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CN-122003738-A - Negative electrode active material and method for producing same

CN122003738ACN 122003738 ACN122003738 ACN 122003738ACN-122003738-A

Abstract

The present invention provides a negative electrode active material comprising negative electrode active material particles, wherein the negative electrode active material particles comprise a porous carbon structure, and amorphous low-valence nano-silicon oxides are dispersed in the porous carbon structure, wherein the low-valence nano-silicon oxides comprise various states of SiOx, wherein x <1.0, and the average particle diameter of the low-valence nano-silicon oxides obtained by image processing using a cross-section TEM image is 50nm or less. Thus, a negative electrode active material capable of maintaining battery characteristics and increasing capacity can be provided.

Inventors

  • TAKAKAZU HIROSE
  • Gao Yangta
  • Ohki yusuke
  • Travel on a small trip

Assignees

  • 信越化学工业株式会社

Dates

Publication Date
20260508
Application Date
20241007
Priority Date
20231011

Claims (11)

  1. 1. A negative electrode active material comprising negative electrode active material particles, characterized in that, The anode active material particles include a porous carbon structure, An amorphous low-valence nano silicon oxide is dispersed in the porous carbon structure, The low-valence nano-silicon oxide comprises various states of SiOx, wherein x <1.0, The particle diameter of the low-valence nano silicon oxide obtained by image processing using a cross-sectional TEM image is 50nm or less on average.
  2. 2. The negative electrode active material according to claim 1, wherein the low-valent nano-silicon oxide is in a substantially 0-valent, 1-valent, or 2-valent composite state.
  3. 3. The anode active material according to claim 1, wherein when the anode active material particles are measured by solid-state 29 Si-MAS-NMR, no hydrogen is detected in the vicinity of the low-valent nano-silicon oxide.
  4. 4. The anode active material according to claim 1, wherein x increases from the center of the porous carbon structure toward the surface layer for the low-valent nano silicon oxide dispersed in the porous carbon structure.
  5. 5. The anode active material according to claim 1, wherein at least a part of the porous carbon structure has a carbon-carbon double bond.
  6. 6. The anode active material according to claim 1, wherein a ratio of the porous carbon structure to the anode active material particles as a whole is 38 mass% or more and 63 mass% or less.
  7. 7. The anode active material according to claim 1, wherein the low-valent nano-silicon oxide has a broad peak having a peak top in the vicinity of-87 ppm in solid-state 29 Si-MAS-NMR measurement.
  8. 8. The negative electrode active material according to claim 1, wherein a crystal grain size of 0-valent Si constituting the low-valent nano silicon oxide calculated by using a scherrer equation is in a range of 1nm to 5nm based on a peak obtained by measuring the negative electrode active material particles by X-ray diffraction measurement.
  9. 9. The negative electrode active material according to claim 1, wherein the negative electrode active material particles have a G/D ratio of 0.85 to 1.15 and a Si/G ratio of 0.25 to 0.5.
  10. 10. The anode active material according to claim 1, wherein the porous carbon structure is dominant in IUPAC classification, has a surface area of 1400m 2 /g or more, and has a pore volume of 1cm 3 /g or more.
  11. 11. A method for producing a negative electrode active material having negative electrode active material particles, characterized by comprising the steps of producing negative electrode active material particles in which amorphous low-valence nano silicon oxide is dispersed in a porous carbon structure, The method comprises the following steps: a step of preparing a porous carbon structure; A step of depositing silicon inside the porous carbon structure by flowing monosilane gas into the porous carbon structure under heating; a step of cooling a material obtained by depositing silicon inside the porous carbon structure to 50 ℃ or lower, and And a step of introducing oxygen diluted with nitrogen gas into a material obtained by depositing silicon inside the porous carbon structure after the cooling, while maintaining the temperature of the material obtained by depositing silicon inside the porous carbon structure at 50 ℃ or lower, thereby converting at least a part of the silicon into low-valence nano silicon oxide.

Description

Negative electrode active material and method for producing same Technical Field The present invention relates to a negative electrode active material and a method for producing the same. Background In recent years, small electronic devices typified by mobile terminals and the like have been widely spread, and further miniaturization, weight saving and longevity have been strongly demanded. In response to such market demands, in particular, a secondary battery that is small and lightweight, and is capable of achieving high energy density is being developed. The secondary battery is not limited to application to small electronic devices, but is also being studied to application to large electronic devices typified by automobiles and the like, and to application to power storage systems typified by houses and the like. Among them, lithium ion secondary batteries are expected because they are small in size, easy to realize high capacity, and also can obtain higher energy density than lead batteries and nickel-cadmium batteries. The lithium ion secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode includes a negative electrode active material involved in charge-discharge reaction. As the negative electrode active material, a carbon-based active material is widely used, however, further improvement in battery capacity is demanded according to recent market demands. In order to increase the battery capacity, silicon is being studied as a negative electrode active material. The reason for this is that the theoretical capacity of silicon (4199 mAh/g) is 10 times or more greater than the theoretical capacity of graphite (372 mAh/g), and thus a great improvement in the battery capacity can be expected. The development of silicon materials as negative electrode active material is not limited to simple silicon, and compounds such as alloys and oxides are under study. In addition, regarding the shape of the active material, studies have been made on a standard coating type or an integrated type directly deposited on a current collector as for the carbon-based active material. However, when silicon is used as a main material of the negative electrode active material, the negative electrode active material expands and contracts during charge and discharge, and thus is likely to be broken mainly in the vicinity of the surface layer of the negative electrode active material. In addition, an ionic substance is generated in the active material, and the negative electrode active material is easily broken. If the surface layer of the negative electrode active material is broken, a new surface is generated, and the reaction area of the active material increases. At this time, the decomposition reaction of the electrolyte occurs on the fresh surface, and a coating of the electrolyte decomposition product is formed on the fresh surface, so that the electrolyte is consumed. Therefore, the cycle characteristics are liable to be degraded. To improve the initial efficiency and cycle characteristics of the battery, various studies have been made on a negative electrode active material and an electrode structure for a lithium ion secondary battery using a silicon material as a main material. Specifically, for the purpose of obtaining good cycle characteristics and high safety, a vapor phase method is employed to simultaneously deposit silicon and amorphous silicon dioxide (refer to, for example, patent document 1). In addition, in order to obtain high battery capacity and safety, a carbon material (electron conductive material) is provided on the surface layer of the silicon oxide particles (refer to, for example, patent document 2). Further, in order to improve cycle characteristics and obtain high input/output characteristics, an active material containing silicon and oxygen is produced, and an active material layer having a high oxygen ratio in the vicinity of a current collector is formed (see, for example, patent document 3). In order to improve cycle characteristics, oxygen is contained in the silicon active material so that the average oxygen content is 40at% or less and the oxygen content is large in a position close to the current collector (see, for example, patent document 4). In addition, in order to improve the initial charge/discharge efficiency, a nanocomposite containing a Si phase and SiO 2、My O metal oxide is used (refer to, for example, patent document 5). In order to improve cycle characteristics, siO x (0.8≤x≤1.5, particle diameter range=1 μm to 50 μm) is mixed with a carbon material and calcined at high temperature (see, for example, patent document 6). In order to improve cycle characteristics, the molar ratio of oxygen to silicon in the negative electrode active material is set to 0.1 to 1.2, and the active material is controlled so that the difference between the maximum value and the minimum value of the molar ratio in the vicinity