JP7416576B2 - Lithium ion secondary battery manufacturing method and lithium ion secondary battery - Google Patents

Description

The present invention relates to a method for manufacturing a lithium ion secondary battery and a lithium ion secondary battery.

Since lithium secondary batteries are power devices with high energy density, they have recently been widely used as power sources for terminals such as notebook computers and mobile phones. As a lithium ion secondary battery, a lithium ion secondary battery is known that uses a carbon material for the negative electrode and an ionic liquid having a bis(fluorosulfonyl)imide anion in which a lithium ion salt is dissolved in the electrolyte (for example, Patent Document 1 to Patent Document 3)

Patent Document 1 discloses a method in which the lithium ion salt concentration in the electrolytic solution is set to 1.0 mol/L or more and the viscosity of the electrolytic solution is set to a predetermined viscosity or less in order to improve the initial charge/discharge efficiency. ing.

Japanese Patent Application Publication No. 2018-156724 Japanese Patent Application Publication No. 2007-207675 Patent No. 5329310

However, the method described in Patent Document 1 is not sufficient as a method for improving initial charge/discharge efficiency, and there is room for improvement. Therefore, it has been desired to develop other methods for improving initial charge/discharge efficiency.

The present invention has been made to solve the above-mentioned problems, and can be realized as the following forms.
(1) According to one embodiment of the present invention, a method for manufacturing a lithium ion secondary battery is provided. The manufacturing method of this lithium ion secondary battery is
As an electrolyte, an ionic liquid containing bis(fluorosulfonyl)imide anion as an anion component is used.
A method for manufacturing a lithium ion secondary battery using glass fiber having a porosity of 70% or more as a separator provided between a positive electrode and a negative electrode, the method comprising:
preparing a lithium secondary battery intermediate using the positive electrode, the negative electrode, the separator, and the electrolyte;
a step of subjecting the lithium secondary battery intermediate to a high temperature treatment at 35° C. or higher and 75° C. or lower for 8 hours or more and 30 hours or less,
The high temperature treatment is performed before the first charge.
In addition, the present invention can be realized as the following forms.

(1) According to one embodiment of the present invention, a method for manufacturing a lithium ion secondary battery is provided. The manufacturing method of this lithium ion secondary battery is
As an electrolyte, an ionic liquid containing bis(fluorosulfonyl)imide anion as an anion component is used.
A method for manufacturing a lithium ion secondary battery using glass fiber having a porosity of 70% or more as a separator provided between a positive electrode and a negative electrode, the method comprising:
preparing a lithium secondary battery intermediate using the positive electrode, the negative electrode, the separator, and the electrolyte;
The method includes a step of subjecting the lithium secondary battery intermediate to a high temperature treatment at 35° C. or higher and 75° C. or lower for 8 hours or more and 30 hours or less.

According to this method of manufacturing a lithium ion secondary battery, initial charge/discharge efficiency can be improved.

(2) In the above-described method for manufacturing a lithium ion secondary battery, the high temperature treatment may be performed at a temperature of 45°C or higher and 75°C or lower.

According to this method of manufacturing a lithium ion secondary battery, the initial charge/discharge efficiency can be further improved.

(3) In the above method for manufacturing a lithium ion secondary battery, the high temperature treatment may be performed for 10 hours or more and 24 hours or less.

According to this method of manufacturing a lithium ion secondary battery, the initial charge/discharge efficiency can be further improved.

Note that the present invention can be realized in various forms, for example, in the form of a lithium ion secondary battery manufactured by a lithium ion secondary battery manufacturing method.

A. Embodiment A1. Method for manufacturing a lithium ion secondary battery A method for manufacturing a lithium ion secondary battery, which is an embodiment of the present invention, includes (i) manufacturing a lithium secondary battery intermediate using a positive electrode, a negative electrode, a separator, and an electrolyte; and (ii) a step of subjecting the lithium secondary battery intermediate to a high-temperature treatment at 35° C. or higher and 75° C. or lower for 8 hours or more and 30 hours or less.

According to the method for manufacturing a lithium ion secondary battery of the present embodiment, by performing high temperature treatment before the first charge, the first charge/discharge efficiency can be improved. Although this mechanism is not certain, the presumed mechanism is that deposits derived from the ionic liquid are generated on the negative electrode surface, and the deposits promote stable formation of an SEI (Solid Electrolyte Interface) film on the negative electrode surface during the first charge. This is considered to be the reason why stable charging and discharging behavior was achieved.

The method for manufacturing a lithium ion secondary battery of this embodiment uses an ionic liquid containing bis(fluorosulfonyl)imide anion as an anion component as an electrolyte, and a separator provided between a positive electrode and a negative electrode with a porosity of 70. This is particularly effective when using glass fibers with a content of % or more. The mechanism for this is not clear, but the presumed mechanism is that a unique side reaction occurs due to the use of glass fibers as a separator, or that the dense structure of glass fibers causes the ionic liquid to reach the opposing negative electrode surface. This is thought to be due to the acceleration of the deposition of the origin.

In this embodiment, the preparation step of preparing a lithium secondary battery intermediate using a positive electrode, a negative electrode, a separator, and an electrolyte is a step of preparing a lithium secondary battery intermediate using a positive electrode, a negative electrode, a separator, and an electrolyte. This is the process of assembling the battery intermediate. The preparation step is not limited to this, and a lithium secondary battery intermediate may be prepared by obtaining a lithium secondary battery intermediate assembled in advance.

In this embodiment, first, a positive electrode and a negative electrode are manufactured, and then a laminate in which a separator is sandwiched between the positive electrode and the negative electrode is manufactured. Next, this laminate is placed in an aluminum laminate packaging material and sealed leaving an opening for injecting the electrolyte to obtain a battery before injection. Thereafter, an electrolytic solution is injected into the pre-injected battery through the opening, and after the injection, the opening is sealed to obtain a lithium secondary battery intermediate.

After the preparation step, the lithium secondary battery intermediate is subjected to high temperature treatment at 35° C. or higher and 75° C. or lower for 8 hours or more and 30 hours or less. The conditions of the high-temperature treatment in this embodiment are characterized by being at 35° C. or higher and 75° C. or lower for 8 hours or more and 30 hours or less.

From the viewpoint of improving the initial charge/discharge efficiency, the temperature of the high temperature treatment is 35°C or higher, preferably 40°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher. On the other hand, from the viewpoint of improving the initial charge/discharge efficiency, the temperature of the high temperature treatment is 75°C or lower, preferably 70°C or lower. The mechanism by which the improvement in initial charge/discharge efficiency is suppressed by increasing the temperature of high-temperature treatment higher than 75°C is not clear, but the presumed mechanism is that deposits derived from the ionic liquid are excessively produced on the negative electrode surface. This is thought to be due to an increase in the resistance component.

Moreover, from the viewpoint of improving the initial charge/discharge efficiency, the time of the high temperature treatment is 8 hours or more, preferably 10 hours or more, more preferably 12 hours or more, and even more preferably 15 hours or more. On the other hand, from the viewpoint of improving the initial charge/discharge efficiency, the high temperature treatment time is 30 hours or less, preferably 24 hours or less, and more preferably 20 hours or less. Moreover, from the viewpoint of reducing manufacturing time, the time for high temperature treatment is preferably 24 hours or less, more preferably 20 hours or less. The mechanism by which the improvement in initial charge/discharge efficiency is suppressed by increasing the high-temperature treatment time for longer than 30 hours is not clear, but one possible mechanism is that deposits derived from the ionic liquid are excessively produced on the negative electrode surface. This is thought to be due to an increase in the resistance component.

A2. Lithium Ion Secondary Battery The lithium ion battery according to this embodiment includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte.

The positive electrode and negative electrode of this embodiment each include an electrode active material, a conductive agent, a current collector, and a binder.

The positive electrode active material used in the positive electrode of this embodiment is not particularly limited as long as it is capable of intercalating and deintercalating lithium ions. Examples of the positive electrode active material include metal oxides, composite oxides of lithium and transition metals, metal chalcogenides, and conductive polymer compounds. Examples of the metal oxide include CuO, Cu ₂ O, MnO ₂ , MoO ₃ , V ₂ O ₅ , CrO ₃ , MoO ₃ , Fe ₂ O ₃ , Ni ₂ O ₃ and CoO ₃ . Examples of the metal chalcogenide include TiS ₂ , MoS ₂ , NbSe ₃ and the like. Examples of the conductive polymer compound include polyacene, polyparaphenylene, polypyrrole, polyaniline, and the like.

As the positive electrode active material, a composite oxide of lithium and a transition metal is preferable because it is easy to obtain a high voltage. Examples of composite oxides of lithium and transition metals include LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO ₄ , _LiNix Co _(1-x) O ₂ , LiMna _{Ni b} Co _c (a+b+c) =1), etc. In addition, composite oxides of lithium and transition metals doped with small amounts of elements such as fluorine, boron, aluminum, chromium, zirconium, molybdenum, iron, etc., and lithium composite oxides whose particle surfaces are doped with carbon, MgO, Al, etc. ₂ O ₃ , SiO ₂ or the like may be used as the positive electrode active material. Furthermore, two or more of the above materials may be used in combination as the positive electrode active material. The amount of the positive electrode active material is not particularly limited, but may be, for example, 3 mg/cm ² or more and 10 mg/cm ² or less.

The negative electrode active material used in the negative electrode of this embodiment is not particularly limited as long as it is capable of intercalating and deintercalating metallic lithium or lithium ions. Examples of negative electrode active materials include carbon materials, metal materials, lithium transition metal nitrides, crystalline metal oxides, amorphous metal oxides, silicon compounds, conductive polymers, and the like. Examples of the carbon material include natural graphite, artificial graphite, non-graphitizable carbon, and easily graphitizable carbon. Examples of the metal material include metal lithium, alloys, tin compounds, and the like. Specific examples of the negative electrode active material include Li ₄ TiO ₁₂ and NiSi ₅ C ₆ . Furthermore, two or more of the above types may be used in combination as the negative electrode active material. The amount of the negative electrode active material is not particularly limited, but may be, for example, 1 mg/cm ² or more and 5 mg/cm ² or less.

The conductive agent of this embodiment used for the positive electrode and the negative electrode is not particularly limited, and examples thereof include carbon black such as acetylene black and Kettin black. In addition, as a conductive agent, instead of carbon black, natural graphite (scaly graphite, flaky graphite, earthy graphite, etc.), artificial graphite, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) Conductive materials such as powders, metal fibers, conductive ceramic materials, etc. may also be used. Furthermore, two or more of the above-described types may be used in combination as the conductive material. The amount of the conductive material added is not particularly limited, but is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 20% by mass or less, based on the amount of positive electrode active material or the amount of negative electrode active material.

The current collector used in the positive electrode of this embodiment is not particularly limited, and examples thereof include aluminum, titanium, stainless steel, nickel, fired carbon, conductive polymer, conductive glass, and the like. In addition, for the purpose of improving adhesiveness, conductivity, and oxidation resistance, materials whose surfaces are treated with carbon, nickel, titanium, silver, etc., such as aluminum or copper, may be used as the current collector for the positive electrode. .

The current collector used in the negative electrode of this embodiment is not particularly limited, and examples thereof include copper, stainless steel, nickel, aluminum, titanium, fired carbon, conductive polymer, conductive glass, Al-Cd alloy, etc. . Furthermore, for the purpose of improving adhesiveness, conductivity, and oxidation resistance, a material whose surface is treated with carbon, nickel, titanium, silver, etc., such as copper, may be used as the current collector for the negative electrode.

The surface of the current collector used for the positive electrode or the negative electrode may be subjected to oxidation treatment. Further, the shape of the current collector may be a foil, a film, a sheet, or a net. Further, as the current collector, a punched or expanded object may be used, and a molded object such as a lath object, a porous object, or a foam object may be used. The thickness of the current collector is not particularly limited, but may be, for example, 1 μm or more and 100 μm or less.

The binder of this embodiment is not particularly limited, but for example, polyvinylidene fluoride (PVDF) can be used. Furthermore, instead of PVDF, for example, PVDF copolymer resin, fluororesin, styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), styrene-acrylonitrile copolymer, etc. may be used as the binder. good. As the PVDF copolymer resin, for example, a copolymer resin of PVDF and hexafluoropropylene (HFP), perfluoromethyl vinyl ether (PFMV), or tetrafluoroethylene (TFE) may be used. As the fluororesin, for example, polytetrafluoroethylene (PTFE), fluororubber, etc. may be used. As other binders, for example, polysaccharides such as carboxymethyl cellulose (CMC), and thermoplastic resins such as polyimide resins may be used. Moreover, as a binder, two or more of the above-mentioned types may be used in combination. The amount of the binder added is not particularly limited, but is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 20% by mass or less, based on the amount of positive electrode active material or negative electrode active material.

The method for manufacturing the electrode of this embodiment is not particularly limited. The electrode manufacturing method includes, for example, preparing an electrode material in the form of a slurry by mixing an electrode active material, a conductive material, a binder, etc. with a dispersion medium, then applying the electrode material to a current collector, and then adding the dispersion medium to the electrode material. One example is a method of volatilizing.

A viscosity modifier may be used to form the electrode material into a slurry. The viscosity modifier is not particularly limited, but for example, a water-soluble polymer can be used. Examples of viscosity modifiers include celluloses such as carboxymethylcellulose salts, methylcellulose, ethylcellulose, hydroxymethylcellulose, hydroxypropylmethylcellulose, and hydroxyethylmethylcellulose; polycarboxylic acid compounds such as polyacrylic acid and sodium polyacrylate; polyvinylpyrrolidone, etc. Compounds having a vinylpyrrolidone structure; Examples include polyacrylamide, polyethylene oxide, polyvinyl alcohol, sodium alginate, xanthan gum, carrageenan, guar gum, agar, starch, and the like. Moreover, as a viscosity modifier, two or more of the above-mentioned types may be used in combination. As the viscosity modifier, carboxymethylcellulose salt is preferred.

The non-aqueous electrolyte of this embodiment is a solution in which a lithium salt is dissolved as an electrolyte in a solvent for transmitting lithium ions. As the electrolyte in this embodiment, an ionic liquid containing bis(fluorosulfonyl)imide anion as an anion component is used. Specifically, an ionic liquid containing bis(fluorosulfonyl)imide anion (FSI anion) as an anion component is used. Since an electrolytic solution using such an ionic liquid is nonflammable, the resulting lithium secondary battery has excellent safety. Furthermore, a battery with high performance, high energy density, and high voltage can be obtained even during high rate charging and discharging. The method for preparing the FSI anion is not particularly limited, but includes, for example, a method of reacting fluorosulfonic acid with urea. Note that impurities can be confirmed by analysis using a plasma emission spectrometer (ICP).

Further, the anion component contained in the ionic liquid may include anions other than FSI anions. Examples of anions other than FSI anions include BF ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , NO ₃ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ (hereinafter also referred to as "TFSI"). , (C ₂ F ₅ SO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ CO ₂ ^- , C ₃ F ₇ CO ₂ ^- , CH ₃ CO ₂ ^- , (CN) ₂ N ^-, etc. can be mentioned. Furthermore, two or more of the above-mentioned anions may be used in combination as anions other than the FSI anion.

In the ionic liquid contained in the lithium secondary battery of this embodiment, the cation to be combined with the above-mentioned FSI anion is not particularly limited, but it is preferable to use a cation that forms an ionic liquid with a melting point of 50° C. or less. By doing so, it is possible to suppress an increase in the viscosity of the non-aqueous electrolyte, and it is also possible to suppress a decrease in discharge capacity.

Examples of the above-mentioned cation include compounds containing elements such as N, P, S, O, C, and Si, and having a chain structure or a cyclic structure such as a 5-membered ring or a 6-membered ring as a skeleton. It will be done.

Examples of cyclic structures such as 5-membered rings and 6-membered rings include furan ring, thiophene ring, pyrrole ring, pyridine ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, furazane ring, imidazole ring, and pyrazole ring. , pyrazine ring, pyrimidine ring, pyridazine ring, pyrrolidine ring, piperidine ring, benzofuran ring, isobenzofuran ring, indole ring, isoindole ring, indolizine ring, and carbazole ring.

Among these cations, chain or cyclic compounds containing nitrogen are particularly preferred because they are industrially inexpensive and chemically and electrochemically stable.

Examples of cations containing nitrogen include alkylammoniums such as triethylammonium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-methyl-1-propyl-pyrrolidinium, and methylpropylpyrrolidinium. Examples include peridinium.

The lithium salt to be dissolved in the ionic liquid as the supporting electrolyte for the non-aqueous electrolyte is not particularly limited as long as it is a lithium salt that is normally used as an electrolyte for the non-aqueous electrolyte. be able to. Examples of such lithium salts include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiN(CF ₃ SO ₂ ) ₂ (LiTFSI), LiN( Examples include FSO ₂ ) ₂ (LiFSI), LiBC ₄ O ₈ , and the like. Two or more of these lithium salts may be used in combination. As the lithium salt, LiFSI and LiTFSI are preferred.

It is preferable that such a lithium salt is normally contained in the ionic liquid at a concentration of 0.1 mol/kg or more and 3.0 mol/kg or less, and a concentration of 0.3 mol/kg or more and 2.0 mol/kg or less. More preferably, it is contained in the ionic liquid at a concentration of 0.5 mol/kg or more and 1.5 mol/kg or less.

A separator is a member provided between a positive electrode and a negative electrode to isolate the positive electrode and the negative electrode. Glass fiber is used as the separator in this embodiment. The porosity of the glass fiber of this embodiment is 70% or more. By combining such a separator with the above-mentioned ionic liquid containing the FSI anion, the impregnation of the ionic liquid into the separator is significantly improved compared to conventional separators, and the internal resistance of the battery is significantly reduced. The output characteristics and cycle characteristics of a lithium ion secondary battery using an ionic liquid as an electrolyte are improved.

Here, in this specification, "porosity" is a value calculated from the apparent density of the separator and the true density of the solid content of the constituent materials using the following formula.
Porosity (%) = 100 - (apparent density of separator / true density of material solid content) x 100

The lithium secondary battery of this embodiment can be formed into a cylindrical shape, a coin shape, a square shape, or any other arbitrary shape.The basic configuration of the battery is the same regardless of the shape, and the design can be changed depending on the purpose. It can be implemented by For example, a cylindrical type is a wound body in which a negative electrode formed by applying a negative electrode active material to a negative electrode current collector and a positive electrode formed by applying a positive electrode active material to a positive electrode current collector are wound through a separator. It is obtained by storing the battery in a battery can, injecting a non-aqueous electrolyte, and sealing it with insulating plates placed on the top and bottom. In addition, when applied to a coin-type lithium secondary battery, a disc-shaped negative electrode, a separator, a disc-shaped positive electrode, and a stainless steel plate are stacked and stored in a coin-shaped battery can, and a non-aqueous electrolyte is injected. sealed.

B. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples.

<Example 1>
[Preparation of positive electrode]
90 g of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ as a positive electrode active material, 4 g of SuperP (registered trademark) (manufactured by Timcal) and 2 g of TIMREX (registered trademark) KS6 (manufactured by Timcal) as conductive agents. A positive electrode paint with a solid content of 68% by mass was obtained by mixing 4 g of polyvinylidene fluoride (PVDF) (manufactured by Kureha Corporation) as a binder and 47 g of N-methyl-2-pyrrolidone as a dispersion medium using a planetary mixer. Ta. This positive electrode paint was applied onto an aluminum foil (thickness: 15 μm) as a current collector using a coating machine, and then dried under reduced pressure at 130° C. and then subjected to a roll press treatment to obtain a positive electrode.

[Preparation of negative electrode]
95.5 g of graphite was used as a negative electrode active material, 0.5 g of SuperP (registered trademark) (manufactured by Timcal) was used as a conductive agent, 2 g of CMC (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was used as a thickener, and SBR (manufactured by JSR Co., Ltd.) was used as a binder. A negative electrode coating material with a solid content of 49% by mass was obtained by mixing 2 g of 100 g of pure water as a dispersion medium using a planetary mixer. This negative electrode paint was coated on an electrolytic copper foil (thickness: 10 μm) as a current collector using a coating machine, dried under reduced pressure at 130° C., and then subjected to roll press treatment to obtain a negative electrode.

[Assembling lithium ion secondary battery]
After producing a laminate having a structure in which glass fiber with a thickness of 30 [μm] was sandwiched between the above-mentioned positive electrode and the above-mentioned negative electrode as a separator, the positive electrode terminal was ultrasonically welded to the positive electrode, and the negative electrode terminal was attached to the negative electrode. Ultrasonic welded. Thereafter, this laminate was placed in an aluminum laminate packaging material and sealed leaving an opening for liquid injection to obtain a battery before liquid injection. In this example, the area of the positive electrode was 18 cm ² and the area of the negative electrode was 19.35 cm ² . Next, a solution of 1.2 mol/kg of LiFSI dissolved in a mixed solvent of N-methyl-N-propylpyrrolidinium and FSI was injected as an electrolyte into the battery before injection, and the opening was closed. By sealing, a lithium secondary battery intermediate was obtained.

[High temperature treatment]
The obtained lithium secondary battery intermediate was not restrained with a jig or the like, but was left standing in a constant temperature bath and subjected to high temperature treatment at 50° C. for 12 hours. Through the above steps, a lithium ion secondary battery was obtained.

As Examples other than Example 1 and Comparative Examples, lithium ion secondary batteries were also produced by the same method as Example 1, except that the separator physical properties and high temperature treatment conditions shown in Table 1 below were used. The initial charge/discharge efficiency of the produced lithium ion secondary battery was calculated by the following method.

[Charge and discharge test of lithium ion secondary battery]
As a test for calculating the initial charging/discharging efficiency, the produced lithium ion secondary battery was charged with CCCV (Constant Current, Constant Voltage) for 12 hours at a current value of 0.2C, and then the lithium ion secondary battery was charged with CCCV (Constant Current, Constant Voltage) at a current value of 0.2C. CC (Constant Current) discharge was performed at a current value of 2C. The charging/discharging voltage range was set to 2.7V-4.2V. The initial charge/discharge efficiency indicates the ratio of the initial discharge capacity to the initial charge capacity (initial discharge capacity/initial charge capacity). Note that the 0.2C current value indicates a current value that is 0.2 times the current value of 1C that can discharge the cell capacity in one hour.

The results obtained are shown in Table 1 below.

The following was found from Table 1. That is, from the results of Examples 1 to 6, when using an ionic liquid containing bis(fluorosulfonyl)imide anion as an anion component as an electrolyte and using glass fiber with a porosity of 70% or more as a separator, It was found that by performing a predetermined high temperature treatment, the initial charge/discharge efficiency became 80% or more.

On the other hand, from the results of Comparative Examples 5 to 10, when a material other than glass fiber such as polyolefin, cellulose, or polyimide is used as a separator, the initial charge/discharge efficiency is 80% or more even when high temperature treatment is performed. It turns out that this is not the case.

In addition, by comparing Examples 1 to 6 and Comparative Examples 1 to 4, it was found that the high temperature treatment conditions were 35°C or higher and 75°C or lower for 8 hours or more and 30 hours or less. It was found that the initial charge/discharge efficiency was improved compared to the previous case.

Further, by comparing Example 1 and Example 4, it was found that the initial charge/discharge efficiency was improved by performing the high temperature treatment at 50°C rather than at 40°C.

The present invention is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments and examples that correspond to the technical features in each form described in the summary column of the invention may be used to solve some or all of the above-mentioned problems, or to solve the above-mentioned problems. In order to achieve some or all of the effects, it is possible to replace or combine them as appropriate. Further, unless the technical feature is described as essential in this specification, it can be deleted as appropriate.

Claims (3)

As an electrolyte, an ionic liquid containing bis(fluorosulfonyl)imide anion as an anion component is used.
A method for manufacturing a lithium ion secondary battery using glass fiber having a porosity of 70% or more as a separator provided between a positive electrode and a negative electrode, the method comprising:
preparing a lithium secondary battery intermediate using the positive electrode, the negative electrode, the separator, and the electrolyte;
a step of subjecting the lithium secondary battery intermediate to a high temperature treatment at 35° C. or higher and 75° C. or lower for 8 hours or more and 30 hours or less,
The method for manufacturing a lithium ion secondary battery, wherein the high temperature treatment is performed before the first charge. A method for manufacturing a lithium ion secondary battery according to claim 1, comprising:
A method for manufacturing a lithium ion secondary battery, wherein the high temperature treatment is performed at a temperature of 45°C or higher and 75°C or lower. A method for manufacturing a lithium ion secondary battery according to claim 1 or 2, comprising:
A method for manufacturing a lithium ion secondary battery, wherein the high temperature treatment is performed for 10 hours or more and 24 hours or less.