JPWO2013175715A1 - Powder for negative electrode material of lithium ion secondary battery, lithium ion secondary battery negative electrode and lithium ion secondary battery using the same - Google Patents

Abstract

In the spectrum of SiOx (0.4 ≦ x ≦ 1.2) measured by nuclear magnetic resonance spectroscopy for 29Si, the peak index attributed to zero-valent Si and the peak attributed to tetravalent Si Lithium ion secondary characterized in that the value of the ratio of the indices is 0.65 or more and 0.80 or less and the peak of the peak attributed to tetravalent Si is in the range of −110 ppm or more and −105 ppm or less Battery negative electrode powder. By using this negative electrode material powder, a lithium ion secondary battery having a large charge / discharge capacity and good cycle characteristics can be obtained.

Description

  The present invention relates to a powder for a negative electrode material capable of obtaining a lithium ion secondary battery having a large discharge capacity and good cycle characteristics. Moreover, this invention relates to the lithium ion secondary battery negative electrode and lithium ion secondary battery which used this powder for negative electrode materials.

  In recent years, with the remarkable development of portable electronic devices, communication devices, and the like, there is a strong demand for the development of secondary batteries with high energy density from the viewpoints of economy and miniaturization and weight reduction of the devices. Currently, high energy density secondary batteries include nickel cadmium batteries, nickel metal hydride batteries, lithium ion secondary batteries and polymer batteries. Among these, lithium ion secondary batteries have a much longer lifespan and higher capacity than nickel cadmium batteries and nickel metal hydride batteries, and thus the demand thereof has shown high growth in the power supply market.

  FIG. 1 is a diagram illustrating a configuration example of a coin-shaped lithium ion secondary battery. As shown in FIG. 1, the lithium ion secondary battery maintains the electrical insulation between the positive electrode 1, the negative electrode 2, the separator 3 impregnated with the electrolyte, and the positive electrode 1 and the negative electrode 2, and seals the battery contents. It consists of a gasket 4. When charging / discharging is performed, lithium ions reciprocate between the positive electrode 1 and the negative electrode 2 through the electrolytic solution of the separator 3.

The positive electrode 1 includes a counter electrode case 1a, a counter electrode current collector 1b, and a counter electrode 1c. Lithium cobaltate (LiCoO ₂ ) and manganese spinel (LiMn ₂ O ₄ ) are mainly used for the counter electrode 1c. The negative electrode 2 is composed of a working electrode case 2a, a working electrode current collector 2b, and a working electrode 2c. The negative electrode material used for the working electrode 2c is generally an active material capable of occluding and releasing lithium ions (negative electrode active material). ), A conductive aid and a binder.

  Conventionally, carbon-based materials have been used as negative electrode active materials for lithium ion secondary batteries. As a new negative electrode active material having a higher capacity of a lithium ion secondary battery than conventional ones, a composite oxide of lithium and boron, a composite oxide of lithium and a transition metal (V, Fe, Cr, Mo, Ni, etc.) Si, Ge, or a compound containing Sn and N and O, Si particles whose surface is coated with a carbon layer by chemical vapor deposition, and the like have been proposed.

  However, although any of these negative electrode active materials can improve the charge / discharge capacity and increase the energy density, expansion and contraction at the time of occlusion and release of lithium ions are increased. Therefore, lithium ion secondary batteries using these negative electrode active materials are insufficient in sustainability of discharge capacity (hereinafter referred to as “cycle characteristics”) due to repeated charge and discharge.

On the other hand, it has been attempted to use silicon oxide powder represented by SiO _x (0 <x ≦ 2) such as SiO as the negative electrode active material. Silicon oxide can be a negative electrode active material having a larger effective charge / discharge capacity because it has less degradation such as collapse of the crystal structure and generation of an irreversible material due to insertion and extraction of lithium ions during charge / discharge. Therefore, by using silicon oxide as the negative electrode active material, the capacity is higher than when carbon is used, and the cycle characteristics are better than when a high capacity negative electrode material such as Si or Sn alloy is used. A lithium ion secondary battery has been obtained.

  Patent Document 1 discloses a silicon oxide containing active silicon whose spectrum measured by solid-state NMR satisfies a predetermined condition as a silicon oxide that can be used as such a negative electrode active material.

JP 2001-220125 A

  However, when the present inventors investigated characteristics of a lithium ion secondary battery using the silicon oxide described in Patent Document 1 as a negative electrode active material, neither charge / discharge capacity nor cycle characteristics are still sufficient. There was a problem.

  The present invention has been made in view of this problem, and used a negative electrode material powder capable of obtaining a lithium ion secondary battery having a large charge / discharge capacity and good cycle characteristics, and the negative electrode material powder. It aims at providing a lithium ion secondary battery negative electrode and a lithium ion secondary battery.

In order to solve the above-mentioned problems, the present inventors made a silicon oxide powder under various conditions, and examined the characteristics of a lithium ion secondary battery using this as a negative electrode material. As a result, in the powder of SiO _x (0.4 ≦ x ≦ 1.2), in the spectrum measured by nuclear magnetic resonance spectroscopy for ²⁹ Si, the peak index S 0 attributed to zero-valent Si, 4 The ratio S0 / S4 of the peak index S4 attributed to valence Si is 0.65 or more and 0.80 or less, and the peak attributed to tetravalent Si is in the range of −110 ppm or more and −105 ppm or less. It was found that the lithium ion secondary battery using this SiO _x powder as the negative electrode material has good charge / discharge capacity and cycle characteristics.

  The present invention has been made on the basis of the above knowledge, and the gist thereof is as follows. (1) to (3) lithium ion secondary battery negative electrode powder, (4) lithium ion secondary battery negative electrode, And the lithium ion secondary battery of (5) below.

(1) It consists of SiO _x (0.4 ≦ x ≦ 1.2), and in the spectrum measured by nuclear magnetic resonance spectroscopy for ²⁹ Si, the peak index attributed to zero-valent Si and the tetravalent The ratio of the index of the peak attributed to Si is 0.65 or more and 0.80 or less, and the peak of the peak attributed to tetravalent Si is in the range of −110 ppm or more and −105 ppm or less. Powder for negative electrode material of lithium ion secondary battery.

(2) The powder for a lithium ion secondary battery negative electrode material as described in (1) above, wherein the peak of the peak attributed to tetravalent Si is in the range of −110 ppm or more and −108 ppm or less in the spectrum. .

(3) The powder for a negative electrode material for a lithium ion secondary battery as described in (1) or (2) above, wherein a conductive carbon film is provided on the surface of the powder composed of SiO _x .

(4) A lithium ion secondary battery negative electrode using the lithium ion secondary battery negative electrode powder according to any one of (1) to (3).

(5) A lithium ion secondary battery using the lithium ion secondary battery negative electrode according to (4).

  In the present invention, the “index” of a peak attributed to zero-valent or tetravalent Si in a spectrum measured by nuclear magnetic resonance spectroscopy refers to the area of each peak separated by a Gaussian distribution, and the calculation method is as follows. It will be described later.

  By using the powder for a lithium ion secondary battery negative electrode material of the present invention and the lithium ion secondary battery negative electrode, a lithium ion secondary battery having excellent discharge capacity and initial efficiency and good cycle characteristics can be obtained. . In addition, the lithium ion secondary battery of the present invention has excellent discharge capacity and initial efficiency, and good cycle characteristics.

FIG. 1 is a diagram illustrating a configuration example of a coin-shaped lithium ion secondary battery. FIG. 2 shows the NMR spectrum of the SiO _x powder. FIG. 3 is a diagram showing a configuration example of a silicon oxide production apparatus.

1. Powder for negative electrode material of lithium ion secondary battery of the present invention The powder for negative electrode material of lithium ion secondary battery of the present invention consists of SiO _x (0.4 ≦ x ≦ 1.2), and nuclear magnetic resonance spectroscopy of ²⁹ Si In the spectrum measured by the method (NMR; Nuclear Magnetic Resonance) (hereinafter, also simply referred to as “NMR spectrum”), the index of the peak attributed to zero-valent Si and the index of the peak attributed to tetravalent Si The ratio value is 0.65 or more and 0.80 or less, and the peak of the peak attributed to tetravalent Si is in the range of −110 ppm or more and −105 ppm or less.

Nuclear magnetic resonance is a resonance phenomenon that occurs when a substance containing an atomic nucleus having a magnetic moment (for example, ¹ H, ¹³ C, ²⁹ Si) is placed in a magnetic field and an electromagnetic wave having a frequency satisfying the resonance condition is applied thereto. It is. According to the NMR spectrum, it is possible to detect a bonding state of a nucleus having a magnetic moment with surrounding atoms as a chemical shift.

The structure of SiO _x targeted by the present invention has not been elucidated in detail, and it is considered that the composition is composed of a portion close to SiO ₂ and a portion made of Si. In a lithium ion secondary battery using SiO _x as a negative electrode material, lithium ions are occluded and released in a portion made of Si, and this portion repeats expansion and contraction every charge and discharge. At this time, the portion whose composition is close to SiO ₂ relaxes the volume change (or stress) due to the expansion and contraction of Si during occlusion and release of lithium ions, and contributes to the structural stability of the negative electrode. It is necessary that the number is sufficiently large.

Here, in a portion of the SiO _x where the composition is close to SiO ₂ , most of Si is in a state of being bonded to O, and Si in this state is tetravalent. Moreover, Si is in a bonded state at a portion made of Si, and Si in this state is zero-valent. In the NMR spectrum, the peak index increases as the proportion of the structure to which the peak belongs increases. Therefore, in the NMR spectrum, the smaller the value S0 / S4 of the ratio of the peak index S0 attributed to zero-valent Si and the peak index S4 attributed to tetravalent Si, the closer the composition is to SiO ₂ It can be said that there are many compared to the part consisting of

When the present inventors examined, when the value of S0 / S4 was 0.65 or more and 0.80 or less, it turned out that a lithium ion secondary battery with favorable charging / discharging capacity | capacitance and cycling characteristics is obtained. . When the value of S0 / S4 is less than 0.65, the charge / discharge capacity decreases. This is presumably because the portion where the composition is close to SiO ₂ increases. Further, when the value of S0 / S4 is larger than 0.80, there are few portions whose composition is close to SiO ₂ that works for occlusion of lithium ions, relaxation of volume change (or stress) due to expansion and contraction of Si at the time of lithium ion release. Therefore, the cycle characteristics are lowered.

^In the NMR spectrum for ²⁹ Si, tetravalent Si has a peak near −110 ppm. The peak of the tetravalent Si shifts in a direction where the numerical value of the peak position increases as the number of bond defects increases in the portion of the SiO _x in which the composition is close to SiO ₂ (leftward in FIG. 2 described later). Moreover, the peak position shifts in the direction in which the numerical value of the peak position becomes smaller (the right direction in FIG. 2 described later) as the number of bond defects and the higher crystallinity.

In the portion where the composition is close to SiO ₂ , when there are many bond defects, the charge / discharge capacity becomes small. This is because the function of relaxing the volume change (or stress) due to expansion and contraction during charge / discharge is weakened, the negative electrode structure is destroyed, and the amount of lithium ions that can be occluded and released is reduced.

Furthermore, if the expansion and contraction due to charge and discharge are repeated, the negative electrode structure is further destroyed, and lithium ions cannot be occluded, resulting in insufficient cycle characteristics. Therefore, it is preferable that the number of bond defects is small in the portion where the composition is close to SiO ₂ . However, when there are too few bond defects, that is, when the crystallinity is high, the lithium ion conductivity is low, and therefore a portion made of Si does not contribute to the charge / discharge capacity of the lithium ion secondary battery.

As a result of investigations by the present inventors, when the numerical value of the peak position of tetravalent Si is larger than −105 ppm, the number of bond defects increases in the portion where the composition is close to SiO ₂ and the cycle characteristics become insufficient. On the other hand, when the value of the peak position of tetravalent Si is less than −110 ppm, the crystallinity is high and the lithium ion conductivity is low in the portion where the composition is close to SiO ₂ , so the charge / discharge capacity is small.

As a result of the above examination, in the NMR spectrum, the ratio value S0 / S4 of the peak index S0 attributed to zero-valent Si and the peak index S4 attributed to tetravalent Si was 0.65 or more, 0.80 If the peak of the peak attributed to tetravalent Si is SiO _x in the range of −110 ppm or more and −105 ppm or less, by using this SiO _x as a negative electrode material, the charge / discharge capacity is large, and It was found that a lithium ion secondary battery having good cycle characteristics can be obtained. The peak peak attributed to tetravalent Si is preferably in the range of −110 ppm or more and −108 ppm or less.

The particle size of the SiO _x powder is preferably D50 = 1 to 10 μm. D50 is the particle diameter or median diameter when the cumulative weight is 50% of the total weight in the particle size distribution measurement by the laser light diffraction method.

The SiO _x powder preferably has a conductive carbon film on the surface. The low conductivity of the SiO _x powder can be supplemented by the conductive carbon film, and the charge / discharge capacity and cycle characteristics of the lithium ion secondary battery can be improved. The conductive carbon film does not need to cover the entire particle of the SiO _x powder, and it is sufficient that the film is formed on a part of the surface of the particle.

2. NMR Measurement Method FIG. 2 is a diagram showing an NMR spectrum of SiO _x powder. In the figure, the peak attributed to tetravalent Si has a peak near −110 ppm, and the peak attributed to zero-valent Si has a peak near −70 ppm.

  The measurement conditions of the spectrum by NMR are as shown in Table 1. The sample is dried at 250 ° C. for 3 hours under vacuum, then placed in a sealed sample tube and measured in that state.

Then, for the obtained spectrum, a peak attributed to zero-valent Si and a peak attributed to tetravalent Si are separated by a Gaussian distribution, and the center value, height, and dispersion of each peak are μ, A, As σ ² , a peak function fn (x) (n = 0, 4) represented by the following formula (1) is obtained. f0 (x) is a peak function of a peak attributed to zero-valent Si, and f4 (x) is a peak function of a peak attributed to tetravalent Si.
fn (x) = A [1 / {(2π) ^1/2 σ} exp {− (x−μ) ² / (2σ ² )}] (1)

  The indexes S0 and S4 of each peak are calculated as Sn = ∫fn (x) dx (n = 0, 4) from the peak function fn (x) of each peak. By using this, the value of the ratio of the peak index attributed to zero-valent Si and the peak index attributed to tetravalent Si is calculated as S0 / S4.

3. 3. Method for producing powder for negative electrode material of lithium ion secondary battery of the present invention 3-1. Method for Producing SiO _x Powder FIG. 3 is a diagram illustrating a configuration example of a silicon oxide production apparatus. This apparatus includes a vacuum chamber 5, a raw material chamber 6 disposed in the vacuum chamber 5, and a deposition chamber 7 disposed on the upper portion of the raw material chamber 6.

  The raw material chamber 6 is formed of a cylindrical body, and a cylindrical raw material container 8 and a heating source 10 surrounding the raw material container 8 are disposed at the center thereof. As the heating source 10, for example, an electric heater can be used.

  The deposition chamber 7 is configured by a cylindrical body arranged so that its axis coincides with the raw material container 8. A deposition base 11 made of stainless steel is provided on the inner peripheral surface of the deposition chamber 7 for vapor deposition of gaseous SiO generated by sublimation in the raw material chamber 6. The deposition base 11 is also heated by a heating source (not shown).

  A vacuum device (not shown) for discharging atmospheric gas is connected to the vacuum chamber 5 that accommodates the raw material chamber 6 and the deposition chamber 7, and the gas is discharged in the direction of arrow A.

When SiO _x is produced using the production apparatus shown in FIG. 3, Si powder and SiO ₂ powder are blended at a predetermined ratio as raw materials, and mixed granulated raw material 9 that is mixed, granulated and dried is used. The mixed granulated raw material 9 is filled in the raw material container 8 and heated (heated by a heating source 10) in an inert gas atmosphere or vacuum to generate (sublimate) SiO. Gaseous SiO generated by the sublimation rises from the raw material chamber 6 and enters the deposition chamber 7, is vapor-deposited on the surrounding deposition base 11, and is deposited as SiO _x precipitates 12. Thereafter, the SiO _x precipitate 12 is removed from the precipitation base 11 and pulverized using a ball mill or the like to obtain SiO _x powder. Was denoted as SiO _x for powder such as by oxide film on the surface of the powder after pulverization of SiO _x deposit 12 is formed, the value of x is to vary from 1.

The vapor deposition rate for depositing gaseous SiO on the deposition substrate 11 is 10 to ²⁰ kg / m ^{2 in} the initial stage (2 hours from the start of sublimation of SiO), and then about 3 kg / m ² . By pulverizing the SiO _x precipitate 12 thus obtained, in the NMR spectrum, the ratio value S0 / of the ratio of the peak index S0 attributed to zero-valent Si and the peak index S4 attributed to tetravalent Si A SiO _x powder having a value of S4 of 0.65 or more and 0.80 or less and a peak peak attributed to tetravalent Si in a range of −110 ppm or more and −105 ppm or less can be obtained.

Assuming that the vapor deposition rate at the time of vapor deposition of SiO on the deposition substrate 11 is less than 10 kg / m ² from the initial stage, for example, about 3 kg / m ² , the portion of the SiO _x precipitate 12 in contact with the deposition substrate 11 is used. , The number of bond defects in the portion close to SiO ₂ increases, and the structure grows while maintaining the structural defects. Therefore, the SiO _x powder obtained by pulverizing the SiO _x precipitate 12 has a large number of bonding defects in the portion where the composition is close to SiO ₂ as a whole, and the peak peak attributed to tetravalent Si is more than −105 ppm. growing.

On the other hand, the deposition rate at the time of depositing the gaseous SiO on deposition substrate 11, when greater than 20 kg / ^{m 2,} and the initial not stage only even subsequently when and 10-20 kg / ^{m 2} Since the disproportionation reaction of the SiO _x precipitate 12 proceeds and the crystallinity becomes high, the peak peak attributed to tetravalent Si becomes less than −110 ppm. The disproportionation reaction refers to a reaction represented by the following formula (1) in which Si and SiO ₂ are generated from SiO _x .
2SiO _x → xSiO ₂ + (2-x) Si (1)

The temperature of the precipitation base 11 is 450 ° C. or more and 800 ° C. or less, and the thickness of the SiO _x precipitate 12 is 10 mm or less. When the temperature of the precipitation base 11 is less than 450 ° C., the SiO _x precipitate 12 on the precipitation base 11 is in a supercooled state and is formed in a dendrite shape, so that the SiO _x precipitate 12 becomes porous. . In lithium ion secondary batteries using porous SiO _x powder as a negative electrode material, the destruction of the bond between Si and O due to expansion and contraction of the SiO _x powder when charging and discharging are repeated is earlier than in the case where it is not porous. Therefore, the charge / discharge capacity decreases rapidly and the cycle characteristics are inferior.

When the temperature of the deposition substrate 11 is higher than 800 ° C., crystalline Si clusters are generated by the disproportionation reaction represented by the above formula (1). The expansion coefficient of Si during charging of the lithium ion secondary battery is as large as 4.4 times that of SiO. Therefore, in the lithium ion secondary battery using the SiO _x powder in which the crystalline Si clusters are generated as the negative electrode material, Si and O due to charge / discharge are compared with the case in which the crystalline Si clusters are not generated. The bond is easily broken and the cycle characteristics are inferior.

If the SiO precipitate 12 is thicker than 10 mm, it becomes difficult to detect the surface temperature of the SiO precipitate 12 due to the low thermal conductivity of SiO itself. Therefore, even if the temperature of the precipitation base 11 is 800 ° C. or lower, the surface temperature of the SiO _x precipitate 12 becomes higher than 800 ° C., and there is a possibility that a disproportionation reaction of SiO occurs.

4). Method for Forming Conductive Carbon Film The conductive carbon film is formed on the surface of the SiO _x powder by CVD or the like. Specifically, SiO _x powder is put into a rotary kiln and held for a certain period of time in a gas atmosphere at a predetermined temperature. As the gas, a hydrocarbon gas or an organic substance-containing gas, or a mixed gas of a hydrocarbon gas or an organic substance-containing gas and an inert gas is used. The temperature and holding time of the gas atmosphere are set according to the thickness of the conductive carbon film to be formed. The presence or absence of the conductive carbon film can be confirmed by, for example, surface analysis of the SiO _x powder using an X-ray photoelectron spectrometer (XPS). As a result, if C (carbon) is detected, it can be determined that a conductive carbon film is formed on the surface of the SiO _x powder.

5. Configuration of Lithium Ion Secondary Battery A configuration example of a coin-shaped lithium ion secondary battery using the negative electrode powder for a lithium ion secondary battery of the present invention will be described with reference to FIG. The basic configuration of the lithium ion secondary battery shown in FIG.

  The negative electrode material used for the working electrode 2c which comprises the negative electrode 2 can be comprised with the powder for negative electrode materials (active material) of this invention, another active material, a conductive support material, and a binder. The content of the negative electrode material powder of the present invention in the negative electrode material (the ratio of the mass of the negative electrode material powder of the present invention to the total mass of the constituent materials excluding the binder among the constituent materials of the negative electrode material) is 20% by mass. That's it. Other active materials for the negative electrode material powder need not necessarily be added. As the conductive additive, for example, acetylene black or carbon black can be used, and as the binder, for example, polyvinylidene fluoride can be used.

  In order to confirm the effect of the present invention, the following tests were conducted and the results were evaluated.

1. Test conditions Si _x and SiO ₂ powder were blended, and mixed, granulated and dried mixed granulated raw materials were used as raw materials, and SiO _x was deposited on the deposition substrate using the apparatus shown in FIG. The SiO _x precipitate was pulverized using an alumina ball mill to obtain a powder having D50 = 50 μm. This powder had an O / Simol ratio (x value of SiO _x ) of 1.02. This is because an oxide film is formed on the surface of the powder.

In addition, a SiO _x powder having a conductive carbon film on the surface was also produced. The conductive carbon film was formed by putting SiO _x powder into a rotary kiln and treating it in a hydrocarbon gas atmosphere at 850 ° C. for 15 minutes.

Table 2 shows the value S0 / S4 of the ratio of the index S0 of the peak attributed to zero-valent Si to the index S4 of the peak attributed to tetravalent Si in the NMR spectrum for ²⁹ Si of the SiO _x powder, and The position of the apex of the peak attributed to tetravalent Si and the presence or absence of the conductive carbon film are shown.

  Examples 1 to 6 of the present invention shown in Table 2 have peak index ratio values S0 / S4 of 0.65 to 0.80, and the position of the peak apex attributed to tetravalent Si is −110 ppm or more and −105 ppm or less. Met. In Comparative Examples 1 to 5, at least one of the peak index ratio value S0 / S4 or the peak vertex position attributed to tetravalent Si did not satisfy the definition of the present invention.

Among the inventive examples 1 to 6, the SiO _x powder of the inventive examples 1 to 5 having no conductive carbon film had a specific resistance of 100000 Ωcm or more, whereas the inventive example 6 having the conductive carbon film was used. The SiO _x powder was 2.5 ± 0.5 Ωcm.

The specific resistance ρ (Ωcm) of the SiO _x powder was calculated using the formula ρ = R × A / L. Here, R: electrical resistance (Ω) of the sample, A: bottom area (cm ² ) of the sample, and L: thickness (cm) of the sample. The specific resistance measurement sample was filled with 0.20 g of SiO _x powder in a powder resistance measurement jig (jig part: stainless steel with an inner diameter of 20 mm, frame part: made of polytetrafluoroethylene) at 20 kgf / cm ² . Molded by pressing for 60 seconds. The electrical resistance of the sample was measured by a two-terminal method using a digital multimeter (VOAC7513, manufactured by Iwatatsu Measurement Co., Ltd.). The thickness of the sample was measured with a micrometer.

These SiO _x powders were used as a negative electrode active material, and carbon black as a conductive additive and a binder were blended therein to produce a negative electrode material. The compounding ratio of the negative electrode material was SiO _x powder: carbon black: binder = 7: 2: 1. Using this negative electrode material and Li metal as the positive electrode material, the coin-shaped lithium ion secondary battery shown in FIG. 1 was produced.

2. Test Results The lithium ion secondary battery produced under the above conditions was evaluated using the initial efficiency and cycle capacity maintenance rate as indices. These results are shown in Table 2 together with the test conditions. Here, the charge / discharge capacity is the average of the charge capacity at the first charge and the discharge capacity at the first discharge after the manufacture of the lithium ion secondary battery. The cycle characteristic is a value (%) of the ratio of the charge / discharge capacity at the 100th cycle to the charge / discharge capacity at the first cycle. The numerical values shown in Table 2 are the charge / discharge capacity and the cycle characteristics when Inventive Example 4 is taken as 100. The overall evaluation is ◎ (excellent) when the charge / discharge capacity is 95% or more and the cycle characteristic is 95% or more, and ○ (good) when the charge / discharge capacity is 90% or more and the cycle characteristic is 80% or more. The case where the charge / discharge capacity was less than 90% or the cycle characteristic was less than 80% was evaluated as x (impossible).

Among the comparative examples, the comparative example 1 has a peak position attributed to tetravalent Si of −104 ppm, which is larger than −105 ppm, and the SiO _x powder has many structural defects. Therefore, the cycle characteristics are as low as 55%. It was. Further, in Comparative Examples 2 to 5, the position of the peak apex attributed to tetravalent Si is −116 to −112 ppm, which is less than −110 ppm, and the composition in the SiO _x powder is crystalline at a portion close to SiO ₂ . Therefore, the charge / discharge capacity was as low as 55% to 85%. Therefore, all the comparative examples were evaluated as x.

  In all of the examples of the present invention, the charge / discharge capacity was 92% or more and the cycle characteristics were 80% or more, and the overall evaluation was good or bad. In particular, Examples 3 to 6 of the present invention had excellent charge and discharge capacities of 95% or more and cycle characteristics of 88% or more, and the overall evaluation was ◎.

  Further, when the present invention examples 5 and 6 having the same peak index ratio value S0 / S4 and the positions of the peaks of the peaks attributed to tetravalent Si are compared, the present invention example 6 having the conductive carbon film is compared. However, the charge / discharge capacity and cycle characteristics were more excellent.

  By using the powder for a lithium ion secondary battery negative electrode material of the present invention and the lithium ion secondary battery negative electrode, a lithium ion secondary battery having excellent discharge capacity and initial efficiency and good cycle characteristics can be obtained. . In addition, the lithium ion secondary battery of the present invention has excellent discharge capacity and initial efficiency, and good cycle characteristics. Therefore, the present invention is a useful technique in the field of secondary batteries.

1: positive electrode, 1a: counter electrode case, 1b: counter electrode current collector, 1c: counter electrode,
2: negative electrode, 2a: working electrode case, 2b: working electrode current collector,
2c: working electrode, 3: separator, 4: gasket, 5: vacuum chamber,
6: Raw material chamber, 7: Precipitation chamber, 8: Raw material container, 9: Mixed granulated raw material,
10: Heat source, 11: Precipitation substrate, 12: SiO _x precipitate

Claims (5)

In the spectrum of SiO _x (0.4 ≦ x ≦ 1.2) measured by nuclear magnetic resonance spectroscopy for ²⁹ Si, the peak index attributed to zero-valent Si and the attribute to tetravalent Si The value of the ratio of the index of the peak to be obtained is 0.65 or more and 0.80 or less, and the peak of the peak attributed to tetravalent Si is in the range of −110 ppm or more and −105 ppm or less. Powder for secondary battery negative electrode material.   The powder for a lithium ion secondary battery negative electrode material according to claim 1, wherein the peak of the peak attributed to tetravalent Si is in the range of -110 ppm or more and -108 ppm or less in the spectrum. 3. The powder for a negative electrode material for a lithium ion secondary battery according to claim 1, further comprising a conductive carbon film on a surface of the powder made of SiO _x .   The lithium ion secondary battery negative electrode using the powder for lithium ion secondary battery negative electrode materials in any one of Claims 1-3.   The lithium ion secondary battery using the lithium ion secondary battery negative electrode of Claim 4.

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