JP6690189B2 - Stabilized lithium powder, negative electrode using the same, and lithium ion secondary battery - Google Patents

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 lighter and have higher capacity than nickel cadmium batteries, nickel hydride batteries, etc., and are therefore widely applied as power sources for portable electronic devices. It is also a strong candidate as a power source to be installed in hybrid vehicles and electric vehicles. With the recent miniaturization and higher functionality of portable electronic devices, it is expected that the lithium-ion secondary batteries used as the power sources for these devices will have even higher capacities.

Currently, as negative electrode active materials for electrochemical devices such as lithium ion secondary batteries, many alloy-based negative electrode active materials such as silicon and silicon oxide, which have a larger charge / discharge capacity than carbon materials such as graphite, are being studied. However, when such a material is used as the negative electrode active material, irreversible capacity is generated. As a solution to this problem, there is known a pre-doping technique for suppressing the irreversible capacity in the lithium-ion battery by preliminarily doping lithium ions into the negative electrode of the lithium-ion secondary battery.
As one of them, there has been proposed a method in which metallic lithium powder is used, and a mixture of the metallic lithium powder, a binder, and a conductive material is applied on 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, but the doping step involves removing Li metal of stabilized lithium powder by the press. Dope progresses by exposing.
Therefore, the characteristics required for the stabilized lithium powder are not only the improvement in the stability of lithium but also the doping characteristics that produce excellent battery characteristics.

JP, 2008-98151, A

  However, the stabilized lithium powder as described in the above-mentioned patent documents often has a spherical shape, and when the 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 the cause is that defects such as cracks are 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 problems of the above-mentioned conventional technology, and does not deteriorate the initial charge / discharge efficiency when a battery is formed, and stabilized lithium powder capable of efficient doping 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 by having a coating film on the surface of lithium particles and further having a defective portion in a part thereof.

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

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

  Further, in the stabilized lithium powder of the present invention, it is preferable that the central angle of the fan of the defective portion is 5 ° or more and 150 ° or less.

  When the average Feret 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 Feret diameter is defined as the distance between the two longest points in the particle as shown in FIG.

  When the depth of the defective 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, there is provided a stabilized lithium powder capable of performing efficient doping without deteriorating the initial charging / discharging efficiency of a battery, and a negative electrode and a lithium secondary battery using the same. be able to.

It is a schematic diagram of the SEM observation image of the stabilized lithium powder which has a fan-shaped defect part. It is a schematic cross section of the lithium ion secondary battery of this embodiment.

  Preferred embodiments of the present invention will be described below. The present invention is not limited to the embodiments below.

<Stabilized lithium powder>
The stabilized lithium powder of the present embodiment is characterized in that, in the stabilized lithium powder having a coating on the surface of lithium particles, the stabilized lithium powder has a defective portion in a part thereof.

  Further, the entire shape of the stabilized lithium powder ignoring the defective portion is usually substantially spherical.

(Defect part)
The shape of the defective portion is not particularly limited, and may be fan-shaped, square-shaped, circular, or the like, but fan-shaped is more preferable.

In the present embodiment, the stabilized lithium powder partially having a defect means that the surface of the stabilized lithium powder has a recess as shown in FIG. In addition, the presence or absence of a defect part was judged by observing a sample stage by rotating and tilting it using a scanning electron microscope (SEM). The depth R of the defective portion is from the deepest portion of the defective portion when the width of the opening of the defective portion is L in 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 where it was divided into two equal parts, and measurement was performed on at least 200 stabilized lithium powders to obtain an average value.

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

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

  Regarding the method of measuring the central angle, when the area of the observed image of the stabilized lithium powder observed by SEM is the minimum, the side of the defective portion is extended and the protractor is used for the measurement. The above operation was performed on at least 200 stabilized lithium powders, and an average value was obtained.

When the depth R of the defective portion and the shape and central angle of the defective portion are within the above ranges, the stress during pressing is concentrated on the defective portion, the stabilized lithium powder is easily crushed, and efficient doping of lithium is performed. Is possible.

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

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

(Method for producing stabilized lithium powder)
The stabilized lithium powder of the present embodiment was prepared by adding a lithium ingot to hydrocarbon oil, heating it to a temperature equal to or higher than the melting point of lithium, and stirring the molten lithium-hydrocarbon oil mixture for a sufficient time. After that, the dispersion liquid is gradually cooled with continued stirring, and carbon dioxide (CO ₂ ) is brought into contact with the dispersion liquid in a sufficiently cooled state to form a stable coating film on the surface, which is then dried. It

A heat-resistant container with a baffle plate attached to the inner wall is used as the container, and the container is inclined at an angle of 3 ° or more and 10 ° or less to perform stirring. The number of rotations 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.

  The hydrocarbon oil is preferably 1 to 30 parts by mass, and more preferably 2 to 15 parts by mass, from the viewpoint of uniform dispersibility after melting, 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 of the dispersion liquid after cooling is preferably 100 ° C or lower, more preferably 50 ° C or lower. Further, it is preferable that the dispersion liquid is gradually cooled over 1 hour or more.

  The carbon dioxide is preferably added in an amount of 0.01 to 0.18 part by mass to the molten lithium-hydrocarbon oil mixture, based on 1 part by mass of the lithium ingot, and 0.08 to 0.1 part by mass. More preferably. The stirring condition during the production of the dispersion is preferably 1000 rpm or more in order to bring about sufficient contact between the introduced carbon dioxide and the dispersed metal.

<Negative electrode>
The negative electrode 20 can be produced by forming the negative electrode active material layer 24 on the 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 thin metal plate (metal foil) such as copper, nickel or their alloys, and 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 necessary amount of a negative electrode conductive additive.
(Negative electrode active material)
As the negative electrode active material, a carbon material such as graphite, non-graphitizable carbon, graphitizable carbon, and low temperature calcined carbon capable of inserting and extracting (intercalating / deintercalating or doping / dedoping) lithium ions. , Al, Si, Sn, and other metals that can be combined with lithium, silicon oxide such as SiO, SiO ₂ , or mixtures thereof, and oxides such as TiO ₂ , SnO ₂ , Fe ₂ O ₃ Examples thereof include particles containing a crystalline / amorphous compound, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), and the like.
(Binder for negative electrode)
As the negative electrode binder, in addition to fluororesin such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), cellulose, styrene / butadiene rubber, ethylene / propylene rubber, polyimide resin, polyamideimide resin, and polyacrylic acid Resins may be mentioned.
(Conductive assistant for negative electrode)
Examples of the conductive additive for the negative electrode include acetylene black, furnace black, carbon nanotubes and the like.

(Method for preparing mixture of stabilized lithium powder and negative electrode active material)
A 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 produced by the above process in a solvent, stirring this, and then drying the solvent.

At this time, the solvent 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.

(Method of manufacturing negative electrode doped with lithium)
A conductive auxiliary agent, a binder and a solvent were mixed at a predetermined ratio with a mixture of the stabilized lithium powder and the negative electrode active material produced by the above process to prepare a slurry for forming an active material layer, and then the slurry was applied to a copper foil. By applying and drying, a negative electrode active material layer containing stabilized lithium powder is formed. Then, the negative electrode active material layer containing the stabilized lithium powder is pressure-molded by a roller press and heat-treated in vacuum to obtain a lithium-doped negative electrode.

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

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

  The lithium-ion secondary battery 100 can be manufactured by manufacturing the lithium-doped negative electrode 20 manufactured as described above, the positive electrode 10, and the separator 18 impregnated with the electrolyte as shown in FIG. 2. Here, the positive electrode 10 can be manufactured by forming the positive electrode active material layer 14 on the positive electrode current collector 12. In the drawing, reference numerals 60 and 62 denote positive electrode and negative electrode extraction electrodes, 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 or an alloy thereof or stainless can be used.

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

(Cathode 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 a counter anion (for example, PF ₆ ⁻ ) of the lithium ions. There is no particular limitation as long as it can reversibly proceed, and a known electrode active material can be used. For example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (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, M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, Cr) Oxide, lithium vanadium compound (LiV ₂ O ₅ ), olivine type LiMPO ₄ (where M is one or more elements or VO selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al and Zr) 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 to each other and also binds the positive electrode active material to the current collector 12. Any binder can be used as long as it can bond as described above, and examples thereof include fluororesins such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). Further, other than the above, as the binder, for example, cellulose, styrene / butadiene rubber, ethylene / propylene rubber, polyimide resin, polyamideimide resin, or the like may be used. Further, 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 and the like. 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) can be used. , Polyphosphazene, etc.) and a lithium salt such as LiClO ₄ , LiBF ₄ , LiPF ₆ or an alkali metal salt mainly containing lithium, and the like. Examples of the polymerization initiator used for complexing include a photopolymerization initiator or a thermal polymerization initiator compatible with the above monomers.

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 assistant for positive electrode)
The conductive additive 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 additive can be used. Examples thereof include carbon-based materials such as graphite and carbon black, fine metal powders such as copper, nickel, stainless steel, and iron, a mixture of carbon materials and fine metal powders, and conductive oxides such as ITO.

The content of the binder in the positive electrode active material layer 14 is not particularly limited, but it is preferably 1 to 10 parts by mass based on the sum of the masses of the positive electrode active material, the conductive additive and the binder. By setting the contents of the positive electrode active material and the binder within the above ranges, it is possible to suppress the tendency of the obtained positive electrode active material layer 14 that the amount of the binder is too small to form a strong positive electrode active material layer. Further, the amount of the binder that does not contribute to the electric capacity is increased, and it is possible to suppress the tendency that it is difficult to obtain a sufficient volume energy density.

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 inside of the separator 18. The electrolyte is not particularly limited, and for example, in the present embodiment, an electrolyte solution containing a lithium salt (aqueous electrolyte solution, electrolyte solution using an organic solvent) can be used. However, since the electrolytic aqueous solution has a low decomposition voltage electrochemically, the withstand voltage at the time of charging is limited to a low level. Therefore, an electrolytic solution (nonaqueous electrolytic solution) using an organic solvent is preferable. As the electrolytic solution, a solution in which a lithium salt is dissolved in a non-aqueous solvent (organic solvent) is preferably used. The lithium salt is not particularly limited, and a 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 and (CF ₃ SO ₂ ) ₂ NLi are used. be able to.

Examples of the organic solvent include aprotic high-dielectric constant solvents such as ethylene carbonate and propylene carbonate, and acetic acid esters such as dimethyl carbonate and ethyl methyl carbonate, and aprotic low viscosity such as propionic acid esters. Solvents may be mentioned. It is desirable to use these aprotic high dielectric constant solvents and aprotic low viscosity solvents together in 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 as a mixture with the above-mentioned organic solvent.
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 this electrolyte at a temperature of 25 ° C. is preferably 0.01 S / m or more, and is adjusted depending on the type of electrolyte salt or its concentration.

When the electrolyte is a solid electrolyte or a gel electrolyte, poly (vinylidene fluoride) or the like can be contained as a polymer material.
Further, various additives may be added to the electrolytic solution of the present embodiment, if necessary. As the additive, for example, vinylene carbonate for the purpose of improving the cycle life, methyl vinylene carbonate, etc., biphenyl for the purpose of preventing overcharge, alkylbiphenyl, etc., various carbonate compounds for the purpose of deoxidation and dehydration, various Examples thereof include carboxylic acid anhydrides, various nitrogen-containing and sulfur-containing compounds.

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

  Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1]
(Preparation of stabilized lithium powder)
A stainless steel resin flask container having a baffle attached to its inner wall was added with 100 g of a lithium ingot manufactured by Kanto Kagaku Co., Ltd. and Carnation hydrocarbon oil manufactured by Witco Co., Ltd., 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 the molten state for 10 minutes at a rotation speed of 5000 rpm with the container tilted at 5 °, and then cooled to room temperature over 1 hour while maintaining the stirring. After cooling, 5 g of carbon dioxide was supplied to the surface for 5 minutes while continuing stirring to fill the surface. When all the carbon dioxide was added, this stirring was stopped, and the obtained powder was washed with hexane to obtain a stabilized lithium powder.

(Method for preparing 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 prepared in a dry room with a dew point of -50 ° C to -40 ° C according to the following procedure. To 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 the stabilized lithium powder and the negative electrode active material prepared by the above method, 2 parts by mass of acetylene black as a conductive aid, 15 parts by mass of polyamideimide as a binder, and 82 parts by mass of N-methylpyrrolidone as a solvent were mixed. Then, a slurry for forming an active material layer was prepared. This slurry was applied on one surface of a copper foil having a thickness of 14 μm as a current collector so that the amount of the lithium-doped active material applied was 2.0 mg / cm ^2, and dried at 100 ° C. for stabilization. A negative electrode active material layer containing lithium powder was formed. After that, the negative electrode active material layer containing the stabilized lithium powder formed on the current collector with a roller press at a pressure of 150 kgf / cm ² was pressure-molded, and heat-treated in vacuum at 350 ° C. for 3 hours to obtain lithium. A negative electrode active material doped with was obtained.

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

[Examples 2 to 8]
The stabilized lithium powders of Examples 2 to 8 were obtained in the same manner as in Example 1 except that the stirring speed was changed to the value shown in Table 1 among the conditions for producing the stabilized lithium powder. In addition, using the obtained stabilized lithium powder, lithium ion secondary batteries for evaluation of Examples 2 to 8 were produced in the same manner as in Example 1.

[Examples 9 to 17]
The stabilized lithium powders of Examples 9 to 17 were 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 conditions for producing the stabilized lithium powder. Further, using the obtained stabilized lithium powder, lithium ion secondary batteries for evaluation of Examples 9 to 17 were produced in the same manner as in Example 1.

[Examples 18 to 27]
The stabilized lithium powders of Examples 18 to 27 were obtained in the same manner as in Example 1 except that the heating temperature was changed to the value shown in Table 1 among the conditions for producing the stabilized lithium powder. In addition, using the obtained stabilized lithium powder, lithium ion secondary batteries for evaluation of Examples 18 to 27 were produced in the same manner as in Example 1.

[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 having no baffle on the inner wall was used and the container was not tilted.

<Measurement of initial charge / discharge efficiency>
Regarding the evaluation lithium-ion secondary batteries produced in the examples and comparative examples, a secondary battery charge / discharge tester (manufactured by Hokuto Denko Co., Ltd.) was used, and the voltage range was set from 0.005 V to 2.5 V, 1 C = 1600 mAh Charging / discharging was performed at a current value of 0.05 C when the value was / g. Thus, the initial charge capacity, the initial discharge capacity and the initial charge / discharge efficiency were obtained. The initial charge / discharge efficiency (%) is the ratio of the initial discharge capacity to the initial charge capacity (100 x initial discharge capacity / initial charge capacity). The higher the initial charge / discharge efficiency, the smaller the irreversible capacity, which means that the excellent doping effect is obtained.

<Measurement of FD of Stabilized Lithium Powder, Presence / Absence of Defects, Center Angle when Defects are Fan-shaped, and Ratio of Depth R to FD>
Regarding the stabilized lithium powder produced in the examples and comparative examples, the stabilized lithium powder was observed at an accelerating voltage of 1 kV using a field emission scanning electron microscope (JSM-6700F), and FD, the presence or absence of a defect, and a defect The center angle and the ratio of the depth R to the FD in the case of a fan shape were 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 defective portion, and the lithium ion ions prepared using the stabilized lithium powder having this defective portion Regarding the initial charge / discharge characteristics of the secondary battery, a higher initial charge / discharge efficiency can be obtained as compared with the initial charge / discharge characteristics of the lithium-ion secondary battery manufactured using the stabilized lithium powder of Comparative Example 1 having no defective portion. It was confirmed.

By using the stabilized lithium powder of the present invention for pre-doping, an electrode with few defects such as cracks can be produced. Further, by using the electrode obtained by the above manufacturing method, it is possible to provide a lithium ion secondary battery having improved initial efficiency.

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 ... Laminated body, 50 ... Case, 60 , 62 ... Lead, 100 ... Lithium ion secondary battery

Claims (6)

In a stabilized lithium powder having a coating on the surface of lithium particles,
The stabilized lithium powder have a defect in a part thereof,
The stabilized lithium powder is characterized in that the shape of the defective portion is fan-shaped . The stabilized lithium powder according to claim 1 , wherein a central angle of the fan of the defective portion is 5 ° or more and 150 ° or less.   The FD is 0.1 μm or more and 106 μm or less, where FD is the average Feret diameter of the stabilized lithium powder, and the stabilized lithium powder according to claim 1 or 2.   4. When the depth of the defective portion of the stabilized lithium powder is R, R is 0.05 times or more and 0.78 times or less of FD, The method according to claim 1. Stabilized lithium powder.   A negative electrode in which the negative electrode is doped with lithium using the stabilized lithium powder according to any one of claims 1 to 4. A lithium ion secondary battery comprising the negative electrode according to claim 5, a positive electrode, and an electrolyte.

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