JP2008258030A - Negative active material for nonaqueous electrolyte secondary battery, its manufacturing method, and manufacturing method of nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method capable of simply manufacturing a nonaqueous electrolyte secondary battery having excellent cycle life. <P>SOLUTION: A negative active material is manufactured by a manufacturing method by a halogenation process which mixes and treats a material for a negative active material and an inorganic compound containing a halogen element. By manufacturing the negative active material by mixing and treating the material for the negative active material the inorganic compound containing the halogen element, reaction with an electrolyte was able to suppress. Although mixing and treatment in the halogenation process are specifically not limited if halogen can be introduced into the surface or the inside of the material for negative active material, by adopting mechanochemical treatment, the halogen element can be introduced more stably. One advantage is that the mechnochemical treatment is relatively simple. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a negative electrode active material for a nonaqueous electrolyte secondary battery capable of realizing a nonaqueous electrolyte secondary battery excellent in charge / discharge efficiency and cycle life, a method for producing the same, and a nonaqueous electrolyte secondary battery employing the negative electrode active material It relates to the manufacturing method.

  With the recent spread of portable electronic devices such as portable personal computers, portable phones, handy video cameras, etc., non-aqueous electrolyte secondary batteries having high voltage and high energy density have been widely used as power sources. Also, from the viewpoint of environmental problems, battery cars and hybrid cars using electric power as a part of power have been put into practical use. For this reason, a secondary battery having a higher capacity has been demanded in recent years.

  Until now, carbon materials such as graphite have been used for the negative electrode active material, but the theoretical capacity of graphite as a negative electrode active material is as low as 372 mAh / g, so that the theoretical capacity of tin (Sn) or silicon (Si) is used. It is considered to use a metal material having a large thickness.

  The theoretical capacity of tin is 994 mAh / g, and the theoretical capacity of silicon is 4199 mAh / g, which is much larger than that of graphite, and the practical application of high-capacity secondary batteries can be expected.

  However, in the negative electrode using such a metal material such as Sn or Si as an active material, the volume change during charging is large, and a side reaction between the active material and the electrolyte during charging / discharging occurs, resulting in low charge / discharge efficiency and increased resistance. And it was a cause of capacity deterioration. Various methods have been proposed for the purpose of improving the cycle life of such a negative electrode active material.

  For example, Patent Document 1 proposes that a chlorine compound that is electrochemically lower than the negative electrode active material is added to the electrolytic solution to form a chlorine-containing film on the surface of the negative electrode active material, thereby suppressing the reaction with the electrolytic solution. is doing. However, the negative electrode disclosed in Patent Document 1 does not always satisfy the cycle life although a certain effect is seen in improving the capacity retention rate.

  Patent Document 2 reports that the reaction between the active material and the electrolytic solution is suppressed by replacing a part of hydrogen in the electrolytic solution solvent with halogen, thereby improving the charge / discharge efficiency. However, although the negative electrode disclosed in Patent Document 2 has a certain effect in improving the capacity retention rate, an electrolytic solution using a fluorinated solvent generally has a large viscosity and becomes a problem in terms of output. It was not always satisfactory.

Patent Document 3 proposes that the surface of Si or Si alloy is fluorinated by plasma treatment or immersion treatment. However, although the negative electrode disclosed in Patent Document 3 has a certain effect in reducing the amount of gas generated and improving the capacity retention rate, the manufacturing process is performed by reducing the plasma at a high temperature and holding the pressure near the vacuum. As a result, the processing cost is high and the manufacturing method is not suitable for mass synthesis.
JP 2005-317399 A JP 2006-294403 A JP 2005-11696 A

  The present invention has been made in view of the above circumstances, and a non-aqueous electrolyte secondary that can provide a battery excellent in charge and discharge efficiency and cycle life by suppressing the reaction between the negative electrode active material and the electrolytic solution by a simple process. An object to be solved is to provide a negative electrode active material for a battery, a method for producing the same, and a method for producing a nonaqueous electrolyte secondary battery employing the negative electrode active material for a nonaqueous electrolyte secondary battery.

  In order to solve the above-mentioned problems, the present inventors have intensively studied and, as a result, completed the following invention. (1) That is, the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention that solves the above-described problems includes a negative electrode active material containing an element that can electrochemically react with lithium and a halogen element It is characterized by comprising a halogenation step of mixing and processing with a halogen introducing agent which is an inorganic compound containing at least one kind.

  That is, the negative electrode active material is characterized by mixing and processing a halogen introducing agent which is an inorganic compound containing at least one halogen element, and the mixing and processing in the halogenation process is not particularly limited, but mechanochemical processing By adopting, it becomes possible to introduce a halogen element more stably. It is one of the advantages that the mechanochemical treatment is a relatively simple treatment.

  Here, the negative electrode active material is selected from the group consisting of aluminum (Al), zinc (Zn), silver (Ag), antimony (Sb), tin (Sn), silicon (Si), and germanium (Ge). It is desirable to contain at least one of the following. These elements have large theoretical capacities and can be expected to increase in capacity when applied to batteries.

Then, as the halogen introduction agent, (a) LiF, 1 or more compounds of LiI and LiBr, (b) the general formula _{^{(1): Li X M 1}} F y (M 1 = Al, P, B, Sn, Si, Ti and / or Zr; 1 ≦ x ≦ 3; y = 4 or 6), (c) General formula (2): M ² F _z (M ² = Al, Sb, Ba, Bi, B, Ca, Co, Cu, Ge, Fe, La, Mg, Mn, Mo, Ni, Si, Ag, Na, Sr, S, Sn, Ti, W, Y, Zn and / or Zr; It is desirable that any one of fluorine compounds represented by 1 ≦ z ≦ 6).

  Here, the halogen introduction agent is desirably mixed in an amount of 2% by mass or more and less than 50% by mass based on the sum of the mass of the negative electrode active material and the halogen introduction agent.

(2) The negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention that solves the above problems is a negative electrode active material produced by the production method described in (1).

(3) And the manufacturing method of the nonaqueous electrolyte secondary battery of this invention which solves the said subject has the manufacturing method demonstrated in (1) as a process of manufacturing a negative electrode active material, It is characterized by the above-mentioned.

  Since the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has the above-described configuration, it is possible to improve the stability of the produced negative electrode active material with respect to the non-aqueous electrolyte. The cycle life is improved by applying to a secondary battery. Moreover, since reaction with a nonaqueous electrolyte can be suppressed, high charge / discharge efficiency can be maintained.

  Conventionally, when a negative electrode is formed by forming a negative electrode active material, a negative electrode paste is prepared using polyvinylidene fluoride (PVDF) containing fluorine as a binder. Therefore, the negative electrode active material in the negative electrode is fluorine. Although it was covered with a rich organic layer, the electrolyte solution can penetrate into PVDF, and the electrolyte solution comes into contact with the surface of the negative electrode active material, so that it has little effect on suppressing side reactions with the electrolyte solution. It was. In the method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, a mechanochemical reaction such as mechanical alloying, mechanical milling, or mechanofusion is used as a mixing / reaction method of the negative electrode active material and a halogen introducing agent. Can be used. Thereby, the side reaction with a negative electrode active material and electrolyte solution can be suppressed, and charge / discharge efficiency and cycle life can be improved significantly.

(Non-aqueous electrolyte secondary battery negative electrode active material and method for producing the same)
The negative electrode active material for a non-aqueous electrolyte secondary battery according to this embodiment is an active material that is employed for the negative electrode of a non-aqueous electrolyte secondary battery. An example of the non-aqueous electrolyte secondary battery is a lithium secondary battery. The nonaqueous electrolyte secondary battery itself will be described in detail later.

  The method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery according to this embodiment includes a halogenation step and other necessary steps.

  The halogenation process is a process in which the negative electrode active material and the halogen introducing agent are mixed and processed. That is, it is intended to contain a halogen element on the surface or inside of the negative electrode active material.

  The process of mixing and processing includes a process of mixing and processing a halogen-introducing agent in a solid state and a negative electrode active material, a process of mixing and processing a halogen-introducing agent into a negative electrode active material by liquefying or dissolving it. Although it can be employed, it is desirable to perform the mixing treatment in a solid state. Here, examples of the process of introducing a halogen element derived from the halogen introducing agent into the negative electrode active material material after mixing include a mechanochemical process and a process of promoting reaction or diffusion by heating. In particular, it is desirable to employ a mechanochemical reaction as a method of mixing and processing. As a mechanochemical reaction, it is desirable to employ a process similar to a grinding operation called mechanical milling, mechanical alloying, or mechanofusion.

  A layer containing a large amount of halogen element derived from the halogen introducing agent may be formed on the surface of the negative electrode active material by performing a pulverizing operation using a ball mill or the like in a state where the negative electrode active material and the halogen introducing agent are mixed. it can. The apparatus for performing the pulverization operation is not particularly limited, but a ball mill such as a rotary type, a vibration type, a planetary type, and a stirring type can be employed. In the mechano-fusion method, a hammer mill can be adopted.

  The atmosphere for mixing and treating the negative electrode active material and the halogen introducing agent is not particularly limited in the air (in the air) or in an inert atmosphere such as argon or nitrogen, but an inert atmosphere (in particular in argon) should be adopted. Is desirable.

  The treatment time may be appropriately selected depending on the amount of treatment, but 1 to 30 hours can be employed. The treatment time is set to be longer than the time necessary for the halogen element (or halogen introducing agent) to be introduced into the material in an amount necessary to suppress the reaction between the negative electrode active material and the electrolytic solution.

  In the halogenation step in the present specification, introduction of a halogen introducing agent into the negative electrode active material causes a chemical reaction in a narrow sense to proceed to produce a compound that is completely different from the negative electrode active material and the halogen introducing agent that are raw materials. Of course, when halogen elements derived from halogen introduction agents diffuse or react from the surface to the inside to form alloys, solid solutions, intermetallic compounds, etc. (so-called mechanical alloying), they react electrochemically with lithium. It includes the case where the possible element or compound is finely mixed with the halogen introducing agent and / or the halogen element or compound derived from the halogen introducing agent.

Here, the negative electrode active material is a material containing an element that can electrochemically react with lithium. For example, it is preferable to include at least one member selected from the group consisting of aluminum, zinc, silver, antimony, tin, silicon, germanium, and lead (Pb), and include aluminum, zinc, silver, antimony, tin, silicon, and germanium. More desirably, it comprises at least one of the group. Among these, it is desirable to select silicon, tin, silver, germanium, and antimony, and it is more desirable to select silicon and tin. Further, it is more desirable to select Ti—Si, Ag—Sn, Sn—Sb, Ag—Ge, Cu—Sn, or Ni—Sn as a preferable alloy. These elements are desirably employed as simple metals or alloys. In the case of an alloy, two or more desirable metal elements may be selected (for example, SnCuSb). Then, it graphite which is generally conventional, carbon black, carbon materials such as acetylene black, Li _(3-x) nitrides such as _Co x _N, also be mixed and metal lithium.

  The form of the negative electrode active material is not particularly limited, but can be powdered. For example, the volume average particle size is desirably about 0.1 μm to 50 μm, and more desirably about 0.1 μm to 30 μm. As the form of the negative electrode active material to be finally produced, powder is desirable, so that the form of the negative electrode active material is powdered, or the powder is obtained by performing a grinding operation as a kind of mechanochemical reaction described later as a halogenation step. It can also be converted.

  The halogen introducing agent is an inorganic compound containing at least one halogen element. By selecting from inorganic compounds, there is no risk of gas generation from organic substances during charging and discharging.

The halogen-introducing agent, a compound containing a (Sn in SnF ₂₎ lithium electrochemically reactive elements such as SnF ₂ is desirable from the viewpoint of high capacity. On the other hand, a compound containing lithium and an electrochemically inactive element (for example, copper) is preferable from the viewpoint of improving the cycle life because the inactive element becomes a relaxation phase during the volume expansion during charging. As the halogen element to be contained, fluorine that has a large effect of suppressing oxidation of the negative electrode active material is preferable. In addition, when a compound having a large mass ratio of the halogen element is employed in the halogen introduction agent, an effect can be obtained with a small amount of mixing.

  The halogen introducing agent will be described with specific examples. First, (a) one or more compounds of LiF, LiI, and LiBr are desirable. In particular, it is desirable to employ LiF.

As the halogen introduction agent, (b) the general formula _{^{(1): Li X M 1}} F y (M 1 = Al, P, B, Sn, Si, Ti and / or Zr; 1 ≦ x ≦ 3; y = Fluorine compound represented by 4 or 6) is desirable. Particularly ^{M 1} it is desirable to employ P, Sn, and Si. Specific examples include fluorine compounds containing alkali metals such as Li ₃ AlF ₆ , LiPF ₆ , LiBF ₄ , Li ₂ SnF ₆ , Li ₂ SiF ₆ , Li ₂ TiF ₆ , and Li ₂ ZrF ₆ .

As the halogen introducing agent, (c) general formula (2): M ² F _z (M ² = Al, Sb, Ba, Bi, B, Ca, Co, Cu, Ge, Fe, La, Mg, Mn , Mo, Ni, Si, Ag, Na, Sr, S, Sn, Ti, W, Y, Zn and / or Zr; 1 ≦ z ≦ 6) is desirable. Particularly ^{M 2 Ba, Co, Mg,} Fe, Si, Sn, Ti, we are desirable to employ a Y. Specifically, AlF ₃ , SbF ₃ , SbF ₅ , BaF ₂ , BiF ₃ , BiF ₅ , BF ₃ , CaF ₂ , CeF ₃ , CeF ₄ , CoF ₂ , CoF ₃ , CuF ₂ , IF ₅ , FeF ₂ , _{FeF 3, LaF 3, MgF 2} , MnF 2, MnF 3 MoF 6, NiF 2, SF 4, SF 6, SrF 2, SnF 2, SnF 4, TiF 3, TiF 4, WF 6, YF 3, ZnF 2, Fluorine compounds such as ZrF ₄ can be exemplified. The average particle size of the halogen introducing agent to be mixed is desirably about 0.1 μm to 50 μm, and more desirably about 0.1 μm to 30 μm.

  Here, the halogen introduction agent is desirably mixed in an amount of 2% by mass or more and less than 50% by mass based on the sum of the mass of the negative electrode active material and the halogen introduction agent. As the lower limit of the mixing amount, a sufficient effect can be exhibited by mixing 2% by mass or more, and particularly an excellent effect can be achieved by mixing 10% by mass or more. By setting the upper limit of the mixing amount to less than 50% by mass, a decrease in battery capacity per unit mass of the negative electrode active material can be suppressed, and by setting it to 30% by mass or less, sufficient battery capacity can be realized.

(Nonaqueous electrolyte secondary battery and manufacturing method thereof)
The nonaqueous electrolyte secondary battery of this embodiment has a positive electrode, a negative electrode, an electrolyte, and other necessary members.

  As the negative electrode, the above-described negative electrode active material for a non-aqueous electrolyte secondary battery is employed. A negative electrode paste prepared by mixing a negative electrode active material with a binder and slurrying with an organic solvent is applied to a current collector and dried to form a sheet.

  Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, EPDM, NBR, and fluororubber. A metal foil formed from copper, nickel, stainless steel, nickel-plated steel or the like is usually used for the negative electrode current collector. A conductive material (for example, carbon black such as acetylene black or amorphous carbon fine particles such as needle coke) may be added to the negative electrode as appropriate.

  Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, NN-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran and the like. However, it is not limited to this.

  As the positive electrode, a positive electrode paste obtained by slurrying a positive electrode active material, a binder, and a conductive material with an organic solvent or water is applied to a current collector and dried to form a sheet. Usually, aluminum, stainless steel, nickel-plated steel, or the like is used for the positive electrode current collector. The binder, the conductive material, and the organic solvent can be the same as those for the negative electrode.

As the positive electrode active material, TiS ₂ , TiS ₃ , MoS ₃ , FeS ₂ , Li _(1-x) MnO ₂ , Li _(1-x) Mn ₂ O ₄ , Li _(1-x) CoO ₂ , Li _{(1 -x) NiO 2, LiV 2 O} 3, V 2 O 5 and the like. In addition, X in these positive electrode active materials shows the number of 0-1. Further, a material obtained by adding or substituting a transition metal such as Li, Mg, Al, or Co, Ti, Nb, or Cr may be used. Moreover, not only these lithium-metal composite oxides are used alone, but also a plurality of them can be mixed and used. Among these, the lithium-metal composite oxide is preferably at least one of a lithium manganese-containing composite oxide having a layered structure or a spinel structure, a lithium nickel-containing composite oxide, and a lithium cobalt-containing composite oxide.

  In addition, a conductive polymer such as polyaniline or polypyrrole, or an organic radical material such as poly (2,2,6,6-tetramethylpiperidinoxymethacrylate) (PTMA) may be used for the positive electrode. The positive electrode is preferably one in which a positive electrode mixture obtained by mixing a conductive material and a binder as necessary with the above-described positive electrode active material is bonded to a current collector to form a positive electrode mixture layer.

  Examples of the electrolyte include those obtained by dissolving a supporting salt in an organic solvent, ionic liquids, and those obtained by dissolving a supporting salt in an ionic liquid. You may mix and use an organic solvent and an ionic liquid. The organic solvent is not particularly limited as long as it is an organic solvent that can be usually used for an electrolyte solution of a lithium secondary battery. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones And oxolane compounds can be used.

  In particular, propylene carbonate, ethylene carbonate (EC), 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate, and the like, and mixed solvents thereof are suitable.

  Among these organic solvents mentioned in the examples, in particular, by using one or more non-aqueous solvents selected from the group consisting of carbonates and ethers, a battery excellent in solubility, dielectric constant and viscosity of the supporting salt This is preferable because the battery can be provided with high charge / discharge efficiency.

In addition, the ionic liquid is not particularly limited as long as it is an ionic liquid that can be used for an electrolytic solution of a lithium secondary battery. For example, the cation component may be 1-methyl-3-ethylimidazolium having high conductivity. cations include dimethylethyl methoxy ammonium cations like, and an anionic ^{_{component, BF 4 -, LiN (SO}} 2 C 2 F 5) 2 - and the like. The kind of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) _2, LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and the like, and organic salts thereof It is preferably at least one derivative.

  The concentration of the supporting salt is not particularly limited, and it is preferable to select the concentration appropriately in consideration of the types of the supporting salt and the solvent depending on the use. For the purpose of forming a stable film, vinylene carbonate, vinyl ethylene carbonate, or the like may be mixed in the electrolytic solution.

  Moreover, as a lithium secondary battery to which this manufacturing method can be applied, in addition to the above-described constituent elements, known constituent elements such as a separator that electrically insulates between the positive and negative electrodes and a battery case can be applied. Needless to say.

  The separator plays a role of electrically insulating the positive electrode and the negative electrode and holding the electrolytic solution. For example, a porous synthetic resin film, particularly a polyolefin polymer (polyethylene, polypropylene) porous film may be used. The separator is preferably larger than the positive electrode and the negative electrode in order to ensure insulation between the positive electrode and the negative electrode.

  The battery case is not particularly limited in shape, material, and the like. For example, the battery case can have various shapes such as a coin shape, a cylindrical shape, and a square shape.

  Nonaqueous electrolyte secondary batteries (lithium secondary batteries) in Examples and Comparative Examples were produced according to the following production procedure.

(Preparation of negative electrode)
First, metal powders were mixed in the blending amounts shown in Table 1 and mechanical alloying was performed in an argon gas atmosphere to prepare No. 1 to 4 negative electrode active material powders. For mechanical alloying, a high-speed planetary ball mill (05.101) manufactured by Fritsch was used. The inner surface of the container of the ball mill has a carbide lining specification, and the ball as a grinding medium is a bearing steel ball (SUJ2) of φ2 × 10 ⁻³ m. The mass ratio of the raw material powder and the ball was 1:12, and the volume of the ball in the pot volume was 44% by volume. As a lubricant, stearic acid was used in an amount of 0.5% by mass based on the total mass. The revolution number was set to 300 rpm and the rotation number was set to 650 rpm, and the mixture was pulverized and mixed for 2 hours to obtain a negative electrode active material material powder.

  Next, as a halogenation process for mixing and treating the negative electrode active material powder and the halogen introducing agent, mechanical alloying treatment as mechanochemical treatment was performed under the same conditions as described above. The mixing ratio of the negative electrode active material powder and the halogen introducing agent was as shown in Table 2, and negative electrode active materials of Test Examples 1 to 13 were obtained.

  85 parts by mass of the negative electrode active material powder of each test example obtained, 5 parts by mass of ketjen black as a conductive material, and 10 parts by mass of PVDF as a binder were mixed to obtain a negative electrode material. This negative electrode material is dispersed in NMP to form a slurry, and this slurry is applied on a current collector made of an electrolytic copper foil having a thickness of 18 μm so that the mixed material mass becomes 5.0 mg / φ14 mm, and then dried and press-molded. Thus, a negative electrode plate was obtained. Next, this negative electrode plate was extracted with a circular punch having a diameter of 14 mm and vacuum-dried at 120 ° C. for 6 hours to obtain a negative electrode.

  Regarding the negative electrode active material powder No. 5, predetermined graphite was mixed with the negative electrode active material powder No. 1 in a slurry and applied in the same manner to produce an electrode.

(Battery assembly)
Electrolytic solution prepared by dissolving LiPF ₆ as a supporting electrolyte at a concentration of 1 mol / L in a mixed organic solvent of 30% by volume of EC and 70% by volume of DEC, using the above electrode as a test electrode, metallic lithium as a counter electrode Then, a coin-type battery (CR2025 type) was produced in a dry box and used as a test battery of a corresponding test example.

(Initial charge / discharge, initial capacity measurement method)
The initial charge / discharge of the produced test battery of each test example was performed under the following conditions. First, constant current charging at a charging current 0.10mA / cm ² to 0.01 V, was constant current discharge to 1.5V at a discharge current 0.10mA / cm ^2. Then, constant current charging at a charging current 0.385mA / cm ² to 0.01 V, and a constant current discharge to 1.5V at a discharge current 0.385mA / cm ^2. The discharge capacity at this time was defined as the initial discharge capacity. The measurement was performed in an atmosphere at 25 ° C.

(Cycle characteristic test method)
After the initial charge and discharge, a constant current charging at a charging current 0.385mA / cm ² to 0.01 V, was repeated discharge current 0.385mA / cm ² at 30 cycles to perform constant current discharge until 1.5V. The cycle was repeated in an atmosphere at 25 ° C.

  From the discharge capacity at the 30th cycle and the initial discharge capacity, the discharge capacity retention ratio (%) was determined by the following formula. Moreover, according to the following formula | equation, the charging / discharging efficiency (%) of the 30th cycle was calculated | required. Table 2 shows the charge / discharge cycle results of the test batteries of each test example.

Discharge capacity retention rate (%) = [(discharge capacity at 30th cycle) / (initial discharge capacity)] × 100 (%)
Charging / discharging efficiency (%) = [(30th cycle discharge capacity) / (30th cycle charge capacity)] × 100 (%)

  As is apparent from Table 2, since Test Examples 1 to 11 and 13 in which the halogen introduction agent was reacted showed higher charge / discharge efficiency and capacity retention than Test Example 12, the halogen introduction agent and the negative electrode active material It was confirmed that the charge and discharge efficiency and the capacity retention rate during the charge and discharge cycle were improved in the test battery employing the manufactured negative electrode active material by mechanochemical treatment of the material powder.

  That is, it has been clarified that a negative electrode active material produced by mixing a negative electrode active material and a halogen introducing agent and performing a mechanochemical treatment exhibits high stability. This is because the halogen-introducing agent and the negative electrode active material powder are mechanochemically treated so that the layer having a large fluorine content formed on the surface of the manufactured negative electrode active material reacts with the negative electrode active material and the electrolytic solution. It can be assumed that it originates from the fact that it is suppressed.

  On the other hand, in Test Example 12 in which the halogen introducing agent was not mixed, both the charge / discharge efficiency and the capacity retention rate were low. It can be assumed that this is because the reaction between the negative electrode active material and the electrolytic solution cannot be suppressed because halogen is not introduced into the surface of the negative electrode active material.

  Further, when the results of the test battery of Test Example 1 and the test battery of Test Example 13 are compared, both the charge / discharge efficiency and the capacity retention rate are greatly improved by increasing the mixing amount of the halogen introducing agent by 1%. I was able to. In particular, it became clear that the capacity retention rate was 13%, and a dramatic effect was demonstrated. The mixing amount of the halogen introducing agent has a critical point that exhibits a high effect in the range of more than 1% and 2% or less. I found out that

  As described above, a negative electrode active material obtained by mechanochemical treatment of a metal material electrochemically reactive with lithium and an inorganic compound containing at least one halogen element is used for the negative electrode, so It was revealed that a battery excellent in charge / discharge efficiency and cycle characteristics can be obtained by suppressing the reaction with the liquid.

Claims (9)

  It comprises a halogenation step in which a negative electrode active material containing an element capable of electrochemically reacting with lithium and a halogen introducing agent which is an inorganic compound containing at least one halogen element are mixed and processed. A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery.   The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the halogenating step performs a mechanochemical treatment.   The negative electrode active material is at least one selected from the group consisting of aluminum (Al), zinc (Zn), silver (Ag), antimony (Sb), tin (Sn), silicon (Si), and germanium (Ge). The manufacturing method of the negative electrode active material for nonaqueous electrolyte secondary batteries of Claim 1 or 2 containing this.   The method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the halogen introducing agent is one or more kinds of compounds of LiF, LiI, and LiBr. The halogen introducing agent is represented by the general formula (1): Li _X M ¹ F _y (M ¹ = Al, P, B, Sn, Si, Ti and / or Zr; 1 ≦ x ≦ 3; y = 4 or 6) The manufacturing method of the negative electrode active material for nonaqueous electrolyte secondary batteries in any one of Claims 1-4 which is a fluorine compound represented by these. The halogen introducing agent has the general formula (2): M ² F _z (M ² = Al, Sb, Ba, Bi, B, Ca, Co, Cu, Ge, Fe, La, Mg, Mn, Mo, Ni, 6. A non-volatile compound according to claim 1, which is a fluorine compound represented by Si, Ag, Na, Sr, S, Sn, Ti, W, Y, Zn and / or Zr; 1 ≦ z ≦ 6). A method for producing a negative electrode active material for a water electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the halogen introducing agent is 2% by mass or more and less than 50% by mass based on the sum of the mass of the negative electrode active material and the halogen introducing agent. A method for producing a negative electrode active material.   A negative electrode active material for a non-aqueous electrolyte secondary battery obtained by the production method according to claim 1. A method for producing a non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, and an electrolyte,
A method for producing a nonaqueous electrolyte secondary battery, wherein the negative electrode active material of the negative electrode is produced by the method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 7. .