JP2016194141A - Stabilized lithium powder and lithium ion secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stabilized lithium powder capable of promoting doping without generating a defect, such as a crack in an anode and improving an initial charge-discharge efficiency.SOLUTION: The stabilized lithium powder has a stabilized coating on the surface of a lithium particle. The stabilized coating has a peak A having a half value width of 35 cmor less when a peak existing in a range of 1750 cmto 1900 cmin a Raman spectrum is set to the peak A.SELECTED DRAWING: Figure 2

Description

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

  Lithium ion secondary batteries are widely applied as power sources for portable electronic devices because they are lighter and have a higher capacity than nickel cadmium batteries, nickel metal hydride batteries, and the like. It is also a promising candidate as a power source for use in hybrid vehicles and electric vehicles. With the recent miniaturization and higher functionality of portable electronic devices, further increase in capacity is expected for lithium ion secondary batteries that serve as these power sources.

  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.

  On the other hand, the use of silicon oxide (SiO), which has better cycle characteristics than metal silicon, is also being studied. However, silicon oxide has a larger irreversible capacity than metal silicon. Since the amount of lithium that contributes to charging and discharging is uniquely determined by the amount of lithium in the positive electrode, an increase in irreversible capacity in the negative electrode leads to a decrease in capacity of the entire battery.

  In order to reduce this irreversible capacity, a technique (Li doping) in which metallic lithium is brought into contact with the negative electrode in advance and lithium is doped into the negative electrode before charging / discharging is started has been proposed.

  Patent Document 1 proposes a stabilized lithium powder in which a dispersion coating is formed on the surface of lithium particles to improve the handling property in order to suppress the high reactivity of lithium.

  Usually, an electrode used in a lithium ion secondary battery has a step of forming a layer containing a negative electrode active material on a current collector and then bringing it into close contact with a press. Dope advances by exposing. Therefore, the characteristics required for the stabilized lithium powder are not only for improving the stability of lithium, but also for doping characteristics that produce excellent battery characteristics.

Japanese National Patent Publication No. 8-505440

  However, when the negative electrode is doped with lithium using the stabilized lithium powder described in the above patent document, there is a problem that the initial charge / discharge efficiency of a battery using the negative electrode is lowered. As a result of intensive studies, the present inventors have found that conventional stabilized lithium powder stabilized films have high toughness, and a large pressing pressure is required in the dope process, so that defects such as cracks are generated in the negative electrode. It was.

  On the other hand, when the press pressure is reduced in order to suppress damage to the negative electrode, the stabilized lithium powder cannot be crushed, so that the dope does not proceed efficiently and the reduction of the irreversible capacity is not achieved.

  The present invention has been made in view of the above-described problems of the prior art, and it is possible to advance the dope without causing defects such as cracks in the negative electrode. When the negative electrode is used, a battery is obtained. It is an object of the present invention to provide a stabilized lithium powder capable of improving the initial charge / discharge efficiency and a lithium ion secondary battery using the same.

In order to achieve the above object, the stabilized lithium powder according to the present invention is a stabilized lithium powder having a stabilized film on the surface of lithium particles, and the stabilized film has a Raman spectrum of 1750 cm ^{−1 to} 1900 cm ^−. A peak existing in the range of ¹ is defined as a peak A, and the half width of the peak A is 35 cm ⁻¹ or less.
According to this, when the half width of the peak A is 35 cm ⁻¹ or less, the toughness is sufficiently lowered as the stabilized lithium powder, so that the stabilized coating is sufficiently crushed even with a small press pressure, and the dope is efficient. The improved initial charge / discharge characteristics can be obtained.

Further, in the Raman spectrum of the stabilized lithium ^powder, the peak B to peak present in the range of 400cm ^-1 ~650cm -1, if the height ratio of the peak A and the peak B was set to B / A, B / It is preferable that A ≦ 0.15. According to this, the peak A is derived from LiH and the peak B is derived from Li ₂ O, and the more the LiH having low toughness is present in the stabilized film, the easier the stabilized film is crushed. Here, the smaller the height ratio B / A of peak A and peak B is, the higher the ratio of LiH in the stabilized coating is. When B / A ≦ 0.15, the stabilization is achieved. The ratio of LiH is suitable for reducing the toughness of the coating, and improved initial charge / discharge characteristics can be obtained.

  By using the stabilized lithium powder according to the present invention, it becomes possible to progress the doping without causing defects such as cracks in the negative electrode, and a lithium ion secondary battery with improved initial charge / discharge efficiency using the negative electrode Can be obtained.

It is a schematic cross section of the lithium ion secondary battery of this embodiment. It is a figure which shows the Raman spectrum of the stabilized lithium powder of this embodiment, and is a figure which shows the height of peak A, a half value width, and the height of peak B. It is the figure which expanded the peak A of FIG. 2, and is a figure which shows peak height, a half value width, and a baseline.

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

<Stabilized lithium powder>
Stabilized lithium powder of the present embodiment is a stabilized lithium powder with a stabilizing coating on the surface of the lithium particles wherein the stabilizing coating in the Raman spectrum, peaks present in the range of 1750cm ^-1 ~1900cm ^-1 Is a peak A, and the half width of the peak A is 35 cm ⁻¹ or less.

The full width at half maximum of the peak A is more preferably 20 cm ⁻¹ or less, and further preferably 10 cm ⁻¹ or less. The smaller the half width is, the more the toughness of LiH contained in the stabilizing coating is further reduced, and the stabilization coating is easily crushed.

The stabilized lithium powder, in the Raman ^spectrum, the peaks present in the range of 400cm ^-1 ~650cm -1 and peak B, if the height ratio of the peak A and the peak B was set to B / A, B / A ≦ 0.15 is preferable, B / A ≦ 0.12 is more preferable, and B / A ≦ 0.10 is still more preferable. Since the ratio of LiH in the stabilized coating increases as B / A is closer to 0, the toughness of the stabilized coating decreases, and the stabilized coating can be more easily crushed.

Examples of the compound contained in the stabilization coating include hydrides, oxides, hydroxides, carbonates, sulfides, and the like, specifically, LiH, Li ₂ O, LiOH, Li ₂ CO ₃ , Li _2. S etc. are mentioned.

(Method for producing stabilized lithium powder)
In the stabilized lithium powder of this embodiment, a lithium ingot was added to hydrocarbon oil, this was heated to a melting point or higher of lithium, and this molten lithium-hydrocarbon oil mixture was stirred for a sufficient time to form a dispersion. After that, carbon dioxide (CO ₂ ) is brought into contact with stirring while forming a stabilized coating on the surface, and stirring at a high temperature is performed for a sufficient time to reduce the toughness of the stabilizing coating in this state. It is manufactured by continuing and then gradually cooling and drying it.

  From the viewpoint of uniform dispersibility after melting, the hydrocarbon oil is preferably 1 to 30 parts by mass, more preferably 2 to 15 parts by mass when the lithium ingot is 1 part by mass.

  The stirring time of the molten lithium-hydrocarbon oil mixture is preferably 5 minutes or more.

  The stirring speed of the molten lithium-hydrocarbon oil mixture is preferably 1000 rpm or more.

  When the lithium ingot is 1 part by mass, the carbon dioxide is preferably added in an amount of 0.1 to 5 parts by mass, more preferably 0.1 to 2 parts by mass. Since carbon dioxide is preferably introduced to the surface of this mixture, the stirring conditions during the production of the dispersion are such that the stirring during carbon dioxide introduction is sufficient to provide sufficient contact between the introduced carbon dioxide and the dispersed metal. The speed is preferably 1000 rpm or more.

  The stirring time after forming the above-mentioned stabilizing film is preferably 120 minutes or more, in order to further reduce the toughness of the stabilizing film, the stirring time is further increased, more preferably 180 minutes or more, the temperature at that time Is preferably 200 ° C. or higher.

  The temperature after cooling the dispersion is preferably 100 ° C. or lower, and more preferably 50 ° C. or lower. Moreover, it is preferable that the said dispersion liquid is gradually cooled over 1 hour or more.

  Thus, it is possible to adjust the intensity | strength and half value width of the peak A and the peak B by adjusting the temperature and stirring time which were mentioned above.

<Negative electrode>
The negative electrode 20 can be produced by forming a negative electrode active material layer 24 on a negative electrode current collector 22 as described later.

(Current collector for negative electrode)
The negative electrode current collector 22 may be a conductive plate material, and for example, a metal thin plate (metal foil) such as copper, nickel, an alloy thereof, or stainless steel can be used.

(Negative electrode active material layer)
The negative electrode active material layer 24 is mainly composed of a negative electrode active material, a negative electrode binder, and a negative electrode conductive additive in an amount necessary.

(Negative electrode active material)
Examples of the negative electrode active material include silicon oxide (SiO _x ) and metal silicon (Si).

(Binder for negative electrode)
The negative electrode binder bonds the negative electrode active materials and the current collector 22 together with the negative electrode active materials. The binder is not particularly limited as long as the above-described bonding is possible, and examples thereof include fluorine resins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). In addition to the above, for example, cellulose, styrene / butadiene rubber, ethylene / propylene rubber, polyimide resin, polyamideimide resin, or the like may be used as the binder. Further, as the binder, an electron conductive conductive polymer or an ion conductive conductive polymer may be used. Examples of the electron conductive conductive polymer include polyacetylene. In this case, since the binder also exhibits the function of the conductive auxiliary agent particles, it is not necessary to add the conductive auxiliary agent. As the ion-conductive conductive polymer, for example, those having ion conductivity such as lithium ion can be used. For example, polymer compounds (polyether-based polymer compounds such as polyethylene oxide and polypropylene oxide) , Polyphosphazene, etc.) and a lithium salt such as LiClO ₄ , LiBF ₄ , LiPF ₆ , or an alkali metal salt mainly composed of lithium, and the like. Examples of the polymerization initiator used for the combination include a photopolymerization initiator or a thermal polymerization initiator that is compatible with the above-described monomer.

  The content of the binder in the negative electrode active material layer 24 is not particularly limited, but is preferably 0.5 to 5 parts by mass with respect to the mass of the negative electrode active material.

(Conductive aid for negative electrode)
The conductive aid for the negative electrode is not particularly limited as long as it improves the conductivity of the negative electrode active material layer 24, and a known conductive aid can be used. Examples thereof include carbon-based materials such as graphite and carbon black, metal fine powders such as copper, nickel, stainless steel, and iron, a mixture of carbon materials and metal fine powders, and conductive oxides such as ITO.

<Method for producing lithium-doped negative electrode>
(Method for producing negative electrode)
A negative electrode active material, a conductive additive, and a binder are mixed and dispersed in a solvent such as water or N-methyl-2-pyrrolidone to prepare a paste-like negative electrode slurry. Next, the negative electrode slurry is applied to one or both sides of a negative electrode current collector such as a copper foil using a comma roll coater, for example, and the solvent is evaporated in a drying furnace. Thereafter, it is pressure-formed by a roller press and heat-treated in a vacuum to form a negative electrode. In addition, when apply | coating to both surfaces of a negative electrode collector, it is desirable that the thickness of the coating film used as a negative electrode active material layer is the same film thickness on both surfaces.

(Method of doping lithium into the negative electrode)
The negative electrode doped with lithium is applied to the negative electrode active material layer formed on the negative electrode current collector by applying the dispersion in which the stabilized lithium powder is dispersed, and after drying, is pressed to form a negative electrode active material. Lithium doping progresses and is produced. For the dispersion of the stabilized lithium powder, a dehydrated solvent such as N-methylpyrrolidone, toluene, xylene, methyl ethyl ketone and the like can be used.

  The pressing method is not particularly limited, and a known method such as a hand press or a roller press can be used.

<Positive electrode>
The positive electrode 10 can be produced by forming the positive electrode active material layer 14 on the positive electrode current collector 12 as described later.

(Current collector for positive electrode)
The positive electrode current collector 12 may be a conductive plate material, and for example, a metal thin plate (metal foil) such as aluminum, an alloy thereof, or stainless steel can be used.

(Positive electrode active material layer)
The positive electrode active material layer 14 is mainly composed of a positive electrode active material, a positive electrode binder, and a necessary amount of positive electrode conductive additive.

(Positive electrode active material)
Examples of the positive electrode active material include occlusion and release of lithium ions, desorption and insertion (intercalation) of lithium ions, or doping and dedoping of lithium ions and counter anions (for example, PF ₆ ⁻ ) of the lithium ions. The electrode is not particularly limited as long as it can be reversibly advanced, and a known electrode active material can be used. For example, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganese spinel (LiMn ₂ O ₄ ), and the general formula: LiNi _x Co _y Mn _z MaO ₂ (x + y + z + a = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ a ≦ 1, and M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr) Oxide, lithium vanadium compound (LiV ₂ O ₅ ), olivine type LiMPO ₄ (where M is one or more elements selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr, or VO) shown), and composite metal oxides of lithium titanate _{(Li 4 Ti 5 O 12)} , LiNi x Co y Al z O 2 (0.9 <x + y + z <1.1) , etc.

(Binder for positive electrode)
There is no limitation in particular as a binder for positive electrodes, The thing similar to the binder for negative electrodes described above can be used.

(Conductive aid for positive electrode)
There is no limitation in particular as a conductive support agent for positive electrodes, The thing similar to the conductive support agent for negative electrodes described above can be used.

(Nonaqueous electrolyte)
The nonaqueous electrolytic solution has an electrolyte dissolved in a nonaqueous solvent, and may contain a cyclic carbonate and a chain carbonate as a nonaqueous solvent.

  The cyclic carbonate is not particularly limited as long as it can solvate the electrolyte, and a known cyclic carbonate can be used. For example, ethylene carbonate, propylene carbonate, butylene carbonate, and the like can be used.

  The chain carbonate is not particularly limited as long as the viscosity of the cyclic carbonate can be reduced, and a known chain carbonate can be used. Examples thereof include diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. In addition, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, and the like may be mixed and used.

  The ratio of the cyclic carbonate and the chain carbonate in the non-aqueous solvent is preferably 1: 9 to 1: 1 by volume.

(Electrolytes)
The electrolytes include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ , CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , _{3 CF 2 SO 2) 2,} LiN (CF 3 SO 2) (C 4 F 9 SO 2), LiN (CF 3 CF 2 CO) 2, lithium salts such as LiBOB can be used. In addition, these lithium salts may be used individually by 1 type, and may use 2 or more types together. In particular, LiPF ₆ is preferably included from the viewpoint of conductivity.

When LiPF ₆ is dissolved in a non-aqueous solvent, the concentration of the electrolyte in the non-aqueous electrolyte is preferably adjusted to 0.5 to 2.0 mol / L (M). When the concentration of the electrolyte is 0.5 mol / L or more, the conductivity of the nonaqueous electrolytic solution can be sufficiently secured, and a sufficient capacity can be easily obtained during charging and discharging. Moreover, by suppressing the electrolyte concentration to within 2.0 mol / L, it is possible to suppress an increase in the viscosity of the non-aqueous electrolyte, to sufficiently secure the mobility of lithium ions, and to obtain a sufficient capacity during charging and discharging. It becomes easy.

Even when LiPF ₆ is mixed with another electrolyte, the lithium ion concentration in the non-aqueous electrolyte is preferably adjusted to 0.5 to 2.0 mol / L, and the lithium ion concentration from LiPF ₆ is 50 mol%. More preferably, it is contained.

<Lithium ion secondary battery>
FIG. 1 shows a schematic cross-sectional view of the lithium ion secondary battery of the present embodiment.

  The lithium ion secondary battery 100 can be produced by producing the lithium-doped negative electrode 20 produced as described above, 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. The positive electrode 10, the separator 18, and the negative electrode 20 are laminated to prepare a laminated body 30, and, for example, the laminated body 30 is put in a bag-shaped aluminum laminated film outer body 50 prepared in advance, and the lithium salt is used as an electrolyte. A lithium ion secondary battery can be manufactured by injecting a non-aqueous electrolyte solution containing and sealing the outer package. In the drawings, reference numerals 60 and 62 denote a positive electrode and a negative electrode, respectively.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  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]
(Production of stabilized lithium powder)
A stainless steel resin flask reactor was added with 100 g of Kanto Chemical lithium ingot and Witco Carnation hydrocarbon oil, and the inside of the vessel was replaced with dry argon. Next, the reactor was heated to 200 ° C. to melt lithium, and then 100 g of carbon dioxide was supplied to the surface over 5 minutes with continued stirring to form a stabilized coating. After all the carbon dioxide was added, the reactor was heated to 250 ° C. and stirred for a further 260 minutes. Then, it cooled to room temperature over 1 hour, maintaining stirring. The obtained powder was washed with hexane to obtain stabilized lithium powder.

(Preparation of negative electrode)
A slurry for forming an active material layer was prepared by mixing 83 parts by mass of SiOx as a negative electrode active material, 2 parts by mass of acetylene black as a conductive additive, 15 parts by mass of polyamideimide as a binder, and 82 parts by mass of N-methylpyrrolidone as a solvent. . This slurry was applied as a current collector to one surface of a copper foil having a thickness of 14 μm, dried at 100 ° C., then pressure-formed by a roller press, and heat-treated at 350 ° C. in a vacuum for 3 hours to form a negative electrode active material layer A negative electrode having a thickness of 22 μm was obtained.

(Preparation of negative electrode doped with lithium)
On the negative electrode obtained by the above method, a dispersion obtained by dispersing 100 parts by mass of the stabilized lithium powder in 100 parts by mass of dehydrated N-methylpyrrolidone was used. the coating is cm ^2, and dried at 100 ° C.. Then, it pressurized by the force of 30 kN with the hand press, and doped the lithium to the negative electrode, and the negative electrode doped with lithium was obtained.

(Production of evaluation lithium-ion secondary battery)
The negative electrode prepared above and lithium cobalt oxide as a positive electrode are put in an aluminum laminate pack with a separator made of a polyethylene microporous film interposed therebetween, and 1M LiPF ₆ solution ( After injecting a solvent: ethylene carbonate / diethyl carbonate = 3/7 (volume ratio)), vacuum sealing was performed to produce a lithium ion secondary battery for evaluation.

<Measurement of half width of peak A and B / A in stabilized film>
For stabilized lithium powder prepared in Example 1, by Raman spectroscopy using a green laser of 532 nm, as shown in FIG. 2, the peak A present in the range of 1750~1900cm ^-1, 400~650cm ^-1 The peak B which exists in the range of was obtained.

As shown in FIG. 3 performs first obtained baseline 3 removal of the spectrum, the half width and the peak A peak heights A present in the range of 1750～1900Cm ^-1, in the range of ^{400～650Cm -1} The height of the existing peak B was obtained.
The full width at half maximum of peak A is the length of the line segment formed by drawing the straight line 2 parallel to the horizontal axis at the midpoint of peak A height 1 and the two intersections of the straight line and peak A. . The height of the peak was defined as the height from the base line to the peak, with a line connecting the start point and end point of the peak as a straight line. Regarding peak B, a plurality of peaks may appear. In that case, the highest peak among the peaks appearing in the frequency range was adopted.

<Confirmation of defects in negative electrode>
About the lithium dope negative electrode produced in Example 1, it was confirmed visually that the defect did not generate | occur | produce in the negative electrode.

<Measurement of cycle capacity retention ratio>
About the lithium ion secondary battery for evaluation produced in Example 1, using a secondary battery charge / discharge test apparatus (manufactured by Hokuto Denko Co., Ltd.), the voltage range is 2.5 V to 4.2 V in a thermostatic bath at a temperature of 25 ° C. Then, charging and discharging were performed for one cycle at a current value of 0.05 C, and the initial charge / discharge efficiency was determined according to the following formula 1.
Formula 1: Initial charge / discharge efficiency = (discharge capacity / charge capacity) × 100
The higher the initial charge / discharge efficiency, the lower the irreversible capacity, which means that superior doping characteristics are obtained.

[Examples 2 to 12]
The stabilized lithium powders of Examples 2 to 12 were obtained in the same manner as in Example 1 except that the production conditions of the stabilized lithium powder were changed to those shown in Table 1. Moreover, the lithium ion secondary battery for evaluation of Examples 2-12 was produced like Example 1 using the obtained stabilized lithium powder.

Table 1 shows the results of various measurements described in Example 1 for the evaluation results of Example 1 and the evaluation lithium ion secondary batteries of Examples 2 to 12. From Table 1, in all of Examples 1 to 12, stabilized lithium powder having a peak A half-width of 35 cm ⁻¹ or less was obtained. The half width of peak A was controlled by the stirring time at high temperature. Moreover, in Examples 1-12 in which the half width of the peak A was 35 cm ⁻¹ or less, no defects occurred in the negative electrode, and thus the initial charge / discharge efficiency was 80% or more. In particular, when the half width of peak A was 10 cm ⁻¹ or less and B / A was 0.12 or less, a high initial charge / discharge efficiency of 90% or more was exhibited. B / A was controlled by the amount of carbon dioxide introduced.

[Comparative Examples 1-2]
The stabilized lithium powders of Comparative Examples 1 and 2 were obtained in the same manner as in Example 1 except that the production conditions of the stabilized lithium powder were changed to those shown in Table 1. Moreover, the lithium ion secondary battery for evaluation of Comparative Examples 1-2 was produced like Example 1 using the obtained stabilized lithium powder.

[Comparative Example 3]
A lithium ion secondary battery for evaluation of Comparative Example 3 was produced in the same manner as in Example 1 using stabilized lithium powder (trade name: SLMP) manufactured by FMC.

Table 1 shows the results of various measurements described in Example 1 performed on the evaluation lithium ion secondary batteries of Comparative Examples 1 to 3. In Comparative Examples 1 to 3, since the half width of peak A is 36 cm ⁻¹ or more, defects are generated in the negative electrode during doping, and the initial charge and discharge efficiency is 71.8% or less, which is a low value compared to the examples. It was.

  Stabilized lithium powder capable of allowing dope to proceed without causing defects such as cracks in the negative electrode and improving the initial charge / discharge efficiency of the battery using the negative electrode, and lithium ion secondary using the same A battery can be provided.

DESCRIPTION OF SYMBOLS 1 ... Peak height, 2 ... Half width, 3 ... Baseline, 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, 60, 62 ... lead, 100 ... lithium ion secondary battery.

Claims (3)

A stabilized lithium powder with a stabilizing coating on the surface of the lithium particles wherein the stabilizing lithium powder in the Raman ^spectrum, the peaks present in the range of 1750cm ^-1 ~1900cm -1 and peak A, a half of the peak A A stabilized lithium powder having a value range of 35 cm ⁻¹ or less. Wherein in the Raman spectrum of the stabilized lithium ^powder, the peak B to peak present in the range of 400cm ^-1 ~650cm -1, when the height ratio of the peak A and peak B and B / A, B / A ≦ The stabilized lithium powder according to claim 1, which is 0.15. A lithium ion secondary battery comprising: a negative electrode doped with lithium using the stabilized lithium powder according to claim 1; a positive electrode; and an electrolyte.

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