Negative electrode active material for non-aqueous electrolyte secondary batteries and method for producing the same

Abstract

To provide a negative electrode active material for a non-aqueous electrolyte secondary battery, which has high capacity as well as good cycle characteristics and initial efficiency.SOLUTION: A negative electrode active material for a non-aqueous electrolyte secondary battery includes negative electrode active material particles containing silicon compound particles that contain a silicon compound (SiOx: 0.5≤x≤1.6), the silicon compound particles including a Li compound. The negative electrode active material particles are at least partially covered by a carbon coating. The coating amount of the carbon coating in the negative electrode active material particles is greater than 0% by mass, and equal to or less than 1% by mass, with respect to the total of the silicon compound particles and the carbon coating. The carbon coating includes a coating that comprises at least one compound among a compound with an O-C=O bond and a compound with a C-C bond, and the silicon compound particles include crystalline Li2SiO3 as the Li compound.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a negative electrode active material for a non-aqueous electrolyte secondary battery and a method for producing the same. [Background technology]

[0002] In recent years, small electronic devices such as mobile terminals have become widespread, and there is a strong demand for further miniaturization, weight reduction, and longer lifespan. In response to these market demands, development is progressing on secondary batteries that are particularly small, lightweight, and capable of achieving high energy density. These secondary batteries are being considered not only for small electronic devices but also for large electronic devices such as automobiles, and for power storage systems such as those found in homes.

[0003] Among these, lithium-ion secondary batteries are highly anticipated because they are easy to miniaturize and increase capacity, and they can achieve a higher energy density than lead-acid batteries and nickel-cadmium batteries.

[0004] The lithium-ion secondary battery described above comprises an electrolyte along with a positive electrode, a negative electrode, and a separator, and the negative electrode contains a negative electrode active material that is involved in the charge and discharge reaction.

[0005] While carbon materials (carbon-based active materials) are widely used as negative electrode active materials, recent market demands require further improvements in battery capacity. To improve battery capacity, the use of silicon as a negative electrode active material is being considered. This is because the theoretical capacity of silicon (4199 mAh / g) is more than 10 times greater than that of graphite (372 mAh / g), so a significant improvement in battery capacity can be expected. The development of silicon materials as negative electrode active materials is being considered not only for pure silicon but also for compounds such as alloys and oxides. Furthermore, the shape of the active material is being considered from the standard coated type for carbon-based active materials to an integrated type that is directly deposited on the current collector.

[0006] However, when silicon is used as the main raw material for the negative electrode active material, the negative electrode active material expands and contracts during charging and discharging, making it prone to cracking, mainly near the surface of the negative electrode active material. In addition, ionic substances are generated inside the active material, making the negative electrode active material more susceptible to cracking. When the surface of the negative electrode active material cracks, a new surface is created, increasing the reaction area of ​​the active material. At this time, a decomposition reaction of the electrolyte occurs on the new surface, and a film of electrolyte decomposition products is formed on the new surface, thus consuming the electrolyte. As a result, the cycle characteristics tend to deteriorate.

[0007] To date, attempts have been made to improve the initial efficiency and cycle characteristics of batteries by doping silicon oxide, which is the negative electrode active material, with lithium (see, for example, Patent Document 1 below). By incorporating lithium into the silicon oxide, which is the negative electrode active material, it is possible to reduce the irreversible component when it is used as a negative electrode, and thus an improvement in initial efficiency can be expected. Furthermore, this improvement in initial efficiency can be expected to increase the capacity of lithium-ion secondary batteries.

[0008] However, although the initial efficiency of silicon oxide, the negative electrode active material, is improving, it is still lower than that of current positive electrode materials such as LiCoO2 (lithium cobalt oxide) (see, for example, Patent Document 2), and further efficiency improvements are needed. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2011-222153 [Patent Document 2] Japanese Patent Publication No. 2020-113495 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention has been made in view of the above problems, and an object thereof is to provide a negative electrode active material for a non-aqueous electrolyte secondary battery that has a high capacity and good cycle characteristics and initial efficiency. Another object of the present invention is to provide a method for producing such a negative electrode active material for a non-aqueous electrolyte secondary battery.

Means for Solving the Problems

[0011] In order to solve the above object, the present invention has negative electrode active material particles, and the negative electrode active material particles contain silicon compound particles containing a silicon compound (SiO x : 0.5 ≦ x ≦ 1.6), and the silicon compound particles contain a Li compound. The negative electrode active material for a non-aqueous electrolyte secondary battery is characterized in that at least a part of the negative electrode active material particles is coated with a carbon coating, and the coating amount of the carbon coating in the negative electrode active material particles is more than 0% by mass and 1% by mass or less with respect to the total of the silicon compound particles and the carbon coating. The carbon coating includes a coating composed of at least one of a compound having an O-C=O bond and a compound having a C-C bond, and the silicon compound particles include crystalline Li2SiO3 as the Li compound. A negative electrode active material for a non-aqueous electrolyte secondary battery is provided.

[0012] Since the negative electrode active material of the present invention contains negative electrode active material particles including silicon compound particles, it has a high battery capacity. Further, since the SiO2 component part in the silicon compound, which is destabilized during the insertion and desorption of lithium during charge and discharge of the battery, is previously modified with another Li compound, the irreversible capacity generated during charging can be reduced. Further, since these negative electrode active material particles contain a carbon coating, they have appropriate conductivity, and the capacity retention rate and the initial efficiency can be improved. Furthermore, when the coating amount of the carbon coating is more than 0% by mass and 1% by mass or less, a high-capacity negative electrode active material can be obtained without impairing the capacity of the silicon compound particles. Further, by including a coating composed of at least one of a compound having an O-C=O bond and a compound having a C-C bond, the binding property of the binder during the preparation of the aqueous slurry is improved. As a result, the battery characteristics are improved. Further, since it contains Li2SiO3, which is a lithium compound stable to water, gas generation is suppressed even in the aqueous slurry, and a stable state can be maintained. As a result, the initial efficiency and the capacity retention rate can be improved. Hereinafter, the negative electrode active material particles containing silicon compound particles are also referred to as silicon-based active material particles. Further, the negative electrode active material containing these silicon-based active material particles is also referred to as a silicon-based active material.

[0013] At this time, it is preferable that the intensity ratio of the intensity Ia near 290 eV due to the O-C=O bond and the intensity Ib near 285 eV due to the C-C bond obtained by X-ray photoelectron spectroscopy (XPS) of the negative electrode active material is 0 ≦ Ia / Ib ≦ 3.0.

[0014] If Ia / Ib is within this range, the binding property of the binder during the preparation of the aqueous slurry is improved, and as a result, the battery characteristics are improved. If Ia / Ib is 0 or more, the compatibility with the slurry is improved, the slurry dispersibility is improved, and as a result, the battery characteristics are improved. On the other hand, if Ia / Ib is 3.0 or less, side reactions on the surface of the active material during charge and discharge are suppressed, and the battery characteristics are improved.

[0015] Furthermore, it is preferable that the negative electrode active material satisfies the condition that 1 ≤ Ie / Ic ≤ 18.5, where Ic is the intensity around 2θ = 47.5° due to Si obtained by X-ray diffraction, and Ie is the intensity around 2θ = 18.7° due to Li2SiO3.

[0016] When the intensity ratio Ie / Ic is 18.5 or less, gas generation in aqueous slurries can be suppressed, making it easier to ensure slurry stability. On the other hand, when the intensity ratio Ie / Ic is 1 or more, the doped Li is more stable, and gas generation in aqueous slurries can be suppressed.

[0017] In this case, it is preferable that the peak full width at half maximum around 2θ = 18.7°, which is due to Li2SiO3 obtained by X-ray diffraction of the negative electrode active material, is 0.5° or more and 3.0° or less.

[0018] Thus, by having a peak full width at half maximum (FWHM) of 2θ = 18.7°, obtained by X-ray diffraction, that is between 0.5° and 3.0°, the elution of alkaline components into the aqueous slurry can be suppressed, resulting in better battery characteristics.

[0019] Furthermore, in the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, it is preferable that the crystallite size resulting from the Si(220) crystal plane obtained by X-ray diffraction of the negative electrode active material is 5 nm or less.

[0020] If the crystallite size due to the Si(220) crystal plane is within the above range, better battery characteristics can be obtained.

[0021] Furthermore, the negative electrode active material 29 Preferably, the Si-MAS-NMR spectrum has at least one peak in at least one of the following chemical shift values: -80 ppm or more and less than -70 ppm, -70 ppm or more and less than -60 ppm, and -60 ppm or more and less than -30 ppm.

[0022] As chemical shift values, peaks around -60 ppm to less than -30 ppm originate from low-valence silicon oxides, peaks around -70 ppm to less than -60 ppm originate from the Li6Si2O7 component, and peaks around -80 ppm to less than -70 ppm originate from the Li2SiO3 component. Therefore, having at least one peak in at least one of the above regions can suppress the elution of alkaline components into the aqueous slurry, resulting in better battery characteristics. It should be noted that while a peak originating from the Li6Si2O7 component may be present in the region around -70 ppm to less than -60 ppm, it is more preferable that it is substantially absent. In other words, it is more preferable to have at least one of the peaks around -60 ppm to less than -30 ppm and the peak around -80 ppm to less than -70 ppm than to have a peak in the region around -70 ppm to less than -60 ppm.

[0023] At this time, the negative electrode active material 29 It is preferable that, when the peak intensity of the peak obtained from the Si-MAS-NMR spectrum in the region of chemical shift value between -60 ppm and less than -30 ppm is denoted as If, the peak intensity of the peak obtained in the region of chemical shift value between -70 ppm and less than -60 ppm is denoted as Ih, and the peak intensity of the peak obtained in the region of chemical shift value between -80 ppm and less than -70 ppm is denoted as Ii, both of the following conditions are satisfied: 0 ≤ If / Ii ≤ 0.23 and 0 ≤ Ih / Ii ≤ 1.1.

[0024] Silicon-based compound particles having these NMR peaks can suppress the elution of alkaline components into aqueous slurries, resulting in better battery characteristics. As mentioned above, the peaks around the region of -70 ppm to less than -60 ppm originate from the Li6Si2O7 component, and it is substantially preferable for these peaks to be absent, with Ih / Ii=0 being even more preferable.

[0025] Furthermore, in the negative electrode active material for a non-aqueous electrolyte secondary battery of the present invention, it is preferable that the intensity ratio Id / Ig of the D band to the G band as determined by Raman spectroscopy of the negative electrode active material is 0 ≤ Id / Ig ≤ 2.0.

[0026] Thus, if 0 ≤ Id / Ig ≤ 2.0, peeling of the carbon film due to expansion and contraction and side reactions on the carbon surface can be suppressed, resulting in better battery characteristics.

[0027] Furthermore, it is preferable that the ratio of the Si peak intensity to the G band intensity, ISi / Ig, obtained by Raman spectroscopy of the negative electrode active material is 0 ≤ ISi / Ig ≤ 5.0.

[0028] Thus, if 0 ≤ ISi / Ig ≤ 5.0, surface exposure of silicon-based compound particles can be suppressed while delaying gas generation in the aqueous slurry, resulting in better battery characteristics.

[0029] Furthermore, it is preferable that the median diameter of the silicon compound particles is 0.5 μm or more and 20 μm or less.

[0030] If the median diameter is 0.5 μm or larger, the area on the surface of the silicon compound particles where side reactions occur is small, thus reducing the consumption of excess lithium and maintaining a high battery cycle life. Furthermore, if the median diameter is 20 μm or smaller, expansion during lithium insertion is small, making it less prone to cracking and less likely to develop fissures. In addition, because the expansion of the silicon compound particles is small, for example, negative electrode active material layers, which are commonly used, are less likely to be damaged by mixing carbon active materials with silicon-based active materials.

[0031] Furthermore, the negative electrode active material particles may either not contain Li2CO3, or a portion of their outermost layer may be coated with crystalline Li2CO3, and the negative electrode active material may satisfy the following conditions: the peak intensity Ij, caused by Li2CO3, around 2θ=21°, relative to the intensity Ic, caused by Si, obtained by X-ray diffraction, satisfies 0 ≤ Ij / Ic ≤ 10.

[0032] When crystalline Li2CO3 ionic material is present in the outermost layer of the negative electrode active material particles, the binder binding properties during aqueous slurry preparation are improved. When Ij / Ic ≤ 10, the pH of the aqueous slurry can be kept within an appropriate range, suppressing gas generation and viscosity reduction. Furthermore, from the perspective of both improved binder binding and pH increase, it is preferable that the material does not contain substantially crystalline Li2CO3.

[0033] Furthermore, the negative electrode active material for the non-aqueous electrolyte secondary battery of the present invention may be covered with a carbon layer different from the carbon coating.

[0034] Furthermore, in the negative electrode active material for non-aqueous electrolyte secondary batteries of the present invention, the peak originating from the G band obtained by Raman spectroscopy of the negative electrode active material is 1588 cm⁻¹. -1 ~1598cm -1 It is preferable that it is coated with a carbon film.

[0035] Thus, a peak originating from the G band, as determined by Raman spectroscopy, is observed at 1588 cm⁻¹ on the outermost layer of the silicon compound. -1 ~1598cm -1 Because the carbon film coating ensures good conductivity, better battery characteristics can be obtained.

[0036] Furthermore, in order to achieve the above objective, the present invention provides a non-aqueous electrolyte secondary battery characterized by containing any of the above-mentioned negative electrode active materials for non-aqueous electrolyte secondary batteries.

[0037] Such secondary batteries have high cycle life and initial efficiency, and can be manufactured industrially to a competitive advantage.

[0038] Furthermore, the present invention provides a mobile terminal, an electric vehicle, and a power storage system, characterized by comprising the above-mentioned non-aqueous electrolyte secondary battery.

[0039] A non-aqueous electrolyte secondary battery equipped with the negative electrode active material for non-aqueous electrolyte secondary batteries of the present invention can be used in these applications.

[0040] Furthermore, in order to achieve the above objective, the present invention provides a method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, comprising a silicon compound (SiO x The present invention provides a method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, comprising the steps of: producing silicon compound particles containing (0.5 ≤ x ≤ 1.6); inserting Li into the silicon compound particles to produce Li2SiO3 as a Li compound; further comprising the step of coating at least a portion of the silicon compound particles with a carbon film simultaneously with or after the step of inserting Li into the silicon compound particles; wherein the amount of carbon film coating on the negative electrode active material particles is greater than 0% by mass and 1% by mass or less of the total of the silicon compound particles and the carbon film; and the carbon film coating is made up of at least one of a compound having an OC=O bond and a compound having a CC bond.

[0041] This method for producing negative electrode active materials for non-aqueous electrolyte secondary batteries makes it possible to obtain non-aqueous negative electrode active materials that have high battery capacity and good cycle retention rates, taking advantage of the inherent properties of silicon oxide modified with Li.

[0042] In this case, it is preferable to perform the step of inserting Li into the silicon compound particles by an electrochemical method or a method involving a redox reaction. [Effects of the Invention]

[0043] The negative electrode active material of the present invention can improve the stability of the slurry produced during the manufacture of secondary batteries. Using this slurry, an industrially usable coating can be formed, substantially improving battery capacity, cycle characteristics, and initial charge-discharge characteristics. Furthermore, secondary batteries containing this negative electrode active material are industrially viable and exhibit good battery capacity, cycle characteristics, and initial charge-discharge characteristics. Similar effects can be obtained in electronic devices such as mobile terminals, power tools, electric vehicles, and power storage systems using the secondary battery of the present invention.

[0044] Furthermore, the method for producing a negative electrode active material of the present invention can improve the stability of the slurry produced during the manufacture of secondary batteries, and can produce a negative electrode material that can improve battery capacity, cycle characteristics, and initial charge-discharge characteristics. [Brief explanation of the drawing]

[0045] [Figure 1] This is a cross-sectional view showing an example of the configuration of a negative electrode for a non-aqueous electrolyte secondary battery containing the negative electrode active material of the present invention. [Figure 2] This is a bulk modification apparatus that can be used when producing the negative electrode active material of the present invention. [Figure 3] This is an exploded view showing an example of the configuration (laminated film type) of a lithium-ion secondary battery containing the negative electrode active material of the present invention. [Modes for carrying out the invention]

[0046] The following describes embodiments of the present invention, but the present invention is not limited thereto.

[0047] As described above, as one method of increasing the battery capacity of a lithium-ion secondary battery, using a negative electrode using a silicon-based active material as a main material has been considered for use as the negative electrode of a lithium-ion secondary battery. A lithium-ion secondary battery using a silicon-based active material as a main material is desired to have an initial efficiency and cycle characteristics that are almost equivalent to those of a lithium-ion secondary battery using a carbon material (carbon-based negative electrode active material), but a negative electrode material showing cycle stability equivalent to that of a non-aqueous electrolyte secondary battery using a carbon material (carbon-based negative electrode active material) has not been proposed. In addition, particularly a silicon compound containing oxygen has a low initial efficiency as compared with a carbon material (carbon-based negative electrode active material), and thus the improvement in battery capacity is limited accordingly.

[0048] Therefore, the present inventors have intensively studied to obtain a negative electrode active material that enables easy production of a non-aqueous electrolyte secondary battery having a high battery capacity and good cycle characteristics and initial efficiency, and have reached the present invention.

[0049] [Negative electrode active material of the present invention] The negative electrode active material for a non-aqueous electrolyte secondary battery of the invention has negative electrode active material particles. Further, the negative electrode active material particles contain silicon compound particles containing a silicon compound (SiO x : 0.5 ≤ x ≤ 1.6). Furthermore, the silicon compound particles contain a Li compound. Also, at least a part of the negative electrode active material particles is coated with a carbon coating, and the coating amount of the carbon coating in the negative electrode active material particles is more than 0% by mass and 1% by mass or less with respect to the total of the silicon compound particles and the carbon coating, and the carbon coating includes a coating composed of at least one of a compound having an O-C=O bond and a compound having a C-C bond. Further, the silicon compound particles contain crystalline Li2SiO3 as the Li compound.

[0050] Such negative electrode active materials have high battery capacity because they contain negative electrode active material particles containing silicon compounds. Furthermore, since the SiO2 component portion of the silicon compound, which becomes unstable during lithium insertion and removal during battery charging and discharging, is pre-modified with another Li compound, irreversible capacity generated during charging can be reduced. In addition, it contains a carbon coating, and since the amount of carbon coating is greater than 0% by mass and less than or equal to 1% by mass relative to the total of the silicon compound and the carbon coating layer, it has appropriate conductivity without impairing capacity. As a result, it achieves high capacity, high capacity retention rate, and high initial efficiency. Moreover, by including a coating consisting of at least one compound having an OC=O bond and a compound having a CC bond, the binding to the binder is improved. As a result, battery characteristics are improved. Furthermore, because it contains Li2SiO3, a lithium compound that is stable in water, gas generation is suppressed even in aqueous slurries, and a stable state can be maintained, as a result, initial efficiency and capacity retention rate can be improved. XPS measurement can be performed, for example, under the following conditions. XPS ·Equipment: X-ray photoelectron spectrometer, • X-ray source: Monochromatic Al Kα rays, • X-ray spot diameter: 100 μm Ar ion gun sputtering conditions: 0.5kV 2mm x 2mm.

[0051] [Composition of the negative electrode] Next, the configuration of the negative electrode of a secondary battery containing the negative electrode active material of the present invention will be described.

[0052] Figure 1 shows a cross-sectional view of a negative electrode containing the negative electrode active material of the present invention. As shown in Figure 1, the negative electrode 10 has a negative electrode active material layer 12 on a negative electrode current collector 11. This negative electrode active material layer 12 may be provided on both sides of the negative electrode current collector 11, or on only one side. Furthermore, if the negative electrode active material for non-aqueous electrolyte secondary batteries of the present invention is used, the negative electrode current collector 11 may be omitted.

[0053] [Negative electrode current collector] The negative electrode current collector 11 is made of a material that has excellent conductivity and high mechanical strength. Examples of conductive materials that can be used for the negative electrode current collector 11 include copper (Cu) and nickel (Ni). It is preferable that this conductive material does not form intermetallic compounds with lithium (Li).

[0054] The negative electrode current collector 11 preferably contains carbon (C) and sulfur (S) in addition to the main element. This is because it improves the physical strength of the negative electrode current collector. In particular, if the active material layer expands during charging, the presence of the above elements in the current collector has the effect of suppressing electrode deformation, including the current collector. The content of the above elements is not particularly limited, but it is preferably 100 ppm or less. This is because a higher deformation suppression effect can be obtained.

[0055] Furthermore, the surface of the negative electrode current collector 11 may or may not be roughened. A roughened negative electrode current collector is, for example, a metal foil that has been electrolytically treated, embossed, or chemically etched. A non-roughened negative electrode current collector is, for example, a rolled metal foil.

[0056] [Negative electrode active material layer] The negative electrode active material layer 12 may contain multiple types of negative electrode active materials, such as carbon-based active materials, in addition to silicon-based active material particles. Furthermore, for battery design purposes, it may also contain other materials such as thickeners (also called "binding agents" or "binders") and conductive additives. The negative electrode active material may also be in particulate form.

[0057] Furthermore, as described above, the negative electrode active material of the present invention is SiO x It contains silicon-based active material particles consisting of (0.5 ≤ x ≤ 1.6). These silicon-based active material particles are made of silicon oxide material (SiO₂). x The ratio of x to x is 0.5 ≤ x ≤ 1.6, and it is preferable that the composition is such that x is close to 1. This is because high cycle characteristics can be obtained. Note that the composition of the silicon oxide material in this invention does not necessarily mean 100% purity, and may contain trace amounts of impurity elements or Li.

[0058] Furthermore, in this invention, the lower the crystallinity of the silicon compound (crystallinity of Si crystallites), the better. Specifically, when the negative electrode active material is measured by X-ray diffraction using Cu-Kα rays, it is preferable that the crystallite size due to the Si(220) crystal plane obtained by the X-ray diffraction is 5 nm or less. It is also preferable that the full width at half maximum of the diffraction peak due to the (220) crystal plane obtained by X-ray diffraction is 1.5° or more. In particular, it is preferable that the diffraction peak is broad and does not have a distinct peak. Thus, by having particularly low crystallinity and a small amount of Si crystals, it is possible not only to improve battery characteristics but also to produce a stable Li compound.

[0059] The crystallite size attributable to this Si(220) crystal plane can be calculated by XRD peak analysis. Crystallite size calculation by XRD can be performed, for example, under the following conditions. For broad peaks, the analysis can be performed using the TOPAS software, for example, under the following conditions. XRD measurement • Equipment: Bruker D2 PHASER ·X-ray source:Cu • Divergence slit: 0.5° • Incident solar angle: 4° • Solar receiving side: 4° Calculation of crystallite size • Analysis software: DIFFRAC.TOPAS • Analysis method: Peak fitting method · Emission Profile: CuKa5.lam • Function: FP (First Principle) function • Refinement Option: Select "Caluculate Error" and "Use Exploration".

[0060] Furthermore, while the median diameter of the silicon compound particles is not particularly limited, it is preferably between 0.5 μm and 20 μm (by volume). This is because within this range, lithium ions are more easily intercepted and released during charging and discharging, and the silicon-based active material particles are less likely to crack. If the median diameter is 0.5 μm or more, the surface area is not too large, making it less likely to cause side reactions during charging and discharging, and thus reducing the irreversible capacity of the battery. On the other hand, if the median diameter is 20 μm or less, it is preferable because the silicon-based active material particles are less likely to crack and less likely to have newly formed surfaces.

[0061] Furthermore, in the present invention, the silicon-based active material may contain not only Li2SiO3 but also Li4SiO4 and Li6Si2O7 as Li compounds in the silicon compound. Since Li silicates such as Li4SiO4 and Li6Si2O7 are relatively more stable than other Li compounds, silicon-based active materials containing these Li compounds can obtain more stable battery characteristics. These Li compounds can be obtained by selectively changing a portion of the SiO2 component generated inside the silicon compound to a Li compound, thereby modifying the silicon compound.

[0062] The Li compounds inside the negative electrode active material particles and silicon compound particles can be quantified by NMR (nuclear magnetic resonance). NMR measurements can be performed, for example, under the following conditions. 29 Si MAS NMR (Magic Angle Rotation Nuclear Magnetic Resonance) • Equipment: Bruker 700NMR spectrometer, • Probe: 4mm HR-MAS rotor, 50μL • Sample rotation speed: 10 kHz, ·Measurement environment temperature: 25℃

[0063] Furthermore, in the present invention, electrochemical methods and oxidation-reduction reaction methods can be used when modifying the silicon compound. In particular, when the silicon compound is modified using electrochemical methods and oxidation-reduction reactions, the battery characteristics of the negative electrode active material are improved. In addition, in the modification, it is preferable to not only insert Li into the silicon compound but also to stabilize the Li compound by heat treatment and remove Li from the silicon compound. This further improves the stability of the negative electrode active material to the slurry, such as its water resistance. Furthermore, the modification of the silicon compound may be combined with physical methods such as thermal doping. However, in the negative electrode active material of the present invention, the amount of carbon coating on the negative electrode active material particles must be greater than 0% by mass and 1% by mass or less relative to the total of the silicon compound particles and the carbon coating. Furthermore, the carbon coating must consist of at least one compound having an OC=O bond and a compound having a CC bond.

[0064] Furthermore, in the negative electrode active material of the present invention, the silicon compound is 29 Preferably, the chemical shift values ​​obtained from the Si-MAS-NMR spectrum have a peak originating from the low-valence region of silicon oxides in the region between -60 ppm and less than -30 ppm, a peak originating from the Li6Si2O7 region in the region between -70 ppm and less than -60 ppm, and a peak originating from the Li2SiO3 region in the region between -70 ppm and less than -60 ppm. Thus, by modifying to Li silicate, the stability in the slurry is further improved.

[0065] Furthermore, as described above, in the present invention, since the silicon compound particles in the silicon-based active material particles contain a carbon coating on at least a portion of their surface, appropriate conductivity can be obtained.

[0066] Furthermore, in the negative electrode active material of the present invention, it is preferable that the intensity ratio of the intensity Ia, which is due to the OC=O bond and obtained by X-ray photoelectron spectroscopy (XPS), and the intensity Ib, which is due to the CC bond and is due to the OC=O bond and is due to the CC bond, is 0 ≤ Ia / Ib ≤ 3.0. If Ia / Ib is within this range, the binding properties of the binder during aqueous slurry preparation are improved, resulting in improved battery characteristics. If Ia / Ib is 0 or greater, the compatibility with the slurry is improved, slurry dispersibility is improved, and as a result, battery characteristics are improved. On the other hand, if Ia / Ib is 3.0 or less, side reactions on the surface of the active material during charging and discharging are suppressed, and battery characteristics are improved.

[0067] Furthermore, in the negative electrode active material of the present invention, it is preferable that the intensity Ie at approximately 2θ = 18.7°, which is due to Li2SiO3, satisfies the condition 1 ≤ Ie / Ic ≤ 18.5, relative to the intensity Ic at approximately 2θ = 47.5°, which is due to Si obtained by X-ray diffraction. When the intensity ratio Ie / Ic is 18.5 or less, gas generation in aqueous slurry can be suppressed, making it easier to ensure the stability of the slurry. On the other hand, when the intensity ratio Ie / Ic is 1 or more, the doped Li is more stabilized, and gas generation in aqueous slurry can be suppressed.

[0068] Furthermore, it is preferable that the peak full width at half maximum (FWHM) around 2θ = 18.7°, which is caused by Li2SiO3 obtained by X-ray diffraction of the negative electrode active material, be between 0.5° and 3.0°. This suppresses the elution of alkaline components into the aqueous slurry, resulting in better battery characteristics.

[0069] Furthermore, the negative electrode active material of the present invention 29 Preferably, the Si-MAS-NMR spectrum has at least one peak in at least one of the following chemical shift values: -80 ppm or more and less than -70 ppm, -70 ppm or more and less than -60 ppm, and -60 ppm or more and less than -30 ppm.

[0070] As chemical shift values, peaks around -60 ppm to less than -30 ppm originate from low-valence silicon oxides, peaks around -70 ppm to less than -60 ppm originate from the Li6Si2O7 component, and peaks around -80 ppm to less than -70 ppm originate from the Li2SiO3 component. Therefore, having at least one peak in at least one of the above regions can suppress the elution of alkaline components into the aqueous slurry, resulting in better battery characteristics. It should be noted that while a peak originating from the Li6Si2O7 component may be present in the region around -70 ppm to less than -60 ppm, it is more preferable that it is substantially absent. In other words, it is more preferable to have at least one of the peaks around -60 ppm to less than -30 ppm and the peak around -80 ppm to less than -70 ppm than to have a peak in the region around -70 ppm to less than -60 ppm.

[0071] At this time, the negative electrode active material 29 It is preferable that, when the peak intensity of the peak obtained from the Si-MAS-NMR spectrum in the region of chemical shift value between -60 ppm and less than -30 ppm is denoted as If, the peak intensity of the peak obtained in the region of chemical shift value between -70 ppm and less than -60 ppm is denoted as Ih, and the peak intensity of the peak obtained in the region of chemical shift value between -80 ppm and less than -70 ppm is denoted as Ii, both of the following conditions are satisfied: 0 ≤ If / Ii ≤ 0.23 and 0 ≤ Ih / Ii ≤ 1.1.

[0072] Silicon-based compound particles having these NMR peaks can suppress the elution of alkaline components into aqueous slurries, resulting in better battery characteristics. As mentioned above, the peaks around the region of -70 ppm to less than -60 ppm originate from the Li6Si2O7 component, and it is substantially preferable for these peaks to be absent, with Ih / Ii=0 being even more preferable.

[0073] Furthermore, in the negative electrode active material for non-aqueous electrolyte secondary batteries of the present invention, it is preferable that the intensity ratio Id / Ig of the D band to the G band as determined by Raman spectroscopy of the negative electrode active material is 0 ≤ Id / Ig ≤ 2.0. When 0 ≤ Id / Ig ≤ 2.0, peeling of the carbon film due to expansion and contraction and side reactions on the carbon surface can be suppressed, resulting in better battery characteristics.

[0074] Furthermore, it is preferable that the ratio of Si peak intensity to G band intensity, ISi / Ig, obtained by Raman spectroscopy of the negative electrode active material is 0 ≤ ISi / Ig ≤ 5.0. When 0 ≤ ISi / Ig ≤ 5.0, surface exposure of silicon-based compound particles is suppressed while delaying gas generation in the aqueous slurry, resulting in better battery characteristics.

[0075] Furthermore, the negative electrode active material particles may either not contain Li2CO3, or have a portion of their outermost layer coated with crystalline Li2CO3, and the negative electrode active material may satisfy the condition that the peak intensity Ij, caused by Li2CO3, around 2θ=21°, relative to the intensity Ic, caused by Si, obtained by X-ray diffraction, satisfies 0 ≤ Ij / Ic ≤ 10.

[0076] When crystalline Li2CO3 ionic material is present in the outermost layer of the negative electrode active material particles, the binder binding properties during aqueous slurry preparation are improved. When Ij / Ic ≤ 10, the pH of the aqueous slurry can be kept within an appropriate range, suppressing gas generation and viscosity reduction. Furthermore, from the perspective of both improved binder binding and pH increase, it is preferable that the material does not contain substantially crystalline Li2CO3.

[0077] Furthermore, the negative electrode active material for the non-aqueous electrolyte secondary battery of the present invention may be covered with a carbon layer different from the carbon coating.

[0078] Furthermore, in the negative electrode active material for non-aqueous electrolyte secondary batteries of the present invention, the peak originating from the G band obtained by Raman spectroscopy of the negative electrode active material is 1588 cm⁻¹. -1 ~1598cm-1 It is preferable that the silicon compound is coated with a carbon film. In this way, the outermost layer of the silicon compound has a peak originating from the G band at 1588 cm² as determined by Raman spectroscopy. -1 ~1598cm -1 Because the carbon film coating ensures good conductivity, better battery characteristics can be obtained.

[0079] [Method for manufacturing a negative electrode] Next, an example of a method for manufacturing the negative electrode of the non-aqueous electrolyte secondary battery of the present invention will be described.

[0080] First, we will explain the manufacturing method of the negative electrode material contained in the negative electrode. First, silicon compounds (SiO x Silicon compound particles containing (0.5 ≤ x ≤ 1.6) are prepared. Next, Li is inserted into these silicon compound particles to produce Li2SiO3 as a Li compound. In the present invention, the step of coating at least a portion of the silicon compound particles with a carbon film is further included simultaneously with or after the step of inserting Li into the silicon compound particles. At this time, the carbon film coating is carried out so that the amount of carbon film coating on the negative electrode active material particles is more than 0 mass% and 1 mass% or less of the total of the silicon compound particles and the carbon film, and the carbon film is composed of at least one of a compound having an OC=O bond and a compound having a CC bond.

[0081] More specifically, the negative electrode active material is manufactured, for example, by the following procedure.

[0082] First, the raw materials for generating silicon oxide gas are heated in the presence of an inert gas or under reduced pressure in a temperature range of 900°C to 1600°C to generate silicon oxide gas. In this case, the raw materials are a mixture of metallic silicon powder and silicon dioxide powder, and considering the presence of surface oxygen in the metallic silicon powder and trace amounts of oxygen in the reactor, it is desirable that the molar ratio of the mixture be in the range of 0.8 < metallic silicon powder / silicon dioxide powder < 1.3. The Si crystallites in the particles are controlled by changing the charging range and vaporization temperature, as well as by heat treatment after generation. The generated gas is deposited on an adsorption plate. The deposited material is removed when the temperature inside the reactor is lowered to below 100°C, and then crushed and powdered using a ball mill, jet mill, etc.

[0083] Next, Li is inserted into the silicon-active material particles prepared as described above to produce Li2SiO3 as a Li compound. At this time, one or more of Li6Si2O7 and Li4SiO4 may also be included in addition to Li2SiO3. Li insertion is preferably carried out by an electrochemical method or a redox method.

[0084] In electrochemical reforming, there are no particular limitations on the apparatus structure, but for example, bulk reforming can be performed using the bulk reforming apparatus 20 shown in Figure 2. The bulk reforming apparatus 20 has a bath 27 filled with an organic solvent 23, a positive electrode (lithium source, reforming source) 21 placed in the bath 27 and connected to one side of the power supply 26, a powder storage container 25 placed in the bath 27 and connected to the other side of the power supply 26, and a separator 24 provided between the positive electrode 21 and the powder storage container 25. Silicon oxide powder 22 is stored in the powder storage container 25. Silicon compounds (silicon oxide particles) are stored in the powder storage container, and a voltage is applied to the powder storage container containing the silicon oxide particles and the positive electrode (lithium source) by the power supply. This allows lithium to be inserted into and removed from the silicon compound particles, thereby reforming the silicon oxide powder 22. The obtained silicon oxide can be stabilized by heat treatment at 400 to 800°C to obtain the Li compound.

[0085] As the organic solvent 23 in the bathtub 27, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, fluoromethylmethyl carbonate, difluoromethylmethyl carbonate, etc., can be used. In addition, as the electrolyte salt contained in the organic solvent 23, lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), etc., can be used.

[0086] The positive electrode 21 may be made of Li foil, or it may be made of a Li-containing compound. Examples of Li-containing compounds include lithium carbonate, lithium oxide, lithium cobaltate, lithium iron olivine, lithium nickelate, and lithium vanadium phosphate.

[0087] After electrochemical lithium-doping modification, the slurry may be washed with alkaline water containing dissolved lithium carbonate, lithium oxide, or lithium hydroxide, alcohol, a weak acid, or pure water. Washing can dissolve excess alkaline components, improving slurry stability.

[0088] In the oxidation-reduction modification method, for example, lithium can be inserted by first immersing silicon active material particles in solution A, which is a solution of lithium dissolved in an ether-based solvent. A polycyclic aromatic compound or a linear polyphenylene compound may also be added to solution A. The resulting silicon oxide can be stabilized by heat treatment at 400-800°C to stabilize the Li compound. Alternatively, after lithium insertion, the active lithium can be removed from the silicon active material particles by immersing them in solution B, which contains a polycyclic aromatic compound or a linear polyphenylene compound or its derivative. The solvent in solution B can be, for example, an ether-based solvent, a ketone-based solvent, an ester-based solvent, an alcohol-based solvent, an amine-based solvent, or a mixture thereof. Washing may be performed with alkaline water containing lithium carbonate, lithium oxide, or lithium hydroxide, alcohol, a weak acid, or pure water. Washing removes excess alkaline components, improving slurry stability.

[0089] As the ether-based solvent used in solution A, diethyl ether, tert-butyl methyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or a mixture thereof can be used. Among these, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, and diethylene glycol dimethyl ether are particularly preferred. These solvents are preferably dehydrated and preferably deoxygenated.

[0090] Furthermore, as the polycyclic aromatic compound contained in solution A, one or more of the following can be used: naphthalene, anthracene, phenanthrene, naphthalene, pentacene, pyrene, triphenylene, coronene, chrysene, and their derivatives. As the linear polyphenylene compound, one or more of the following can be used: biphenyl, terphenyl, and their derivatives.

[0091] The polycyclic aromatic compounds included in solution B may include one or more of the following: naphthalene, anthracene, phenanthrene, naphthalene, pentacene, pyrene, triphenylene, coronene, chrysene, and their derivatives.

[0092] Furthermore, as the ether-based solvent for solution B, diethyl ether, tert-butyl methyl ether, tetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or a mixture thereof can be used.

[0093] As ketone solvents, acetone, acetophenine, and the like can be used.

[0094] Suitable ester solvents include methyl formate, methyl acetate, ethyl acetate, propyl acetate, and isopropyl acetate.

[0095] Examples of alcohol-based solvents that can be used include methanol, ethanol, propanol, and isopropyl alconol.

[0096] As amine-based solvents, methylamine, ethylamine, and ethylenediamine can be used.

[0097] When performing Li-doping using these electrochemical methods or oxidation-reduction reactions, a film is formed from the carbon components contained in the reaction solution. This film can consist of at least one compound having an OC=O bond and a compound having a CC bond. Furthermore, after performing Li-doping using the above electrochemical methods or oxidation-reduction reactions, heat treatment can also be performed to create a film consisting of at least one compound having an OC=O bond and a compound having a CC bond.

[0098] Furthermore, when forming a coating consisting of at least one compound having an OC=O bond and a compound having a CC bond, which are essential for the negative electrode active material of the present invention, for example by the electrochemical method described above or by Li doping by a redox reaction, in addition to these methods, Li doping can also be performed by inserting Li into the negative electrode active material particles by a thermal doping method. In this case, for example, the negative electrode active material particles can be modified by mixing them with LiH powder or Li powder and heating them in a non-oxidizing atmosphere. An Ar atmosphere can be used as a non-oxidizing atmosphere. More specifically, first, LiH powder or Li powder and silicon oxide powder are thoroughly mixed in an Ar atmosphere, sealed, and homogenized by stirring the sealed container. Then, the mixture is heated in the range of 700°C to 750°C to perform the modification. In this case, in order to detach Li from the silicon compound, the powder may be thoroughly cooled after heating and washed with alkaline water containing dissolved lithium carbonate, lithium oxide, or lithium hydroxide, alcohol, a weak acid, or pure water. Washing can dissolve excess alkaline components and improve slurry stability.

[0099] Furthermore, a carbon layer different from the aforementioned carbon film (also referred to as a "second carbon layer") may be formed on the surface of the powder material obtained after lithium insertion. This carbon layer is effective in further improving the battery characteristics of the negative electrode active material.

[0100] For forming a carbon layer (second carbon layer) on the surface of powder material, thermal decomposition CVD is preferred. In thermal decomposition CVD, silicon oxide powder is placed in a furnace, and the furnace is filled with hydrocarbon gas to raise the furnace temperature. The decomposition temperature is not particularly limited, but it is especially desirable to be below 1000°C. More preferably below 950°C, as this can suppress unintended disproportionation of silicon oxide. The hydrocarbon gas is not particularly limited, but C n H m A composition of 2 ≥ n is desirable because it results in lower manufacturing costs and better physical properties of the decomposition products.

[0101] <Aqueous anode slurry composition> A water-based negative electrode slurry composition can be obtained by mixing the negative electrode active material prepared as described above with other materials such as a negative electrode binder and conductive additive as needed, and then adding water (organic solvents can also be added in addition to water). By using such a water-based negative electrode slurry composition to prepare the negative electrode, a secondary battery with high capacity and good initial charge / discharge characteristics can be made.

[0102] Next, the above-mentioned aqueous negative electrode slurry composition is applied to the surface of the negative electrode current collector and dried to form a negative electrode active material layer. At this time, heating and pressing may be performed as needed. In this way, a negative electrode can be manufactured.

[0103] <Lithium-ion rechargeable battery> Next, as a specific example of the non-aqueous electrolyte secondary battery of the present invention described above, a laminate film type lithium-ion secondary battery will be explained.

[0104] [Configuration of a laminate film type rechargeable battery] The laminate film type lithium-ion secondary battery 30 shown in Figure 3 mainly consists of a wound electrode body 31 housed inside a sheet-like outer casing member 35. This wound electrode body 31 has a separator between the positive and negative electrodes and is wound. There are also cases where a laminated structure with a separator between the positive and negative electrodes is housed without winding. In both electrode bodies, a positive electrode lead 32 is attached to the positive electrode and a negative electrode lead 33 is attached to the negative electrode. The outermost part of the electrode body is protected by protective tape.

[0105] The positive and negative electrode leads 32 and 33 are led out in one direction, for example, from the inside to the outside of the outer casing member 35. The positive electrode lead 32 is made of a conductive material such as aluminum, and the negative electrode lead 33 is made of a conductive material such as nickel or copper.

[0106] The exterior component 35 is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order. In this laminate film, the outer edges of the fusion layers of two films are fused together or bonded together with an adhesive so that the fusion layer faces the electrode body 31. The fusion part is, for example, a film such as polyethylene or polypropylene, and the metal part is, for example, aluminum foil. The protective layer is, for example, nylon.

[0107] An adhesive film 34 is inserted between the outer casing member 35 and the positive and negative electrode leads to prevent outside air from entering. This material can be, for example, polyethylene, polypropylene, or polyolefin resin.

[0108] The positive electrode, for example, has a positive electrode active material layer on both sides or one side of the positive electrode current collector, similar to the negative electrode 10 in Figure 1.

[0109] The positive electrode current collector is formed from a conductive material such as aluminum.

[0110] The positive electrode active material layer contains any one or two or more kinds of positive electrode materials capable of intercalating and deintercalating lithium ions, and may contain other materials such as a positive electrode binder, a positive electrode conductive aid, a dispersant, etc. according to the design. In this case, the details regarding the positive electrode binder and the positive electrode conductive aid are the same as, for example, the negative electrode binder and the negative electrode conductive aid already described.

[0111] As the positive electrode material, a lithium-containing compound is desirable. Examples of this lithium-containing compound include a composite oxide composed of lithium and a transition metal element, or a phosphate compound having lithium and a transition metal element. Among these positive electrode materials, compounds having at least one or more of nickel, iron, manganese, and cobalt are preferable. As these chemical formulas, for example, Li x M1O2 or Li y M2PO4. In the formula, M1 and M2 represent at least one or more transition metal elements. The values of x and y represent different values depending on the charge and discharge state of the battery, but are generally represented by 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

[0112] Examples of the composite oxide having lithium and a transition metal element include lithium cobalt composite oxide (Li x CoO2), lithium nickel composite oxide (Li x NiO2), lithium nickel cobalt composite oxide, etc. Examples of the lithium nickel cobalt composite oxide include lithium nickel cobalt aluminum composite oxide (NCA), lithium nickel cobalt manganese composite oxide (NCM), etc.

[0113] Examples of the phosphate compound having lithium and a transition metal element include lithium iron phosphate compound (LiFePO4) or lithium iron manganese phosphate compound (LIfe 1-u Mn u PO4 (0 < u < 1)), etc. By using these positive electrode materials, a high battery capacity can be obtained and excellent cycle characteristics can also be obtained.

[0114] [Negative electrode] The negative electrode has a configuration similar to the negative electrode 10 for lithium-ion secondary batteries shown in Figure 1 above, and for example, has negative electrode active material layers on both sides of the current collector. It is preferable that the negative electrode charging capacity is greater than the electrical capacity (charging capacity as a battery) obtained from the positive electrode active material. This makes it possible to suppress the deposition of lithium metal on the negative electrode.

[0115] The positive electrode active material layer is provided on a portion of both sides of the positive electrode current collector, and similarly, the negative electrode active material layer is also provided on a portion of both sides of the negative electrode current collector. In this case, for example, the negative electrode active material layer provided on the negative electrode current collector has a region where there is no opposing positive electrode active material layer. This is to ensure a stable battery design.

[0116] In the region where the negative electrode active material layer and the positive electrode active material layer do not face each other, the effects of charging and discharging are minimal. Therefore, the state of the negative electrode active material layer is maintained as it was immediately after formation, allowing for accurate and reproducible investigation of the composition of the negative electrode active material, regardless of whether charging or discharging is performed.

[0117] [Separator] A separator separates the positive and negative electrodes, preventing current short circuits caused by contact between the two electrodes while allowing lithium ions to pass through. This separator is formed from a porous membrane made of, for example, synthetic resin or ceramic, and may have a laminated structure in which two or more porous membranes are stacked. Examples of synthetic resins include polytetrafluoroethylene, polypropylene, and polyethylene.

[0118] [Electrolyte] At least a portion of the active material layer, or the separator, is impregnated with a liquid electrolyte. This electrolyte contains an electrolyte salt dissolved in a solvent and may also contain other materials such as additives.

[0119] For example, non-aqueous solvents can be used as solvents. Examples of non-aqueous solvents include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, 1,2-dimethoxyethane, or tetrahydrofuran. Among these, it is desirable to use at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or ethylmethyl carbonate, as this will yield better properties. In this case, even more advantageous properties can be obtained by combining high-viscosity solvents such as ethylene carbonate and propylene carbonate with low-viscosity solvents such as dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate. This is because the dissociability and ion mobility of the electrolyte salt are improved.

[0120] It is preferable that the solvent additive contains an unsaturated carbon-bonded cyclic carbonate ester. This is because a stable film is formed on the negative electrode surface during charging and discharging, which suppresses the decomposition reaction of the electrolyte. Examples of unsaturated carbon-bonded cyclic carbonate esters include vinylene carbonate or vinylethylene carbonate.

[0121] Furthermore, it is preferable to include a sultone (cyclic sulfonic acid ester) as a solvent additive, as this improves the chemical stability of the battery. Examples of sultones include propanesultone and propenesultone.

[0122] Furthermore, the solvent preferably contains an acid anhydride, as this improves the chemical stability of the electrolyte. Examples of acid anhydrides include propanedisulfonic acid anhydride.

[0123] The electrolyte salt may contain one or more light metal salts, such as lithium salts. Examples of lithium salts include lithium hexafluoride phosphate (LiPF6) and lithium tetrafluoroborate (LiBF4).

[0124] The electrolyte salt content is preferably 0.5 mol / kg to 2.5 mol / kg relative to the solvent. This is because it allows for high ionic conductivity.

[0125] [Manufacturing method for laminate film type rechargeable batteries] First, a positive electrode is fabricated using the positive electrode material described above. First, the positive electrode active material is mixed with a positive electrode binder and a positive electrode conductive additive as needed to form a positive electrode mixture, which is then dispersed in an organic solvent to form a positive electrode mixture slurry. Next, the mixture slurry is applied to the positive electrode current collector using a coating device such as a die coater with a knife roll or die head, and the mixture is dried with hot air to obtain a positive electrode active material layer. Finally, the positive electrode active material layer is compressed and molded using a roll press or similar device. At this time, heating may be used, and the compression may be repeated multiple times.

[0126] Next, using the same procedure as for the production of the negative electrode 10 for the lithium-ion secondary battery described above, a negative electrode is fabricated by forming a negative electrode active material layer on the negative electrode current collector.

[0127] When manufacturing the positive and negative electrodes, active material layers are formed on both sides of the positive and negative electrode current collectors. At this time, the length of the active material coating on both sides of either electrode may be staggered (see Figure 1).

[0128] Next, the electrolyte is prepared. Then, the positive electrode lead 32 is attached to the positive electrode current collector and the negative electrode lead 33 is attached to the negative electrode current collector by ultrasonic welding or the like. Next, the positive electrode and negative electrode are laminated or wound together with a separator in between to create a wound electrode body 31, and protective tape is adhered to its outermost circumference. Next, the wound electrode body is molded into a flat shape. Next, the wound electrode body is sandwiched between folded film-like outer casing members 35, and then the insulating parts of the outer casing members are bonded together by heat fusion, sealing the wound electrode body with only one side open. Next, an adhesive film is inserted between the positive electrode lead, the negative electrode lead and the outer casing members. Next, a predetermined amount of the prepared electrolyte is poured in through the opening and vacuum impregnation is performed. After impregnation, the opening is bonded by vacuum heat fusion. In this way, a laminate film type secondary battery 30 can be manufactured.

[0129] In the non-aqueous electrolyte secondary battery of the present invention, such as the laminate film type secondary battery 30 prepared as described above, it is preferable that the negative electrode utilization rate during charging and discharging is 93% or more and 99% or less. If the negative electrode utilization rate is in the range of 93% or more, the initial charging efficiency will not decrease, and the battery capacity can be greatly improved. Furthermore, if the negative electrode utilization rate is in the range of 99% or less, safety can be ensured because Li will not precipitate. [Examples]

[0130] The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0131] (Example 1-1) A laminate film type secondary battery 30, as shown in Figure 3, was fabricated using the following procedure.

[0132] First, the positive electrode was fabricated. The positive electrode active material was lithium nickel cobalt aluminum composite oxide (LiNi 0.7 Co 0.25 Al 0.05 95 parts by mass of O) was mixed with 2.5 parts by mass of a positive electrode conductive additive (acetylene black) and 2.5 parts by mass of a positive electrode binder (polyvinylidene fluoride, PVDF) to form a positive electrode mixture. The positive electrode mixture was then dispersed in an organic solvent (N-methyl-2-pyrrolidone, NMP) to form a paste-like slurry. The slurry was then applied to both sides of the positive electrode current collector using a coating apparatus with a die head and dried in a hot air drying apparatus. A positive electrode current collector with a thickness of 15 μm was used. Finally, compression molding was performed using a roll press.

[0133] Next, the anode was fabricated. First, the silicon-based active material was prepared as follows: A raw material (vaporized starting material) made by mixing metallic silicon and silicon dioxide was placed in a reactor and vaporized in a vacuum atmosphere of 10 Pa. The vaporized material was deposited on an adsorption plate, and after sufficient cooling, the deposited material was removed and pulverized in a ball mill. Subsequently, the silicon compound was modified by inserting lithium into the silicon compound particles using a redox method. First, the anode active material particles were immersed in a solution (Solution A) in which lithium pieces and the aromatic compound naphthalene were dissolved in tetrahydrofuran (hereinafter referred to as THF). Solution A was prepared by dissolving naphthalene in the THF solvent at a concentration of 0.2 mol / L, and then adding 12% by mass of lithium pieces to this THF and naphthalene mixture. The temperature of the solution when immersing the anode active material particles was 20°C, and the immersion time was 20 hours. After that, the anode active material particles were filtered off. Through the above process, lithium was inserted into the negative electrode active material particles.

[0134] The obtained silicon compound particles were heat-treated under an argon atmosphere at a temperature of 650°C or lower for 24 hours to stabilize the Li compound.

[0135] In this manner, the negative electrode active material particles (silicon-based active material particles) were modified. After modification, they were washed with a solvent. Through the above process, negative electrode active material particles were prepared.

[0136] XRD measurement of the obtained negative electrode active material particles, 29 Si-NMR measurements, Raman spectroscopy, and particle size distribution measurements were performed.

[0137] The silicon-based active material prepared as described above was mixed with a carbon-based active material in a mass ratio of 2:8 to create the negative electrode active material. Here, the carbon-based active material used was a mixture of natural graphite and artificial graphite coated with a pitch layer in a mass ratio of 5:5. The median diameter of the carbon-based active material was 20 μm.

[0138] Next, the prepared negative electrode active material, conductive additive 1 (carbon nanotubes, CNTs), conductive additive 2 (carbon nanoparticles with a median diameter of approximately 50 nm), styrene-butadiene rubber (styrene-butadiene copolymer, hereinafter referred to as SBR), and carboxymethylcellulose (hereinafter referred to as CMC) were mixed in a dry mass ratio of 92.5:1:1:2.5:3, and then diluted with pure water to obtain a negative electrode mixture slurry. The above SBR and CMC are negative electrode binders (negative electrode binders).

[0139] Furthermore, electrolytic copper foil (15 μm thick) was used as the negative electrode current collector. Finally, the negative electrode mixture slurry was applied to the negative electrode current collector and dried in a vacuum atmosphere at 100°C for 1 hour. After drying, the amount of negative electrode active material deposited per unit area on one side of the negative electrode (also called area density) was 5 mg / cm². 2 That was the case.

[0140] Next, fluoroethylene carbonate (FEC), ethylene carbonate (EC), and diethyl carbonate (DEC) were mixed as solvents, and then an electrolyte salt (lithium hexafluoride phosphate: LiPF6) was dissolved to prepare the electrolyte. In this case, the solvent composition was FEC:EC:DEC = 1:2:7 by volume ratio, and the electrolyte salt content was 1.0 mol / kg relative to the solvent. Furthermore, 1.5% by mass of vinylene carbonate (VC) was added to the obtained electrolyte.

[0141] Next, the secondary battery was assembled as follows. First, an aluminum lead was ultrasonically welded to one end of the positive electrode current collector, and a nickel lead was welded to the negative electrode current collector. Subsequently, the positive electrode, separator, negative electrode, and separator were stacked in this order and wound in the longitudinal direction to obtain a wound electrode body. The end of the winding was secured with PET protective tape. The separator used was a 12 μm laminated film made of porous polyethylene sandwiched between films made of porous polypropylene. Next, the electrode body was sandwiched between the outer casing members, and the outer edges, excluding one side, were heat-sealed to house the electrode body inside. The outer casing members were made of aluminum laminate film, which consisted of nylon film, aluminum foil, and polypropylene film. Subsequently, the prepared electrolyte was injected through the opening, impregnated under a vacuum atmosphere, and then heat-sealed.

[0142] The cycle characteristics and initial charge-discharge characteristics of the secondary battery fabricated as described above were evaluated.

[0143] The cycle characteristics were investigated as follows: First, to stabilize the battery, two charge-discharge cycles were performed at 0.2C in a 25°C atmosphere, and the discharge capacity of the second cycle was measured. Subsequently, charge-discharge was performed until the total number of cycles reached 299, and the discharge capacity was measured each time. Finally, the discharge capacity at the 300th cycle, obtained with 0.2C charge-discharge, was divided by the discharge capacity of the second cycle to calculate the capacity retention rate (hereinafter also simply referred to as the retention rate). For normal cycles, i.e., from the 3rd cycle to the 299th cycle, charge-discharge was performed at 0.7C and discharge at 0.5C.

[0144] When investigating the initial charge-discharge characteristics, the initial efficiency (sometimes called the initial charge efficiency) was calculated. The initial efficiency was calculated using the formula: Initial Efficiency (%) = (Initial Discharge Capacity / Initial Charge Capacity) × 100. The ambient temperature was the same as when investigating the cycle characteristics. Furthermore, this initial efficiency was calculated using the discharge capacity up to 1.2V.

[0145] (Examples 1-2, 1-3, Comparative Examples 1-1, 1-2) By adjusting the temperature and time conditions during cleaning with the modified solvent, secondary batteries were fabricated under the same conditions as in Example 1-1, except for adjusting the amount of carbon coating, as shown in Table 1, and each evaluation was performed. As shown in Table 1, good initial efficiency and capacity retention were obtained when the carbon coating amount was greater than 0% by mass and less than or equal to 1% by mass for the silicon compound represented by SiOx. In Comparative Example 1-1, with a carbon coating amount of 1.2% by mass, a decrease in initial efficiency and capacity retention was observed due to side reactions of the carbon coating during charging and discharging. In Comparative Example 1-2, with a carbon coating amount of 0% by mass, both initial efficiency and capacity retention were poor due to the inability to achieve conductivity.

[0146] [Table 1]

[0147] (Examples 2-1 to 2-4) As shown in Table 2, the Ia / Ib intensity ratio in the negative electrode active material particles was adjusted. This can be adjusted by the heat treatment conditions (temperature, pressure) after lithium insertion. In addition, a secondary battery was fabricated under the same conditions as in Example 1-1, and each evaluation was performed, with the results shown in Table 2.

[0148] [Table 2]

[0149] As shown in Table 2, particularly good initial efficiency and capacity retention were obtained in the range of 0 ≤ Ia / Ib ≤ 3.0. Since the side reactions caused by the carbon film during charging are due to compounds with OC=O bonds, suppressing the side reactions by not having too many compounds with OC=O bonds improved both the initial efficiency and capacity retention. On the other hand, in Example 2-4, where Ia / Ib > 3.0, the number of compounds with OC=O bonds increases, leading to more side reactions by the carbon film of the rechargeable battery, and slightly lowering the initial efficiency and capacity retention. For these reasons, it is preferable that Ia / Ib be in the range of 0 ≤ Ia / Ib ≤ 3.0.

[0150] (Examples 3-1 to 3-7) As shown in Table 3, the XRD intensity ratio of the Li compound Li2SiO3 was adjusted. This adjustment was performed by adjusting the amount of Li inserted. In addition, a secondary battery was fabricated under the same conditions as in Example 1-1, and each evaluation was performed. The results are shown in Table 3.

[0151] [Table 3]

[0152] As shown in Table 3, lowering the Ie / Ic ratio resulted in improvements in both initial efficiency and capacity retention. This is because increasing the amount of inserted Li reduces the XRD intensity ratio of Li2SiO3, leading to greater modification of the irreversible components of the silicon compound. On the other hand, although not shown in the table, when the intensity ratio Ie / Ic is 1 or higher, the doped Li is more stable, and gas generation can be suppressed in aqueous slurries, so it is preferable to maintain an intensity ratio of Ie / Ic of 1 or higher.

[0153] (Examples 4-1 to 4-6) Next, as shown in Table 4, the full width at half maximum (FWHM) of the Li2SiO3 obtained from the XRD spectrum was adjusted. This can be adjusted by changing the Li content. Furthermore, a secondary battery was fabricated under the same conditions as in Example 1-1, and each evaluation was performed; the results are shown in Table 4.

[0154] [Table 4]

[0155] If the full width at half maximum (FWHM) exceeds 3.0°, the Li content becomes high, and the FWHM of Li2SiO3 widens. In this case, gas generation in the slurry becomes significant, which ultimately leads to a decrease in battery performance. The FWHM of Li2SiO3 is preferably between 0.5° and 3.0°.

[0156] (Examples 5-1 to 5-5) Next, as shown in Table 5, the crystallite size of the Si(220) plane was adjusted. This can be adjusted by thermal loading of the silicon oxide. Furthermore, a secondary battery was fabricated under the same conditions as in Example 1-1, and each evaluation was performed; the results are shown in Table 5.

[0157] [Table 5]

[0158] As shown in Table 5, good capacity retention was observed in the crystallite size range of 5 nm or less.

[0159] (Examples 6-1 to 6-5) Next, the If / Ii and Ih / Ii were adjusted as shown in Table 6. This can be adjusted by the heat treatment conditions of the Li-containing silicon oxide. A secondary battery was also fabricated under the same conditions as in Example 1-1, and each evaluation was performed, with the results shown in Table 6.

[0160] [Table 6]

[0161] As shown in Table 6, with If / Ii being 0.23 or less and Ih / Ii being 1.1, the doped Li was sufficiently stabilized, resulting in slightly weaker bonding with the binder, which in turn resulted in good battery characteristics.

[0162] (Examples 7-1 to 7-8) Next, as shown in Table 7, the intensity ratio Id / Ig of the D band to the G band, and the intensity ratio ISi / Ig of the Si peak intensity to the G band were adjusted by Raman spectroscopy. This can be adjusted by the conditions during thermal CVD (heating conditions, temperature, pressure, gas flow rate). In addition, a secondary battery was fabricated under the same conditions as in Example 1-1, and each evaluation was performed, with the results shown in Table 7.

[0163] [Table 7]

[0164] As shown in Table 7, when Id / Ig is between 0 and 2.0, the amount of non-conductive diamond structure carbon is reduced, resulting in good initial efficiency and capacity retention. Furthermore, in the range of ISi / Ig between 0 and 5, the silicon compound is sufficiently coated, ensuring sufficient conductivity and resulting in good initial efficiency and capacity retention.

[0165] (Examples 8-1 to 8-7) Next, as shown in Table 8, the D10 and D50 (median diameter) of the silicon compound particles were varied. This can be adjusted by the degree of grinding and classification. Furthermore, secondary batteries were fabricated under the same conditions as in Example 1-1, and each evaluation was performed; the results are shown in Table 8.

[0166] [Table 8]

[0167] As shown in Table 8, when the median diameter of the silicon compound was 0.5 μm or greater and D10 was 2 μm or greater, the initial efficiency and retention rate were further improved. This is thought to be because the surface area of ​​the silicon compound particles was not too large, thus suppressing side reactions. On the other hand, when the median diameter was 20 μm or less and D10 was 16 μm or less, the particles were less likely to break during charging, and SEI (solid electrolyte interface) formation due to newly formed surfaces was less likely during charging and discharging, thus suppressing the loss of reversible Li. In addition, when the median diameter of the silicon compound particles was 20 μm or less, the amount of expansion of the silicon compound particles during charging was not excessive, thus preventing physical and electrical breakdown of the negative electrode active material layer due to expansion.

[0168] (Examples 9-1 to 9-5) Next, as shown in Table 9, the Li compound Li2CO3 was prepared. Li2CO3 can be adjusted by controlling the exposure time to air. A secondary battery was also fabricated under the same conditions as in Example 1-1, and each evaluation was performed. The results are shown in Table 2.

[0169] [Table 9]

[0170] As shown in Table 9, when the Ij / Ic intensity ratio was 10 or less, the initial efficiency was good, and as a result, the battery characteristics were also good.

[0171] (Examples 10-1 to 10-8) Next, as shown in Table 10, hydrocarbon gas was introduced during the heat treatment after lithium insertion to form a carbon film on the surface, creating a carbon film on the outermost surface of the silicon compound with different G-band peak positions in Raman spectroscopy. The G-band peak was adjusted by controlling the processing temperature. Secondary batteries were also fabricated under the same conditions as in Example 1-1, and each evaluation was performed, with the results shown in Table 10.

[0172] [Table 10]

[0173] As shown in Table 10, the G-band peak is at 1588 cm. -1 ~1598cm -1 When a carbon film within this range is present on the outermost surface of the silicon compound, conductivity is improved, and furthermore, the elution of Li from the Li compound can be suppressed, thereby suppressing the rise in pH in the aqueous slurry and improving the stability of the aqueous slurry. By using this slurry, good electrodes can be obtained, and as a result, good battery characteristics can be obtained. The G-band peak is 1598 cm⁻¹. -1 Over 1600cm -1 However, the stabilization of the Li compound was insufficient, and the conductivity of the formed carbon film was also insufficient, resulting in a slight deterioration of the battery characteristics.

[0174] This specification includes the following embodiments: [1]: Having negative electrode active material particles, The negative electrode active material particles are silicon compounds (SiO xIt contains silicon compound particles containing (0.5 ≤ x ≤ 1.6), The silicon compound particles are a negative electrode active material for a non-aqueous electrolyte secondary battery, wherein the silicon compound particles contain a Li compound. The negative electrode active material particles are coated with a carbon film, at least a portion of them. The amount of carbon coating on the negative electrode active material particles is greater than 0% by mass and less than or equal to 1% by mass relative to the total of the silicon compound particles and the carbon coating. The carbon coating comprises a coating consisting of at least one compound having an OC=O bond and a compound having a CC bond. The silicon compound particles are characterized in that the Li compound contains crystalline Li2SiO3, making it a negative electrode active material for a non-aqueous electrolyte secondary battery. [2]: The negative electrode active material is the negative electrode active material for a non-aqueous electrolyte secondary battery described in [1] above, wherein the intensity ratio of the intensity Ia at around 290 eV due to OC=O bonds and the intensity Ib at around 285 eV due to CC bonds, obtained by X-ray photoelectron spectroscopy, is 0 ≤ Ia / Ib ≤ 3.0. [3]: The negative electrode active material is a negative electrode active material for a non-aqueous electrolyte secondary battery according to [1] or [2] above, wherein the intensity Ie, which is due to Li2SiO3, is 1 ≤ Ie / Ic ≤ 18.5 compared to the intensity Ic, which is due to Si, obtained by X-ray diffraction, with respect to the intensity Ie, which is due to Li2SiO3, with respect to the intensity Ie, which is due to Si, with respect to the intensity Ie, which is due to Li2SiO3, with respect [4]: A negative electrode active material for a non-aqueous secondary battery, any of the above [1] to [3], wherein the peak full width at half maximum around 2θ = 18.7°, due to Li2SiO3, obtained by X-ray diffraction of the negative electrode active material, is 0.5° or more and 3.0° or less. [5]: A negative electrode active material for a non-aqueous secondary battery, any of the above [1] to [4], wherein the crystallite size due to the Si(220) crystal plane obtained by X-ray diffraction of the negative electrode active material is 5 nm or less. [6]: The negative electrode active material 29A negative electrode active material for a non-aqueous secondary battery, as determined from the Si-MAS-NMR spectrum, having at least one peak in at least one of the following regions: -80 ppm or more and less than -70 ppm, -70 ppm or more and less than -60 ppm, and -60 ppm or more and less than -30 ppm. [7]: The negative electrode active material 29 Obtained from Si-MAS-NMR spectra, As the chemical shift value, if we set the peak intensity of the peak obtained in the region between -60 ppm and -30 ppm as the If value, As a chemical shift value, the peak intensity of the peak obtained in the region between -70 ppm and -60 ppm is taken as Ih. When the peak intensity obtained in the region of chemical shift values ​​between -80 ppm and less than -70 ppm is denoted as Ii, 0 ≤ If / Ii ≤ 0.23, 0 ≤ Ih / Ii ≤ 1.1 The negative electrode active material for a non-aqueous secondary battery according to [6] above, which satisfies both of the following conditions. [8]: A negative electrode active material for a non-aqueous electrolyte secondary battery according to any of the above [1] to [7], wherein the intensity ratio Id / Ig of the D band to the G band as determined by Raman spectroscopy of the negative electrode active material is 0 ≤ Id / Ig ≤ 2.0. [9]: A negative electrode active material for a non-aqueous electrolyte secondary battery, any of the above [1] to [8], wherein the ratio of Si peak intensity to G band intensity ISi / Ig obtained by Raman spectroscopy of the negative electrode active material is 0 ≤ ISi / Ig ≤ 5.0.

[10] : A negative electrode active material for a non-aqueous electrolyte secondary battery according to any of the above [1] to [9], wherein the median diameter of the silicon compound particles is 0.5 μm or more and 20 μm or less.

[11] : The negative electrode active material particles are Does it not contain Li2CO3? A negative electrode active material for a non-aqueous electrolyte secondary battery, wherein a portion of the outermost layer is coated with crystalline Li2CO3, and the negative electrode active material is any of the above [1] to

[10] , wherein the peak intensity Ij at around 2θ=21° due to Li2CO3 is 0≦Ij / Ic≦10 compared to the intensity Ic at around 2θ=47.5° due to Si obtained by X-ray diffraction.

[12] : A negative electrode active material for a non-aqueous electrolyte secondary battery according to any of [1] to

[11] above, which is covered with a carbon layer different from the carbon film.

[13] : Raman spectroscopy of the negative electrode active material revealed a peak originating from the G band at 1588 cm⁻¹. -1 ~1598cm -1 A negative electrode active material for a non-aqueous electrolyte secondary battery, which is coated with a carbon film, as described in [1] to

[12] above.

[14] : A non-aqueous electrolyte secondary battery characterized by containing any of the negative electrode active materials for non-aqueous electrolyte secondary batteries described in [1] to

[13] above.

[15] : A mobile device having the non-aqueous electrolyte secondary battery described in

[14] above.

[16] : An electric vehicle equipped with the non-aqueous electrolyte secondary battery described in

[14] above.

[17] : A power storage system comprising the non-aqueous electrolyte secondary battery described in

[14] above.

[18] : A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, comprising negative electrode active material particles, Silicon compounds (SiO x A process for producing silicon compound particles containing (0.5 ≤ x ≤ 1.6), The process involves inserting Li into the silicon compound particles to produce Li2SiO3 as a Li compound. Includes, The process further includes, simultaneously with or after the step of inserting Li into the silicon compound particles, a step of coating at least a portion of the silicon compound particles with a carbon film, A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, characterized in that the amount of carbon coating on the negative electrode active material particles is greater than 0% by mass and 1% by mass or less of the total amount of the silicon compound particles and the carbon coating, and the carbon coating is made up of at least one of a compound having an OC=O bond and a compound having a CC bond.

[19] : A method for producing the negative electrode active material for a non-aqueous electrolyte secondary battery according to

[18] , wherein the step of inserting Li into the silicon compound particles is performed by an electrochemical method or a method by an oxidation-reduction reaction.

[0175] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of Symbols]

[0176] 10...Negative electrode, 11...Negative electrode current collector, 12...Negative electrode active material layer, 20...Bulk reforming unit, 21...Positive electrode (lithium source, reforming source), 22...Silicon compound particles, 23…Organic solvent, 24…Separator, 25... Powder storage container, 26... Power supply, 27... Bathtub, 30...Lithium secondary battery (laminated film type), 31...Electrode body, 32... Positive lead (positive aluminum lead), 33... Negative electrode lead (negative electrode nickel lead), 34...Adhesive film, 35...Exterior components.

Claims

1. Having negative electrode active material particles, The negative electrode active material particles are silicon compounds (SiO ｘ It contains silicon compound particles containing (0.5 ≤ x ≤ 1.6), The silicon compound particles are a negative electrode active material for a non-aqueous electrolyte secondary battery, wherein the silicon compound particles contain a Li compound. The negative electrode active material particles are coated with a carbon film, at least a portion of them. The amount of carbon coating on the negative electrode active material particles is greater than 0% by mass and less than or equal to 1% by mass relative to the total of the silicon compound particles and the carbon coating. The carbon coating includes a coating having a compound having an O-C=O bond and a compound having a C-C bond. The silicon compound particles are composed of crystalline Li as the Li compound. ２ SiO ３ A negative electrode active material for a non-aqueous electrolyte secondary battery, characterized by containing the following:

2. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, characterized in that the intensity ratio of the intensity Ia at around 290 eV due to O-C=O bonds and the intensity Ib at around 285 eV due to C-C bonds, obtained by X-ray photoelectron spectroscopy, is 0 < Ia / Ib ≤ 3.

0.

3. The negative electrode active material has an intensity Ic around 2θ = 47.5° due to Si, obtained by X-ray diffraction, and Li ２ SiO ３ The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the intensity Ie around 2θ = 18.7° due to satisfies 1 ≤ Ie / Ic ≤ 18.

5.

4. Li obtained by X-ray diffraction of the negative electrode active material ２ SiO ３ The negative electrode active material for a non-aqueous secondary battery according to claim 3, characterized in that the peak half-width at approximately 2θ = 18.7° due to the above is 0.5° or more and 3.0° or less.

5. The negative electrode active material for a non-aqueous secondary battery according to claim 1 or 2, characterized in that the crystallite size resulting from the Si(220) crystal plane obtained by X-ray diffraction of the negative electrode active material is 5 nm or less.

6. The negative electrode active material ２９ The negative electrode active material for a non-aqueous secondary battery according to claim 1 or 2, characterized in that, as a chemical shift value obtained from the Si-MAS-NMR spectrum, it has at least one peak in at least one of the following regions: -80 ppm or more and less than -70 ppm, -70 ppm or more and less than -60 ppm, and -60 ppm or more and less than -30 ppm.

7. of the negative electrode active material ２９ obtained from the Si-MAS-NMR spectrum As the chemical shift value, if is the peak intensity of the peak obtained in the region between -60 ppm and -30 ppm. As a chemical shift value, the peak intensity of the peak obtained in the region between -70 ppm and -60 ppm is taken as Ih. When the peak intensity obtained in the region of chemical shift values ​​between -80 ppm and less than -70 ppm is denoted as Ii, 0 ≤ If / Ii ≤ 0.23, 0 ≤ Ih / Ii ≤ 1.1 The negative electrode active material for a non-aqueous secondary battery according to claim 6, characterized in that it satisfies both of the following conditions.

8. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the intensity ratio Id / Ig of the D band and G band obtained by Raman spectroscopy of the negative electrode active material is 0 ≤ Id / Ig ≤ 2.

0.

9. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the ratio of Si peak intensity to G band intensity ISi / Ig obtained by Raman spectroscopy of the negative electrode active material is 0 ≤ ISi / Ig ≤ 5.

0.

10. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the median diameter of the silicon compound particles is 0.5 μm or more and 20 μm or less.

11. The aforementioned negative electrode active material particles are Li ２ CO ３ Does it not contain, A portion of the outermost layer is crystalline Li ２ CO ３ The negative electrode active material is coated with Li, and the intensity Ic around 2θ = 47.5° due to Si obtained by X-ray diffraction ２ CO ３ The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that the peak intensity Ij around 2θ = 21° due to satisfies 0 ≤ Ij / Ic ≤ 10.

12. The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that it is covered with a carbon layer different from the carbon film.

13. Raman spectroscopy of the aforementioned negative electrode active material revealed a peak originating from the G band at 1588 cm⁻¹. －１ ~1598cm －１ The negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, characterized in that it is coated with a carbon film.

14. A non-aqueous electrolyte secondary battery characterized by comprising the negative electrode active material for a non-aqueous electrolyte secondary battery described in claim 1 or claim 2.

15. A mobile terminal characterized by comprising a non-aqueous electrolyte secondary battery as described in claim 14.

16. An electric vehicle characterized by comprising a non-aqueous electrolyte secondary battery as described in claim 14.

17. A power storage system characterized by comprising a non-aqueous electrolyte secondary battery as described in claim 14.

18. A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, which includes negative electrode active material particles, Silicon compounds (SiO ｘ A step to produce silicon compound particles containing (0.5 ≤ x ≤ 1.6), By inserting Li into the silicon compound particles, Li is obtained as a Li compound. ２ SiO ３ The process of generating and Includes, The process further includes, simultaneously with or after the step of inserting Li into the silicon compound particles, a step of coating at least a portion of the silicon compound particles with a carbon film, A method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery, characterized by coating the negative electrode active material particles with a carbon film such that the amount of carbon film covering them is greater than 0% by mass and 1% by mass or less relative to the total amount of the silicon compound particles and the carbon film, and the carbon film is composed of at least one of a compound having an O-C=O bond and a compound having a C-C bond.

19. The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to claim 18, characterized in that the step of inserting Li into the silicon compound particles is carried out by an electrochemical method or a method by an oxidation-reduction reaction.

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