JP2017082303A - Stabilized lithium powder, negative electrode using the same, and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stabilized lithium powder that can suppress damage to a negative electrode during pre-doping and improve the initial charge/discharge efficiency.SOLUTION: Provided is a stabilized lithium powder having a coating on the surface of lithium particles and having a fan-shaped lacking part having a central angle of 5 to 150° in a portion thereof, and in which the average Feret diameter (FD) preferably is 0.1 to 106 μm.EFFECT: In said stabilized lithium powder, the stress during pressing is concentrated at the lacking part and the stabilized lithium powder can be easily crushed, and the doping can be performed with a small pressing pressure, thereby the cracking of negative electrode can be suppressed and the stabilized lithium powder is swiftly crushed to also promote uniform doping, and when making a lithium secondary battery using said negative electrode, the initial charge/discharge efficiency can be improved.SELECTED DRAWING: Figure 1

Description

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

  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.

Currently, many researches have been conducted on negative electrode active materials for electrochemical devices such as lithium ion secondary batteries, such as silicon and silicon oxide, which have a larger charge / discharge capacity than carbon materials such as graphite. However, when such a material is used as the negative electrode active material, an irreversible capacity is generated. As a solution to this problem, a pre-doping technique is known that suppresses the irreversible capacity in a lithium ion battery by doping lithium ions in advance mainly on the negative electrode of the lithium ion secondary battery.
As one of them, a method has been proposed in which metallic lithium powder is used, and a mixture comprising the metallic lithium powder, a binder, and a conductive material is applied onto the active material layer to perform pre-doping (see Patent Document 1).

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.

JP 2008-98151 A

  However, many of the stabilized lithium powders described in the above-mentioned patent documents are spherical. If spherical stabilized lithium powder is used, there is a problem that the initial charge / discharge characteristics of the battery deteriorate. there were. As a result of intensive studies, the present inventors have found that a defect such as a crack is generated in the negative electrode in the step of pressing and adhering the stabilized lithium powder.

  The present invention has been made in view of the above-described problems of the prior art, and a stabilized lithium powder capable of performing efficient dope without deteriorating initial charge / discharge efficiency when the battery is formed, and the same An object of the present invention is to provide a lithium secondary battery using.

  In order to solve the above-mentioned problems, the stabilized lithium powder of the present invention is characterized in that it has a coating on the surface of the lithium particles, and further has a deficient portion in a part thereof.

  According to this, stress at the time of pressing is concentrated on the defect portion, the stabilized lithium powder is easily crushed, and doping can be performed with a small pressing pressure, so that cracking of the negative electrode can be suppressed. Moreover, uniform dope can also be advanced because a stabilized lithium powder is crushed rapidly. Thereby, when a lithium secondary battery is produced using this negative electrode, the initial charge / discharge efficiency can be improved.

  In the stabilized lithium powder of the present invention, it is further preferable that the defect portion has a fan-shaped defect in an image observed with a scanning electron microscope (SEM).

  In the stabilized lithium powder of the present invention, the center angle of the fan of the defect portion is preferably 5 ° or more and 150 ° or less.

  When the average ferret diameter of the stabilized lithium powder of the present invention is FD, the FD is preferably 0.1 μm or more and 106 μm or less. The ferret diameter is defined by the longest distance between two points in the particle as shown in FIG.

  When the depth of the defect portion of the stabilized lithium powder of the present invention is R, R is 0.05 times or more and 0.78 times or less of FD.

  According to these, the initial charge / discharge efficiency is further improved.

  According to the present invention, a stabilized lithium powder capable of performing efficient dope without deteriorating initial charge / discharge efficiency when formed into a battery, and a negative electrode and a lithium secondary battery using the same are provided. be able to.

It is a schematic diagram of the SEM observation image of the stabilized lithium powder which has a fan-shaped defect | deletion part. 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 of the present embodiment is characterized in that in the stabilized lithium powder having a film on the surface of the lithium particles, the stabilized lithium powder has a deficient portion in a part thereof.

  Moreover, the whole shape ignoring the defect | deletion part of stabilized lithium powder is a substantially spherical shape normally.

(Defect)
The shape of the defect portion is not particularly limited, such as a fan shape, a square shape, or a circular shape, but is preferably a fan shape.

The stabilized lithium powder having a deficient part in the present embodiment means that the surface of the stabilized lithium powder has a recess as shown in FIG. In addition, the presence or absence of the defect | deletion part was judged by using a scanning electron microscope (SEM: Scanning Electron Microscope) and observing a sample stand changing rotation and inclination. The depth R of the defect portion is the stabilized lithium powder that can be observed when the area of the stabilized lithium powder in the SEM observation image is minimum. L was defined as the distance to the point that bisects, and measurements were made on at least 200 stabilized lithium powders, and the average value was obtained.

The depth R of the defect portion of the stabilized lithium powder is preferably 0.05 times or more and 0.78 times or less of FD. Further, it is preferably 0.3 times or more and 0.78 times or less of FD.

  The central angle of the stabilized lithium powder fan is preferably 5 ° or more and 150 ° or less. Further, it is more preferably 10 ° or more and 90 ° or less.

  The central angle was measured using a protractor by extending the side of the defect when the area of the observed image of the stabilized lithium powder observed with the SEM was minimized. The above operation was performed on at least 200 stabilized lithium powders, and an average value was obtained.

When the depth R of the defect part and the shape and center angle of the defect part are within the above ranges, the stress during pressing is concentrated on the defect part, and the stabilized lithium powder can be easily crushed. Is possible.

  The average ferret diameter of the stabilized lithium powder is preferably from 0.1 μm to 106 μm from the viewpoint of uniform dispersibility on the electrode surface after application. Further, it is more preferably 1 μm or more and 53 μm or less.

  The ferret diameter was measured by binarizing the observed image of the stabilized lithium powder observed by SEM and obtaining the image by image analysis. This operation was performed on at least 200 stabilized lithium powders, and an average value was obtained. The ferret diameter is defined as the longest distance between two points in the particle.

(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, the mixture is gradually cooled in a state where stirring is continued, and in a state where the dispersion is sufficiently cooled, carbon dioxide (CO ₂ ) is contacted to form a stable film on the surface and dried. The

As the container, a heat-resistant container having a baffle plate attached to the inner wall is used, and stirring is performed while the container is inclined at an angle of 3 ° to 10 °. The rotation speed is preferably 1000 rpm or more, more preferably 4000 rpm or more and 6000 rpm or less. The size of the baffle plate is not particularly limited, but is preferably about 1 to 5% of the container radius.

  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 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.

  The carbon dioxide, when the lithium ingot is 1 part by mass, is preferably added in an amount of 0.01 to 0.18 parts by mass to the molten lithium-hydrocarbon oil mixture, and 0.08 to 0.1 parts by mass. More preferably. Moreover, it is preferable that the stirring conditions at the time of manufacturing the dispersion be 1000 rpm or more in order to bring sufficient contact between the introduced carbon dioxide and the dispersed metal.

<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 an amount of a negative electrode conductive additive as required.
(Negative electrode active material)
As the negative electrode active material, carbon materials such as graphite, non-graphitizable carbon, graphitizable carbon, and low-temperature calcined carbon capable of occluding and releasing lithium ions (intercalation / deintercalation or doping / dedoping) Mainly composed of metal that can be combined with lithium such as Al, Si, and Sn, silicon oxide such as SiO, SiO ₂ , or a mixture thereof, and oxide such as TiO ₂ , SnO ₂ , and Fe ₂ O ₃ Examples thereof include particles containing a crystalline / amorphous compound, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), or the like.
(Binder for negative electrode)
Negative electrode binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), as well as cellulose, styrene / butadiene rubber, ethylene / propylene rubber, polyimide resin, polyamideimide resin, and other polyacrylic acid-based binders Resin.
(Conductive aid for negative electrode)
Examples of the conductive aid for the negative electrode include acetylene black, furnace black, and carbon nanotube.

(Method for preparing a mixture of stabilized lithium powder and negative electrode active material)
The mixture of the stabilized lithium powder and the negative electrode active material is obtained by dispersing the stabilized lithium powder and the negative electrode active material prepared in the above-described process in a solvent, stirring the resultant, and then drying the solvent.

At this time, the solvent to be used is a dehydrated solvent such as N-methylpyrrolidone, toluene, xylene, or methyl ethyl ketone.

  The stirring method is not particularly limited, and a known method such as a magnetic stirrer or a hybrid mixer can be used.

(Production method of negative electrode doped with lithium)
A mixture of the stabilized lithium powder and negative electrode active material prepared in the above process is mixed with a conductive additive, a binder, and a solvent at a predetermined ratio to prepare a slurry for forming an active material layer. The negative electrode active material layer containing the stabilized lithium powder is formed by applying and drying. Thereafter, the negative electrode active material layer containing the stabilized lithium powder is pressure-molded by a roller press and heat-treated in a vacuum to obtain a lithium-doped negative electrode.

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

<Lithium ion secondary battery>
FIG. 2 shows a schematic cross-sectional view of the lithium ion secondary battery of the present embodiment.

  The lithium ion secondary battery 100 can be manufactured by manufacturing the lithium-doped negative electrode 20, the positive electrode 10, and the separator 18 impregnated with the electrolyte as shown in FIG. 2 as described above. 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.

<Positive electrode>
(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 binder, and a conductive auxiliary agent in an amount as necessary.

(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)
The positive electrode binder binds the positive electrode active materials and the current collector 12 together with the positive 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. Alternatively, an electron conductive conductive polymer or an ion conductive conductive polymer may be used as the binder. Examples of the electron conductive conductive polymer include polyacetylene. In this case, since the binder also exhibits the function of the conductive assistant particles, it is not necessary to add the conductive assistant. 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 positive electrode active material layer 14 is not particularly limited, but when added, it is preferably 0.5 to 5 parts by mass with respect to the mass of the positive electrode active material.

(Conductive aid for positive electrode)
The conductive auxiliary agent for the positive electrode is not particularly limited as long as it improves the conductivity of the positive electrode active material layer 14, and a known conductive auxiliary agent 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.

Although content of the binder in the positive electrode active material layer 14 is not specifically limited, It is preferable that it is 1-10 mass parts on the basis of the sum of the mass of a positive electrode active material, a conductive support agent, and a binder. By making content of a positive electrode active material and a binder into the said range, in the obtained positive electrode active material layer 14, the amount of binders is too small and the tendency which cannot form a strong positive electrode active material layer can be suppressed. In addition, the amount of the binder that does not contribute to the electric capacity increases, and the tendency that it is difficult to obtain a sufficient volume energy density can be suppressed.

The content of the conductive additive in the positive electrode active material layer 14 is not particularly limited, but when added, it is preferably 0.5 to 5 parts by mass with respect to the mass of the positive electrode active material.

<Electrolyte>
The electrolyte is contained in the positive electrode active material layer 14, the negative electrode active material layer 24, and the separator 18. The electrolyte is not particularly limited, and for example, in the present embodiment, an electrolytic solution containing a lithium salt (electrolyte aqueous solution, electrolyte solution using an organic solvent) can be used. However, the electrolyte aqueous solution is preferably an electrolyte solution (non-aqueous electrolyte solution) using an organic solvent because the electrochemical decomposition voltage is low, so that the withstand voltage during charging is limited to a low level. As the electrolytic solution, a lithium salt dissolved in a non-aqueous solvent (organic solvent) is preferably used. It does not specifically limit as lithium salt, The lithium salt used as an electrolyte of a lithium ion secondary battery can be used. For example, as the lithium salt, inorganic acid anion salts such as LiPF ₆ , LiBF ₄ , LiClO ₄ , LiFSI, and LiBOB, organic acid anion salts such as LiCF ₃ SO ₃ , (CF ₃ SO ₂ ) ₂ NLi, and the like are used. be able to.

Moreover, as the organic solvent, for example, aprotic high dielectric constant solvents such as ethylene carbonate and propylene carbonate, aprotic low viscosity such as acetic acid esters and propionic acid esters such as dimethyl carbonate and ethyl methyl carbonate, etc. A solvent is mentioned. It is desirable to use these aprotic high dielectric constant solvents and aprotic low viscosity solvents in combination at an appropriate mixing ratio. Furthermore, ionic liquids using imidazolium, ammonium, and pyridinium type cations can be used. The counter anion is not particularly limited, and examples thereof include BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ^{− and the} like. The ionic liquid can be used by mixing with the organic solvent described above.
The concentration of the lithium salt in the electrolytic solution is preferably 0.5 to 2.0 M from the viewpoint of electrical conductivity. The conductivity of the electrolyte at 25 ° C. is preferably 0.01 S / m or more, and is adjusted by the type of electrolyte salt or its concentration.

When the electrolyte is a solid electrolyte or gel electrolyte, poly (vinylidene fluoride) or the like can be contained as a polymer material.
Furthermore, you may add various additives in the electrolyte solution of this embodiment as needed. Examples of additives include vinylene carbonate and methyl vinylene carbonate for the purpose of improving cycle life, biphenyl and alkyl biphenyl for the purpose of preventing overcharge, various carbonate compounds for the purpose of deoxidation and dehydration, Carboxylic anhydride, various nitrogen-containing and sulfur-containing compounds can be mentioned.

  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 container with a baffle plate attached to the inner wall was added with 100 g of Kanto Chemical lithium ingot and Witco Carnation hydrocarbon oil, and the inside of the container was replaced with dry argon. Next, this container was heated to 200 ° C. to melt the lithium ingot. The mixture was stirred in a molten state for 10 minutes at a rotational speed of 5000 rpm with the container tilted at 5 °, and then cooled to room temperature over 1 hour while maintaining stirring. After cooling, 5 g of carbon dioxide was supplied to the surface for 5 minutes with continued stirring and filled. The stirring was stopped when all of the carbon dioxide was added, and the resulting powder was washed with hexane to obtain stabilized lithium powder.

(Method for preparing a mixture of stabilized lithium powder and negative electrode active material)
Using the stabilized lithium powder, a mixture of the stabilized lithium powder and the negative electrode active material was produced in the following procedure in a dry room having a dew point of minus 50 ° C. to minus 40 ° C. In 50 parts by mass of N-methylpyrrolidone, 100 parts by mass of the negative electrode active material (SiO) and 7 parts by mass of the stabilized lithium powder were added to obtain a mixture. The obtained mixture was stirred with a magnetic stirrer at room temperature for 24 hours to obtain a mixture of the stabilized lithium powder and the negative electrode active material.

(Preparation of negative electrode doped with lithium)
83 parts by mass of a mixture of stabilized lithium powder and negative electrode active material prepared by the above method, 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 are mixed Thus, a slurry for forming an active material layer was prepared. The slurry is applied to one surface of a copper foil having a thickness of 14 μm as a current collector so that the application amount of the active material doped with lithium is 2.0 mg / cm ^2, and is stabilized by drying at 100 ° C. A negative electrode active material layer containing lithium powder was formed. Then, the negative electrode active material layer containing the stabilized lithium powder formed on the current collector at a pressure of 150 kgf / cm ² by a roller press is pressure-molded and heat-treated at 350 ° C. for 3 hours in a vacuum. A negative electrode active material doped with was obtained.

(Production of evaluation lithium-ion secondary battery)
The lithium-doped negative electrode prepared above and the counter electrode obtained by bonding a lithium metal foil to a copper foil as the positive electrode are put in an aluminum laminate pack with a separator made of a polyethylene microporous film interposed therebetween, and this aluminum laminate A 1M LiPF ₆ solution (solvent: EC / DEC = 3/7 (volume ratio)) as an electrolytic solution was injected into the pack, and then vacuum-sealed to produce a lithium ion secondary battery for evaluation.

[Examples 2 to 8]
Except having changed the stirring speed into the value shown in Table 1 among the preparation conditions of stabilized lithium powder, it carried out similarly to Example 1, and obtained the stabilized lithium powder of Examples 2-8. Moreover, the evaluation lithium ion secondary battery of Examples 2-8 was produced like Example 1 using the obtained stabilized lithium powder.

[Examples 9 to 17]
Stabilized lithium powder of Examples 9 to 17 was obtained in the same manner as in Example 1 except that the stirring time was changed to the value shown in Table 1 among the preparation conditions of the stabilized lithium powder. Moreover, the lithium ion secondary battery for evaluation of Examples 9-17 was produced like Example 1 using the obtained stabilized lithium powder.

[Examples 18 to 27]
Except having changed the heating temperature into the value shown in Table 1 among the preparation conditions of stabilized lithium powder, it carried out similarly to Example 1, and obtained the stabilized lithium powder of Examples 18-27. Moreover, the lithium ion secondary battery for evaluation of Examples 18-27 was produced like Example 1 using the obtained stabilized lithium powder.

[Comparative Example 1]
A lithium ion secondary battery for evaluation of Comparative Example 1 was produced in the same manner as in Example 1 except that a stainless steel resin flask container without a baffle on the inner wall was used and the container was not tilted.

<Measurement of initial charge / discharge efficiency>
About the lithium ion secondary battery for evaluation produced in the Example and the comparative example, using a secondary battery charge / discharge test apparatus (made by Hokuto Denko Co., Ltd.), the voltage range is 0.005 V to 2.5 V, and 1C = 1600 mAh. Charge / discharge was performed at a current value of 0.05 C when / g. Thereby, initial charge capacity, initial discharge capacity, and initial charge / discharge efficiency were determined. The initial charge / discharge 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 charge / discharge efficiency, the lower the irreversible capacity, which means that an excellent doping effect is obtained.

<Measurement of Stabilized Lithium Powder FD, Presence of Defects, Center Angle when Defects are Fan-shaped and Ratio of Depth R to FD>
With respect to the stabilized lithium powder produced in the examples and comparative examples, the stabilized lithium powder was observed with a field emission scanning electron microscope (JSM-6700F) at an acceleration voltage of 1 kV, and FD, presence / absence of a defect portion, defect portion The ratio of the depth R with respect to the center angle and FD in the case where is a fan shape was measured. The measurement results are shown in Table 1.

  As shown in Table 1, it was confirmed that the stabilized lithium powders produced in Examples 1 to 27 had a defect part, and the lithium ion powder produced using the stabilized lithium powder having this defect part. The initial charge / discharge characteristics of the secondary battery are higher than the initial charge / discharge characteristics of the lithium ion secondary battery manufactured using the stabilized lithium powder of Comparative Example 1 having no defect. It was confirmed.

An electrode with few defects such as cracks can be produced by using the stabilized lithium powder of the present invention for pre-doping. In addition, a lithium ion secondary battery with improved initial efficiency can be provided by using the electrode obtained by the above manufacturing method.

DESCRIPTION OF SYMBOLS 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 ... Case, 60 62 ... Lead 100 ... Lithium ion secondary battery

Claims (7)

  A stabilized lithium powder having a coating on the surface of lithium particles, wherein the stabilized lithium powder has a deficient portion in a part thereof.   2. The stabilized lithium powder according to claim 1, wherein the defect portion has a fan-shaped defect in an image observed with a scanning electron microscope (SEM).   The stabilized lithium powder according to claim 2, wherein a central angle of the fan of the defect portion is 5 ° or more and 150 ° or less.   4. The stabilized lithium powder according to claim 1, wherein FD is 0.1 μm or more and 106 μm or less, where an average ferret diameter of the stabilized lithium powder is FD. 5.   5. The method according to claim 1, wherein R is 0.05 times or more and 0.78 times or less of FD, where R is a depth of the defect portion of the stabilized lithium powder. Stabilized lithium powder.   The negative electrode which doped lithium to the negative electrode using the said stabilized lithium powder of any one of Claims 1 thru | or 5. A lithium ion secondary battery comprising the negative electrode according to claim 6, a positive electrode, and an electrolyte.

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