WO2020166658A1 - Active material - Google Patents

Abstract

The present invention provides a novel active material which is capable of enhancing the cycle characteristics, while being also capable of enhancing the high-rate characteristics by reducing or eliminating a plateau region in the discharge profile.　An active material which is characterized by being composed of active material particles that contain silicon and a compound represented by chemical formula MxSiy (wherein x and y satisfy 0.1 ≤ x/y ≤ 7.0, and M represents one or more elements among semimetal elements and metal elements other than Si), and which is also characterized in that: the content of elemental Si is more than 50 wt%; the content of oxygen atoms (O) is less than 30 wt%; D50 is less than 4.0 μm and Dmax is less than 25 μm as determined by laser diffraction/scattering particle size distribution measurement; the full width at half maximum of peak A that is observed at 2θ = 28.42° ± 1.25° in the X-ray diffraction pattern obtained using a CuKα1 ray is 0.25° or more; and one or more substances among silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide and stainless steel are present within the active material particles.

Description

Active material

The present invention relates to an active material, a negative electrode using the same, and a solid-state battery.

In recent years, with the development of applications such as electric vehicles and smartphones, there is a growing demand for higher capacity and longer life of batteries. Currently, most of the negative electrodes of commercially available batteries use a carbon material (also referred to as “graphite”) as the negative electrode active material, but in terms of capacity, the theoretical limit has already been reached, and a new negative electrode active material Development is needed. One of the promising candidates is an active material containing silicon (also referred to as “Si-containing active material”).

The Si-containing active material has a potential that the capacity per mass is 5 to 10 times that of graphite. However, on the other hand, it has a problem that the electron conductivity is not higher than that of graphite.
Therefore, in order to increase the electron conductivity of the Si-containing active material, it has been proposed to add a conductive auxiliary agent, for example, for the purpose of imparting electron conductivity between the current collector and the active material. For example, Patent Document 1 discloses that the periphery of a core particle containing silicon is coated with a silicon solid solution such as Mg ₂ Si, CoSi, or NiSi, and the surface thereof is further coated with a conductive material such as graphite or acetylene black. There is.

The Si-containing active material also undergoes a large volume change due to the insertion and desorption of lithium ions, and repeats expansion and contraction during charge and discharge cycles, so separation with the conductive auxiliary agent tends to occur as charge and discharge are repeated, and as a result, cycle However, there is a problem that the battery performance is deteriorated and the safety of the battery is deteriorated by causing deterioration of the battery and a decrease in energy density.

In order to solve this problem, for example, Patent Document 2 discloses active material particles containing silicon and having an average particle diameter of 5 μm or more and 25 μm or less. By setting the average particle diameter of the active material particles to 5 μm or more, the specific surface area of the original active material can be reduced, and thus the contact area between the electrolyte and the new surface of the active material can be reduced. It is described that the suppression effect of is increased.

Further, in Patent Document 3, an electrode material for a lithium secondary battery, which comprises particles of a solid-state alloy containing silicon as a main component, is used as an electrode material having a high efficiency of lithium insertion/desorption. Disclosed is an electrode material for a lithium secondary battery, characterized in that particles are microcrystalline silicon or amorphized silicon, in which microcrystalline or amorphous particles composed of elements other than silicon are dispersed. ..

Furthermore, in Patent Document 4, a negative electrode active material for a lithium secondary battery containing silicon, copper and oxygen as main constituent elements, wherein Cu ₃ Si and an average crystallite diameter (Dx) measured by an X-ray diffraction method are used. Discloses a negative electrode active material for a lithium secondary battery, which contains silicon particles of 50 nm or less and has a peak intensity ratio (Cu ₃ Si/Si) of 0.05 to 1.5 calculated from XRD measurement results. ..

Japanese Patent Laid-Open No. 2000-285919 JP, 2008-123814, A JP, 2010-135336, A JP, 2016-35825, A

In the above-mentioned Patent Document 3, a material in which fine crystals or amorphous materials composed of elements other than silicon are dispersed in silicon, or a material in which an alloy of silicon elements is dispersed in silicon is used as a negative electrode active material. Use as a substance is disclosed. Since only silicon in the negative electrode active material contributes to the insertion/desorption of lithium ions, if the occupancy ratio of silicon is reduced, the capacity is reduced, while the expansion and contraction of the negative electrode active material can be suppressed. Theoretically, it should be possible to improve the cycle characteristics.
However, for example, when an alloy of elements other than silicon is mixed in silicon and actually used as a negative electrode active material of a lithium secondary battery, it has been found that the cycle characteristics cannot be improved to an expected degree. It was

Further, it has been studied to use a Si-containing negative electrode active material as a negative electrode active material in combination with a carbon material (Graphite) such as graphite. However, when a Si-containing negative electrode active material is used as a negative electrode active material in combination with a carbon material, both of them operate separately due to the difference in their respective charge/discharge curve profiles, which makes it difficult to control.
When the present inventor examined this point, as compared with the discharge profile of the carbon material (Graphite), the discharge profile of the Si-containing negative electrode active material is different in the plateau region from the operating potential of the carbon material (Graphite). It has been found that when the contained negative electrode active material is used as a negative electrode active material in combination with a carbon material, a step portion is generated in the charge/discharge curve, which is one of the causes that are difficult to control. Therefore, it can be considered that by reducing or eliminating the plateau region in the discharge profile of the Si-containing negative electrode active material, the step portion at the rising portion of the charge/discharge curve can be reduced or eliminated, and control can be facilitated.

Furthermore, rapid charge and discharge characteristics are required for lithium secondary batteries, and improvement of high rate characteristics is also required.

Therefore, the present invention relates to a silicon-containing active material, which has a new active material capable of enhancing the cycle characteristics, reducing or eliminating the plateau region in the discharge profile, and further improving the high rate characteristics. It is intended to be provided. In particular, it is intended to provide a new active material capable of further improving cycle characteristics.

The present invention relates to silicon and a chemical formula M _x Si _y (where x and y satisfy 0.1≦x/y≦7.0, and M is a metalloid element other than Si and a metal element). A compound represented by one or two or more types), and active material particles containing
The content of Si element in the active material is more than 50 wt%, the content of oxygen atom (O) is less than 30 wt%,
Regarding D ₅₀ and D _max (referred to as “D ₅₀ ”and “D _max ”, respectively) obtained by measurement by a laser diffraction scattering particle size distribution measurement method, D ₅₀ is less than 4.0 μm and D _max is less than 25 μm. Yes,
In the X-ray diffraction pattern measured by an X-ray diffractometer (XRD) using CuKα1 ray, the full width at half maximum of peak A appearing at 2θ=28.42°±1.25° is 0.25° or more,
We propose an active material characterized in that one or more of silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide and stainless steel are present inside the active material particles.

The active material proposed by the present invention can be used as a negative electrode active material. In addition, the active material of the present invention can be used in batteries such as liquid batteries and solid batteries, and can be preferably used in solid batteries. In particular, the active material of the present invention is advantageously used in a solid battery containing a sulfide solid electrolyte as the solid electrolyte. The solid-state battery using the active material of the present invention can have improved cycle characteristics and high rate characteristics. In particular, the active material proposed by the present invention is silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide or stainless steel, because the active material particles present inside the particles, due to expansion and contraction The effect of cracking can be reduced, and cycle characteristics can be further improved.
In addition, the active material proposed by the present invention can reduce or eliminate the plateau region in the discharge profile, so that it not only exhibits the effect when used alone, but also in combination with, for example, a carbon material (Graphite), a battery, especially a solid material. It can be suitably used as a negative electrode active material for a battery, especially a solid secondary battery such as a solid lithium secondary battery, and further, high rate characteristics can be improved.

FIG. 3 is a diagram showing a discharge profile of a non-aqueous electrolyte secondary battery using the sample obtained in Example 1 as an active material. FIG. 5 is a diagram showing a discharge profile of a non-aqueous electrolyte secondary battery using the sample obtained in Comparative Example 1 as an active material. It is a diffraction pattern figure of the silicon powder material which is a standard sample for X-ray diffraction made from NIST. FIG. 7 is a diagram comparing and comparing the diffraction patterns of the sample obtained in Reference Example 1, ICDD card numbers: 00-005-0565 (chemical formula: Si) and 01-071-0187 (chemical formula: TiSi ₂ ) cards. .. 1 is a diagram showing a cross section of an active material particle of the present invention (Example 2).

Next, the present invention will be described based on an example of the embodiment. However, the present invention is not limited to the example of the embodiment described below.

<Active material>
An active material according to an example of the present embodiment (hereinafter referred to as “main active material”) includes silicon and a chemical formula MxSiy (where x and y satisfy 0.1≦x/y≦7.0, M Is a compound represented by one or more of metalloid elements other than Si and metal elements), and active material particles containing the compound (hereinafter referred to as “main active material particles”). The active material is an aggregate of the active material particles.

(silicon)
In the active material particles, silicon also means Si capable of inserting and releasing lithium ions. That is, the main active material particles have a function as main active material particles by containing silicon.
Here, silicon mainly refers to pure silicon, but may contain an element that forms a solid solution with Si to form a Si solid solution. In this case, the Si solid solution may have a function as an active material.

The proportion of silicon in the main active material is preferably 30 wt% or more of the main active material, more preferably 40 wt% or more, and even more preferably 50 wt% or more.
In the active material, silicon is preferably the main component of the active material in order for the proportion of silicon to affect the charge/discharge capacity and increase the charge/discharge capacity. Above all, the proportion of silicon in the substance is preferably more than 50 wt %, and particularly preferably 60 wt% or more.

(Chemical formula M _x Si _y )
The active material particles have a chemical formula M _x Si _y (where x and y satisfy 0.1≦x/y≦7.0, and M is one of metalloid elements other than Si and metal elements). Or a compound represented by two or more kinds).
By containing the compound represented by M _x Si _y , the present active material particles can further improve the cycle characteristics, and can further reduce or eliminate the plateau region in the discharge profile, and further have high rate characteristics. Can be improved.

The compound represented by the chemical formula M _x Si _y (0.1≦x/y≦7.0) is called so-called silicide.
“M” in the chemical formula M _x Si _y is one or more of metalloid elements and metal elements other than Si. That is, M may be a metalloid element other than Si, a metal element, or a combination of two or more of metalloid elements and metal elements.
Examples of the metalloid element and the metal element include elements such as B, Ti, V, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ta, and W, and among them, B, Ti, Mn, Fe, Co, Ni, Y, Zr, Nb, Mo, Ta and W are preferable. Further, among them, B, Ti, Mn, Fe, Co and Ni are preferable, and among them, B, Ti, Mn and Fe are particularly preferable.

“X/y” in the chemical formula M _x Si _y is preferably 0.1 or more and 7.0 or less, particularly 0.2 or more or 4.0 or less, and among them 0.3 or more or 3.0 or less, Among them, 0.4 or more or 2.0 or less is more preferable.
Further, “x” in the chemical formula M _x Si _y is preferably 0.5 or more and 15 or less, more preferably 0.75 or more or 13 or less, and further preferably 1 or more or 11 or less.
On the other hand, “y” is preferably 0.5 or more and 27 or less, more preferably 0.75 or more or 23 or less, and even more preferably 1 or more or 19 or less.

Specific examples of the silicide include titanium silicide (TiSi ₂ , TiSi, Ti ₅ Si ₄ , Ti ₅ Si ₃ ), cobalt silicide (CoSi ₂ , CoSi, CoSi, Co ₂ Si, Co ₃ Si), nickel silicide (NiSi). ₂ , NiSi, Ni ₃ Si ₂ , Ni ₂ Si, Ni ₅ Si ₂ , Ni ₃ Si), manganese silicide (Mn ₁₁ Si ₁₉ , MnSi, Mn ₅ Si ₃ , Mn ₅ Si ₂ , Mn ₃ Si), iron silicide (FeSi ₃ , FeSi, Fe ₅ Si ₃ , Fe ₃ Si), niobium silicide (NbSi ₂ , Nb ₅ Si ₃ , Nb ₃ Si), copper silicide (Cu ₃ Si, Cu ₆ Si, Cu ₇ Si), boron silicide (B ₃ Si, B ₆ Si) Zirconium silicide (ZrSi ₂ , ZrSi, Zr ₅ Si ₄ , Zr ₃ Si ₂ , Zr ₅ Si ₃ , Zr ₂ Si, Zr ₄ Si), vanadium silicide (VSi ₂ , V ₆ Si) ₅ , V ₅ Si ₃ , V ₃ Si), tungsten silicide (WSi ₂ , W ₅ Si ₃ ), tantalum silicide (TaSi ₂ , Ta ₅ Si ₃ , Ta ₂ Si, Ta ₃ Si), yttrium silicide (Y ₃ Si) ₅ , YSi, Y ₅ Si ₄ , Y ₅ Si ₃ ) and the like. However, it is not limited to these.

(Compound A)
The active material particles contain one or more compounds (also referred to as “compound A”) of silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide and stainless steel, and The compound is present inside the active material particles.
Since such a compound A exists inside the particles of the present active material particles, when the present active material is used as, for example, an active material of a secondary battery and charging and discharging are repeated, the present active material particles expand and contract. The effect of cracking due to repetition can be reduced, and cycle characteristics can be further improved.

Note that whether or not the compound A exists inside the active material particles can be determined by observing the cross section of the active material particles. In addition, as described later in Examples, it is determined by observing the cross section of the active material particles in the electrode cross section using a field emission scanning electron microscope (FE-SEM) and energy dispersive X-ray analysis (EDS). be able to.

The content of the above compound A present inside the particles of the active material (when two or more kinds are contained, the total content thereof) is more than 0 wt% and preferably less than 15 wt% with respect to the active material. Above all, more than 0.001 wt% is more preferable, above 0.01 wt% is more preferable, and above 0.10 wt% is still more preferable. On the other hand, it is more preferably less than 9 wt%, more preferably less than 7 wt%, still more preferably less than 2 wt%, especially less than 1 wt%.

The content of compound A above can be calculated based on the results of gas analysis and ICP analysis. For example, in the case of containing silicon nitride, the content of nitrogen element (wt%) is measured by gas analysis, the nitrogen is considered to be derived from silicon nitride, and the content of silicon nitride (wt%) is calculated. be able to. When zirconium oxide is contained, the content (wt%) of zirconium should be calculated by measuring the content (wt%) of zirconium by ICP analysis and assuming that this zirconium is derived from zirconium oxide. You can

In order to allow the compound A to exist inside the particles of the active material particles, it is preferable to add the compound A as described later. However, the method is not limited to this.

The active material particles may contain "other components" as necessary.
Examples of the "other components" include silicon-containing substances such as silicon compounds. Here, examples of the silicon compound include Si ₃ N ₄ and SiC.
Further, as the “other component”, for example, not one as a constituent element of the compound represented by the chemical formula M _x Si _y , but one or more elements out of a metalloid element and a metal element other than Si are included. It may be contained as a metal, an oxide, a carbide, a nitride or the like. Specifically, one of H, Li, B, C, O, N, F, Na, Mg, Al, P, K, Cu, Ca, Ga, Ge, Ag, In, Sn and Au, or Examples thereof include metals, oxides, carbides, nitrides, and other compounds having two or more elements. As the above-mentioned element, one or more of H, Li, B, C, O, N, F, Na, Mg, Al, P, K, Ca, Ga, Ge, Ag, In, Sn and Au, among others, or Two or more elements are preferable, and one or more elements selected from H, Li, B, C, O, N, F, Al, P and Sn are particularly preferable. At this time, in the present active material, the content of the “other component” is preferably less than 15 at %, more than 0 at% or less than 12 at %, among them more than 1 at% or less than 10 at %, and further among them. It is preferably more than 2 at% or less than 7 at %.

When the active material particles contain a carbon (C) element as the “other component”, the content thereof is preferably less than 5 wt% of the amount of the active material, particularly less than 4 wt %, and particularly less than 3 wt %. When the content of C element in the active material has the above upper limit, it is possible to suppress the decrease in capacity. In the evaluation of Examples and Comparative Examples, which will be described later, the numerical value of the charge capacity is the basis of the present invention, and the present invention distinguishes itself from an active material containing a large amount of C and having a low capacity.

(Carbon component species)
When the active material contains a carbon (C) element as the “other component”, the carbon is roughly classified into carbon derived from an organic substance and carbon corresponding to an inorganic substance.
Here, examples of carbon that corresponds to the inorganic substance include diamond and graphite. A carbon material having a regular layered structure such as graphite occludes a large amount of Li (≧300 mAh/g), and is not preferable as carbon corresponding to the inorganic substance contained in the active material. As the carbon corresponding to the inorganic substance contained in the active material, one having a low Li occlusion capacity (<300 mAh/g) is preferable. Specific examples include activated carbon, carbon black, coke, carbon fiber, and amorphous carbon. Of these, activated carbon, coke, carbon fiber and amorphous carbon are preferable.
Therefore, as the carbon component species contained in the active material, carbon derived from an organic substance or carbon corresponding to an inorganic substance having a low Li storage capacity (<300 mAh/g) (ex: activated carbon, coke, carbon fiber, amorphous carbon) ) Is preferred.

The active material particles may contain inevitable impurities derived from the raw materials.
However, the content of unavoidable impurities in the active material is preferably, for example, less than 2 wt %, more preferably less than 1 wt %, and most preferably less than 0.5 wt. When the content of the unavoidable impurities in the active material has the above upper limit, it is possible to suppress the decrease in capacity.

The active material particles may contain a Si oxide containing a Si element. Examples of the Si oxide include SiO _a (0<a≦2). Specifically, SiO, SiO _2, etc. can be mentioned.

(Content ratio of each component)
The content of the Si element in the active material is preferably more than 50 wt %. Above all, it is preferably more than 52 wt %, particularly preferably more than 60 wt %, more preferably more than 63 wt %, and even more preferably more than 65 wt %. On the other hand, the content of the Si element in the active material is, for example, preferably less than 98 wt%, more preferably less than 88 wt%, further preferably less than 82 wt%, and even more preferably 78 wt%. It is preferably less than.
The content of the Si element here means the total amount of the Si element contained in the active material. Therefore, the content of the Si element can be the total amount of the Si element mainly derived from silicon and the Si element derived from the compound represented by M _x Si _y .
In the present active material, the content of Si element having the above lower limit can suppress the decrease in capacity. On the other hand, when the content of the Si element has the upper limit, expansion and contraction of the active material can be suppressed, and cycle characteristics can be improved.

The oxygen (O) element content in the active material is preferably less than 30 wt %. Above all, it is preferably less than 20 wt%, particularly preferably less than 15 wt%, further preferably less than 10 wt%, and further preferably less than 5 wt%. Further, the content of oxygen (O) element in the active material is, for example, preferably more than 0 wt%, more preferably more than 0.1 wt%, and particularly preferably more than 0.2 wt%. Above all, it is preferably more than 0.6 wt %.
When the content of the oxygen (O) element in the present active material has the above upper limit, it is possible to suppress an increase in the ratio of the oxygen (O) element that does not contribute to charging and discharging, and suppress a decrease in capacity and charging/discharging efficiency. it can. So-called SiO (silicon monoxide) is a substance containing about 36% oxygen in the stoichiometric composition, and is different from the present invention in that it has low capacity and charge/discharge efficiency. On the other hand, when the content of the oxygen (O) element has the above lower limit, it is possible to prevent a rapid reaction with oxygen in the atmosphere.

The content of M in the active material is preferably less than 38 wt %. Above all, it is more preferably less than 35% by weight, more preferably less than 32% by weight, and particularly preferably less than 29% by weight. In addition, the content of M in the active material is preferably more than 2 wt%, more preferably more than 5 wt%, particularly preferably more than 8 wt%, and more preferably more than 12 wt%. ..
When the content of M in the active material has the above lower limit, expansion and contraction of the active material can be suppressed, and cycle characteristics can be improved. On the other hand, when the content of M in the active material has the above upper limit, it becomes possible to suppress the decrease in capacity.

The ratio (M/Si) of the content (wt%) of M to the content (wt%) of the Si element in the active material is, for example, preferably greater than 0.020, and more preferably 0.052. It is preferably large, particularly preferably larger than 0.078, and particularly preferably larger than 0.183.
On the other hand, the ratio of the content of M to the content of Si element (M/Si) is, for example, preferably less than 0.961, more preferably less than 0.767, and particularly less than 0.572. Is preferable, and particularly less than 0.414 is particularly preferable.
When the ratio of the content of M to the content of Si element in the active material has the above lower limit, expansion and contraction of the active material can be suppressed, and cycle characteristics can be improved. On the other hand, when the ratio of the content of M to the content of Si element in the present active material has the above upper limit, it becomes possible to suppress the decrease in capacity.

The content of each element is the amount of element which is quantified by chemical analysis such as inductively coupled plasma (ICP) emission spectroscopic analysis in which the active material is completely dissolved.
On the other hand, the oxygen element content can be measured using an oxygen/nitrogen analyzer (for example, manufactured by LECO). In addition, when an oxide such as zirconium oxide is contained, it is a numerical value including oxygen derived from them.

(Feature 1 in X-ray diffraction pattern)
In the X-ray diffraction pattern measured by an X-ray diffractometer (XRD) using CuKα1 rays, this active material has a full width at half maximum of peak A appearing at 2θ=28.42°±1.25° of 0.25. It is preferably at least °.
The peak A appearing at 2θ=28.42°±1.25° is a peak corresponding to the (111) plane of the space group Fd-3m of silicon.

When there are a plurality of peaks in the range of 2θ=28.42°±1.25°, the peak closest to 2θ=28.42° is defined as peak A among them.
Further, the criterion for determining whether or not the peak A appears in the range of 2θ=28.42°±1.25°, that is, the criterion for differentiating from noise will be described later in the embodiment, and therefore is described here. Is omitted.

In the X-ray diffraction pattern measured by an X-ray diffractometer (XRD) using CuKα1 rays, the region where peak A appears is 2θ=28.42°±1.25°, and 2θ=28.42°± It may be 0.63°, in which 2θ=28.42°±0.31°, and in particular 2θ=28.42°±0.21°.

The full width at half maximum of peak A is preferably 0.25° or more, more preferably more than 0.50°, still more preferably more than 0.60°, and particularly more than 0.70°. Is preferred, and more preferably greater than 0.75°. On the other hand, the full width at half maximum of peak A is, for example, preferably less than 2.0°, more preferably less than 1.5°, particularly preferably less than 1.2°, and further 1.0 It is preferably less than °.
Since the full width at half maximum of the peak A has the above lower limit, the present active material can improve the cycle characteristics and can reduce or eliminate the plateau region in the discharge profile, and can improve the discharge characteristics at a high rate. On the other hand, when the full width at half maximum of peak A has the above upper limit, it is possible to suppress a decrease in charge/discharge capacity or charge/discharge efficiency.

In order to adjust the full width at half maximum of peak A in the present active material to fall within the above range, for example, the above M may be added to a raw material in a predetermined amount, melted, cast, and further modified as described below. Good. However, the method is not limited to this.

Further, the active material, the peak intensity of the peak B attributable to the compound represented by the chemical formula M _x Si _y and I _B, when the peak intensity of the peak A was I _A, wherein for the I _B I _A the ratio of _(I a / I _B) is preferably less than 1.

Here, the “peak B belonging to the compound represented by the chemical formula M _x Si _y ” means a peak that appears when the above compound is present.
Such “peak B” refers to the peak having the maximum peak intensity among the peaks derived from the compound represented by the chemical formula M _x Si _y , so-called silicide.
Further, when there are a plurality of types of M _x Si _y, the total value of the peak intensities of the maximum peaks derived from each compound is treated as the intensity of “peak B”.

In the X-ray diffraction pattern measured by an X-ray diffractometer (XRD) using CuKα1 ray, the region where the peak B appears differs depending on the type of the compound represented by the chemical formula M _x Si _y . As a specific example, the case of TiSi ₂ and Mn ₁₁ Si ₁₉ will be described. TiSi ₂ (ICDD card number: 01-071-0187) has a maximum peak at 2θ=39.11°, and Mn ₁₁ Si ₁₉ (ICDD card number: 03-065-2862) has 2θ. It is known to have a maximum peak at =42.00°. However, since these peak positions may shift, it is preferable to confirm the range of ±1.25° based on each peak position by looking at the entire diffraction pattern.
The criteria for determining whether or not the peak B has appeared is the same as that for the peak A, and the details thereof will be described later in Examples, so description thereof will be omitted here.

In this active material, the ratio of the _{I A} with respect to the _{I B (I A / I B} ) , for example, more preferably less than 0.90, is preferably Among them less than 0.80, especially 0. It is preferably less than 72, more preferably less than 0.40.
In order to suppress the reduction in the charge-discharge efficiency, the _{I A} ratio _(I A / _{I B)} for the _{I B} is preferably greater than preferably greater than 0.01, among others 0.05, It is particularly preferable that it is greater than 0.10.
This active material, said that the ratio of the I _A for _{I B (I A / I B} ) has the above upper limit can be reduced or eliminated the plateau region more reliably in the discharge profile.

In the active material, to adjust the ratio of the I _A with respect to the I _B and (I A _{/ I B)} in the above range, for example, to melt and adding the M by a predetermined amount starting material, cast, described further below It suffices to carry out such a modification treatment. However, the method is not limited to this.

(Feature 2 in X-ray diffraction pattern)
In the X-ray diffraction pattern measured by an X-ray diffractometer (XRD) using CuKα1 ray, the active material preferably has a peak intensity I _A of the peak _A of, for example, less than 20,000 cps, and particularly less than 7,000 cps. It is preferable that it is, particularly preferably less than 4000 cps, more preferably less than 3000 cps, and even more preferably less than 2000 cps. On the other hand, the peak intensity I A of the peak _A is preferably, for example, more than 100 cps, more preferably more than 200 cps, and particularly preferably more than 400 cps.
When the peak intensity I _A has the upper limit, the plateau region in the discharge profile can be reduced or eliminated. On the other hand, when the peak intensity I _A has the above lower limit, it is possible to suppress a decrease in charge/discharge efficiency.
In the active material, in order to adjust the peak intensity I _A of the peak A within the above range, for example, a predetermined amount of the above M is added to the raw material, melted, cast, and further modified as described below. You can do this. However, the method is not limited to this.

By the way, in Patent Document 4, the peak intensity of silicon and the peak intensity of silicide are compared with each other, and the one having high peak intensity of silicide is disclosed. However, in each case, since the amount of silicide is relatively large relative to that of silicon, the capacity obtained as the negative electrode active material is inferior. On the other hand, in the present active material, since the amount of silicide is less than a certain amount, that is, the amount of silicon that can contribute to charge and discharge is large, the capacity obtained as the negative electrode active material is relatively high, and the peak intensity of silicon is It has a characteristic that it is lower than the peak intensity of silicide.

_(D 50 _{· D max)}
D ₅₀ of the active _material, i.e. D ₅₀ according to the volume particle size distribution measurement obtained by the measurement by a laser diffraction scattering particle size distribution measurement method is preferably less than 4.0 .mu.m, and more to be among them less than 3.9μm It is particularly preferably less than 3.4 μm, more preferably less than 3.2 μm, still more preferably less than 3.0 μm, still more preferably less than 2.8 μm. Further, it is preferably less than 2.5 μm. On the other hand, the D ₅₀ of the active material is preferably larger than 0.01 μm, more preferably larger than 0.05 μm, particularly preferably larger than 0.1 μm, and further preferably larger than 0.5 μm. Furthermore, it is preferable that it is larger than 1.0 μm.
The D ₅₀ according to this measuring method means a 50% volume cumulative particle diameter, that is, a cumulative 50% diameter from the finer of the cumulative percentage notation of the volume-converted particle diameter measured value in the volume-based particle size distribution chart.
When the D _{50 of the} present active material has the above upper limit, the influence of expansion and contraction can be reduced, and the contact with the solid electrolyte in the solid battery electrode can be secured. On the other hand, when the D _{50 of the} present active material has the above lower limit, an increase in the number of contacts with the solid electrolyte due to an increase in the specific surface area can be suppressed, and an increase in contact resistance can be suppressed.
The D _{50 of the} present active material can be adjusted by changing the crushing condition and the crushing condition. However, the adjustment method is not limited to these.

D _max, i.e. D _max by volume particle size distribution measurement obtained by measuring by a laser diffraction scattering particle size distribution measuring method of the present active material is preferably less than 25 [mu] m, more preferably among them less than 20 [mu] m, in particular 15μm It is preferably less than 10 μm, and more preferably less than 10 μm. On the other hand, D _{max of the} present active material is, for example, preferably larger than 0.5 μm, more preferably larger than 1.0 μm, particularly preferably larger than 3.0 μm, and further preferably 5.0 μm. It is preferably large.
The D _max according to the measuring method means 100% volume cumulative particle diameter, that is, the cumulative 100% diameter in terms of cumulative percentage of the particle diameter measurement value converted into volume in the volume-based particle size distribution chart.
When the D _{max of the} present active material has the above upper limit, it is possible to reduce a risk that a gap is formed between the active material and the solid electrolyte in the solid battery electrode, and the risk of breaking through the separator layer.

(Particle shape)
The particle shape of the active material is not particularly limited. For example, a spherical shape, a polyhedral shape, a spindle shape, a plate shape, a scaly shape, an amorphous shape, or a combination thereof can be used. For example, it has been confirmed that the particles are spherical according to the gas atomizing method, and that when they are pulverized by a jet mill or the like, the particles are broken along the grain boundaries, resulting in an irregular shape.

(True density)
The true density of the present active material is, for example, preferably more than 2.4 g/cm ^3, more preferably more than 2.5 g/cm ³ , particularly preferably more than 2.7 g/cm ³ , and further 2 It is preferably larger than 0.9 g/cm ³ . On the other hand, the true density of the active material, that for example, preferably less than 3.9 g / cm ^3, preferably less than Above all 3.8 g / cm ^3, in particular less than 3.7 g / cm ³ preferable.
When the true density of the present active material has the above lower limit, the electrode density can be improved and the energy density can be improved. On the other hand, since the true density of the present active material has the upper limit described above, it is possible to suppress the occurrence of the problem that the content of Si element in the active material decreases and the capacity decreases.
The true density of the present active material can be adjusted by the amount of M, for example. However, the method is not limited to this.

(Specific surface area)
The specific surface area (SSA) of the present active material is, for example, preferably larger than 2.0 m ² /g, more preferably larger than 2.5 m ² /g, particularly preferably larger than 3.0 m ² /g, Further, it is preferably larger than 3.3 m ² /g. On the other hand, the specific surface area (SSA) of the active material is, for example, preferably less than 140.0 m ² /g, more preferably less than 60.0 m ² /g, and most preferably less than 50.0 m ² /g. Is preferable, and particularly preferably less than 30.0 m ² /g, and more preferably less than 10.0 m ² /g.
When the SSA of the present active material has the above lower limit, the surface is sufficiently modified and the electrode resistance can be reduced. On the other hand, when the active material SSA has the above upper limit, it is possible to suppress an increase in the number of contacts with the solid electrolyte and suppress an increase in contact resistance.
The SSA of the active material can be adjusted by, for example, pulverizing conditions or modifying conditions. However, the adjustment method is not limited to these.

<Method for producing active material>
This active material is obtained by mixing silicon or a silicon (Si)-containing substance, M or an M-containing substance, compound A and, if necessary, other raw material, heating and melting to alloy them, and if necessary, It can be obtained by crushing or crushing, classifying if necessary, and then reforming using a reformer utilizing a strong impact force. However, the method is not limited to this.
Here, the above-mentioned "silicon or silicon (Si)-containing substance" is meant to include pure silicon and silicon oxide, as well as silicon-containing substances such as silicon compounds such as Si ₃ N ₄ and SiC.

Examples of the compound A include silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide, and stainless steel. Among these, one kind may be a combination of two or more kinds. May be.
As described above, the addition compound A may be mixed with other raw materials, may be mixed in the crushing or pulverizing step, and may be mixed in the classifying step. Alternatively, it may be in a previous stage. Above all, it is preferable to add it during the modification treatment step.

As the alloying method, a known method can be adopted. For example, this active material is obtained by mixing silicon or a silicon (Si)-containing substance, the above M or the above M-containing substance, and optionally other raw materials and heating them to obtain a molten liquid, and then an atomizing method. Alternatively, the alloy may be alloyed by the above method, or may be melted as described above, cast by a roll casting method, and further pulverized in a non-oxygen atmosphere to be alloyed.
Other alloying methods may be used.

When the raw material is heated as described above to form a molten liquid, M _x Si _y is generated when the molten liquid is cooled. However, as the method of melting the metal in the present invention, it is preferable not to perform the arc melting step as described in JP-A-2010-135336. This is because, as described in paragraph [0029] of Japanese Patent Application Laid-Open No. 2011-518943 and paragraph [0011] of Japanese Patent Application Laid-Open No. 2014-513197, when arc melting is performed, oxidation may occur due to residual air. Is. Once a large amount of oxygen is taken into the raw material, it is difficult to remove it in a later step.

As the above-mentioned atomization method, for example, the apparatus shown in FIG. 2 of WO 01/081033 pamphlet is used, and the pressure wave generated by causing boiling due to spontaneous nucleation is used and dropped into the cooling medium. It is preferable to employ a method of alloying molten metal (this alloying method is referred to as "steam explosion atomizing method" in the present specification).

After the above alloying, it is preferable to crush or pulverize if necessary, and classify as necessary to adjust the particle size.

The reforming treatment using a reforming device that uses a strong impact force is a reforming treatment that uses a device that can perform mechanical milling or mechanical alloying depending on the condition settings. (SSA) can be increased, and a process for the ratio of the _{I a} with respect to the _{I B} as described above and _(I a / _{I B)} may be less than 1.
Incidentally, for example, JP-A-planetary ball mill as described in 2010-135336 JP, as compared with the case of using the above apparatus, Si element content is large and in a sample the amount of M is small, the relative said I _B it is difficult to the ratio of I _a and _(I a / _{I B)} to less than 1. Further, when the treatment is carried out by a planetary ball mill, a vibrating ball mill, an attritor, a ball mill or the like, stronger coagulation occurs particularly in an active material having a small amount of silicide as in the present application, so that D ₅₀ or It becomes larger than the range of D _max . This is not suitable as a negative electrode active material used for solid-state batteries.

Further, for example, in the prior art documents, there is proposed a method of producing silicide by reacting Si powder and powder of an element forming a silicide with Si in a ball mill. However, in that case, since the reaction occurs nonuniformly, the risk of the raw material element remaining as it is becomes high, and it is not suitable as a production method for obtaining the object of the present invention.

As the above-mentioned reforming treatment, for example, a treatment device having a rotary blade in the reaction tank is used, and the peripheral speed of the rotating blade is set to, for example, 3.0 m/s or more and 20.0 m/s or less, It is preferable to use beads having a particle size of, for example, 1500 times or more and 4000 times or less with respect to the D _{50 of the} active material as a medium to be charged in the above.
Considering that the pin mill is, for example, about 100 m/s or more and 130 m/s or less, it can be said that the peripheral speed of the rotary blade is slower than the peripheral speed at the time of fine pulverization processing. From this point of view, the peripheral speed of the rotary blade is preferably, for example, 4.0 m/s or more or 17.0 m/s or less, and particularly 4.5 m/s or more or 15.0 m/s or less, of which 5.0 m /S or more or 12.0 m/s or less is preferable. Even when the size of the stirring blade is changed, the same effect can be obtained by adjusting the peripheral speeds.

Also, the above-mentioned reforming treatment is preferably carried out in a low oxygen atmosphere, preferably in an inert atmosphere such as nitrogen or argon.

In a crusher such as a bead mill or a ball mill, it is said that the medium put into the reaction tank can be crushed to about 1/1000 of its size. Therefore, the use of beads having a particle size of, for example, 1500 times or more and 4000 times or less with respect to D _{50 of the} present active material means that the surface modification is performed preferentially over the pulverization.
From this viewpoint, the particle size of the medium charged into the reaction vessel is preferably 4 mmφ or more and 10 mmφ or less, more preferably 5 mmφ or more or 8 mmφ or less, and further preferably 6 mmφ or more or 7 mmφ or less.
As the material of the medium, for example _{SiO 2, Al 2 O 3,} ZrO 2, SiC, Si 3 N 4, WC , etc. can be cited, among _{others, Al 2 O 3, ZrO 2} , SiC, Si 3 N 4 is preferable.

<Use of active material>
The present active material can be preferably used as a negative electrode active material for batteries, especially solid batteries, and solid secondary batteries such as solid lithium secondary batteries. For example, it can be suitably used as a negative electrode active material of a solid battery containing a sulfide solid electrolyte as the solid electrolyte.

<This negative electrode>
The negative electrode according to this embodiment (hereinafter, referred to as “main negative electrode”) contains the present active material.
The present negative electrode is a member composed of a negative electrode mixture.
The negative electrode mixture includes, for example, a main active material, a binder if necessary, a conductive material if necessary, a solid electrolyte if necessary, and graphite as another negative electrode active material if necessary. It may be contained. Further, the present negative electrode can be formed by applying a negative electrode mixture on a negative electrode current collector.
The present negative electrode can be used, for example, in a solid state battery. More specifically, it can be used for a lithium solid state battery. The lithium solid state battery may be a primary battery or a secondary battery, but among them, it is preferably used for a lithium secondary battery.

The term “solid state battery” as used herein includes not only a solid state battery that does not contain any liquid substance or gelled substance as an electrolyte, but also a solid state battery that contains a small amount, for example, 10 wt% or less of a liquid substance or gelled substance as an electrolyte.

(binder)
The binder is not particularly limited as long as it is a material that can be used for the negative electrode. For example, polyimide, polyamide, polyamide imide, etc. may be mentioned. These may be used alone or in combination of two or more (hereinafter, these may be collectively referred to as "polyimide or the like"). Further, a binder other than these may be used in combination.
The details of the binder can be the same as those of known binders, and thus the description thereof is omitted here.

(Conductive material)
The binder is not particularly limited as long as it is a material that can be used for the negative electrode. Examples thereof include fine metal powder and powder of conductive carbon material such as acetylene black. When metal fine powder is used as the conductive material, it is preferable to use fine powder of a metal having lithium ion conductivity such as Sn, Zn, Ag and In, or an alloy of these metals.

(Solid electrolyte)
Examples of the solid electrolyte include a sulfide solid electrolyte, an oxide solid electrolyte, a nitride solid electrolyte, a halide solid electrolyte, and the like. Among them, a sulfide solid electrolyte containing a sulfur (S) element is preferable. ..

The sulfide solid electrolyte may be any of a crystalline material, glass ceramics and glass. For example _{Li 3 PS 4, Li 10 GeP} 2 S 12, Li 3.25 Ge 0.25 P 0.75 S 4, 30Li 2 S · 26B 2 S 3 · 44LiI, 63Li 2 S · 36SiS 2 · Li 3 PO 4 _{, 57Li 2 S · 38SiS 2 ·} 5Li 4 Si 4, 70Li 2 S · 30P 2 S 5, 50Li 2 S · 50GeS 2, Li 7 P 3 S 11, Li 3.25 P 0.95 S 4, Li 7- Examples thereof include compounds represented by _x PS _6-x Ha _x (0.2<x<1.8) (Ha represents one or more kinds of halogen elements). However, it is not limited to these.
The oxide solid electrolyte, the nitride solid electrolyte, and the halide solid electrolyte can be the same as known ones, and thus the description thereof is omitted here.

(Graphite)
As described above, by coexisting the present active material and graphite as the negative electrode active material in the negative electrode mixture, it is possible to obtain both high capacity due to silicon and good cycle characteristics due to graphite. it can.
In particular, since the active material does not have a plateau region or has a small plateau region in the discharge profile as described above, when used in combination with a carbon material (Graphite), it is possible to prevent the formation of a step in the discharge profile. It is preferable because it is easy to control when used as a negative electrode active material in combination with a carbon material (Graphite) such as graphite.

(Compound composition)
An example of the compounding composition of the binder and the conductive material when the present negative electrode is used in a non-aqueous electrolyte battery is shown.
The content of the binder is preferably 1 to 25 parts by mass with respect to 100 parts by mass of the active material, and more preferably 2 parts by mass or more or 20 parts by mass or less.
When the conductive material is mixed, the content of the conductive material is preferably 1 to 15 parts by mass, and particularly 2 parts by mass or more or 10 parts by mass or less based on 100 parts by mass of the active material. Is more preferable.
When graphite is blended as the negative electrode active material, the content of graphite is 0.5:95 to 50:50, particularly 0.5:95 to 20:50 in terms of the mixing mass ratio of the main active material and graphite. It is preferably 80.

(Method for manufacturing this negative electrode)
The present negative electrode includes, for example, the above-mentioned main active material (particulate), a binder, a conductive material, the above-mentioned solid electrolyte as necessary, a solvent, and optionally other materials such as a carbon material (Graphite). It may be formed by mixing and to prepare a negative electrode mixture, coating the negative electrode mixture on the surface of a current collector made of Cu or the like, and drying the mixture, and then pressing it as necessary. it can. Alternatively, the main active material (in the form of particles), the conductive material, the powder of the solid electrolyte, and the carbon material (Graphite), if necessary, may be mixed, press-molded, and then appropriately processed to be manufactured.

Drying after applying the negative electrode mixture to the surface of the current collector is preferably performed for 1 hour to 10 hours, particularly 1 hour to 7 hours in a non-oxygen atmosphere such as a nitrogen atmosphere or an argon atmosphere.

Here, a method for producing the present negative electrode when polyimide is used as a binder will be described.

First, the main active material (particulate), a polyimide precursor compound, an organic solvent such as N-methyl-2-pyrrolidone, and if necessary, a conductive material such as fine metal powder or acetylene black or a carbon material (Graphite) And the like are mixed to prepare a negative electrode mixture, and this negative electrode mixture is applied to the surface of a current collector made of Cu or the like.
At this time, a polyamic acid (polyamic acid) can be used as the polyimide precursor compound.

After the negative electrode mixture is applied to the surface of the current collector, the coating film can be heated to volatilize the organic solvent, and at the same time, the polyimide precursor compound can be polymerized to obtain a polyimide.
At this time, by adjusting the polymerization conditions of the precursor compound, the polyimide can be planarly adhered to the surface of the active material particles, and the active materials can be connected in a beaded shape via the connection site made of the polyimide. You can

As a result of studies conducted by the present inventors, it was found that it is advantageous to carry out multi-step heating as a polymerization condition for the precursor compound. In particular, it is advantageous to carry out heating in at least two stages, preferably at least three stages, more preferably four stages. For example, in the case of performing the two-step heating, the first-step heating is preferably performed at 100 to 150°C, and the second-step heating is preferably performed at 200 to 400°C.
Regarding the heating time, it is preferable that the heating time of the first step is the same as or longer than the heating time of the second step. For example, it is preferable to set the heating time for the first step to 120 to 300 minutes, particularly 180 minutes or more or 240 minutes or less, and the heating time for the second step to 30 to 120 minutes, especially 30 to 60 minutes.

When performing heating in three stages, it is preferable to adopt an intermediate heating temperature between the first stage and the second stage in the above-described two-stage heating.
This intermediate heating is preferably performed at 150 to 190°C. The heating time is preferably the same as the time of the first step and the second step or an intermediate time between the first step and the second step. That is, when performing heating in three stages, it is preferable that the heating time be the same in each stage, or that the heating time be shortened as the stages progress.
Further, when performing heating in four stages, it is preferable to adopt a heating temperature higher than that in the third stage.

Regardless of how many stages the heating is performed, the heating is preferably performed in an inert atmosphere such as nitrogen or argon.
Further, during the heat treatment, it is also preferable to press the active material layer with a pressing member such as a glass plate. By doing so, in a state where the organic solvent is abundant, that is, in a state in which the polyamic acid is saturated in the organic solvent, it is possible to polymerize the polyamic acid, so that the molecular chains of the polyimide to be produced are easily entangled. It will be.

By performing the above multi-step heating, it is possible to gradually volatilize the organic solvent contained in the negative electrode mixture, thereby making it possible to sufficiently increase the molecular weight of the polyimide precursor compound, and at the same time, to make the active material. Polyimide can be fixed on a wide range of the surface of the particle, and three-dimensional mesh-like voids can be formed in the active material layer over the entire thickness direction.

<This non-aqueous electrolyte battery>
Examples of the non-aqueous electrolyte battery according to the present embodiment (hereinafter referred to as “the non-aqueous electrolyte battery”) include a battery that can be composed of the present negative electrode, a positive electrode, a separator, a non-aqueous electrolyte solution, and the like. You can

(Positive electrode)
The positive electrode in the present non-aqueous electrolyte battery has, for example, a positive electrode active material layer formed on at least one surface of a current collector. The positive electrode active material layer contains a positive electrode active material. As the positive electrode active material, those known in the art can be used without particular limitation. For example, various lithium transition metal composite oxides can be used. Examples of such substances include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiCo _0.5 Ni _0.5 O ₂ , LiNi _0.7 Co _0.2 Mn _0.1. O ₂ , Li(Li _x Mn _2x Co _1-3x )O ₂ (in the formula, 0<x<1/3), LiFePO ₄ , LiMn _1-z M _z PO ₄ (in the formula, 0<z≦ 0.1, and M is at least one metal element selected from the group consisting of Co, Ni, Fe, Mg, Zn, and Cu).

(Separator)
In the present non-aqueous electrolyte battery, as the separator used together with the present negative electrode and the positive electrode, a synthetic resin non-woven fabric, a polyolefin such as polyethylene or polypropylene, or a porous film of polytetrafluoroethylene is preferably used.

(Non-aqueous electrolyte)
The non-aqueous electrolytic solution in the present non-aqueous electrolytic solution battery is composed of a solution in which a lithium salt as a supporting electrolyte is dissolved in an organic solvent. Examples of the organic solvent include carbonate-based organic solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, and fluorine-based organic solvents obtained by fluorinating a part of the carbonate-based organic solvent such as fluoroethylene carbonate. Or a combination of two or more thereof is used. Specifically, fluoroethylene carbonate, diethyl fluorocarbonate, dimethyl fluorocarbonate or the like can be used.
The lithium _{salt, CF 3 SO 3 Li, (} CF 3 SO 2) NLi, (C 2 F 5 SO 2) 2 NLi, LiClO 4, LiA1Cl 4, LiPF 6, LiAsF 6, LiSbF 6, LiCl, LiBr, LiI , LiC ₄ F ₉ SO _{3 and the} like. These may be used alone or in combination of two or more.

<This solid battery>
The solid-state battery according to the present embodiment (referred to as “present solid-state battery”) may include a positive electrode, the present negative electrode, and a solid electrolyte layer provided between the positive electrode and the negative electrode. That is, the present active material can be used as a negative electrode active material included in the negative electrode. In other words, the active material can be used in a solid state battery. More specifically, it can be used for a lithium all-solid-state battery. The lithium all-solid-state battery may be a primary battery or a secondary battery, but among them, it is preferably used for the lithium secondary battery.
Examples of the shape of the present solid state battery include a laminate type, a cylindrical type and a square type.

(Solid electrolyte layer)
The solid electrolyte layer is, for example, a method of dropping a slurry containing a solid electrolyte, a binder and a solvent onto a substrate and scraping it off with a doctor blade, a method of cutting the substrate with the slurry and then cutting with an air knife, a screen printing method, etc. It can be manufactured by a method in which a coating film is formed by, followed by heating and drying to remove the solvent. Alternatively, the solid electrolyte powder may be press-molded and then appropriately processed to be manufactured.
What was mentioned above can be used as a solid electrolyte.

(Positive electrode)
For the positive electrode, a positive electrode active material (particulate), a binder, a conductive material, a solid electrolyte, and a solvent are mixed to prepare a positive electrode mixture, and this positive electrode mixture is applied to the surface of a current collector and dried. It can be formed by pressing and then pressing if necessary. Alternatively, the positive electrode active material (particulate), the conductive material, and the powder of the solid electrolyte may be mixed, press-molded, and then appropriately processed to be manufactured.
As the positive electrode active material, those known in the art can be used without particular limitation. For example, various lithium transition metal composite oxides can be used. Examples of such a substance include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiMn _1.5 Ni _0.5 O ₄ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiCo _0.5 Ni _0.5 O ₂ , LiNi _0.7 Co _0.2 Mn _0.1 O ₂ , Li(Li _x Mn _2x Co _1-3x )O ₂ (where 0<x<1/3), LiFePO ₄ , LiMn _1-z M _z PO ₄ ( In the formula, 0<z≦0.1, and M is at least one metal element selected from the group consisting of Co, Ni, Fe, Mg, Zn, and Cu.) and the like.

<Explanation of terms>
In the present specification, when expressed as “X to Y” (X and Y are arbitrary numbers), “preferably larger than X” or “preferably Y” is included together with “meaning X or more and Y or less” unless otherwise specified. It also means "less than".
Further, when expressed as “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), it means “preferably greater than X” or “less than Y”. It also includes intent.

Hereinafter, the present invention will be described in more detail based on the following examples and comparative examples. However, the present invention is not limited to the examples shown below.

<Example 1>
A silicon (Si) ingot and a titanium (Ti) ingot are mixed, heated and melted, and the molten liquid heated to 1700° C. is rapidly cooled using a liquid rapid solidification device (single roll type) to obtain a quenched ribbon alloy. Got The obtained quenched ribbon alloy is roughly crushed using a dry ball mill, and then further dry crushed under a nitrogen atmosphere (atmosphere of less than 1%, the balance being vaporized nitrogen from liquid nitrogen (purity of 99.999% or more)). The particle size was adjusted using to obtain an alloy powder.

The obtained alloy powder was subjected to a reforming treatment by using a nanoparticle surface reforming device (product name “Simroyer”, equipped with a rotary blade in the reaction device). That is, 2 kg of beads as a medium, 50 g of the alloy powder, and silicon nitride powder were put into a container having a capacity of 2 L, the atmosphere was adjusted, and then the treatment was performed at 1500 rpm for 3 hours.
The alloy powder after the treatment was crushed or crushed using a dry crusher to adjust the particle size, and then classified with a sieve having an opening of 75 μm to obtain an alloy powder (sample) as a negative electrode active material.
When chemical analysis of the obtained alloy powder (sample) was performed, Si: 68 wt% and Ti: 23 wt% were found. The amount of carbon (C) element was 1.2 wt %.

<Example 2>
A silicon (Si) ingot and a titanium (Ti) ingot are mixed, heated and melted, and the molten liquid heated to 1700° C. is rapidly cooled using a liquid rapid solidification device (single roll type) to obtain a quenched ribbon alloy. Got The obtained quenched ribbon alloy is roughly crushed using a dry ball mill, and then further dry crushed under a nitrogen atmosphere (atmosphere of less than 1%, the balance being vaporized nitrogen from liquid nitrogen (purity of 99.999% or more)). The particle size was adjusted using to obtain an alloy powder.

The obtained alloy powder was subjected to a reforming treatment using a nanoparticle surface reforming device (product name “SIMOLOYER”, equipped with a rotary blade in the reaction device). That is, 2 kg of beads as a medium, 50 g of the alloy powder, and zirconium oxide powder were put into a container having a capacity of 2 L, the atmosphere was adjusted, and then the treatment was performed at 1500 rpm for 3 hours.
The alloy powder after the treatment was crushed or crushed using a dry crusher to adjust the particle size, and then classified with a sieve having an opening of 75 μm to obtain an alloy powder (sample) as a negative electrode active material.
When chemical analysis of the obtained alloy powder (sample) was performed, Si: 64 wt% and Ti: 25 wt% were found. The amount of carbon (C) element was 0.8 wt %.

<Example 3>
A silicon (Si) ingot and a titanium (Ti) ingot are mixed, heated and melted, and the molten liquid heated to 1700° C. is rapidly cooled using a liquid rapid solidification device (single roll type) to obtain a quenched ribbon alloy. Got The obtained quenched ribbon alloy is roughly crushed using a dry ball mill, and then further dry crushed under a nitrogen atmosphere (atmosphere of less than 1%, the balance being vaporized nitrogen from liquid nitrogen (purity of 99.999% or more)). The particle size was adjusted by using to obtain an alloy powder.

The obtained alloy powder was subjected to a reforming treatment using a nanoparticle surface reforming device (product name “SIMOLOYER”, equipped with a rotary blade in the reaction device). That is, 2 kg of beads as a medium, 50 g of the alloy powder, and zirconium oxide powder were put into a container having a capacity of 2 L, the atmosphere was adjusted, and then the treatment was performed at 1500 rpm for 3 hours.
The alloy powder after the treatment was crushed or crushed using a dry crusher to adjust the particle size, and then classified with a sieve having an opening of 75 μm to obtain an alloy powder (sample) as a negative electrode active material.
When chemical analysis of the obtained alloy powder (sample) was performed, it was Si: 70 wt% and Ti: 20 wt %. The amount of carbon (C) element was 0.6 wt %.

<Example 4>
A silicon (Si) ingot and a titanium (Ti) ingot are mixed, heated and melted, and the molten liquid heated to 1700° C. is rapidly cooled using a liquid rapid solidification device (single roll type) to obtain a quenched ribbon alloy. Got The obtained quenched ribbon alloy is roughly crushed using a dry ball mill, and then further dry crushed under a nitrogen atmosphere (atmosphere of less than 1%, the balance being vaporized nitrogen from liquid nitrogen (purity of 99.999% or more)). The particle size was adjusted using to obtain an alloy powder.

The obtained alloy powder was subjected to a reforming treatment by using a nanoparticle surface reforming device (product name “Simroyer”, equipped with a rotary blade in the reaction device). That is, 2 kg of beads as a medium, 50 g of the alloy powder, and zirconium oxide were charged into a container having a capacity of 2 L, the atmosphere was adjusted, and then the treatment was performed at 1500 rpm for 3 hours.
The alloy powder after the treatment was crushed or crushed using a dry crusher to adjust the particle size, and then classified with a sieve having an opening of 75 μm to obtain an alloy powder (sample) as a negative electrode active material.
When chemical analysis of the obtained alloy powder (sample) was performed, it was Si: 76 wt% and Ti: 17 wt %. The amount of carbon (C) element was 0.9 wt %.

<Example 5>
A silicon (Si) ingot, a titanium (Ti) ingot, and an aluminum (Al) ingot are mixed, heated and melted, and the molten liquid heated to 1700° C. is rapidly cooled by a liquid rapid solidification device (single roll type). After cooling, a quenched ribbon alloy was obtained. The obtained quenched ribbon alloy is roughly crushed using a dry ball mill, and then further dry crushed under a nitrogen atmosphere (atmosphere of less than 1%, the balance being vaporized nitrogen from liquid nitrogen (purity of 99.999% or more)). The particle size was adjusted using to obtain an alloy powder.

The obtained alloy powder was subjected to a reforming treatment using a nanoparticle surface reforming device (product name “SIMOLOYER”, equipped with a rotary blade in the reaction device). That is, 2 kg of beads as a medium, 50 g of the alloy powder, and zirconium oxide powder were put into a container having a capacity of 2 L, the atmosphere was adjusted, and then the treatment was performed at 1500 rpm for 3 hours.
The alloy powder after the treatment was crushed or crushed using a dry crusher to adjust the particle size, and then classified with a sieve having an opening of 75 μm to obtain an alloy powder (sample) as a negative electrode active material.
When the chemical analysis of the obtained alloy powder (sample) was performed, it was Si:69 wt%, Ti:26 wt%, and Al:0.10 wt%. The amount of carbon (C) element was 0.7 wt %.

<Example 6>
A silicon (Si) ingot, a titanium (Ti) ingot, a boron (B) ingot, and an aluminum (Al) ingot are mixed and melted by heating, and the molten liquid heated to 1700° C. Roll type) was used for rapid cooling to obtain a quenched ribbon alloy. The obtained quenched ribbon alloy is roughly crushed using a dry ball mill, and then further dry crushed under a nitrogen atmosphere (atmosphere of less than 1%, the balance being vaporized nitrogen from liquid nitrogen (purity of 99.999% or more)). The particle size was adjusted using to obtain an alloy powder.

The obtained alloy powder was subjected to a reforming treatment using a nanoparticle surface reforming device (product name “SIMOLOYER”, equipped with a rotary blade in the reaction device). That is, 2 kg of beads as a medium, 50 g of the alloy powder, and zirconium oxide powder were put into a container having a capacity of 2 L, the atmosphere was adjusted, and then the treatment was performed at 1500 rpm for 3 hours.
The alloy powder after the treatment was crushed or crushed using a dry crusher to adjust the particle size, and then classified with a sieve having an opening of 75 μm to obtain an alloy powder (sample) as a negative electrode active material.
When the chemical analysis of the obtained alloy powder (sample) was performed, it was Si:65 wt%, Ti:24 wt%, B:0.01 wt%, and Al:0.09 wt%. The amount of carbon (C) element was 0.4 wt %.

<Example 7>
A silicon (Si) ingot and a titanium (Ti) ingot are mixed, heated and melted, and the molten liquid heated to 1700° C. is rapidly cooled using a liquid rapid solidification device (single roll type) to obtain a quenched ribbon alloy. Got The obtained quenched ribbon alloy is roughly crushed using a dry ball mill, and then further dry crushed under a nitrogen atmosphere (atmosphere of less than 1%, the balance being vaporized nitrogen from liquid nitrogen (purity of 99.999% or more)). The particle size was adjusted using to obtain an alloy powder.

The obtained alloy powder was subjected to a reforming treatment using a nanoparticle surface reforming device (product name “SIMOLOYER”, equipped with a rotary blade in the reaction device). That is, 2 kg of beads as a medium, 50 g of the alloy powder, and aluminum oxide powder were put into a container having a capacity of 2 L, the atmosphere was adjusted, and then the treatment was performed at 1500 rpm for 3 hours.
The alloy powder after the treatment was crushed or crushed using a dry crusher to adjust the particle size, and then classified with a sieve having an opening of 75 μm to obtain an alloy powder (sample) as a negative electrode active material.
When chemical analysis of the obtained alloy powder (sample) was performed, Si: 66 wt% and Ti: 25 wt% were found. The amount of carbon (C) element was 0.9 wt %.

<Example 8>
A silicon (Si) ingot and a titanium (Ti) ingot are mixed, heated and melted, and the molten liquid heated to 1700° C. is rapidly cooled using a liquid rapid solidification device (single roll type) to obtain a quenched ribbon alloy. Got The obtained quenched ribbon alloy is roughly crushed using a dry ball mill, and then further dry crushed under a nitrogen atmosphere (atmosphere of less than 1%, the balance being vaporized nitrogen from liquid nitrogen (purity of 99.999% or more)). The particle size was adjusted using to obtain an alloy powder.

The obtained alloy powder was subjected to a reforming treatment using a nanoparticle surface reforming device (product name “SIMOLOYER”, equipped with a rotary blade in the reaction device). That is, 2 kg of beads as a medium, 50 g of the alloy powder, and aluminum oxide powder were put into a container having a capacity of 2 L, the atmosphere was adjusted, and then the treatment was performed at 1500 rpm for 3 hours.
The alloy powder after the treatment was crushed or crushed using a dry crusher to adjust the particle size, and then classified with a sieve having an opening of 75 μm to obtain an alloy powder (sample) as a negative electrode active material.
When chemical analysis of the obtained alloy powder (sample) was performed, it was Si: 66 wt% and Ti: 24 wt %. The amount of carbon (C) element was 0.9 wt %.

<Comparative Example 1>
A silicon (Si) ingot was heated and melted, and the molten liquid heated to 1700° C. was rapidly cooled using a liquid rapid solidification device (single roll type) to obtain a quenched thin strip metal. The obtained quenched thin strip metal is roughly crushed by using a dry ball mill, and then further dry crusher under a nitrogen atmosphere (atmosphere less than 1%, and the balance being vaporized nitrogen from liquid nitrogen (purity 99.999% or more)). The particle size was adjusted using to obtain a metal powder (sample).
When a chemical analysis of the obtained metal powder (sample) was performed, it was Si: 99 wt %.

<Comparative example 2>
Silicon (Si) ingot and massive titanium are mixed at an atomic ratio of 85:15 (weight ratio of 76.8:23.2) and melted using a liquid rapid solidification device (single roll type), and the molten metal is argon gas. Then, it was sprayed on a rotating copper roll and rapidly cooled to produce a Si—Ti alloy. Next, the Si—Ti alloy was pulverized for 2 hours in a planetary ball mill using a silicon nitride ball in an argon gas atmosphere to obtain an alloy powder (sample) electrode material.

<Comparative example 3>
Si and B were used for the solid phase A, and these were made into a mixture with a weight ratio of 19.9:0.1. This mixture was put into a high-frequency melting tank and melted, and the resulting molten alloy was rapidly solidified by a single roll method to obtain a first alloy ingot. Further, Ti and Si were used for the solid phase B, and a mixture of these with an atomic ratio of 1:2 was used. This mixture was put into a high-frequency melting tank and melted, and the obtained alloy melt was rapidly solidified by a single roll method to obtain a second alloy ingot composed of an intermetallic compound represented by a composition formula TiSi ₂ . .. Next, the mixture of the first alloy ingot and the second alloy ingot at a weight ratio of 20:80 was put into a container of a planetary ball mill and pulverized for 1 hour to obtain an alloy powder (sample) electrode material. It was

<Comparative example 4>
Si and Ti were charged and melted in an Ar atmosphere using high frequency induction melting, and an alloy powder (sample) was obtained from the obtained melt by a gas atomization method. When chemical analysis of the obtained alloy powder (sample) was carried out, it was Si: 70 wt% and Ti: 26 wt %.

<Reference example 1>
A silicon (Si) ingot and massive titanium are mixed at an atomic ratio of 85:15, melted using a liquid rapid solidification device (single roll type), and the molten metal is sprayed with argon gas onto a rotating copper roll to quench it. , Si-Ti alloy was prepared. Next, the Si—Ti alloy was roughly pulverized using a dry ball mill to obtain an alloy powder (sample).

<Reference example 2>
First, Si and Ti were charged at a ratio of 81 at% Si-19 at% Ti and were melted in an Ar atmosphere by using high frequency induction melting, and the obtained melt was obtained as an alloy particle by a gas atomizing method. The D50 of the alloy particles was 29 μm.
Next, the alloy particles and the natural graphite are charged in a ratio of alloy particles/natural graphite=95/5 on a mass basis, and nickel (Ni) is added as a conductivity improver to the total weight of the alloy particles and the natural graphite. Was added in an amount of 5% by mass to prepare a mixed powder. This mixed powder was subjected to mechanical alloying treatment for 30 hours using a planetary ball mill (spherical medium made of zirconia) to obtain a negative electrode material (sample).

<Measurement method of various physical properties>
Various physical properties of the alloy powder (sample) (including metal powder (sample) below) obtained in Examples and Comparative Examples were measured as follows.

(Composition analysis)
With respect to the alloy powders (samples) obtained in Examples and Comparative Examples, the content of each element was measured by inductively coupled plasma (ICP) emission spectroscopy. However, regarding oxygen, the content was measured using an oxygen/nitrogen analyzer (manufactured by LECO). Regarding carbon, the content was measured using a carbon/sulfur analyzer (manufactured by Horiba, Ltd.).

_(D 50 _{· D max)}
In a 50 ml beaker, 0.5 g of the alloy powder (sample) obtained in Examples and Comparative Examples and 50 ml of ion-exchanged water containing 20 vol% of ethanol were added, and an ultrasonic homogenizer (Ultrasonic wave manufactured by Nippon Seiki Seisakusho Co., Ltd. was used. Homogenizer US-150E, 20φ tip is used), adjust the dial level so that AMPLITUDE is 80%, apply ultrasonic waves for 5 minutes to disperse the sample in the liquid, and obtain a dispersion liquid. It was
Next, using an automatic sample feeder for a laser diffraction particle size distribution measuring device (“Microtorac SDC” manufactured by Microtrac Bell Co., Ltd.), the dispersion liquid was used as a water-soluble solvent (ion-exchanged water containing 20 vol% of ethanol added). I put it in. The particle size distribution was measured using a laser diffraction particle size distribution analyzer “MT3300II” manufactured by Microtrac Bell Co., Ltd. at a flow rate of 70 mL/sec, and D ₅₀ and D _max were determined from the obtained volume-based particle size distribution chart. ..
The water-soluble solvent used in the measurement was passed through a 60 μm filter, the solvent refractive index was 1.33, the particle permeability condition was reflection, the measurement range was 0.021 to 2000 μm, and the measurement time was 10 seconds. The obtained values were defined as the respective measured values.

(Specific surface area: SSA)
The specific surface area (SSA) of the alloy powders (samples) obtained in Examples and Comparative Examples was measured as follows.
First, 1.0 g of a sample (powder) was weighed in a glass cell (standard cell) for a fully automatic specific surface area measuring apparatus Macsorb (manufactured by Mountech Co., Ltd.) and set in an auto sampler. After replacing the inside of the glass with nitrogen gas, heat treatment was performed at 250° C. for 15 minutes in the nitrogen gas atmosphere. Then, the mixture was cooled for 4 minutes while flowing a mixed gas of nitrogen and helium. After cooling, the sample was measured by the BET single point method.
A mixed gas of 30 vol% nitrogen and 70 vol% helium was used as the adsorption gas during cooling and measurement.

(True density)
The true densities of the alloy powders (samples) obtained in Examples and Comparative Examples were measured as follows.
First, the sample (powder) was put into a sample basket of 10 cm ³ until the 7th minute, and the amount of the put sample was measured. Next, the sample basket containing the sample was set in the true density measuring device BELPycno (manufactured by Mountech Co., Ltd.), the lid of the device was closed, and the measurement was started.
Helium gas was used for the measurement, and the temperature of the measurement part was controlled at 25° C.±0.1° C.

(Observation of cross section of active material)
Using the alloy powders (samples) obtained in the examples and comparative examples, the negative electrode of the electrode prepared as described below was processed by ion milling to give a cross section, and then FE-SEM (device name "SU8220") was used. The cross section of the negative electrode was observed by using Hitachi High Technologies) and EDS (device name “QUANTAX200” detector “XFlash5060F” made by Bruker). Elemental mapping was performed using the above apparatus under the conditions of an acceleration voltage of 6 kV and an emission current of 30 μA. The mapping is performed by selecting one active material particle corresponding to D ₅₀ , enlarging it so that more than half of the field of view is occupied by the selected active material particle, and performing measurement by designating only the area corresponding to the active material particle cross section. (As an example, when mapping to a particle having a D ₅₀ of 2 to 3 μm, it was set to 30,000 times). The integration time was 90 seconds. Note that it is important to set the integrated time so that sufficient strength can be obtained, and the integrated time described above is an example.
From the mapping image, silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide, and a concentrated portion of a specific element contained in stainless steel were confirmed.
In the cross section of the active material, the concentrated portion and the portion other than the concentrated portion were measured by point analysis. It was confirmed that the strength of the element was high. This indicates that silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide, and stainless steel exist inside the active material particles.
As an example, when silicon nitride is included, the concentration part is determined by nitrogen, and when zirconium oxide is included, the concentration part is determined by zirconium.

(Content of substances present in active material particles)
As described above, the presence of any one of silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide and stainless steel was confirmed by using FE-SEM and EDS.
Then, the contents of these substances were calculated based on the results of gas analysis or ICP analysis. For example, in the case of containing silicon nitride, the content of nitrogen element (wt%) was measured by gas analysis, and the content of nitrogen nitride (wt%) was calculated by considering this nitrogen as derived from silicon nitride. .. When zirconium oxide was contained, the zirconium content (wt %) was measured by ICP analysis, and the zirconium oxide content (wt %) was calculated by considering this zirconium as being derived from zirconium oxide.
For example, in Example 1, since the nitrogen element was 2.3 wt% from the gas analysis result, when converted to silicon nitride (Si ₃ N ₄ ), it was 5.8 wt %. Further, in Examples 2 to 4, zirconium was 6.3 wt%, 4.7 wt%, and 0.9 wt%, respectively. Therefore, when converted to zirconium oxide, 8.5 wt%, 6.3 wt%, and 1.2 wt%. Becomes
When aluminum oxide was included, the content (wt%) of aluminum was measured by ICP analysis, and the content (wt%) of aluminum oxide was calculated by considering this aluminum as derived from aluminum oxide. For example, in Examples 6 to 7, aluminum was 2.6 wt% and 2.9 wt%, respectively, so that when converted to aluminum oxide, it becomes 4.9 wt% and 5.5 wt%.

(X-ray diffraction)
An X-ray diffraction pattern (also referred to as “XRD pattern”) was obtained by measurement under the following measurement condition 1 using an X-ray diffraction device (XRD, device name “Ultima IV, manufactured by Rigaku Corporation”) using CuKα1 rays. It was

= XRD measurement condition 1 =
Radiation source: CuKα (line focus), wavelength: 1.541836Å
Operation axis: 2θ/θ, measurement method: continuous, counting unit: cps
Start angle: 15.0°, End angle: 120.0°, Number of integrations: 1 Sampling width: 0.01°, Scan speed: 1.0°/min
Voltage: 40kV, Current: 40mA
Divergence slit: 0.2mm, Divergence vertical restriction slit: 10mm
Scattering slit: open, light receiving slit: open Offset angle: 0°
Goniometer radius: 285 mm, optical system: focusing method Attachment: ASC-48
Slit: Slit for D/teX Ultra Detector: D/teX Ultra
Incident Monochrome: CBO
Ni-Kβ filter: No rotation speed: 50 rpm

The XRD measurement conditions were set and the silicon powder material (ex:SRM640e), which is a standard sample for X-ray diffraction manufactured by NIST, was measured. FIG. 3 shows an XRD pattern of a silicon powder material (ex: SRM640e) which is a standard sample for X-ray diffraction manufactured by NIST. The diffraction peak position and the number of peaks were confirmed by comparing with the card information of ICDD card number: 00-005-0565 (chemical formula: Si). Whether the peak intensity I is about 120,000 cps to 130000 cps for the peak that appears at 2θ=28.42°±1.25°, where the diffraction peak position and the number of peaks are the same as the card information. As an index, it was confirmed that the XRD measurement conditions were set correctly.

In the obtained XRD pattern, it was confirmed that there was no clear peak at 2θ=16.5°±1.5°, and the average value of cps in this range was taken as the intensity I _BG of the background (BG).
When a peak exists in the above range, a 2θ range suitable for defining the intensity I _BG of the background (BG) was selected.
Next, based on the card information of ICDD card number: 00-005-0565 (chemical formula: Si), the difference between the peak intensity I _A of peak _A and the intensity I _BG of background (BG) is calculated as follows. The value of the peak intensity I _A was used. The peak A was a peak corresponding to the (111) plane of Si having the crystal structure of the space group Fd-3m.
Next, the full width at half maximum (FWHM) of peak A was determined and shown in the table as the full width at half maximum of the (111) plane peak of Si in space group Fd-3m.

Here, a method for identifying a compound represented by M _x Si _y will be described.
From the result of the chemical analysis, M in the above compound was estimated, and identification was performed assuming that a compound (M _x Si _y ) containing the M and the Si element is formed. XRD pattern data for analysis was read by using analysis software (product name “PDXL”). After that, automatic search was selected for identification. All subfiles were selected as targets for automatic search, and the element filters were set to include M and Si elements, and the automatic search was performed.
When automatic search was performed, several card numbers were picked up as the crystal phase search results, and crystal phase candidates with high peak coincidence were selected from them. Then, the coincidence between the peak position of the XRD pattern data for analysis and the peak position of the selected crystal phase candidate was confirmed. FIG. 4 is a diagram in which ICDD card numbers: 00-005-0565 (chemical formula: Si) and 01-071-0187 (chemical formula: TiSi ₂ ) cards are collated with the reference example 1. In this way, if you can confirm the peaks that can be assigned to each compound, use them as they are.If there is a deviation in the peak position or the number of peaks, manually re-select from the card numbers picked up as the crystal phase search results. Make a choice. At the time of reselection, the reliability (Quality) of the card set in the ICDD card was used as a reference, and the peak position was confirmed by reselecting the cards in descending order of Quality (S→I→B).
Note that, for example, when there is a factor such that the peak intensity is lowered as a whole, such as when the content of silicon or compound is low, among the peaks described in the ICDD card, only the peak having a relatively high intensity is observed. Care must be taken because peaks with relatively low intensity may not be observed.

By the above, the ICDD card number of the selected compound containing M and Si elements (M _x Si _y ) is read, and the region where the main peak attributed to the compound appears (for example, TiSi of ICDD card number 01-071-0187). _In the case of _{2, in} the case of 2θ=39.11°), the difference between the peak intensity I _B and the intensity of the background (BG) I _BG is defined as the peak intensity I _{B of the} peak B having the maximum intensity. The peak intensity I _{B of the} compound (M _x Si _y ) was used. Then, the ratio of the peak intensity _{I A} of the peak A to the peak intensity _{I B} of a peak B attributable to the compound _(M x Si _y), shown in Table 1.

<Evaluation of characteristics of non-aqueous electrolyte secondary battery>
(Preparation of electrode)
The alloy powders (samples) obtained in Examples and Comparative Examples: conductive material: binder = 85:5:10 (wt%) were mixed so as to have a mixing ratio, and these were mixed with N-methylpyrrolidone. It was dispersed to obtain a negative electrode mixture. Acetylene black was used as the conductive material. Polyimide was used as the binder. This negative electrode mixture was applied on an electrolytic copper foil having a thickness of 15 μm. The coating film was dried to form a negative electrode active material layer to obtain a negative electrode.
At this time, the coating amount was determined in consideration of the surface capacity (mAh/cm ² ). As an example, the surface capacity was set to 2.8 mAh/cm ² for evaluation. For example, in the case of Pure-Si, when the charge capacity is set to 4200 mAh/g, 85 wt% of the sample is contained in the negative electrode active material, so the negative electrode active material layer has a coating amount of 0.78 mg/cm ² . If the charge capacity of the sample is lower than 4200 mAh/g, the coating amount is increased to adjust the same surface capacity.

(Preparation of battery)
The negative electrode obtained as described above was punched into a circle having a diameter of 14 mmφ, and vacuum dried at 160° C. for 6 hours. Then, the electrochemical evaluation cell TOMCEL (registered trademark) was assembled in a glove box under an argon atmosphere. Metal lithium was used as the counter electrode. As the electrolytic solution, an electrolytic solution prepared by dissolving LiPF ₆ in a carbonate-based mixed solvent so as to be 1 mol/l was used. A polypropylene porous film was used as the separator.

(Battery performance evaluation test)
Initial activity was performed by the method described below using the electrochemical evaluation cell TOMCEL (registered trademark) prepared as described above. After the prepared cell for electrochemical evaluation TOMCEL (registered trademark) was allowed to stand for 6 hours, it was charged with a constant current and constant potential at 0.1 C at 25° C. to 0.01 V (when the current value reached 0.01 C). Charging was completed), and constant current discharge was performed at 0.1 C to 1.0 V.
The recording interval during charging/discharging was set so that recording was performed when either 300 seconds or 5.0 mV change was satisfied. With such a setting, recording is performed every 300 seconds in the area where the voltage fluctuation is small, and is recorded every 5.0 mV change in the area where the voltage fluctuation is large. This was repeated 3 cycles. The current value actually set was calculated from the content of the negative electrode active material in the negative electrode.
For Examples 5 to 8 and Comparative Example 3, a sample having an initial charge capacity of more than 3000 mAh/g is “A”, a sample of 1200 mAh/g or more and 3000 mAh/g or less is “B”, and a sample of less than 1200 mAh/g is “C”. Is shown in Table 4. In addition, since the materials classified into C do not have sufficient capacity because of insufficient capacity, the subsequent measurements were stopped.

(Evaluation of discharge profile shape)
The "discharge profile shape" was determined based on the discharge curve of the first cycle obtained above. That is, the obtained discharge curves were linearly approximated, the heights of the correlation coefficients were compared, and they were used as an index of the “discharge profile shape”.
In Tables 2 and 4, the indices are shown when the numerical value of Comparative Example 3 is 100.
At this time, if the potential changes continuously in the section from the initial stage of discharge to the final stage of discharge, that is, if the linearity is high, the correlation coefficient at the time of linear approximation becomes high, and there is no plateau region or the plateau region is small. Will show that.

(High-rate characteristic evaluation)
The discharge rate characteristics were evaluated using the electrochemically evaluated cell TOMCEL which was initially activated by the method described above. First, after constant-current constant-potential charging was performed at 25C at 0.1C to 0.01V (charging was completed when the current value reached 0.01C), constant-current discharging was performed at 5C to 1.0V.
The recording interval during charging/discharging was set so that recording was performed when either 300 seconds or 5.0 mV change was satisfied. With such a setting, recording is performed every 300 seconds in the area where the voltage fluctuation is small, and is recorded every 5.0 mV change in the area where the voltage fluctuation is large.
From the discharge curve at 5C, the "discharge profile shape" was determined as described above and used as the index of the "discharge profile shape" at 5C. The ratio of the "discharge profile shape" index at 5C to the above-mentioned "discharge profile shape" index at 0.1C was defined as "high rate characteristic".
In Tables 2 and 4, the indices are shown when the numerical value of Comparative Example 3 is 100.

(Cycle characteristic evaluation)
A cell TOMCEL for electrochemical evaluation was prepared in the same manner as described above. After the prepared cell for electrochemical evaluation TOMCEL (registered trademark) was allowed to stand for 6 hours, it was charged with a constant current and constant potential at 0.1 C at 25° C. to 0.01 V (when the current value reached 0.01 C). Charging was completed), and constant current discharge was performed at 0.1 C to 1.0 V. This was repeated 3 cycles. The current value actually set was calculated from the content of the negative electrode active material in the negative electrode.
Using the electrochemical evaluation cell TOMCEL after the initial activation as described above, a charge/discharge test was performed by the method described below to evaluate the 45° C. cycle characteristics.
The cell was placed in an environmental tester set so that the environmental temperature for charging/discharging the battery was 45° C., the battery was prepared for charging/discharging, and the cell was allowed to stand for 5 hours so as to reach the environmental temperature. After that, the charging/discharging range was set to 0.01V-1.0V, charging was performed at 0.1C constant current and constant potential and discharging was performed at 0.1C constant current for 1 cycle, and then 1C was performed for 98 charging/discharging cycles. After that, one charge/discharge cycle was performed at 0.1 C, and then 50 charge/discharge cycles were performed at 1 C. went. The C rate was calculated based on the discharge capacity at 25° C. at the time of initial activation and the third cycle.
The percentage (%) of the numerical value obtained by dividing the discharge capacity at the 150th cycle by the discharge capacity at the second cycle was determined as the 45°C cycle characteristic value.
It should be noted that Tables 2 and 4 are shown as indices when the numerical value of Comparative Example 3 is 100.

<Evaluation of solid-state battery characteristics>
(Preparation of battery)
The alloy powders (samples) obtained in the examples and comparative examples were used as the negative electrode active material to prepare an electrode mixture, to prepare a sulfide-based all-solid-state battery, and to evaluate the battery characteristics. An InLi foil was used as the counter electrode, and a powder represented by the composition formula: Li _5.8 PS _4.8 Cl _1.2 was used as the solid electrolyte powder.

(Mixture adjustment)
The electrode mixture powder is prepared by mixing the active material powder, the solid electrolyte powder, and the conductive agent (VGCF (registered trademark)) powder in a mortar in a mass ratio of 4.5:86.2:9.3. Uniaxial press molding was performed at 10 MPa to obtain a mixture pellet.

(Preparation of solid-state battery cell)
The lower opening of a ceramic cylinder (opening diameter 10 mm) with upper and lower openings was closed with an electrode (made of SUS), 0.10 g of solid electrolyte was poured, the upper opening was sandwiched by the electrodes, and uniaxial press molding was performed at 10 MPa. Then, the electrolyte layer was produced. The upper electrode was once removed, an electrode mixture pellet made of a silicon active material was inserted, the upper electrode was mounted again, and uniaxial press molding was performed at 42 MPa, and the mixture pellet and the electrolyte layer were pressure bonded. Remove the lower electrode once, insert the In·Li foil, reattach the lower electrode, and screw between the upper electrode and the lower electrode at a torque pressure of 6 N·m at four locations. An all-solid-state battery equivalent to 6 mAh was produced. At this time, the production of the all-solid-state battery cell was performed in a glove box which was replaced with dry air having an average dew point of −45° C.

(Evaluation of charge capacity)
The capacity confirmation in the battery characteristic evaluation was evaluated by putting the all-solid-state battery in an environmental tester kept at 25° C. and connecting it to a charge/discharge measuring device. Since the cell capacity is 1.6 mAh, 1 C is 1.6 mA. The charge/discharge of the battery was 0.1 C, and the CCCV system was charged to -0.62 V (charging was completed when the current value reached 0.01 C) to obtain the initial charge capacity. The discharge was 0.1 C, and CC discharge was performed up to 0.88 V.
The recording interval during charging/discharging was set so that one point was recorded when either 10 seconds or 1 mV change was satisfied. With such a setting, recording is performed every 10 seconds in the area where the voltage fluctuation is small, and is recorded every 1 mV change in the area where the voltage fluctuation is large.
A sample having an initial charge capacity of more than 3000 mAh/g is shown in Table 3 as “A”, a sample “B” of 1200 mAh/g or more and 3000 mAh/g or less, and a sample “C” of less than 1200 mAh/g. In addition, since the materials classified into C do not have sufficient capacity because of insufficient capacity, the subsequent measurements were stopped.

(Evaluation of discharge profile shape)
The "discharge profile shape" was determined based on the discharge curve obtained above. That is, the obtained discharge curves were linearly approximated, the heights of the correlation coefficients were compared, and they were used as an index of the “discharge profile shape”. In addition, in Table 3, it is shown as an index when the numerical value of Comparative Example 2 is 100. At this time, if the potential changes continuously in the section from the initial stage of discharge to the final stage of discharge, that is, if the linearity is high, the correlation coefficient in the linear approximation becomes high, indicating that there is no or small plateau. become.

(High-rate characteristic evaluation)
High-rate characteristic evaluation was performed using the above-mentioned charged and discharged cells. The evaluation was carried out continuously in the environmental tester kept at 25°C. The battery capacity was calculated based on the above-mentioned charge capacity, and the C rate was determined.
Next, after charging to -0.62V by the 0.1C, CCCV method (charging ends when the current value reaches 0.01C), discharging is performed to 0.88V by the 0.1C, CC method. .. The discharge capacity at this time was set to 0.1 C discharge capacity (A).
Subsequently, the battery was charged to −0.62V by the 0.1C CCCV method (charging was completed when the current value reached 0.01C), and then discharged to 0.88V by the 5C CC method. The discharge capacity at this time was defined as 5C discharge capacity.
“5 C discharge capacity/0.1 C discharge capacity (A)×100” was calculated and evaluated as a high rate characteristic value. In addition, in Table 3, it is shown as an index when the numerical value of Comparative Example 2 is 100.

(Cycle characteristic evaluation)
Cycle evaluation was performed using the cell that underwent the high rate characteristic evaluation described above. The evaluation was carried out continuously in the environmental tester kept at 25°C.
First, as a preliminary preparation, in order to perform the above-mentioned residual discharge of the cell, the initial current value is set to 5 C, and the CV method is used to perform discharge at 0.88 V (discharge is completed when the current value reaches 0.01 C). It was
Next, after charging to -0.62V by the 0.1C, CCCV method (charging ends when the current value reaches 0.01C), discharging is performed to 0.88V by the 0.1C, CC method. .. The discharge capacity at this time was set to 0.1 C discharge capacity (B).
“0.1 C discharge capacity (B)/0.1 C discharge capacity (A)×100” was calculated and evaluated as a cycle characteristic value. In Table 3, the index of Comparative Example 2 is set as 100 and shown as an index.

From the above examples and the test results conducted by the inventors so far, silicon and the chemical formula M _x Si _y (where x and y satisfy 0.1≦x/y≦7.0, and M is A compound represented by one or more of semimetal elements and metal elements other than Si), and an active material comprising active material particles, the content of the Si element in the active material The amount is more than 50 wt%, the content of oxygen atoms (O) is less than 30 wt%, and D ₅₀ and D _max (“D ₅₀ ”and “D _max, respectively) obtained by measurement by a laser diffraction scattering type particle size distribution measurement method are obtained. relates "referred _{to), D 50} of less than 4.0 _{.mu.m, D max} of less than 25 [mu] m, in X-ray diffraction pattern measured by X-ray diffraction apparatus using CuKα1 line (XRD), 2θ = 28. The full width at half maximum of peak A appearing at 42°±1.25° is 0.25° or more, and when observing the cross section of the active material particles, silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide And, if any one or more of stainless steel is an active material characterized by being present inside the active material particles, the cycle characteristics can be enhanced, and the plateau region in the discharge profile can be reduced or eliminated. It has been found that the high rate characteristics can be improved.

Further, with respect to Reference Example 2 as well, the charge capacity described in Table 4 was evaluated.
When a sample such as Reference Example 2 in which Si, natural graphite and a conductivity improver were composited was evaluated, the initial charge capacity was less than 1200 mAh/g. It can be seen that this is a much smaller capacity than the charging capacity expected from the relationship between the Si amount that contributes to the storage and release of Li estimated from each weight% and the theoretical capacity of Si. It was
The reason for this is not clear, but one reason is that the Si occlusion potentials of natural graphite are different. When the ratio Si>natural graphite and the carbon amount is 5% by mass or more, the Li absorption in the natural graphite starts in parallel before the Li absorption in the relatively large amount of Si is completed. Then, the potential drops, and it is considered that the charge end condition is likely to be satisfied, and the charge capacity decreases.

Claims (14)

1. Silicon and a chemical formula M _x Si _y (where x and y satisfy 0.1≦x/y≦7.0, and M is one or two of metalloid elements and metal elements other than Si. And a compound represented by the formula (1) or more.
   The content of Si element in the active material is more than 50 wt%, the content of oxygen atom (O) is less than 30 wt%,
   Regarding D ₅₀ and D _max (referred to as “D ₅₀ ”and “D _max ”, respectively) obtained by measurement by a laser diffraction scattering particle size distribution measurement method, D ₅₀ is less than 4.0 μm and D _max is less than 25 μm. Yes,
   In the X-ray diffraction pattern measured by an X-ray diffraction device (XRD) using CuKα1 ray, the full width at half maximum of the peak A appearing at θ=28.42°±1.25° is 0.25° or more,
   An active material characterized in that one or more of silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide and stainless steel is present inside the active material particles.
2. The content of one kind or two or more kinds of silicon oxide, aluminum oxide, zirconium oxide, silicon carbide, silicon nitride, tungsten carbide, and stainless steel existing inside the active material particles is 0 wt% to the active material. The active material according to claim 1, which is large and less than 15 wt %.
3. In X-ray diffraction pattern measured by X-ray diffractometer (XRD) using CuKα1 line, the peak intensity of the peak B attributable to the compound represented by Formula M _x Si _y and I _B, the peak A when the peak intensity was _{I a,} the ratio of the _{I a} with respect to the _{I B (I a / I B} ) is less than 1, the active material according to claim 1 or 2.
4. The M is one or more elements selected from the group consisting of B, Ti, V, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ta and W. The active material according to any of the above.
5. The active material according to any one of claims 1 to 4, wherein the M is one or more elements selected from B, Ti, Mn and Fe.
6. The active material according to any one of claims 1 to 5, wherein the content of M in the active material is less than 38 wt%.
7. The active material according to any one of claims 1 to 6, wherein the content of the carbon (C) element is less than 5 wt%.
8. The active material according to any one of claims 1 to 7, which has a true density of more than 2.4 g/cm ³ .
9. The active material according to any one of claims 1 to 8, which has a specific surface area (SSA) of more than 2.0 m ² /g.
10. The active material according to any one of claims 1 to 9, which has a specific surface area (SSA) of less than 60.0 m ² /g.
11. The active material according to any one of claims 1 to 10, which is used as a negative electrode active material for a lithium secondary battery.
12. The active material according to any one of claims 1 to 10, which is used as a negative electrode active material for a solid lithium secondary battery.
13. A negative electrode containing the active material according to any one of claims 1 to 10.
14. A solid battery having a positive electrode, a negative electrode, and a solid electrolyte layer provided between the positive electrode and the negative electrode,
    A solid-state battery in which the negative electrode contains the active material according to any one of claims 1 to 10.
    

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