Negative electrode active material for lithium ion secondary battery, method for producing negative electrode active material for lithium ion secondary battery, and lithium ion secondary battery

Abstract

Provided is a negative electrode active material for a lithium ion secondary battery, which is represented by the general formula Li4Ti5O12-xMx, where x is 0 < x < 12, and element M is an element having a lower electronegativity than oxygen.

Description

Technical Field

[0001] The present invention relates to a negative electrode active material for a lithium ion secondary battery, a method for producing a negative electrode active material for a lithium ion secondary battery, and a lithium ion secondary battery. Background Art

[0002] In recent years, with the popularization of small information terminals such as smart phones and tablet PCs, there is a strong desire for the development of small and lightweight secondary batteries with high energy density. In addition, as batteries for electric vehicles represented by hybrid vehicles, there is a strong desire for the development of high-output secondary batteries.

[0003] As a secondary battery that meets such a requirement, there is a lithium ion secondary battery. A lithium ion secondary battery is composed of a negative electrode, a positive electrode, an electrolyte, etc., and a material capable of extracting and inserting lithium is used as an active material of the negative electrode and the positive electrode.

[0004] Generally, graphite is used as the negative electrode of lithium-ion secondary batteries. However, the redox potential of graphite is extremely close to that of lithium. Therefore, when charging at a particularly high output, conductive metallic lithium may precipitate on the graphite negative electrode, causing a short circuit between the negative electrode and the positive electrode.

[0005] Therefore, research has been conducted to use lithium titanate (LiTiO2) which has a higher redox potential than graphite as a negative electrode active material. 4 Ti 5 O 12 ) (For example, refer to Patent Document 1).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application No. 2017-535017 Summary of the invention

[0009] Problems to be solved by the invention

[0010] However, lithium titanate has a low capacity per unit mass, and therefore has a problem in that the battery capacity is poor when applied to a lithium ion secondary battery.

[0011] In view of the above problems of the prior art, an object of one aspect of the present invention is to provide a negative electrode active material for a lithium ion secondary battery which has excellent battery capacity when used in a lithium ion secondary battery.

[0012] Methods for solving problems

[0013] In order to solve the above-mentioned problems, according to one embodiment of the present invention,

[0014] Provided is a negative electrode active material for a lithium ion secondary battery, which has the general formula: Li 4 Ti 5 O 12-x M x express,

[0015] The above x is 0<x<12,

[0016] The element M is an element having lower electronegativity than oxygen.

[0017] Effects of the Invention

[0018] According to one aspect of the present invention, it is possible to provide a negative electrode active material for a lithium ion secondary battery which is excellent in battery capacity when used in a lithium ion secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is an explanatory diagram of the coin-type battery produced in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0020] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and various modifications and substitutions may be made to the following embodiments without departing from the scope of the present invention.

[0021] [Negative electrode active material for lithium ion secondary batteries]

[0022] A configuration example of the negative electrode active material for lithium ion secondary battery according to the present embodiment will be described.

[0023] The negative electrode active material for the lithium ion secondary battery of this embodiment (hereinafter simply referred to as “negative electrode active material”) can be represented by the general formula: Li 4 Ti 5 O 12-x M x express.

[0024] In the above general formula, x satisfies 0<x<12, and the element M is an element having lower electronegativity than oxygen.

[0025] The negative electrode active material according to this embodiment will be described below.

[0026] (1) About composition

[0027] The elements contained in the negative electrode active material of this embodiment and their content ratios are described below.

[0028] (1-1) About Li (lithium) and Ti (titanium)

[0029] The inventors of the present invention have converted the general formula: Li 4 Ti 5 O12 The present invention has been completed by using lithium titanate as a base and applying it to lithium ion secondary batteries to study negative electrode active materials with excellent battery capacity. As a result, it was found that the above-mentioned problem can be solved by replacing part of oxygen with element M as described below.

[0030] Therefore, the negative electrode active material of the present embodiment can contain Li and Ti in a ratio of Li:Ti=4:5 in terms of the ratio of the amount of matter. In addition, considering the accuracy of the evaluation method, etc., the above values ​​are within the range of measurement error, for example, within the range of ±0.1, that is, when the ratio of Li is 3.9 to 4.1 and the ratio of Ti is 4.9 to 5.1, it can be said that the above provisions are satisfied.

[0031] (1-2) About O (oxygen) and M (element M)

[0032] As mentioned above, the capacity per unit mass of lithium titanate is low, so when it is used in lithium ion secondary batteries, there is a problem of reduced capacity. Therefore, the inventors of the present invention have studied methods for increasing the capacity of negative electrode active materials based on lithium titanate. As a result, it was found that by replacing a portion of O with an element with a lower electronegativity than O, the potential from which Li ions are separated can be reduced. For example, the amount of Li ions that can be absorbed and released can be increased within the practical potential range, and when applied to lithium ion secondary batteries, the capacity can be increased. As the above-mentioned practical potential range, for example, 0.5V to 3.0V (vs. Li / Li + ).

[0033] The element M that replaces a part of O may be an element having lower electronegativity than O, and is more preferably one or more selected from S (sulfur), Cl (chlorine), and N (nitrogen).

[0034] The range of x representing the amount of substitution of O by element M is preferably greater than 0 and less than 12 (0<x<12), and more preferably 0.1≤x≤2.0. This is because by making x representing the amount of substitution of O by element M greater than 0.1, the potential for Li ion detachment can be sufficiently reduced, and the effect of capacity improvement can also be fully exerted. In addition, this is because by making x representing the amount of substitution of O by element M less than 2.0, the excessive reduction of the redox potential can be suppressed, and the precipitation of metallic lithium can be suppressed.

[0035] (2) Regarding crystal structure

[0036] The crystal structure of the negative electrode active material of this embodiment is not particularly limited, and preferably has a rock salt structure, and more preferably has a rock salt layered structure. The crystal structure of the negative electrode active material of this embodiment can be a mixed phase of a rock salt structure and a layered structure.

[0037] [Method for producing negative electrode active material]

[0038] A configuration example of a method for producing a negative electrode active material according to the present embodiment will be described.

[0039] According to the method for producing a negative electrode active material of the present embodiment, the negative electrode active material described above can be produced, and therefore, a part of the description of matters that have already been described will be omitted.

[0040] The method for producing the negative electrode active material according to the present embodiment can include, for example, the following raw material compound preparation step and heat treatment step.

[0041] In the raw material compound preparation step, a raw material compound containing lithium (Li), titanium (Ti) and element M (M) in a ratio of Li:Ti:M=4:5:x (0<x<12) in terms of the amount of substance can be prepared. Element M is an element with a lower electronegativity than oxygen as described above.

[0042] Furthermore, in the heat treatment step, the raw material compound prepared in the raw material compound preparation step can be heat treated at 600° C. or higher in an inert gas atmosphere.

[0043] (1) Raw material compound preparation step

[0044] In the raw material compound preparation step, the raw material compound can be prepared so that lithium, titanium, and element M have the same composition ratio as that of the above-mentioned general formula according to the composition ratio of the target negative electrode active material.

[0045] Specifically, in the raw material compound preparation step, as described above, a raw material compound containing lithium (Li), titanium (Ti) and element M (M) in a ratio of Li:Ti:M=4:5:x in terms of the molar ratio can be prepared.

[0046] The mass ratio of Li, Ti, and M can also be changed within the range of ±0.1 according to the reaction rate in the heat treatment process. That is, the ratio of Li can be 3.9 to 4.1, the ratio of Ti can be 4.9 to 5.1, and the ratio of element M can be x-0.1 to x+0.1. In addition, the above x represents the content ratio of element M in the general formula of the negative electrode active material, which can be 0<x<12, preferably 0.1≤x≤2.0.

[0047] In addition, it is not necessary to prepare a separate compound for each element as a raw material, and a compound containing two or more elements simultaneously can be used as a raw material.

[0048] Examples of the raw materials used in preparing the raw material compound include Li 2 O、TiO2 , Li 2 S, LiCl, Li 3 One or more of N, etc.

[0049] In the raw material compound preparation step, it is sufficient to prepare a raw material compound containing the elements in the above-mentioned predetermined ratio. From the viewpoint of facilitating the reaction in the heat treatment step, it is preferred to prepare the raw material compound by mixing through a grinding treatment.

[0050] The grinding conditions are not particularly limited, and for example, the grinding can be performed in a dry manner by setting the grinding container to an inert atmosphere.

[0051] During the grinding step, grinding conditions are selected so that sufficient energy can be imparted to the raw material compounds and the raw material compounds can be uniformly mixed.

[0052] (2) Heat treatment process

[0053] In the heat treatment step, the raw material compound can be heat treated in an inert gas atmosphere at 600° C. or higher. The upper limit of the heat treatment temperature is not particularly limited, but from the viewpoint of suppressing the generation of by-products caused by the decomposition of lithium titanate, the heat treatment temperature is preferably 1000° C. or lower, for example.

[0054] Examples of the inert atmosphere include a rare gas (noble gas) atmosphere and nitrogen gas.

[0055] The heat treatment time in the heat treatment step is not particularly limited, and can be selected based on the amount of the raw material compound to be used in the heat treatment step, etc., so that the reaction proceeds uniformly.

[0056] [Lithium-ion secondary battery]

[0057] The lithium ion secondary battery (hereinafter also referred to as “secondary battery”) of the present embodiment can include a negative electrode including the above-mentioned negative electrode active material.

[0058] Hereinafter, for an example of a configuration of a secondary battery of the present embodiment, each component is described separately. The secondary battery of the present embodiment, for example, includes a positive electrode, a negative electrode and a non-aqueous electrolyte, and is composed of the same components as a general lithium-ion secondary battery. In addition, the embodiments described below are merely illustrative, and the lithium-ion secondary battery of the present embodiment can be implemented in various ways of changes and improvements based on the knowledge of those skilled in the art, taking the following embodiments as an example. In addition, the use of the secondary battery is not particularly limited.

[0059] (positive electrode)

[0060] The positive electrode included in the secondary battery of the present embodiment can contain a known positive electrode active material.

[0061] An example of a method for manufacturing a positive electrode is described below. First, a positive electrode active material (powdered), a conductive material, and a binder (adhesive) are mixed to form a positive electrode mixture, and a target solvent such as activated carbon and viscosity adjustment is further added as needed, and the mixture is kneaded to form a positive electrode mixture paste.

[0062] As the positive electrode active material, various known positive electrode active materials can be used. As the positive electrode active material, for example, LiNiO 2 、LiNiO 2 A positive electrode active material having a layered structure in which Ni (nickel) is substituted with one or more selected from Co (cobalt), Al (aluminum), Mn (manganese), etc., a positive electrode active material having a spinel structure, etc.

[0063] The mixing ratio of each material in the positive electrode mixture becomes a factor that determines the performance of the lithium ion secondary battery, and can therefore be adjusted according to the purpose. The mixing ratio of the materials can be the same as that of the positive electrode of a known lithium ion secondary battery. For example, when the total mass of the solid component of the positive electrode mixture from which the solvent is removed is 100 mass %, the positive electrode mixture can contain a positive electrode active material of 60 mass % to 95 mass %, a conductive material of 1 mass % to 20 mass %, and a binder of 1 mass % to 20 mass %.

[0064] The obtained positive electrode mixture paste is applied to the surface of a current collector made of aluminum foil, for example, and dried to disperse the solvent to produce a sheet-like positive electrode. As required, it can also be pressed by roller pressing to increase the electrode density. The sheet-like positive electrode obtained by this operation can be cut into an appropriate size according to the target battery, etc., and provided for the production of the battery.

[0065] As the conductive material, for example, graphite (natural graphite, artificial graphite, expanded graphite, etc.), acetylene black, Ketjen Black (registered trademark), or other carbon black-based materials can be used.

[0066] As a binder (adhesive) for achieving the function of sticking active material particles, for example, one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, EPDM rubber, styrene butadiene, cellulose resin and polyacrylic acid can be used.

[0067] As required, the positive electrode active material, the conductive material, etc. can be dispersed, and a solvent for dissolving the binder can be added to the positive electrode mixture. As the solvent, specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used. In addition, activated carbon can be added to the positive electrode mixture to increase the double layer capacity.

[0068] The method for producing the positive electrode is not limited to the above-exemplified method, and other methods may be used. For example, the positive electrode mixture may be press-formed and then dried in a vacuum atmosphere.

[0069] (negative electrode)

[0070] The negative electrode can be formed by mixing a binder with the above-mentioned negative electrode active material, adding an appropriate solvent to form a paste of the negative electrode mixture, applying it to the surface of a metal foil collector such as copper, drying it, and compressing it as needed to increase the electrode density.

[0071] As the binder used for the negative electrode, similarly to the positive electrode, a fluorine-containing resin such as PVDF can be used, and as the solvent for dispersing the negative electrode active material and the binder, an organic solvent such as N-methyl-2-pyrrolidone can be used.

[0072] The negative electrode can be produced in the same manner as the positive electrode except that the negative electrode active material is changed to the positive electrode active material.

[0073] (Partition)

[0074] The positive electrode and the negative electrode may be arranged with a separator interposed therebetween as required. The separator separates the positive electrode and the negative electrode and retains the electrolyte. A known separator may be used, for example, a film made of polyethylene, polypropylene or the like having a plurality of minute pores.

[0075] (Non-aqueous electrolyte)

[0076] As the non-aqueous electrolyte, for example, a non-aqueous electrolytic solution can be used.

[0077] As a non-aqueous electrolyte, for example, a non-aqueous electrolyte in which a lithium salt as a supporting salt (supporting electrolyte) is dissolved in an organic solvent can be used. In addition, as a non-aqueous electrolyte, a non-aqueous electrolyte in which a lithium salt is dissolved in an ionic liquid can be used. In addition, an ionic liquid refers to a salt that is composed of cations and anions other than lithium ions and is liquid at room temperature.

[0078] As the organic solvent, one of cyclic carbonates selected from ethylene carbonate, propylene carbonate, butylene carbonate and propylene trifluorocarbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate and dipropyl carbonate, ether compounds such as tetrahydrofuran, 2-methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethyl methyl sulfone and butane sultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, etc. can be used alone, and two or more thereof can be used in combination.

[0079] As a supporting salt, LiPF can be used 6 , LiBF 4 、LiClO4 、LiAsF 6 、LiN(CF 3 SO 2 ) 2 , and their composite salts, etc. Further, the non-aqueous electrolyte may contain a radical scavenger, a surfactant, a flame retardant, and the like.

[0080] In addition, as the non-aqueous electrolyte, a solid electrolyte can be used. The solid electrolyte has the property of being able to withstand high voltage. Examples of the solid electrolyte include inorganic solid electrolytes and organic solid electrolytes.

[0081] Examples of the inorganic solid electrolyte include oxide-based solid electrolytes and sulfide-based solid electrolytes.

[0082] The oxide-based solid electrolyte is not particularly limited, and for example, an oxide-based solid electrolyte containing oxygen (O) and having lithium ion conductivity and electronic insulation can be suitably used. As the oxide-based solid electrolyte, for example, lithium phosphate (Li 3 PO 4 )、Li 3 PO 4 N X 、LiBO 2 N X 、LiNbO 3 、LiTaO 3 , Li 2 SiO 3 , Li 4 SiO 4 -Li 3 PO 4 , Li 4 SiO 4 -Li 3 VO 4 , Li 2 OB 2 O 3 -P 2 O 5 , Li 2 O-SiO 2 , Li 2 OB 2 O 3 -ZnO, Li 1+X Al X Ti 2-X (PO 4 ) 3 (0≤X≤1), Li 1+X Al X Ge 2-X (PO 4 )3 (0≤X≤1), LiTi 2 (PO 4 ) 3 , Li 3X La 2 / 3-X TiO 3 (0≤X≤2 / 3), Li 5 La 3 Ta 2 O 12 , Li 7 La 3 Zr 2 O 12 , Li 6 BaLa 2 Ta 2 O 12 , Li 3.6 Si 0.6 P 0.4 O 4 One or more of the following.

[0083] The sulfide-based solid electrolyte is not particularly limited, and for example, a sulfide-based solid electrolyte containing sulfur (S) and having lithium ion conductivity and electronic insulation can be suitably used. As the sulfide-based solid electrolyte, for example, a sulfide-based solid electrolyte selected from Li 2 SP 2 S 5 , Li 2 S-SiS 2 、LiI-Li 2 S-SiS 2 、LiI-Li 2 SP 2 S 5 、LiI-Li 2 SB 2 S 3 , Li 3 PO 4 -Li 2 S-Si 2 S. Li 3 PO 4 -Li 2 S-SiS 2 、LiPO 4 -Li 2 S-SiS、LiI-Li 2 SP 2 O 5 、LiI-Li 3 PO 4 -P 2 S 5 One or more of the following.

[0084] In addition, as the inorganic solid electrolyte, inorganic solid electrolytes other than those mentioned above may be used, for example, Li 3 N, LiI, Li 3 N-LiI-LiOH, etc.

[0085] The organic solid electrolyte is not particularly limited as long as it is a polymer compound showing ion conductivity, and for example, polyethylene oxide, polypropylene oxide, copolymers thereof, etc. can be used. In addition, the organic solid electrolyte may contain a supporting salt (lithium salt).

[0086] (Shape and structure of secondary battery)

[0087] The lithium-ion secondary battery of the present embodiment described above can be in various shapes such as cylindrical and stacked. Even if any shape is used, if the secondary battery of the present embodiment uses a non-aqueous electrolyte as a non-aqueous electrolyte, the positive electrode and the negative electrode can be stacked across a separator to form an electrode body, and the obtained electrode body is impregnated with a non-aqueous electrolyte. Moreover, the positive electrode collector can be connected to the positive terminal connected to the outside, and the negative electrode collector can be connected to the negative terminal connected to the outside using a collector lead, etc., to form a closed structure of the battery case.

[0088] In addition, as described above, the secondary battery of this embodiment is not limited to the form using a non-aqueous electrolyte as a non-aqueous electrolyte, for example, it can also be made into a secondary battery using a solid non-aqueous electrolyte, that is, a fully solid battery. In the case of making a fully solid battery, the composition other than the negative electrode active material can be changed as needed.

[0089] Example

[0090] Hereinafter, the present invention will be described in further detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples at all.

[0091] (Evaluation Method of Negative Electrode Active Material)

[0092] The composition of the negative electrode active material was evaluated by analysis using an ICP emission spectrometer (725ES, manufactured by VARIAN).

[0093] The oxygen content of the negative electrode active material was evaluated by a non-dispersive infrared absorption method using an oxygen-nitrogen-hydrogen analyzer (ONH836 manufactured by LECO Corporation).

[0094] (Evaluation method of lithium-ion secondary battery)

[0095] The performance of the manufactured lithium ion secondary battery was evaluated as follows.

[0096] After the coin-type batteries made in each embodiment and comparative example were prepared, they were left to stand for about 12 hours. After the open circuit voltage (OCV) stabilized, the current density relative to the positive electrode was set to 0.1 mA / cm 2 The battery was charged to a cutoff voltage of 0.5 V, and after a 1-hour pause, the capacity when the battery was discharged to a cutoff voltage of 3.0 V was defined as the discharge capacity.

[0097] [Example 1]

[0098] (Negative electrode active material)

[0099] The negative electrode active material was prepared by the following steps.

[0100] (1) Raw material compound preparation step

[0101] In Li 2 O、TiO 2 and Li 2 When Li, Ti, and S are mixed, they are weighed so that the mixture contains Li:Ti:S=4:5:0.6 in terms of the molar ratio.

[0102] The weighed raw materials were placed in a grinding container made of zirconium oxide together with zirconium oxide balls, and the inside of the container was replaced with Ar gas. Then, the raw materials were ground using a planetary ball mill to prepare a raw material compound.

[0103] Composition analysis of the obtained raw material compound confirmed that Li 4 Ti 5 O 11.4 S 0.6 In addition, from the diffraction pattern of powder X-ray diffraction, it can be confirmed that it has a rock salt type structure.

[0104] (2) Heat treatment process

[0105] The raw material compound obtained in the raw material compound preparation step was heat treated at 800° C. for 6 hours in an argon atmosphere to obtain a negative electrode active material. Composition analysis of the obtained negative electrode active material confirmed that Li 4 Ti 5 O 11.4 S 0.6 .

[0106] (Coin type battery)

[0107] A lithium ion secondary battery was produced using the obtained negative electrode active material, and the charge and discharge capacity was measured.

[0108] Figure 1As shown, the coin-type battery 10 is composed of a case 11 and an electrode 12 accommodated in the case 11 .

[0109] The case 11 includes a positive electrode can 111 which is hollow and has an open end, and a negative electrode can 112 which is arranged at the opening of the positive electrode can 111. When the negative electrode can 112 is arranged at the opening of the positive electrode can 111, a space for accommodating the electrode 12 is formed between the negative electrode can 112 and the positive electrode can 111.

[0110] The electrode 12 includes a positive electrode 121 , a separator 122 , and a negative electrode 123 , which are stacked in this order. The positive electrode 121 contacts the inner surface of the positive electrode can 111 , and the negative electrode 123 contacts the inner surface of the negative electrode can 112 , and is accommodated in the case 11 .

[0111] In addition, the housing 11 is provided with a gasket 113, and the positive electrode can 111 and the negative electrode can 112 are fixed by controlling their relative movement while being in a non-contact state, that is, maintaining an electrically insulated state. The gasket 113 has a function of sealing the gap between the positive electrode can 111 and the negative electrode can 112 and blocking the inside and outside of the housing 11 in an airtight and liquid-tight manner.

[0112] The coin-type battery 10 was prepared as follows. First, 52.5 mg of the obtained negative electrode active material, 15 mg of acetylene black and 7.5 mg of polytetrafluoroethylene (PTFE) resin were mixed. Then, granulation was performed until the diameter was 11 mm and the weight was about 75 mg to prepare the negative electrode 123, which was dried in a vacuum dryer at 100° C. for 12 hours.

[0113] The coin-type battery 10 was produced in a glove box with an Ar atmosphere whose dew point was controlled at -60°C using the negative electrode 123 , the positive electrode 121 , the separator 122 , and the electrolyte solution.

[0114] As the positive electrode 121 , lithium metal punched into a disk shape with a diameter of 13 mm was used.

[0115] The separator 122 used a polyethylene porous film with a thickness of 25 μm. The electrolyte used a 1 M LiPF 6 The supporting electrolyte was a mixed solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) at a mixing ratio of 4:6 on a volume basis (manufactured by Toyama Pharmaceutical Industries, Ltd.).

[0116] The above-mentioned discharge capacity was measured using a coin-type battery equipped with a negative electrode containing the produced negative electrode active material. As a result, it was confirmed to be 172.7 mAh / g.

[0117] [Comparative Example 1]

[0118] In Li 2O and TiO 2 When mixing, the raw material compounds were weighed and prepared so that the Li and Ti contained in the mixture had a mass ratio of Li:Ti=4:5. The same operation as in Example 1 was carried out to produce a negative electrode active material and a coin-type battery for evaluation.

[0119] Composition analysis of the obtained negative electrode active material confirmed that Li 4 Ti 5 O 12 .

[0120] The above-mentioned discharge capacity was measured using a coin-type battery having a negative electrode including the produced negative electrode active material, and the result was that it was confirmed to be 150.3 mAh / g.

[0121] From the above results, it was confirmed that the negative electrode active material obtained in Example 1 was superior to the negative electrode active material in Comparative Example 1 in that, when used in a lithium ion secondary battery, the battery capacity was improved, and that the negative electrode active material was an excellent material.

[0122] This application claims the priority based on Japanese Patent Application No. 2022-120914 filed in the Japan Patent Office on July 28, 2022, and all the contents of Japanese Patent Application No. 2022-120914 are hereby incorporated by reference into this international application.

Claims

1. A negative electrode active material for a lithium ion secondary battery, which has the general formula: Li4Ti5O 12-x M x express, The above x is 0<x<12, The element M is an element having lower electronegativity than oxygen.

2. The negative electrode active material for lithium ion secondary battery according to claim 1, The element M is one or more selected from S, Cl, and N.

3. The negative electrode active material for lithium ion secondary battery according to claim 1 or 2, The above x is 0.1≤x≤2.

0.

4. A method for producing a negative electrode active material for a lithium ion secondary battery, comprising the following steps: a raw material compound preparation step of preparing a raw material compound containing lithium (Li), titanium (Ti) and element M (M) in a ratio of Li:Ti:M=4:5:x in terms of the amount of substance; and The heat treatment step is to heat treat the raw material compound at a temperature above 600° C. in an inert gas atmosphere. The above-mentioned x is 0<x<12, and the above-mentioned element M is an element having lower electronegativity than oxygen. 5 . A lithium ion secondary battery comprising a negative electrode comprising the negative electrode active material for a lithium ion secondary battery according to claim 1 .

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