JP6609903B2 - Stabilized lithium powder, and negative electrode and lithium ion secondary battery using the same - Google Patents

Description

  The present invention relates to a stabilized lithium powder, and a negative electrode and a lithium ion secondary battery using the same.

  Electrochemical devices typified by lithium-ion secondary batteries using a lithium-containing transition metal oxide typified by lithium cobaltate as the positive electrode and a carbon material that can be doped / undoped with lithium as the negative electrode have a high energy density. Therefore, it is important as a power source for portable electronic devices typified by mobile phones, and the demand for these portable electronic devices is increasing with the rapid spread of these portable electronic devices.

  In addition, many automobiles that are environmentally conscious, such as hybrid cars, have been developed, but lithium ion secondary batteries having a high energy density have attracted a great deal of attention as one of the power sources to be mounted.

  The capacity of the lithium ion secondary battery mainly depends on the active material of the electrode. In general, graphite is used as the negative electrode active material, but it is necessary to use a higher capacity negative electrode active material in order to meet the above requirements. Therefore, metallic silicon (Si) having a much larger theoretical capacity (4210 mAh / g) than the theoretical capacity of graphite (372 mAh / g) has attracted attention.

  As one of the means for improving the performance of such a lithium ion secondary battery, the irreversible capacity of the electrode in the lithium ion electricity storage device is suppressed by previously doping lithium ions mainly on the negative electrode of the lithium on electricity storage device. Pre-doping technology is known.

  For example, Patent Document 1 discloses a vertical pre-doping method using a perforated foil having a through hole in a current collector. In the vertical pre-doping method, in addition to the positive electrode and the negative electrode, a third electrode for supplying lithium ions to the positive electrode and the negative electrode is used.

  In the vertical pre-doping method, the manufacturing process is more complicated than that of a normal lithium ion electricity storage device, and time and cost are required.

  There is also a method of introducing the positive electrode mixture layer or the entire negative electrode mixture layer using a lithium foil. However, since lithium is soft, it is very difficult to apply evenly. In addition, since the handling of the work itself is low, the productivity during mass production may be affected.

  As means for solving these problems, a method has been proposed in which lithium powder is used, and the powder is applied as a solution to perform pre-doping (see Patent Document 2).

  As such a pre-doping method using lithium powder, a stabilized treatment has been developed due to the poor stability of lithium powder. As a method for stabilizing lithium powder, a material having high stability on the surface of metal lithium powder, for example, organic rubber such as NBR (nitrile butadiene rubber) and SBR (styrene butadiene rubber), EVA (ethylene vinyl alcohol copolymer resin) ), Organic resins such as PVDF (polyvinylidene fluoride) and PEO (polyether), and methods using stabilized lithium particles coated with metal lithium particles with an inorganic compound such as a metal compound.

  By using these stabilized lithium particles, it can be stabilized in the air or in a solvent such as toluene or xylene, and lithium alteration can be prevented even in a dry room having a dew point of about minus 40 ° C. Further, since excessive reaction between lithium and the negative electrode active material is suppressed during pre-doping, the amount of heat generated by this reaction can be reduced.

Japanese Patent No. 4126157 JP 2008-98151 A

  However, when an organic polymer is used as the covering portion, the covering portion may be eluted by being exposed to the electrolytic solution in the battery, leading to a decrease in battery performance. In particular, in a high temperature environment or at a high potential, the effect becomes significant due to increased elution and reactivity. On the other hand, in the case where a lithium metal is coated with an inorganic compound such as lithium carbonate or lithium oxide, it is necessary to devise uniform coating because of the properties of the protective layer. Depending on the coating method, uneven doping of the lithium powder to the electrode is likely to occur, and stable and sufficient battery characteristics may not be sufficiently obtained. In view of the above problems, an object of the present invention is to improve the uneven doping of the electrode while maintaining excellent battery performance.

As a result of intensive studies to improve the stable battery characteristics while maintaining the battery performance, the present inventors have formed a ionic liquid in the coating in the stabilized lithium powder having a coating on the surface of the lithium particles. It has been found that by using a stabilized lithium powder for a lithium ion secondary battery characterized by containing a lithium salt with a possible anion, in-plane doping unevenness can be improved and high battery characteristics can be obtained.

The lithium salt with the anion that can form the ionic liquid is present in the coating of lithium particles, and its high ionic conductivity further promotes lithium diffusion when lithium is doped into the electrode. It is considered that the diffusion promoting effect increases the doping efficiency of the electrode, prevents the deactivation of lithium metal during doping, improves the in-plane doping unevenness, and obtains high battery characteristics.

The lithium salt is preferably 0.1% by weight or more and 10% by weight or less based on the entire stabilized lithium powder. By using an electrode made of such stabilized lithium powder, in-plane doping unevenness can be improved and high battery characteristics can be obtained.

The lithium salt is not particularly limited, but bromine anion (Br ⁻ ), boron tetrafluoride anion (BF ₄ ⁻ ), phosphorus hexafluoride anion (PF ₆ ⁻ ), bis (fluorosulfonyl). Imide anion (FSI ⁻ ), bis (perfluoroethylsulfonyl) imide anion (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , trifluorosulfonyl anion (CF ₃ SO ₃ ⁻ ), bis (trifluoromethanesulfonyl) imide anion (N ^{_{(SO 2 CF 3) 2 -}} , TFSI -), tris (perfluoroalkyl) trifluoro phosphate anion, it is composed of at least one anionic selected from the group consisting of ethyl sulfate anion preferred.

Provided is an electrode capable of preventing inactivation of lithium metal during doping, improving in-plane doping unevenness, and obtaining high battery characteristics if the negative electrode is doped with a negative electrode using the stabilized lithium particles. It becomes possible.

The lithium salt includes bis (fluorosulfonyl) imide anion (FSI ⁻ ), bis (perfluoroethylsulfonyl) imide anion (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , trifluorosulfonyl anion (CF ₃ SO ₃ ⁻ ), Consists of at least one anion selected from the group of bis (trifluoromethanesulfonyl) imide anion (N (SO ₂ CF ₃ ) ₂ ⁻ , TFSI ⁻ ), tris (perfluoroalkyl) trifluorophosphate anion, and ethyl sulfate anion. It is preferred that

Further, the lithium salt preferably contains fluorine.

Further, in a lithium ion secondary battery having a negative electrode obtained by doping lithium into the negative electrode using the stabilized lithium particles, a positive electrode, and an electrolyte, a battery having excellent battery characteristics due to a sufficient doping effect is obtained. Can be provided.

According to the present invention, stable battery characteristics can be obtained, and the lithium powder is less likely to be doped unevenly by coating or the like, and stabilized lithium powder capable of obtaining sufficient battery characteristics, a negative electrode using the same, and A lithium ion secondary battery can be provided.

It is a schematic cross section of the stabilized lithium powder of this embodiment. It is a schematic cross section of the lithium ion secondary battery of this embodiment.

  Hereinafter, preferred embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

(Stabilized lithium powder)
The stabilized lithium powder is composed of the particles shown in FIG. These particles are composed of lithium particles 1 and a coating 2 for stabilization, and the overall shape thereof may be spherical as shown in FIG. 1 or various shapes, but may be a distorted shape that is not spherical. preferable.
It is preferable that the stabilized lithium particle comprised at this time is 1-200 micrometers in average particle diameter.
In addition, as a measuring method, stable measurement is possible with an optical microscope, an electron microscope, a particle size distribution meter or the like under an inert atmosphere such as in an inert gas or hydrocarbon oil.

In the film formed on the surface of the lithium particles, bromine anion (Br ⁻ ), boron tetrafluoride anion (BF ₄ ⁻ ), phosphorus hexafluoride anion (PF ₆ ⁻ ), bis (fluorosulfonyl) imide anion (FSI). ⁻ ), Bis (perfluoroethylsulfonyl) imide anion (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , trifluorosulfonyl anion (CF ₃ SO ₃ ⁻ ), bis (trifluoromethanesulfonyl) imide anion (N (SO ₂ CF ₃₎ 2 ^_-, TFSI ^-), but tris (perfluoroalkyl) lithium salt with trifluoroacetic phosphate anion and the like as a preferable example, in particular organic anion, bis (perfluoroethylsulfonyl) imide (C _{2 F 5 SO 2) 2 N} -, trifluorosulfonyl anion CF ₃ SO ₃ ^-), bis (trifluoromethanesulfonyl) imide anion _{(N (SO 2 CF 3)} 2 -, tris (perfluoroalkyl) trifluoro phosphate anion, lithium salt of ethyl sulfate anion, heat stability Many of them have high water stability and are preferable in terms of battery efficiency and pre-dope stability.The stabilized lithium powder is excellent in handleability and can be handled in a dry room with a dew point of about minus 40 ° C. is there.

There is no problem as long as the lithium salt is coated in an amount of lithium particles, but it is preferably 0.1% by weight or more and 10% by weight or less based on the total weight of the stabilized lithium particles. More preferably, they are 1.0 weight% or more and 8.5 weight% or less, More preferably, they are 1.0 weight% or more and 5.0 weight% or less. Within this range, it is possible to reduce the loss of the negative electrode due to excessive heat generation during the production of the negative electrode, improve the in-plane doping unevenness, and produce an electrode capable of obtaining high battery characteristics.

The lithium salt may be a single component or may be mixed, laminated on lithium particles, or scattered.

The film formed on the surface of the lithium particles is not limited in thickness as long as the battery characteristics are not affected. Further, the thickness of the film does not need to be constant, and the shape can be used in various states.

In addition, regarding the composition of the stabilized lithium metal powder, it is possible to identify and quantify the compound present in the powder using solid LiNMR quantification, X-ray photoelectron spectroscopic analysis, X-ray diffraction, or the like.

Furthermore, if the negative electrode is obtained by using the above-described stabilized lithium particles and the negative electrode is subjected to lithium doping, in-plane doping unevenness can be improved. Furthermore, this electrode can provide an electrode that produces excellent battery characteristics.

(Method for producing stabilized lithium powder)
The stabilized lithium powder of the present embodiment is prepared by heating lithium metal to a temperature equal to or higher than its melting point in hydrocarbon oil, stirring molten lithium at a high speed, and then dropping an ionic liquid under specific conditions, And a stabilized lithium powder in which a salt formed from lithium forms a stabilizing layer. Further, as another manufacturing method, there is a method in which the ionic liquid is not added dropwise but added simultaneously with lithium metal from the beginning. Depending on conditions, it is possible to use an ionic liquid as a solvent and a reactant without using hydrocarbon oil. The powder thus produced is washed with hexane, and the obtained powder is dried to complete the stabilized lithium powder of the present embodiment. Using the present invention, other alkali metals such as sodium and potassium can be produced as well.

The type of anion that the ionic liquid can constitute is an anion that has a melting point in the range of minus 35 to plus 100 ° C., has ionic conductivity, and can generally constitute a non-volatile ionic liquid. However, bromine anion (Br ⁻ ), boron tetrafluoride anion (BF ₄ ⁻ ), phosphorus hexafluoride anion (PF ₆ ⁻ ), bis (fluorosulfonyl) imide anion (FSI ⁻ ), bis (perfluoro) Ethylsulfonyl) imide anion (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , trifluorosulfonyl anion (CF ₃ SO ₃ ⁻ ), bis (trifluoromethanesulfonyl) imide anion (N (SO ₂ CF ₃ ) ₂ ⁻ , TFSI ⁻ ), Tris (perfluoroalkyl) trifluorophosphate anion, ethylsulfur Examples include ionic liquids composed of anions such as toanions and various cations and having a melting point at minus 35 to 100 ° C. or lower.

  When the stabilized lithium powder is produced, it can be synthesized while introducing high-purity carbon dioxide gas during stabilization. This makes it possible to produce the stabilized lithium powder of the present invention in which lithium carbonate and lithium oxide are mixed. When the lithium metal is 1% by weight, 0.1 to 10% by weight is preferably added to the dispersion mixture, and more preferably 1 to 3% by weight. Carbon dioxide is preferably introduced below the surface of this mixture, and the vigorous stirring conditions necessary to produce the dispersion result in contact between the carbon dioxide introduced on the dispersion mixture and the dispersed metal. Should be enough to do.

The lithium metal used as a raw material for producing the powder of the present invention is not particularly limited as long as it is in a range that does not hinder the use of the lithium ion secondary battery, and is not particularly limited, square, granular, powder, foil, etc. The lithium metal can be used.

Various hydrocarbon oils can be used as the hydrocarbon oil necessary for producing the stabilized lithium powder of the present invention. As used herein, hydrocarbon oils include various oily liquids consisting primarily of hydrocarbon mixtures, including mineral oils, i.e., liquid products of mineral origin with viscosity limitations recognized as oils, and therefore Including but not limited to petroleum, shale oil, paraffin oil and the like. Typical hydrocarbon oils are, for example, liquid paraffin manufactured by Sanko Chemical Co., Ltd., S type, industrial type, trade names of MORESCO: Moresco White P-40, P-55, P-60, P-70 , P-80, P-100, P-120, P-150, P-200, P-260, P-350P, High Call M series (High Call M-52, High Call M-72, High Call M, manufactured by Kaneda) -172, High Coal M-352, K series (High Coal K-140N, High Coal K-160, High Coal K-230, High Coal K-290, High Coal K-350, and High Coal E-7. Not limited to these, any purified hydrocarbon solvent boiling above the melting point of lithium or sodium metal can be used.

  The hydrocarbon oil is preferably 1 to 50 parts by weight and more preferably 2 to 30 parts by weight from the viewpoint of uniform dispersibility after melting when the lithium metal is 1 part by weight.

  The temperature necessary for producing the stabilized lithium powder of the present invention is preferably equal to or higher than the temperature at which lithium metal melts. Specifically, it is 190 degreeC-250 degreeC, Preferably it is 195 degreeC-240 degreeC, More preferably, it is 200 degreeC-220 degreeC. If the temperature is too low, lithium is solidified, making it difficult to produce lithium powder. If the temperature is too high, vaporization may occur depending on the type of hydrocarbon oil, making it difficult to handle in production.

  The stirring ability necessary for producing the stabilized lithium powder of the present invention depends on the container size and the processing amount, but there is no need to limit the stirring device as long as the stirring method can obtain a desired particle size. It is possible to make fine particles with various agitators and dispersers.

  In addition, when applying the stabilized lithium powder of the present invention to the negative electrode surface, it is preferable to use a stabilized lithium powder to which an ionic liquid is added. In order to prepare this, when applying the stabilized lithium powder to the negative electrode, the stabilized lithium powder to which the ionic liquid is added is used in a method such as mixing various ionic liquids with a lithium-stable organic solvent and using a dispersion solvent. It is possible to apply. An ionic liquid having a high ionic conductivity promotes lithium doping, and it is possible to reduce high battery characteristics and unevenness during doping. The addition amount of the ionic liquid is not particularly limited as long as the application to the negative electrode is not hindered.

  When carbon dioxide is used to produce the stabilized lithium powder of the present invention, it is preferable that the purity is high. The concentration is preferably 98% or more. Since it is a reaction with lithium metal, it is not preferable that there is much water. Moreover, if the purity is low, lithium metal may react with impurities, which is not preferable.

    FIG. 2 shows a schematic cross-sectional view of the lithium ion secondary battery of the present embodiment. Lithium can be doped into the negative electrode by applying the stabilized lithium powder prepared as described above onto the negative electrode active material layer 24 formed on the negative electrode current collector 22.

The lithium ion secondary battery 100 can be manufactured by manufacturing the doped negative electrode 20, the positive electrode 10, and the separator 18 impregnated with the electrolyte as shown in FIG.
Here, the positive electrode 10 can be produced by forming the positive electrode active material layer 14 on the positive electrode current collector 12.
In the drawings, reference numerals 60 and 62 denote a positive electrode and a negative electrode, respectively.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

[Example 1]
10 g of commercially available lithium metal was charged into a stainless steel flask reactor at room temperature in an atmosphere of dry argon. The reactor was installed so that heat control was possible with an oil bath. 50 g of liquid paraffin high coal K-290 (manufactured by Kaneda) marketed in the reactor was added. Next, the reactor was heated to about 200 ° C. using a hot stirrer, and it was confirmed visually that the metal was melted using a stirrer. Next, the lithium powder is finely divided by vigorous stirring using a stirrer, and N, N, N, -trimethyl-N-propylammonium-bis (trifluoromethanesulfonyl) imide (TMPA-TFSI) diluted with a hydrocarbon oil is dispersed. ) Was slowly added in an amount of 0.8% by weight to lithium. Heating was stopped and stirring was continued until the mixture cooled to about 45 ° C. The dispersion was then transferred to a beaker. Further, the lithium dispersion was filtered and washed three times with hexane to remove the hydrocarbon oil medium. The filtrate was dried in an oven to remove a trace amount of solvent, and the resulting free-flowing powder was transferred to a storage bottle to produce a stabilized lithium powder. As a result of measuring the component ratio of this stabilized lithium powder by X-ray diffraction and Li solid NMR, it was found to be a lithium metal having 0.5% by weight of LiTFSI.

<Production of negative electrode>
A slurry for forming an active material layer by mixing 50 parts by mass of a negative electrode active material (silicon oxide), 1 part by mass of acetylene black as a conductive additive, 10 parts by mass of polyamideimide as a binder, and 39 parts by mass of N-methylpyrrolidone as a solvent. Was prepared. After applying this slurry as a current collector to one surface of a copper foil having a thickness of 14 μm, 1 mass of diethyl carbonate (DEC) was added so that the applied amount of the negative electrode active material was 2.0 mg / cm ^2. A partially stabilized lithium dispersion was applied and dried at 100 ° C. to form a negative electrode active material layer. Thereafter, the negative electrode active material layer formed on the current collector was pressure-molded by a roller press, and heat-treated at 350 ° C. for 3 hours in a vacuum to obtain a negative electrode having an active material layer thickness of 22 μm.

<Production of evaluation lithium-ion secondary battery>
The negative electrode produced above and a counter electrode made by bonding a lithium metal foil to a copper foil as a positive electrode are placed in an aluminum laminate pack with a separator made of a polyethylene microporous film interposed therebetween, and the aluminum laminate pack is electrolyzed. After injecting a 1M LiPF ₆ solution (solvent: EC / DEC = 3/7 (volume ratio)) as a liquid, vacuum sealing was performed to produce a lithium ion secondary battery for evaluation.

<Measurement of initial charge / discharge efficiency>
About the lithium ion secondary battery for evaluation produced by the Example and the comparative example, a secondary battery charge / discharge test apparatus (made by Hokuto Denko Co., Ltd.) was used at room temperature, and the voltage range was 0.005V to 2.5V. Charge / discharge was performed at a current value of 0.05 C at 1600 mA / h. Thereby, the initial charge capacity, the initial discharge capacity, and the initial efficiency were obtained. The initial efficiency (%) is the ratio of the initial discharge capacity to the initial charge capacity (100 × initial discharge capacity / initial charge capacity). The higher the initial efficiency, the lower the irreversible capacity, which means that excellent doping efficiency is obtained. The initial discharge efficiency ratio shown in Table 1 was the result of Example 1 when the initial discharge efficiency of Comparative Example 2 was set to 100%, and was found to be a better result than Comparative Examples 1 and 2. .

[Example 2]
The final stabilized lithium powder was produced in the same manner as in Example 1 except that the amount of LiTFSI added was changed so that the component ratio of the stabilized lithium powder was 1% LiTFSI. The test described in Table 1 was carried out by the same evaluation method as in Example 1 and found to have good characteristics.

[Example 3]
The final stabilized lithium powder was prepared in the same manner as in Example 1 except that the amount of LiTFSI added was changed so that the stabilized lithium powder contained 3% LiTFSI. The test described in Table 1 was carried out by the same evaluation method as in Example 1 and found to have good characteristics.

[Example 4]
The final stabilized lithium powder was prepared in the same manner as in Example 1, except that the amount of LiTFSI added was changed so that the stabilized lithium powder contained 10% LiTFSI. The test described in Table 1 was carried out by the same evaluation method as in Example 1 and found to have good characteristics.

[Example 5]
The same method as in Example 3 except that a lithium salt using 1-ethyl-3-methylimidazolium ethyl sulfate as an ionic liquid was used in the same manner as in the preparation of the stabilized lithium powder used in Example 3. Then, a stabilized lithium powder was prepared, and a stabilized lithium powder having a lithium salt amount shown in Table 1 was prepared. Furthermore, the test described in Table 1 was carried out by the same evaluation method as in Example 1, and it was found that the characteristics were good.

[Example 6]
Using the same method as the preparation of the stabilized lithium powder used in Example 3, the component ratio of the finally obtained stabilized lithium powder was adjusted to the value described in Example 6 of Table 1. A stabilized lithium powder was prepared in the same manner as in Example 3 except that the amount of salt added was adjusted, and the test described in Table 1 was carried out by the same evaluation method as in Example 1 with good characteristics. I found out.

[Example 7]
Using the same method as the preparation of the stabilized lithium powder used in Example 3, the component ratio of the finally obtained stabilized lithium powder was adjusted to the value described in Example 7 in Table 1. A stabilized lithium powder was prepared in the same manner as in Example 3 except that the amount of salt added was adjusted, and the test described in Table 1 was carried out by the same evaluation method as in Example 1 with good characteristics. I found out.

[Example 8]
Using a method similar to the production of the stabilized lithium powder used in Example 1, the component ratio of the finally obtained stabilized lithium powder was adjusted to the value described in Example 8 in Table 1. A stabilized lithium powder was prepared in the same manner as in Example 3 except that the amount of salt added was adjusted, and the test described in Table 1 was carried out by the same evaluation method as in Example 1 with good characteristics. I found out.

[Example 9]
Using the same method as the preparation of the stabilized lithium powder used in Example 1, the component ratio of the finally obtained stabilized lithium powder was adjusted to the value described in Example 9 in Table 1. A stabilized lithium powder was prepared in the same manner as in Example 3 except that the amount of salt added was adjusted, and the test described in Table 1 was carried out by the same evaluation method as in Example 1 with good characteristics. I found out.

[Example 10]
Using the same method as the preparation of the stabilized lithium powder used in Example 1, the component ratio of the finally obtained stabilized lithium powder was adjusted to the value described in Example 10 of Table 1. A stabilized lithium powder was prepared in the same manner as in Example 3 except that the amount of salt added was adjusted, and the test described in Table 1 was carried out by the same evaluation method as in Example 1 with good characteristics. I found out.

[Example 11]
Using a method similar to the production of the stabilized lithium powder used in Example 1, the component ratio of the finally obtained stabilized lithium powder was adjusted to the value described in Example 11 of Table 1. A stabilized lithium powder was prepared in the same manner as in Example 3 except that the amount of salt added was adjusted, and the test described in Table 1 was carried out by the same evaluation method as in Example 1 with good characteristics. I found out.

[Example 12]
Using the same method as the preparation of the stabilized lithium powder used in Example 1, the component ratio of the finally obtained stabilized lithium powder was adjusted to the value described in Example 12 of Table 1. A stabilized lithium powder was prepared in the same manner as in Example 3 except that the amount of salt added was adjusted, and the test described in Table 1 was carried out by the same evaluation method as in Example 1 with good characteristics. I found out.

[Example 13]
Using the same method as the preparation of the stabilized lithium powder used in Example 1, the component ratio of the finally obtained stabilized lithium powder was adjusted to the value described in Example 13 of Table 1. A stabilized lithium powder was prepared in the same manner as in Example 3 except that the amount of salt added was adjusted, and the test described in Table 1 was carried out by the same evaluation method as in Example 1 with good characteristics. I found out.

[Comparative Example 1]
As a result of conducting the test described in Table 1 using the commercially available stabilized lithium powder (trade name: SLMP) manufactured by FMC, results inferior to those of the examples were obtained. This is because the coating made of lithium carbonate or lithium oxide, which does not contain anions constituting the ionic liquid, becomes a barrier during pre-doping and hinders reaction with the negative electrode of lithium, resulting in a decrease in discharge capacity and in-plane pre-doping variation. It is thought that this happened.

[Comparative Example 2]
As a result of conducting a productivity confirmation test using a commercially available lithium powder having no coating, the results shown in Table 1 were inferior to those of the examples. This is presumably because lithium without a coating comes into contact with air, the lithium was deactivated, and the electrode due to reaction with air was thermally damaged and deteriorated.

DESCRIPTION OF SYMBOLS 1 ... Lithium particle, 2 ... Stabilization layer, 10 ... Positive electrode, 12 ... Positive electrode collector, 14 ... Positive electrode active material layer, 18 ... Separator, 20 ... Negative electrode, 22 ... Negative electrode collector, 24 ... Negative electrode active material layer 30 ... laminate, 50 ... outer package, 62 ... positive electrode lead, 60 ... negative electrode lead, 100 ... lithium ion secondary battery

Claims (3)

In the stabilized lithium powder having a coating on the surface of lithium particles, the coating consists of a lithium salt with an anion that can form an ionic liquid,
The lithium salt of bis (perfluoroethyl sulfonyl) imide anion _{(C 2 F 5 SO 2)} 2 N -, trifluoromethanesulfonyl anion _(CF 3 SO ₃ ^-), bis (trifluoromethanesulfonyl) imide anion (N ( SO ₂ CF ₃ ) ₂ ⁻ , TFSI ⁻ ), tris (perfluoroalkyl) trifluorophosphate anion, and at least one anion selected from the group of ethyl sulfate anion, stabilization Lithium powder.   The stabilized lithium powder according to claim 1, wherein the lithium salt is 0.1 wt% to 10 wt% or less based on the entire stabilized lithium powder.   The stabilized lithium powder according to claim 1 or 2, wherein the lithium salt contains fluorine.

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