electrode active material-containing layer. 3 ) and E is the concentration (mol / L) of the sultone compound in the non-aqueous electrolyte.

[0277] [2] The secondary battery according to [1], wherein in the total ion chromatogram, a ratio C / A of an area C within the retention time range of 11.5 minutes or more and 12.5 minutes or less to the area A is 0.0003 or more.

[0278] [3] The secondary battery according to [1] or [2], wherein the non-aqueous electrolyte further contains an ester compound represented by the following chemical formula (2):

[0279] Chemical formula (2):

[0280] [ka]

[0281] In chemical formula (2), R is a first hydrocarbon group, and R' is a second hydrocarbon group containing 3 or more carbon atoms.

[0282] [4] The secondary battery according to [3], wherein the non-aqueous electrolyte contains the ester compound in an amount of 10% by mass or more and 90% by mass or less.

[0283] [5] A battery pack including the secondary battery according to any one of [1] to [4].

[0284] [6] An external terminal for applying current; Protection circuit and The battery pack according to [5], further comprising:

[0285] [7] A battery comprising a plurality of the secondary batteries; The battery pack according to [5] or [6], wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

[0286] [8] A vehicle including the battery pack according to any one of [5] to [7].

[0287] [9] The vehicle according to [8], including a mechanism for converting the kinetic energy of the vehicle into regenerative energy. [Explanation of symbols]

[0288] 1...electrode group, 2...container (exterior member), 3...positive electrode, 3a...positive electrode current collector, 3b...positive electrode active material-containing layer, 4...negative electrode, 4a...negative electrode current collector, 4b...negative electrode active material-containing layer, 5...separator, 6...positive electrode lead, 7...negative electrode lead, 8...positive electrode current collector tab, 9...negative electrode current collector tab, 10...sealing plate, 11...insulating member, 12...exterior member, 13...negative electrode terminal, 14...positive electrode terminal, 30...secondary battery with first sealing, 31...secondary battery, 50...battery pack, 51...unit cell, 53...battery assembly, 54...plate Lint wiring board, 55... thermistor, 56... protection circuit, 57... external terminal for energization, 71... automobile, 72... battery pack, 300... vehicle, 301... vehicle power supply, 310... communication bus, 311... battery management device, 312a-c... battery pack, 313a-c... assembled battery monitoring device, 314a-c... assembled battery, 316... positive terminal, 317 negative terminal, 340... inverter, 345... drive motor, 370... external terminal, 380... vehicle ECU, L1, L2... connection line, W... drive wheel.

Claims

1. a positive electrode, a negative electrode, and a non-aqueous electrolyte; the positive electrode includes a positive electrode active material-containing layer that includes sulfur atoms, the non-aqueous electrolyte contains a sultone compound and a cyclic carbonate, In gas chromatography mass spectrometry of the non-aqueous electrolyte, in a total ion chromatogram in which the vertical axis represents detection intensity and the horizontal axis represents retention time, a ratio B / A of an area B within a retention time range of 13.5 minutes or more and 14.5 minutes or less to an area A within a retention time range of 15 minutes or more and 18 minutes or less is 0 or more and 0.000944 or less; A secondary battery that satisfies the following formula (1): Formula (1): 1×10 －６ ≦E / M≦9×10 －４ In formula (1), M is the mass (g / m) of the sulfur atoms per unit volume of the positive electrode active material-containing layer. ３ ) and E is the concentration (mol / L) of the sultone compound in the non-aqueous electrolyte.

2. 2. The secondary battery according to claim 1, wherein in the total ion chromatogram, a ratio C / A of an area C within the retention time range of 11.5 minutes or more and 12.5 minutes or less to the area A is 0.0003 or more.

3. The secondary battery according to claim 1 , wherein the non-aqueous electrolyte further contains an ester compound represented by the following chemical formula (2): Chemical formula (2): 【Chemical 1】 In chemical formula (2), R is a first hydrocarbon group, and R' is a second hydrocarbon group containing 3 or more carbon atoms.

4. The secondary battery according to claim 3 , wherein the non-aqueous electrolyte contains the ester compound in an amount of 10% by mass or more and 90% by mass or less.

5. A battery pack comprising the secondary battery according to any one of claims 1 to 4.

6. An external terminal for applying current; Protection circuit and The battery pack of claim 5 further comprising:

7. a plurality of the secondary batteries; The battery pack according to claim 5 , wherein the secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel.

8. A vehicle including the battery pack of claim 5.

9. 9. The vehicle according to claim 8, further comprising a mechanism for converting kinetic energy of the vehicle into regenerative energy.

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