JP6327211B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

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

  Japanese Unexamined Patent Application Publication No. 2009-187940 (Patent Document 1) discloses a technique for forming a coating film containing an alkylsulfonic acid metal salt on a positive electrode active material.

JP 2009-187940 A

  According to Patent Document 1, gas generation during high-temperature storage can be suppressed by forming a film containing an alkylsulfonic acid metal salt on the surface of the positive electrode active material. The object of the present invention is to further reduce the amount of gas generated during high-temperature storage as compared with such conventional techniques.

The nonaqueous electrolyte secondary battery includes a positive electrode active material and a negative electrode active material. A first film containing a component derived from dilithium disulfonate is formed on the surface of the positive electrode active material. A second coating containing a component derived from dilithium disulfonate and a component derived from vinylene carbonate is formed on the surface of the negative electrode active material. In the second coating, the amount of the component derived from vinylene carbonate is 29 μmol / m ² or more and 58 μmol / m ² or less per unit surface area of the negative electrode active material.

  Patent Document 1 focuses on gas generation on the positive electrode side. However, gas generation can occur not only on the positive electrode side but also on the negative electrode side. In the above non-aqueous electrolyte secondary battery, a second film containing a component derived from dilithium disulfonate is also formed on the surface of the negative electrode active material. Therefore, in the nonaqueous electrolyte secondary battery, gas generation can be suppressed even on the negative electrode side.

  Dilithium disulfonate is a metal salt. It is conceivable that the coating derived from the metal salt alone cannot follow the expansion and contraction of the negative electrode active material, thereby reducing the effect expected of the coating. Therefore, in the above non-aqueous electrolyte secondary battery, the second coating formed on the surface of the negative electrode active material is derived from a component derived from dilithium disulfonate and vinylene carbonate (hereinafter abbreviated as “VC”). The mixed film containing the component to be used. By being a mixed film containing a metal salt and an organic compound, the expansion and contraction resistance of the second film is improved.

Furthermore, in the non-aqueous electrolyte secondary battery, the amount of the component derived from VC in the second coating is 29 μmol / m ² or more and 58 μmol / m ² or less. The reason for this is that if the same amount is less than 29 μmol / m ² , the expansion and shrinkage resistance of the second coating may be insufficient, and if the same amount exceeds 58 μmol / m ² , the amount of gas generation increases rather. This is because there is a possibility.

  According to the above, the amount of gas generated during high temperature storage can be reduced.

It is the schematic which shows an example of a structure of the nonaqueous electrolyte secondary battery which concerns on embodiment of this invention. It is the 1st schematic diagram showing the modification of an electrode group. It is a 2nd schematic diagram which shows the modification of an electrode group.

  Hereinafter, an example of an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described. However, this embodiment is not limited to the following description. In the following description, the nonaqueous electrolyte secondary battery may be simply referred to as “battery”. Further, the positive electrode and the negative electrode may be collectively referred to as “electrode”. For example, “electrode active material” indicates a positive electrode active material or negative electrode active material, “electrode mixture layer” indicates a positive electrode mixture layer or negative electrode mixture layer, and “electrode plate” indicates a positive electrode plate or negative electrode plate. Show.

[Nonaqueous electrolyte secondary battery]
FIG. 1 is a schematic diagram illustrating an example of the configuration of the nonaqueous electrolyte secondary battery according to the present embodiment. A battery 100 shown in FIG. 1 is a sealed battery. The battery 100 includes a battery case 50. Although not shown, the battery case 50 may include a liquid injection port, a safety valve, a pressure type current interruption mechanism (CID), and the like. The pressure type CID is an element that physically cuts off the current path when the internal pressure of the battery exceeds a predetermined pressure (also referred to as “operating pressure”).

[Electrode group]
The battery case 50 contains the electrode group 10 and an electrolytic solution. The outer shape of the electrode group 10 is flat. The electrode group 10 is a laminated (also called “stacked”) electrode assembly. The electrode group 10 includes at least a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate, the negative electrode plate, and the planar shape of the separator are all rectangular. In the electrode group 10, the positive electrode plates and the negative electrode plates are alternately stacked with a separator interposed therebetween. The separator may be bag-shaped. The positive electrode plate and the negative electrode plate may be accommodated in a bag-shaped separator.

  The positive electrode plate is composed of, for example, a positive electrode current collector foil and a positive electrode mixture layer formed on the positive electrode current collector foil. The positive electrode mixture layer may be formed on both main surfaces of the positive electrode current collector foil. The positive electrode mixture layer contains a positive electrode active material, a conductive additive, a binder, and the like. For the positive electrode current collector foil, the positive electrode active material, the conductive additive, and the binder, any material that can be normally used as a positive electrode material for a non-aqueous electrolyte secondary battery can be used without particular limitation.

  The negative electrode plate is composed of, for example, a negative electrode current collector foil and a negative electrode mixture layer formed on the negative electrode current collector foil. The negative electrode mixture layer may be formed on both main surfaces of the negative electrode current collector foil. The negative electrode mixture layer contains a negative electrode active material, a thickener, a binder, and the like. For the negative electrode current collector foil, the negative electrode active material, the thickening material, and the binder, any material that can be normally used as a negative electrode material for a non-aqueous electrolyte secondary battery can be used without particular limitation.

  The electrode group 10 has four open end portions OE in a direction intersecting with the stacking direction of the positive electrode plate and the negative electrode plate. The “open end” refers to an end where the electrolytic solution can enter and exit the electrode group. The end of the electrode group may have irregularities, may be substantially flat, or may be an R portion (curved surface). In FIG. 1, the liquid level Lv <b> 1 is at a position higher than the upper end of the electrode group 10.

  The positive electrode plate and the negative electrode plate repeat expansion and contraction with the charge / discharge cycle. As a result, the electrolytic solution is gradually pushed out from the electrode group, and spots are generated in the electrolytic solution and the support salt distribution inside the electrode group. The unevenness of the supporting salt distribution appears remarkably in the portion not immersed in the electrolyte. When unevenness occurs in the distribution of the supporting salt, the charge / discharge reaction becomes uneven in the in-plane direction of the electrode plate, and cycle deterioration is promoted.

  In the present embodiment, a stacked electrode group 10 having four open end portions OE is employed. Furthermore, the amount of the electrolytic solution is adjusted so that all the open end portions OE are completely immersed in the electrolytic solution. Thereby, the unevenness | corrugation of the support salt distribution accompanying a charging / discharging cycle is suppressed.

  When the liquid level is increased as described above, the space volume in the battery is reduced. The “space volume” is a volume obtained by subtracting the volume of a built-in object (electrode group, electrolyte, etc.) from the internal volume of the battery case. According to this embodiment, the space volume may be 50 mL or less. Normally, when the space volume is reduced to 50 mL or less, the internal pressure of the battery is likely to increase, and the safety valve and the pressure type CID may be activated even when a small amount of gas is generated other than during abnormal conditions (for example, during overcharge). In order to avoid such malfunctions, the operating pressure of the safety valve and pressure type CID must be increased, and the robust design is combined with the large amount of gas generated during normal use (for example, during high temperature storage). It becomes difficult. On the other hand, in this embodiment, since the amount of gas generated during normal use can be reduced, there is a possibility that the operating pressure of the pressure type CID or the like can be kept low even if the space volume in the battery is 50 mL or less.

[Electrolyte]
The electrolytic solution is a liquid electrolyte in which a supporting salt is dissolved in an aprotic solvent. The aprotic solvent (hereinafter, also simply referred to as “solvent”) may be a mixed solvent in which ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), or the like is mixed. The composition of the mixed solvent may be, for example, EC: DMC: EMC = 3: 4: 3. The supporting salt may be a Li salt such as LiPF ₆ or Li [(FSO ₂ ) ₂ N]. The concentration of the supporting salt may be, for example, about 0.5 to 2.0 mol / L.

A disulfonic acid dilithium salt is added to the electrolytic solution of the present embodiment. In this specification, disulfonic acid dilithium salt is
Chemical formula (I): LiO ₃ S— (CH ₂ ) m —SO ₃ Li
The compound represented by is shown.

  In chemical formula (I), m represents an arbitrary integer of 1 or more. m is preferably an integer of 1 to 10, more preferably an integer of 2 to 6, and particularly preferably an integer of 3 to 5.

  The amount of disulfonic acid dilithium salt added is, for example, about 0.5 to 2.0 mass% with respect to the total mass of the electrolytic solution. The dilithium disulfonate added to the electrolytic solution forms a first film on the surface of the positive electrode active material and a second film on the surface of the negative electrode active material during the first charge / discharge or aging.

  The first coating and the second coating include a component derived from dilithium disulfonate. Such a coating prevents the reactive species (for example, fluoride ions, unsolvated solvent molecules, etc.) causing gas generation from approaching the electrode active material due to intramolecular polarization of the disulfonic acid skeleton and large steric hindrance. Conceivable. Moreover, since the film contains a lithium salt, an effect of promoting the approach of lithium ions can be expected.

In this specification, the quantity of the component which comprises a film is represented by the substance quantity per unit surface area (1m < ² >) of an electrode active material. In the first coating formed on the surface of the positive electrode active material, the amount of the component derived from dilithium dilithium salt (hereinafter also referred to as “SO _x Li component amount”) is 1.1 μmol / unit per unit surface area of the positive electrode active material. m ² or more 1.7Myuemuol / m ² or less. This is because in such a range, the effect of reducing the amount of gas generated on the positive electrode side is great. The amount of the SO _x Li component can be adjusted by the addition amount of dilithium disulfonate in the electrolytic solution, the specific surface area of the positive electrode active material, and the like. The amount of SO _x Li component can be measured by ion chromatography (IC). The measurement procedure is as follows.

[Measurement method of SO _x Li component amount]
(1) Disassemble the battery and collect the electrode plate. A test piece of a predetermined area is collected from the electrode plate. The test piece is, for example, a disc-shaped test piece having a diameter of 40 mm. The test piece is washed with a suitable solvent such as EMC. The test piece after washing is immersed in a 50% acetonitrile (ACN) aqueous solution for about 10 minutes. Thereby, an extract containing a film component is obtained. Using an IC device, SO _x ions (for example, SO ₃ ²⁻ , SO ₄ ^2−, etc.) contained in the extract are quantified. By dividing the total amount of each SO _x ion by the area of the electrode plate subjected to the measurement, the SO _x Li component amount per unit area [unit: μmol / cm ² ] is obtained.
(2) The specific surface area [unit: m ² / g] of the electrode active material is measured in advance by the BET method using nitrogen gas. By multiplying the specific surface area of the electrode active material, the basis weight of the electrode mixture layer [unit: g / cm ² ] and the mass ratio [unit:%] of the electrode active material in the electrode mixture layer, the electrode mixture is obtained. The total surface area [unit: m ² / cm ² ] of the electrode active material included in the unit area of the layer is determined.
(3) By dividing the SO _x Li component amount per unit area obtained in (1) above by the total surface area of the electrode active material obtained in (2) above, SO _x per unit surface area of the electrode active material is obtained. The amount of Li component [unit: μmol / m ² ] is determined.

  Furthermore, VC is also added to the electrolytic solution of this embodiment. Therefore, on the surface of the negative electrode active material, reductive decomposition of VC and polymerization of the decomposition product also occur, and the second film becomes a mixed film containing a dilithium dilithium salt and a component derived from VC. The second film can be a film that can follow the expansion and contraction of the negative electrode active material by including an organic component derived from VC. The amount of VC added is, for example, about 0.5 to 2.0% by mass with respect to the total mass of the electrolytic solution.

The amount of SO _x Li component in the second coating can also be measured and calculated by the method described above. The amount of the SO _x Li component in the second coating is preferably 0.6 μmol / m ² or more and 0.9 μmol / m ² or less.

In the present embodiment, the amount of the component derived from VC in the second coating (hereinafter also referred to as “VC component amount”) is 29 μmol / m ² or more and 58 μmol / m ² or less. If the VC component amount is less than 29 μmol / m ² , the expansion / shrinkage resistance of the second coating may be insufficient. Further, when the VC component amount exceeds 58 μmol / m ² , the gas generation amount may rather increase. Unless VC component amount is within the above range, it may be 35μmоl / m ² or more, may be less 44μmоl / m ^2. Thereby, it is expected that the effect of reducing the amount of gas generation is increased. The amount of VC component can be adjusted by the amount of VC added in the electrolytic solution, the specific surface area of the negative electrode active material, and the like. The amount of VC component can be measured by gas chromatography (GC). The measurement procedure is as follows.

[Measurement method of VC component amount]
(1) A predetermined amount of electrolyte is collected from the battery after the initial aging. The measurement sample (electrolytic solution) may be diluted about 10 times using an appropriate solvent such as ACN, for example. The concentration of VC remaining in the electrolytic solution (residual VC concentration) is measured using a GC apparatus. The difference between the VC concentration of the initial electrolyte (initial VC concentration) and the residual VC concentration is obtained. By multiplying the difference by the injection amount of the electrolytic solution, the amount of coated VC [unit: μmol] is obtained.
(2) The specific surface area [unit: m ² / g] of the negative electrode active material is measured in advance by the BET method using nitrogen gas. The specific surface area of the negative electrode active material, the basis weight of the negative electrode mixture layer [unit: g / cm ² ], the mass ratio [unit:%] of the negative electrode active material in the negative electrode mixture layer, and the area of the negative electrode mixture layer [ unit: cm ^2] and by multiplying the total surface area [units of the negative electrode active material contained in the battery: Request m ^2].
(3) By dividing the amount of coated VC obtained in (1) above by the total surface area of the negative electrode active material obtained in (2) above, the amount of VC component per unit surface area of the negative electrode active material [unit: μmol / m ² ] is required.

As described above, the second film is a mixed film containing a component derived from dilithium disulfonate and a component derived from VC. In the present specification, the ratio (percentage) of the SO _x Li component amount to the VC component amount is defined as the mixing ratio. The mixing ratio is preferably 1.2% or more and 2.5% or less. As a result, the effect of reducing the amount of gas generated is expected to increase. If it is in the said range, a mixing ratio is good also as 1.3% or more, and good also as 2.0% or less.

  In addition to the above components, the electrolytic solution of the present embodiment may contain a gas generating agent (also referred to as “overcharge additive”) that promotes the operation of the pressure type CID during overcharge. Examples of the gas generating agent include cyclohexylbenzene (CHB) and biphenyl (BP).

  Hereinafter, although this embodiment is described using an example, this embodiment is not limited to these. In the following description, the unit “C” of the current value indicates a current value at which the rated capacity of the battery can be discharged in one hour.

[Production of non-aqueous electrolyte secondary battery]
As described below, non-aqueous electrolyte secondary batteries according to Samples A1 to A7 and B1 to B4 were produced, and the battery performance was evaluated. Samples A1 to A7 are examples, and samples B1 to B4 are comparative examples.

[Sample A1]
1. Preparation of positive electrode plate The following materials were prepared: Positive electrode active material: LiNi _0.4 Co _0.4 Mn _0.2 O ₂ (specific surface area 0.8 m ² / g)
Conductive aid: Acetylene black Binder: Polyvinylidene fluoride Solvent: N-methyl-2-pyrrolidone Positive electrode current collector foil: Aluminum foil (thickness 12 μm).

  A positive electrode active material, a conductive additive, a binder and a solvent were put into a stirring tank of a stirrer and stirred to prepare a positive electrode slurry. The solid content in the positive electrode slurry was, by mass ratio, positive electrode active material: conductive auxiliary material: binder = 93: 4: 3.

  Using a die coater, a positive electrode slurry was applied to both main surfaces of the positive electrode current collector foil and dried to form a positive electrode mixture layer. The positive electrode mixture layer was rolled using a roll mill, and the positive electrode current collector foil and the positive electrode mixture layer were further cut into predetermined dimensions to obtain a positive electrode plate having a rectangular planar shape.

2. Preparation of Negative Electrode Plate The following materials were prepared: Negative electrode active material: graphite (specific surface area 2.3 m ² / g)
Thickener: Carboxymethylcellulose Binder: Styrene butadiene rubber Solvent: Water Negative electrode current collector foil: Copper foil (thickness 8 μm).

  A negative electrode active material, a thickener, a binder and a solvent were put into a stirring tank of a stirrer and stirred to prepare a negative electrode slurry. In the negative electrode slurry, the solid content was in a mass ratio of negative electrode active material: thickening material: binder = 99: 0.5: 0.5.

  Using a die coater, a negative electrode slurry was applied to both main surfaces of the negative electrode current collector foil and dried to form a negative electrode mixture layer. The negative electrode mixture layer was rolled using a roll mill, and the negative electrode current collector foil and the negative electrode mixture layer were further cut into predetermined dimensions to obtain a negative electrode plate having a rectangular planar shape.

3. Preparation of Separator A 12 μm-thick microporous membrane separator was prepared as a separator substrate. The separator base material had a three-layer structure in which a microporous film made of polyethylene (PE) and a microporous film made of polypropylene (PP) were laminated in the order of PP / PE / PP.

  A slurry was prepared by dispersing alumina particles and an acrylic resin in a solvent using an emulsifying and dispersing apparatus. The slurry was applied to the surface of the separator substrate using a gravure coater and dried. As a result, a heat-resistant layer having a thickness of 4 μm was formed. Furthermore, the separator with a heat-resistant layer (thickness 16 micrometers) whose planar shape is a rectangular shape was obtained by cutting to a predetermined dimension.

4). Production of Electrode Group A laminated unit was produced by laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween. By stacking a plurality of stacked units, a stacked electrode group 10 shown in FIG. 1 was produced. The electrode group 10 has four open end portions OE.

5. Preparation of Electrolyte Solution An electrolyte solution having the following composition was prepared. Solvent composition: [EC: DMC: EMC = 3: 4: 3 (volume ratio)]
Supporting salt: LiPF ₆ (1.1 mol / L)
Gas generating agent: CHB (4 mass%), BP (1 mass).

  Dilithium 1,4-butanedisulfonate was prepared as a dilithium disulfonate. Disulfonic acid dilithium salt and VC were added to the electrolytic solution in the amounts shown in Table 1.

6). As shown in FIG. 1, the electrode group 10 was accommodated in the battery case 50. An electrolytic solution was injected from a liquid injection port (not shown) of the battery case 50. The liquid level Lv1 after the injection was at a position higher than the four open end portions OE. That is, in sample A1, the number of open end portions that are in contact with the liquid surface or located below the liquid surface is “4”. The battery case was sealed by sealing the liquid injection port.

7). Initial aging A battery was placed in a thermostat set at 25 ° C., and charging was performed so that the battery voltage was 3.95 V by charging in a constant current-constant voltage system. Next, the battery was placed in a thermostat set to 60 ° C. and allowed to stand for 24 hours. From the above, a nonaqueous electrolyte secondary battery according to Sample A1 was obtained.

[Samples A2 to A4, B1 to B4]
As shown in Table 1, the nonaqueous electrolytic solutions according to Samples A2 to A4 and B1 to B4 are the same as Sample A1, except that the addition amount of dilithium disulfonate and the addition amount of VC in the electrolytic solution are changed. A secondary battery was obtained.

[Sample A5]
The positive electrode plate, the negative electrode plate, and the separator were cut into long strips. Using a winding device, a positive electrode plate and a negative electrode plate were laminated with a separator interposed therebetween, and these were wound to obtain a wound body. A wound electrode group 20 shown in FIG. 2 was obtained by forming the wound body into a flat shape using a flat plate press. The electrode group 20 has two open end portions OE at both ends of the winding axis Aw. In the electrode group 20, the two R portions in the direction intersecting with the winding axis Aw do not correspond to the opening end portions because the electrolyte solution cannot enter and exit.

  As shown in FIG. 2, the electrode group 20 was accommodated in the battery case 50 so that the winding axis Aw was parallel to the liquid level Lv1. The liquid level Lv1 was higher than the two opening end portions OE. That is, in sample A5, the number of open end portions OE that are in contact with the liquid surface or located below the liquid surface is “2”. Except for these, a nonaqueous electrolyte secondary battery according to Sample A5 was obtained in the same manner as Sample A1. In Table 1, the group configuration of the electrode group according to Sample A5 is described as “horizontal winding type”.

[Sample A6]
For sample A6, a non-aqueous electrolyte secondary battery was fabricated in the same manner as sample A1, except that the amount of electrolyte injected was changed. The liquid level Lv2 illustrated in FIG. 1 indicates the liquid level in the sample A6. The liquid level Lv2 was about half as high as the liquid level Lv1. In sample A6, the number of open end portions OE that are in contact with the liquid surface or located below the liquid surface is “3”.

[Sample A7]
A long belt-like positive electrode plate, negative electrode plate and separator were prepared. The width and length of each member are different from those of the sample A5. Using these members, a wound electrode group 30 shown in FIG. 3 was produced. The electrode group 30 has two open end portions OE at both ends of the winding axis Aw. Similar to the electrode group 20 (see FIG. 2) described above, the two R portions in the direction intersecting the winding axis Aw do not correspond to the opening end portions because the electrolyte solution cannot enter and exit.

  As shown in FIG. 3, the electrode group 30 was accommodated in the battery case 50 so that the winding axis Aw was perpendicular to the liquid level Lv1. The liquid level Lv1 was higher than the two opening end portions OE. In sample A7, the number of open end portions that are in contact with the liquid surface or located below the liquid surface is “2”. A nonaqueous electrolyte secondary battery according to Sample A7 was obtained in the same manner as Sample A1 except for these. In Table 1, the group configuration of the electrode group according to Sample A7 is described as “vertical winding type”.

[Evaluation]
1. Analysis of Film From the battery after the initial aging, the positive electrode plate, the negative electrode plate and the electrolytic solution were recovered. In accordance with the above-described method, "in the first coat, SO _x Li component per unit surface area of the positive electrode active material", "in the second coating, SO _x Li component per unit surface area of the anode active material" and "second The amount of VC component per unit surface area of the negative electrode active material in the coating was measured and calculated. The results are shown in Table 1. The analytical instrument settings and measurement conditions were as follows.

(IC measurement conditions)
Apparatus: “ICS-3000” manufactured by DIONEX
Guard column: “AG-9HC (50 × 2 mm)” manufactured by Thermo
Separation column: “AS-9HC (250 × 2 mm)” manufactured by Thermo
Column temperature: 25 ° C
Eluent: 2.5 mM NaHCO ₃ (50% ACN solution) + α
(Liquid A) 0.17 mM Na ₂ CO ₃ , (Liquid B) 10 mM Na ₂ CO ₃
Gradient elution method (A liquid only → Mixing of A liquid and B liquid)
Eluent flow rate: 0.3 mL / min
Sample introduction amount: 10 μL.

(GC measurement conditions)
Equipment: “Agilent 3000 MicroGC” manufactured by Agilent Technologies
Column: “Molsieve” manufactured by Agilent Technologies
Column temperature: (A) 80 ° C, (B) 80 ° C, (C) 60 ° C
Vaporization chamber temperature: 90 ° C
Carrier gas: (A) Ar, (B) He, (C) He
Carrier flow rate: 5mL / min
Sample injection amount: 0.667 mL.

2. High-rate cycle test In a 25 ° C environment, the following set of “charge pulse” and “discharge pulse” was taken as one cycle, and 3000 high-rate pulse cycles were performed. Charge pulse: current value 4C, 20 seconds Discharge pulse: current value 1C, 80 seconds.

  The resistance increase rate (percentage) was determined by dividing the battery resistance after 3000 cycles by the initial battery resistance. The results are shown in Table 1. In Table 1, the lower the resistance increase rate, the better the high rate cycle characteristics.

3. High-temperature storage test The SOC (State Of Charge) of the battery was adjusted to 85%. An internal pressure sensor was attached to the battery, and the internal pressure before storage was measured. The battery was placed in a thermostat set at 60 ° C. and stored for 100 days. After 100 days, the internal pressure after storage was measured by an internal pressure sensor. By subtracting the internal pressure before storage from the internal pressure after storage, the amount of increase in internal pressure was calculated, and the amount of gas generation was determined from the relationship between the amount of increase in internal pressure and the space volume in the battery. The results are shown in Table 1.

〔Results and discussion〕
As can be seen from Table 1, a first coating containing a component derived from dilithium dilithium salt is formed on the surface of the positive electrode active material, and a component derived from dilithium disulfonate salt is formed on the surface of the negative electrode active material; A second coating film including a component derived from VC is formed, and the amount of the component derived from VC in the second coating film is 29 μmol / m ² or more and 58 μmol / m ² or less per unit surface area of the negative electrode active material. In Samples A1 to A7, the amount of gas generated was significantly reduced as compared with Samples B1 to B4 that did not satisfy such conditions.

Comparing the results of samples A1 to A4, it can be seen that the effect of reducing the amount of gas generation is large when the amount of the component derived from VC in the second coating is in the range of 35 μmol / m ^{2 to} 44 μmol / m ² .

  Samples A1 to A4 had better high rate cycle characteristics than Samples A5 to A7. Since Samples A1 to A4 have many open end portions that are in contact with the liquid surface or located below the liquid surface, it is considered that spots of the supporting salt distribution accompanying the high-rate cycle hardly occur in the electrode group.

  Although the present embodiment has been described by exemplifying a prismatic battery, the present embodiment is not limited to the prismatic battery, and may be applied to, for example, a cylindrical battery, a laminated battery, and the like. This embodiment can be said to be particularly suitable for a large vehicle-mounted battery (for example, a battery having an energy density of 360 Wh / L or more) based on the above characteristics.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10, 20, 30 Electrode group, 50 battery case, 100 battery, Aw winding axis, Lv1, Lv2 liquid level, OE opening end.

Claims (1)

A positive electrode active material and a negative electrode active material;
On the surface of the positive electrode active material, a first film containing a component derived from dilithium disulfonate is formed,
On the surface of the negative electrode active material, a second coating containing a component derived from dilithium disulfonate and a component derived from vinylene carbonate is formed,
The non-aqueous electrolyte secondary battery in which the amount of the component derived from the vinylene carbonate in the second coating is 29 μmol / m ² or more and 58 μmol / m ² or less per unit surface area of the negative electrode active material.

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