JP6731155B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

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

Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries (lithium secondary batteries) are lighter in weight and have higher energy density than existing batteries, so in recent years, so-called portable power sources for vehicles such as personal computers and mobile terminals, and vehicle drives. It is used as a power source. In particular, a lithium ion secondary battery that is lightweight and obtains a high energy density is preferably used as a high output power source for driving vehicles such as electric vehicles (EV), hybrid vehicles (HV), and plug-in hybrid vehicles (PHV). There is.

In order to improve the cycle life and the like of the lithium ion secondary battery, the lithium ion secondary battery is initially charged to form a passivation film called SEI (Solid Electrolyte Interface) film on the negative electrode surface. There is. The film suppresses the decomposition of the non-aqueous electrolyte and enables smooth insertion and desorption of lithium ions.

Then, in order to improve the battery performance, such a coating is modified by adding an additive to the non-aqueous electrolyte. For example, Patent Document 1 proposes to add a difluorophosphate to a non-aqueous electrolyte of a non-aqueous electrolyte secondary battery.

JP, 2014-011072, A

However, as a result of diligent study by the present inventor, in the technique described in Patent Document 1, it has been found that the battery capacity may decrease due to the deposition of metallic lithium (Li) depending on the usage state of the battery. .. That is, it has been found that the technique described in Patent Document 1 has room for improvement in suppressing deterioration of the battery capacity when the battery is used under conditions where metal Li is likely to precipitate.
Therefore, an object of the present invention is to provide a non-aqueous electrolyte secondary battery in which the deterioration of the battery capacity is suppressed even when the battery is used under the condition that metal Li is easily deposited.

The non-aqueous electrolyte secondary battery disclosed herein includes a positive electrode, a negative electrode, and a non-aqueous electrolyte. The non-aqueous electrolyte contains an additive which is a compound containing at least one of a fluorine atom and a phosphorus atom. A coating film (A) is formed on the negative electrode. The formed coating film (A) when the amount of the coating film (B) of the negative electrode formed when the non-aqueous electrolyte does not contain an additive that is a compound containing a fluorine atom or a phosphorus atom is 1 The ratio of the amount of) is 1.03 or more and 1.11.
According to such a configuration, the coating film is scattered on the negative electrode with a high density, and the area of the portion capable of receiving lithium ions through the coating film is larger than the predetermined area of the negative electrode. Therefore, the metal Li is less likely to deposit, and the deterioration of the battery capacity due to the metal Li is less likely to occur. That is, according to such a configuration, it is possible to provide the non-aqueous electrolyte secondary battery in which the deterioration of the battery capacity is suppressed even when the battery is used under the condition that metal Li is easily deposited.

1 is a sectional view schematically showing a lithium ion secondary battery according to an embodiment of the present invention. It is a schematic diagram which shows the structure of the electrode body used for a lithium ion secondary battery. (A) It is a schematic diagram showing the negative electrode in which a small amount of film was formed, (b) It is a schematic diagram showing the negative electrode in which the film was formed moderately, (c) Schematic showing the negative electrode in which a large amount of film was formed. It is a figure. 4 is a graph showing the relationship between the amount of additive to the negative electrode active material and the aging time in the examination in Examples.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that matters other than matters particularly referred to in the present specification and matters necessary for carrying out the present invention (for example, a general configuration and manufacturing process of a non-aqueous electrolyte secondary battery that does not characterize the present invention). Can be understood as a matter of design by a person skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the field. Further, in the following drawings, the same reference numerals are given to the members/sites that have the same effect. Further, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships.

In the present specification, the term “secondary battery” generally refers to an electricity storage device that can be repeatedly charged and discharged, and is a term that includes so-called storage batteries such as lithium-ion secondary batteries and electricity storage elements such as electric double layer capacitors. Hereinafter, the present invention will be described in detail by taking a lithium ion secondary battery as an example.
It should be noted that the present invention is not intended to be limited to those described in the embodiments, and the technical idea of the present invention is to provide another non-aqueous electrolyte secondary battery including another charge carrier (for example, sodium ion). (For example, sodium ion secondary battery)

FIG. 1 is a sectional view schematically showing a lithium ion secondary battery 10 according to an embodiment. FIG. 2 is a schematic diagram showing the configuration of the electrode body 40 used in the lithium ion secondary battery 10. As shown in FIG. 1, the lithium-ion secondary battery 10 includes a battery case 20 and an electrode body 40 (a wound electrode body in FIG. 1).

The battery case 20 includes a case body 21 and a sealing plate 22. The case body 21 has a box shape having a rectangular opening at one end. Here, the case body 21 has a bottomed rectangular parallelepiped shape with an opening on one surface corresponding to the upper surface of the lithium ion secondary battery 10 in a normal use state. The sealing plate 22 is a member that closes the opening of the case body 21. The sealing plate 22 is composed of a substantially rectangular plate. The sealing plate 22 is welded to the peripheral edge of the opening of the case body 21 to form the substantially hexahedral battery case 20. The battery case 20 is mainly composed of, for example, a light weight metal material having good thermal conductivity. Examples of such metallic materials include aluminum, stainless steel, nickel-plated steel, and the like. Although a rectangular case is illustrated here, the battery case 20 is not limited to such a shape. For example, the battery case 20 may be a cylindrical case. The battery case 20 may be in the form of a bag that wraps the electrode body, or may be a so-called laminate type battery case 20.

In the example shown in FIG. 1, a positive electrode terminal 23 (external terminal) and a negative electrode terminal 24 (external terminal) for external connection are attached to the sealing plate 22. A safety valve 30 and a liquid injection port 32 are formed on the sealing plate 22. The safety valve 30 is configured to release the internal pressure of the battery case 20 when the internal pressure rises above a predetermined level (for example, a set valve opening pressure of about 0.3 MPa to 1.0 MPa). Further, FIG. 1 illustrates a state in which the liquid injection port 32 is sealed by the sealing material 33 after the nonaqueous electrolyte 80 is injected.

As shown in FIG. 2, the electrode body 40 includes a strip-shaped positive electrode (positive electrode sheet 50), a strip-shaped negative electrode (negative electrode sheet 60), and strip-shaped separators (separators 72, 74).

The positive electrode sheet 50 includes a strip-shaped positive electrode current collector foil 51 and a positive electrode active material layer 53. For the positive electrode current collector foil 51, for example, an aluminum foil or the like can be used. An exposed portion 52 is provided on one side in the width direction of the positive electrode current collector foil 51 along the edge portion. In the illustrated example, the positive electrode active material layer 53 is formed on both surfaces of the positive electrode current collector foil 51 except for the exposed portion 52 provided on the positive electrode current collector foil 51. However, the positive electrode active material layer 53 may be formed only on one surface of the positive electrode current collector foil 51.

The positive electrode active material layer 53 typically includes a positive electrode active material, a conductive material, a binder (binder), and the like. Examples of the positive electrode active material include a lithium composite metal oxide having a layered structure or a spinel structure (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , LiFeO ₂ , LiMn ₂ O). ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiFePO _4, etc.) can be adopted. As the conductive material, a carbon material such as carbon black (for example, acetylene black or Ketjen black) can be adopted. As the binder, various polymer materials such as polyvinylidene fluoride (PVdF) and polyethylene oxide (PEO) can be adopted.

The negative electrode sheet 60 includes a strip-shaped negative electrode current collector foil 61 and a negative electrode active material layer 63. For the negative electrode current collector foil 61, for example, a copper foil or the like can be used. On one side in the width direction of the negative electrode current collector foil 61, an exposed portion 62 is provided along the edge. In the illustrated example, the negative electrode active material layer 63 is formed on both surfaces of the negative electrode current collector foil 61 except for the exposed portion 62 provided on the negative electrode current collector foil 61. However, the negative electrode active material layer 63 may be formed on only one surface of the negative electrode current collector foil 61.

The negative electrode active material layer 63 typically includes a negative electrode active material, a binder, a thickener, and the like. As the negative electrode active material, for example, carbon materials such as graphite (natural graphite, artificial graphite) and low crystalline carbon (hard carbon, soft carbon) can be used, and among them, graphite can be preferably used. As the binder, various polymer materials such as styrene-butadiene rubber (SBR) can be adopted. As the thickener, various polymer materials such as carboxymethyl cellulose (CMC) can be adopted.

As the separators 72 and 74, for example, a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose or polyamide can be used, and preferably a polyolefin resin (eg, PE , PP) is used. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which a PP layer is laminated on both surfaces of a PE layer). A heat resistant layer (HRL) may be provided on the separators 72 and 74.

In the electrode body 40, as shown in FIG. 2, the positive electrode sheet 50, the negative electrode sheet 60, and the separators 72, 74 are sequentially wound and wound, and the wound electrode body (wound electrode body). 40 has a shape that is flatly pressed and bent along a plane including the winding axis WL. The width b1 of the negative electrode active material layer 63 is slightly wider than the width a1 of the positive electrode active material layer 53. Further, the widths c1 and c2 of the separators 72 and 74 are slightly wider than the width b1 of the negative electrode active material layer 63 (c1, c2>b1>a1). In the example shown in FIG. 2, the exposed portion 52 of the positive electrode current collector foil 51 and the exposed portion 62 of the negative electrode current collector foil 61 are spirally exposed on both sides of the separators 72 and 74, respectively. In the present embodiment, as shown in FIG. 1, in the electrode body 40, the intermediate portions of the positive and negative exposed portions 52 and 62 protruding from the separators 72 and 74 are gathered together, and the positive and negative electrodes arranged inside the battery case 20. The inner terminals 23, 24 are welded to the tip portions 23a, 24a.
Although the electrode body 40 is configured as a wound electrode body in the present embodiment, it may be configured as a laminated electrode body.

In the embodiment shown in FIG. 1, the flat wound electrode body 40 is housed in the battery case 20 along a plane including the winding axis WL. The battery case 20 further contains a non-aqueous electrolyte 80. The nonaqueous electrolyte 80 penetrates into the electrode body 40 from both axial sides of the winding shaft WL (see FIG. 2). It should be noted that FIG. 1 does not strictly show the amount of the non-aqueous electrolyte 80 injected into the battery case 20.

The non-aqueous electrolyte 80 contains an organic solvent (non-aqueous solvent) and a supporting salt. As the non-aqueous solvent, various carbonates, ethers, esters, nitrites, sulfones, lactones and other organic solvents used in the non-aqueous electrolyte of a general lithium ion secondary battery are used without particular limitation. be able to. Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like. Such non-aqueous solvents may be used alone or in appropriate combination of two or more. As the supporting salt, for example, lithium salts such as LiPF ₆ , LiBF ₄ , and LiClO ₄ (preferably LiPF ₆ ) can be preferably used. The concentration of the supporting salt is preferably 0.7 mol/L or more and 1.3 mol/L or less (for example, 1.0 mol/L).

Further, in the present embodiment, the non-aqueous electrolyte 80 contains an additive which is a compound containing at least one of a fluorine atom and a phosphorus atom. The compound containing at least one of a fluorine atom and a phosphorus atom is preferably difluorophosphate, but is not limited to this. Examples of the difluorophosphate include difluorophosphate anion (PO ₂ F ₂ ⁻ ) and cations of alkali metals such as Li, Na and K; cations of alkaline earth metals such as Be, Mg and Ca; tetraalkyl Examples thereof include salts with ammonium cations such as ammonium and trialkylammonium. Among them, lithium difluorophosphate (LiPO ₂ F ₂ ) is preferable.

In the non-aqueous electrolyte, components other than the above-mentioned non-aqueous solvent and supporting salt, for example, a gas generating agent such as biphenyl (BP) and cyclohexylbenzene (CHB) are included in the non-aqueous electrolyte unless the effects of the present invention are significantly impaired. Various additives such as a dispersant, a thickener, and the like may be included.

Further, in the lithium ion secondary battery 10, the coating film (A) is formed on the negative electrode 60 (particularly the negative electrode active material layer 63). With respect to this coating film (A), formation when the amount of the coating film (B) of the negative electrode formed when the non-aqueous electrolyte does not contain an additive which is a compound containing a fluorine atom or a phosphorus atom is 1 The ratio of the amount of the film (A) formed is 1.03 or more and 1.11.

Thus, the amount of the coating film (A) of the negative electrode 60 of the lithium ion secondary battery 10 is in the above range with respect to the case where the non-aqueous electrolyte does not contain an additive which is a compound containing a fluorine atom or a phosphorus atom. By setting the ratio to be within the range, deterioration of the battery capacity can be suppressed even when the battery is used under the condition that metal Li is easily deposited. Here, the use of the battery under the condition that metal Li is likely to be deposited includes, for example, the use of a battery that is charged and discharged at a high rate (for example, 5 C or more) at 0° C. or less (particularly −20° C. or less).

The reason why the deterioration of the battery capacity can be suppressed in this way is presumed as follows.
FIG. 3 is a schematic view showing a negative electrode 60′ having a coating film 90′ formed thereon. FIG. 3(a) shows a case where a small amount of the coating film 90′ is formed, and FIG. 3C shows the case where a large amount of the coating film 90' is formed.
As shown in FIG. 3A, when the amount of the coating film 90′ is small, the coating film 90′ is scattered at a low density, and therefore lithium is intercalated through the coating film 90′ with respect to a predetermined area of the negative electrode 60′. The area of the part that can accept ions is small. Therefore, metal Li is likely to be deposited.
As shown in FIG. 3B, when the amount of the coating 90′ is appropriate, the coating 90′ is scattered at a high density, so that the total surface area of the coating 90′ becomes large. Therefore, the area of the portion capable of receiving lithium ions through the coating film 90′ is larger than the predetermined area of the negative electrode 60′. Therefore, it is difficult for metal Li to deposit.
As shown in FIG. 3C, when the amount of the coating 90′ is large, the coating 90′ has developed in a layered form, and the total surface area of the coating 90′ is small. Therefore, the area of the portion that can receive lithium ions through the coating film 90′ is smaller than the predetermined area of the negative electrode 60′. Therefore, metal Li is likely to be deposited.
Therefore, when the amount of the coating film (B) of the negative electrode formed when the non-aqueous electrolyte does not contain an additive which is a compound containing a fluorine atom or a phosphorus atom, the formed coating film (A) is It is considered that the case where the ratio of the amounts is 1.03 or more and 1.11 or less corresponds to the case of FIG. That is, it is considered that the coating is scattered at a high density, and the area of the portion capable of receiving lithium ions through the coating is large with respect to the predetermined area of the negative electrode 60, and as a result, metal Li is unlikely to deposit. .. As a result, it is considered that the battery capacity is less likely to deteriorate due to the metal Li.

The amount of the coating film (A) can be adjusted by appropriately selecting the amount of an additive that is a compound containing at least one of a fluorine atom and a phosphorus atom added to the non-aqueous electrolyte 80, and the aging condition. it can.

The lithium-ion secondary battery 10 configured as described above can be used for various purposes, and preferred applications include electric vehicles (EV), hybrid vehicles (HV), plug-in hybrid vehicles (PHV), and the like. The driving power source mounted on the vehicle is mentioned. The lithium ion secondary battery 10 can also be used in the form of an assembled battery, which is typically formed by connecting a plurality of batteries in series and/or in parallel.

Examples of the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples.

<Battery No. 1 (battery for reference)>
LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (LNCM) as the positive electrode active material powder, acetylene black (AB) as the conductive material, and polyvinylidene fluoride (PVdF) as the binder were added to the LNCM: A mass ratio of AB:PVdF=90:8:2 was mixed with NMP to prepare a slurry for forming a positive electrode active material layer. This slurry was applied on both sides of a long aluminum foil in a strip shape, dried, and then pressed to produce a positive electrode.
In addition, graphite (C) as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener were added to a mass of C:SBR:CMC=98:1:1. A negative electrode active material layer forming slurry was prepared by mixing with ion-exchanged water in a ratio. The slurry was applied in a strip shape on both surfaces of a long copper foil, dried, and then pressed to prepare a negative electrode. The pressing was performed so that the BET specific surface area of the negative electrode active material layer was 4.5 m ³ /g.
Also, two separator sheets (porous polyolefin sheets) were prepared.
The prepared positive electrode, negative electrode, and two prepared separator sheets were stacked and wound to prepare a wound electrode body. At this time, the separator was interposed between the positive electrode and the negative electrode.
The produced wound electrode body was housed in a battery case having a liquid injection port.
Then, a non-aqueous electrolyte was injected from the liquid inlet of the battery case, and the liquid inlet was hermetically sealed to produce a lithium ion secondary battery assembly. As the non-aqueous electrolyte, a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of EC:DMC:EMC=3:4:3 was used, and a supporting salt was added. LiPF ₆ was dissolved at a concentration of 1.1 mol/L.
The lithium-ion secondary battery assembly was initially charged at a current rate of 5 C, and was aged at 60° C. for 20 hours to obtain No. A lithium ion secondary battery of No. 1 was obtained.

<Battery No. 2>
LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (LNCM) as the positive electrode active material powder, acetylene black (AB) as the conductive material, and polyvinylidene fluoride (PVdF) as the binder were added to the LNCM: A mass ratio of AB:PVdF=90:8:2 was mixed with NMP to prepare a slurry for forming a positive electrode active material layer. This slurry was applied on both sides of a long aluminum foil in a strip shape, dried, and then pressed to produce a positive electrode.
In addition, graphite (C) as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener were added to a mass of C:SBR:CMC=98:1:1. A negative electrode active material layer forming slurry was prepared by mixing with ion-exchanged water in a ratio. The slurry was applied in a strip shape on both surfaces of a long copper foil, dried, and then pressed to prepare a negative electrode. The pressing was performed so that the BET specific surface area of the negative electrode active material layer was 4.5 m ³ /g.
Also, two separator sheets (porous polyolefin sheets) were prepared.
The prepared positive electrode, negative electrode, and two prepared separator sheets were stacked and wound to prepare a wound electrode body. At this time, the separator was interposed between the positive electrode and the negative electrode.
The produced wound electrode body was housed in a battery case having a liquid injection port.
Subsequently, a non-aqueous electrolyte was injected from the liquid inlet of the battery case, and the liquid inlet was hermetically sealed to produce a lithium ion secondary battery assembly. As the non-aqueous electrolyte, a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) in a volume ratio of EC:DMC:EMC=3:4:3 was used, and a supporting salt was added. as of LiPF ₆ was dissolved at a concentration of 1.1 mol / L, what further LiPO ₂ F ₂ was 1mmol added per negative electrode active material 1g as the additive is a compound containing at least either a fluorine atom or a phosphorus atom Using.
This lithium-ion secondary battery assembly was initially charged at a current rate of 5 C, and was aged at 60° C. for 5 hours to obtain No. A lithium ion secondary battery of No. 2 was obtained.

<Battery No. 3-23>
No. 1 except that the amount of the additive added per 1 g of the negative electrode active material, the initial charge rate, the aging temperature, and the aging time were set to the conditions shown in Table 1. Similar to the lithium ion secondary battery of No. 2, No. 3 to 23 lithium ion secondary batteries were obtained.

<Battery No. 24 and 25>
No. 3 except that the concentration of LiPF ₆ as a supporting salt and the aging time were set to the conditions shown in Table 1. Similar to the lithium ion secondary battery of No. 2, No. 24 and 25 lithium ion secondary batteries were obtained.

<Coating amount measurement>
The coating amount of the negative electrode of each lithium ion secondary battery was determined by the AC impedance method. Specifically, each lithium ion secondary battery was adjusted to SOC (State of charge) 60%, placed in a temperature environment of −30° C., and AC impedance measurement was performed in the frequency range of 100000 to 0.01 Hz. The arc obtained by the measurement was subjected to equivalent circuit fitting, and the coating amount was calculated from the fitting result. No. with no additive added No. 1 when the coating amount of the lithium ion secondary battery of No. 1 was set to 1. The ratio of the coating amount of the lithium ion secondary battery of 2 to 25 was calculated. The results are shown in Table 1.

<Evaluation of capacity retention rate after Li precipitation test>
For each of the lithium ion secondary batteries prepared above, the initial capacity was measured according to the following procedure 1 to procedure 3 at a temperature of 25° C. and a voltage range of 3.0 V to 4.1 V.
(Procedure 1) After reaching 3.0 V by a constant current discharge of 1 C, a constant voltage discharge is performed for 2 hours and then a rest for 10 minutes.
(Procedure 2) After reaching 4.1 V by constant current charging of 1 C, charge by constant voltage charging for 2.5 hours, and then pause for 10 minutes.
(Procedure 3) After reaching 3.0 V by a constant current discharge of 1 C, a constant voltage discharge is performed for 2 hours and then a rest for 10 minutes.
Then, the discharge capacity (CCCV discharge capacity) in the discharge from constant current discharge to constant voltage discharge in Procedure 3 was taken as the initial capacity.
Each lithium ion secondary battery was adjusted to SOC 90% and placed under a temperature condition of −30° C. Then, a 1000-cycle rectangular wave cycle test was conducted with a pulse charge/discharge pattern consisting of the following steps 1 and 2.
(Step 1) Pulse charging is performed for 0.1 second at a constant current of 20 C, and then paused for 5 seconds.
(Step 2) Pulse discharge is performed for 0.1 second at a constant current of 20 C, and then paused for 5 seconds.
The battery capacity after 1000 cycles was measured by the same method as the initial capacity, and this was taken as the discharge capacity after 1000 cycles. The capacity retention rate (%) was calculated from the formula: (discharge capacity after 1000 cycles/initial capacity)×100. The results are shown in Table 1.

From Table 1, in the lithium-ion secondary battery containing an additive in which the non-aqueous electrolyte is a compound containing at least one of a fluorine atom and a phosphorus atom, a coating film is formed on the negative electrode, and the coating amount is When the non-aqueous electrolyte has a ratio of 1.03 or more and 1.11 or less with respect to the coating amount when the additive that is a compound containing a fluorine atom or a phosphorus atom is not included, metal Li is easily deposited. It can be seen that the deterioration of the battery capacity is suppressed even when the battery is used (charged/discharged) under the conditions.
Further, FIG. 4 shows a graph showing the relationship between the amount of the additive to the negative electrode active material and the aging time. From FIG. 4, it can be seen that the film amount can be controlled by appropriately selecting the additive amount and the aging time.

Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

10 lithium-ion secondary battery 20 battery case 21 case body 22 sealing plate 23 positive electrode terminal 24 negative electrode terminal 30 safety valve 32 liquid injection port 33 sealing material 40 wound electrode body 50 positive electrode sheet 51 positive electrode current collector foil 52 exposed portion 53 positive electrode active Material layer 60 Negative electrode sheet 61 Negative electrode current collector foil 62 Exposed part 63 Negative electrode active material layers 72, 74 Separator 80 Non-aqueous electrolyte WL Winding shaft

Claims (1)

A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
The non-aqueous electrolyte contains an additive that is a compound containing at least one of a fluorine atom and a phosphorus atom,
A coating (A) is formed on the negative electrode,
The formed coating film (A) when the amount of the coating film (B) of the negative electrode formed when the non-aqueous electrolyte does not contain an additive that is a compound containing a fluorine atom or a phosphorus atom is 1 the amount ratio of) the state, and are 1.03 or 1.11 or less,
The amount of the coating film (A) and the amount of the coating film (B) are amounts obtained from fitting results by performing an equivalent circuit fitting on an arc obtained by the AC impedance method,
Characterized by that
Non-aqueous electrolyte secondary battery.

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