JP-2026075272-A - Negative electrode active material, lithium-ion secondary battery, and method for manufacturing negative electrode active material

Abstract

[Challenge] Suppression of increased resistance. [Solution] The invention comprises a carbon material and a carbon film coating the carbon material, wherein the amount of carbon monoxide desorbed when the temperature is raised to 1600°C at a rate of 10°C/min by heating and generated gas mass spectrometry is 5.0 μmol/g or more and 25 μmol/g or less, the amount of carbon dioxide desorbed when the temperature is raised to 1600°C at a rate of 10°C/min by heating and generated gas mass spectrometry is 1.0 μmol/g or more and 10 μmol/g or less, and the amount of hydrogen desorbed when the temperature is raised to 1600°C at a rate of 10°C/min by heating and generated gas mass spectrometry is 20 μmol/g or more and 50 μmol/g or less. [Selection Diagram] Figure 1

Inventors

• 松原 伸典
• 石井 孝文

Assignees

• トヨタ自動車株式会社
• 国立大学法人群馬大学

Dates

Publication Date

20260508

Application Date

20241022

Claims (5)

1. The material comprises a carbon material and a carbon film coating the carbon material. Mass spectrometry of the generated gas during heating revealed that the amount of carbon monoxide removed when the temperature was increased to 1600°C at a rate of 10°C/min was between 5.0 μmol/g and 25 μmol/g. Mass spectrometry of the generated gas during heating revealed that the amount of carbon dioxide desorbed when the temperature was raised to 1600°C at a rate of 10°C/min was between 1.0 μmol/g and 10 μmol/g. A negative electrode active material in which the amount of hydrogen desorbed when the temperature is raised to 1600°C at a rate of 10°C/min is 20 μmol/g or more and 50 μmol/g or less, as determined by mass spectrometry of the generated gas during heating.
2. Mass spectrometry of the generated gas during heating revealed that the amount of carbon monoxide removed when the temperature was raised to 1600°C at a rate of 10°C/min was between 10 μmol/g and 22 μmol/g. The negative electrode active material according to claim 1, wherein the amount of carbon dioxide desorbed when the temperature is raised to 1600°C at a rate of 10°C/min, as determined by heating gas mass spectrometry, is 3.0 μmol/g or more and 8.0 μmol/g or less.
3. A lithium-ion secondary battery comprising a negative electrode containing the negative electrode active material described in claim 1 or claim 2, a positive electrode, a separator, and an electrolyte.
4. A process of mixing and calcining carbon materials and carbon film precursors to obtain a negative electrode active material precursor, A step of producing a negative electrode active material by contacting the negative electrode active material precursor with nitric acid, The process includes a step of washing and drying the negative electrode active material, A method for producing a negative electrode active material, wherein the concentration of the nitric acid is 7 mol/L or more and 15 mol/L or less.
5. The method for producing a negative electrode active material according to claim 4, wherein the contact time between the negative electrode active material precursor and the nitric acid is 2 minutes or more and 10 minutes or less.

Description

This disclosure relates to a negative electrode active material, a lithium-ion secondary battery, and a method for producing a negative electrode active material. Patent Document 1 (Japanese Patent Application Publication No. 2014-127313) discloses that the amount of acidic functional groups in the graphite material is 1 μeq/ m² or more, and a coating containing sulfur atoms and a charge carrier is formed on the surface of the graphite material. Japanese Patent Publication No. 2014-127313 Figure 1 is a conceptual diagram showing the negative electrode active material in this embodiment.Figure 2 is an example of a schematic flowchart of the method for producing the negative electrode active material in this embodiment.Figure 3 is a schematic diagram showing an example of a lithium-ion secondary battery according to this embodiment.Figure 4 is a schematic diagram showing an example of the electrode body of this embodiment.Figure 5 is a table showing the manufacturing conditions and evaluation results for the negative electrode active material. The embodiments of this disclosure (hereinafter abbreviated as "Embodiments") and examples of this disclosure (hereinafter abbreviated as "Examples") are described below. However, these embodiments and examples do not limit the technical scope of this disclosure. <Negative electrode active material> The negative electrode active material of this disclosure may be applied to any battery. The battery may be, for example, a monopolar battery, a bipolar battery, a non-aqueous secondary battery, or a lithium-ion secondary battery. Hereinafter, the negative electrode active material of this disclosure will be described as a negative electrode active material for a lithium-ion secondary battery, but will not be limited thereto. Figure 1 is a conceptual diagram showing the negative electrode active material in this embodiment. The negative electrode active material 5 includes a carbon material 1 and a carbon film 2 that coats the carbon material 1. Carbon material 1 contains carbon. Examples of carbon contained in carbon material 1 include artificial graphite, natural graphite, soft carbon, hard carbon, carbon black (CB), carbon nanotubes (CNT), and vapor-grown carbon fibers (VGCF). From the viewpoint of conductivity and cost, the carbon contained in carbon material 1 is preferably artificial graphite or natural graphite, and more preferably artificial graphite. The carbon film 2 coats the carbon material 1. The coating of the carbon material 1 with the carbon film 2 is expected to improve the electronic conductivity and durability of the carbon material 1. The carbon film 2 may coat only a portion of the carbon material 1. The carbon film 2 may substantially coat the entire carbon material 1. That is, the carbon film 2 coats at least a portion of the surface of the carbon material 1. The carbon film 2 may have a thickness of, for example, 0.01 μm or more and 0.2 μm or less. If the thickness of the carbon film 2 is less than 0.01 μm, the effect of coating the carbon material 1 with the carbon film 2 may not be achieved. If the thickness of the carbon film 2 exceeds 0.2 μm, the resistance may increase. The thickness of the carbon film 2 can be measured, for example, by the following procedure: A sample is prepared by embedding the negative electrode active material 5 in a resin material. The sample is thinned by FIB (Focused Ion Beam) processing. The sample is observed by STEM (Scanning Transmission Electron Microscope). The arithmetic mean of the values measured for multiple negative electrode active materials 5 may be used as the thickness of the carbon film 2. The carbon film 2 contains carbon. The carbon may, for example, contain pitch carbides. The carbon content in the carbon film 2 relative to the carbon material 1 may be, for example, 0.5% by mass or more and 5.0% by mass or less. If the carbon content in the carbon film 2 relative to the carbon material 1 is less than 0.5% by mass, the carbon film 2 may not be formed. If the carbon content in the carbon film 2 relative to the carbon material 1 exceeds 5.0% by mass, the carbon may aggregate, and the carbon film 2 may not be formed. The carbon content in the carbon film 2 relative to the carbon material 1 may be 1.0% by mass or more and 3.0% by mass or less. The negative electrode active material 5 in this embodiment satisfies the following requirements (1) to (3). (1) When the temperature is raised to 1600°C at a rate of 10°C/min by TPD-MS, the amount of CO removed is 5.0 μmol/g or more and 25 μmol/g or less. (2) When the temperature is raised to 1600°C at 10°C/min by TPD-MS, the amount of CO2 desorbed is 1.0 μmol/g or more and 10 μmol/g or less. (3) When the temperature is raised to 1600°C at a rate of 10°C/min by TPD-MS, the amount of H2 removed is 20 μmol/g or more and 50 μmol/g or less. The above (1) and (2) indicate the presence of acidic functional groups in the carbon film 2 of the negative electrode active materi