WO2020166599A1 - Active material - Google Patents

Abstract

Provided is an active material containing silicon and a compound represented by formula MxSiy (where, x and y satisfy 0.1≤x/y≤7.0, and M is at least one among a metal element and a metalloid element other than Si), wherein the content of M in the active material is greater than 5 wt% and less than 38 wt%, there are at least one peak PA at a wave number of 200 cm-1 to 420 cm-1, at least one peak PB at a wave number of 450 cm-1 to 490 cm-1, and at least one peak PC at a wave number of 500 cm-1 to 525 cm-1 in a Raman spectrum obtained as measured by a Raman spectroscopy, and the area ratio (IPB/IPC) of peak PB to peak PC is at least 0.5. A solid-state battery using the active material can have improved cycle characteristics, can exhibit a discharge profile in which plateau regions are reduced or eliminated, and can also have improved rate characteristics.

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

As disclosed in the above-mentioned Patent Document 3, a material in which microcrystals or amorphous materials composed of elements other than silicon are dispersed in silicon, or an alloy of elements other than silicon is dispersed in silicon. When the material described above is used as the negative electrode active material, only silicon in the negative electrode active material contributes to the insertion/desorption of lithium ions. If the occupying ratio of silicon decreases, the capacity decreases, but expansion and contraction of the negative electrode active material can be suppressed, and theoretically the cycle characteristics should be improved.
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.

Also, in terms of battery characteristics, charge/discharge characteristics in a high current range are also required. That is, it is important that the battery has a high rate characteristic, and improvement of the rate characteristic is required.

Therefore, the present invention can improve the cycle characteristics of the active material containing silicon, reduce or eliminate the plateau region in the discharge profile, and discharge at a high rate while maintaining the profile. It aims to provide a new active material that can.

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 kinds) and a content of the M in the active material is more than 5 wt% and less than 38 wt%, and Raman spectroscopic measurement in the Raman spectrum obtained by measuring by law, the wave number ^{200 cm} -1 ~ has at least one or more peaks _{P a} to 420 cm ^-1, at least one peak P at a wavenumber ^{450 cm} -1 ~ 490 cm ^-1 has a _B, and the wave number ^{500 cm} -1 peak PC to ~ 525 cm ^-1 appears at least one, the active material of the peak area ratio of the PB and PC _I PB _{/ I PC} is 0.5 or more suggest.

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. Moreover, the plateau region in the discharge profile can be reduced or eliminated.
Therefore, the active material proposed by the present invention not only exhibits the effect in a single use, but, for example, in combination with a carbon material (Graphite), a battery, particularly a solid battery, a solid secondary battery such as a solid lithium secondary battery among them. It can be suitably used as a negative electrode active material of a secondary battery.

It is the figure which showed the Raman spectrum which measured the sample obtained in Example 1 and the comparative example 3.

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>
The active material (hereinafter referred to as “main active material”) according to an example of the present embodiment includes silicon and a chemical formula MxSiy (where x and y satisfy 0.1≦x/y≦7.0, M Is one kind or two or more kinds of metalloid elements and metal elements other than Si.).

(Silicone (Si))
In the present active material, silicon also means Si capable of inserting and releasing lithium ions. That is, the present active material has a function as an active material by containing silicon.
Here, silicon mainly refers to pure silicon, but it may contain an element that forms a solid solution with silicon to form a solid solution. In this case, the 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, and more preferably 40 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. The proportion of silicon in the substance is preferably 50 wt% or more, and particularly preferably 60 wt% or more.

(Chemical formula M _x Si _y )
This active material has a chemical formula M _x Si _y (where x and y satisfy 0.1≦x/y≦7.0, and M is one of a metalloid element other than Si and a metal element). Or two or more kinds).
By containing the compound represented by M _x Si _y , the present active material 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, a metal element, or a combination of two or more 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.

(Other ingredients)
The active material 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.
In addition, as the “other component”, for example, not a constituent element of the compound represented by the chemical formula M _x Si _y , but a metal having one or more elements of a metalloid element and a metal element, an oxide It may be contained as a substance, a carbide and a nitride. Specifically, for example, one of H, Li, B, C, O, N, F, Na, Mg, Al, P, K, Cu, Ca, Ga, Ge, Ag, In, Sn and Au. Alternatively, compounds such as metals, oxides, carbides and nitrides having two or more elements can be mentioned. 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 Si-based negative electrode active material, the content of components other than silicon (Si) and compound A is preferably less than 15 at %, more than 0 at% or less than 12 at %, of which 1 at% or more. It is preferable that the amount is large or less than 10 at %, and more preferably more than 2 at% or less than 7 at %.

When the active material contains 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 preferably 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.

The active material may contain unavoidable 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 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 95 wt%, more preferably less than 88 wt%, further preferably less than 82 wt%, and further 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 makes it possible to 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%. On the other hand, the content of the 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 more than 5 wt% and less than 38 wt %. Above all, it is more preferably more than 8% by weight, particularly preferably more than 12% by weight, further preferably more than 15% by weight. On the other hand, the content of M in the active material is, for example, preferably less than 35 wt%, more preferably less than 32 wt%, and particularly preferably less than 29 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 preferably, for example, more than 0.05, and is 0.06 or more. It is preferably large, particularly preferably larger than 0.07, and particularly preferably larger than 0.10.
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 0.96, more preferably less than 0.86, and particularly less than 0.76. Is preferable, and particularly preferably less than 0.56.
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 active material has the above upper limit, the capacity can be maintained.

The content of each element other than oxygen is an element ratio determined 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). The amount of oxygen obtained by such a measuring method means that the amount of oxygen as SiOa (0<a≦2) and an oxygen compound with a metalloid element other than Si and a metal element M are included. ..

(Characteristics of Raman spectrum)
The active material has a Raman spectrum measured by Raman spectroscopy, and has at least one peak P _A derived from the compound represented by the chemical formula M _x Si _y at a wave number of 200 cm ⁻¹ to 420 cm ^−1. appear, the wave number ^{450 cm} -1 ~ 490 cm ^-1, tensile strain peak _{P B} derived from the silicon occurs appears at least one, and peaks _{P C} at a wavenumber ^{500 cm} -1 ~ 525 cm ^-1 appears at least one.
This active material is P _A, P _B, by the P _C appears, tensile strain occurs in the active material particles, so that the state interatomic distance between Si-Si is extended. As a result, distortion of the crystal structure at the time of initial Li insertion can be eliminated, and both durability and rate characteristics can be improved.

The present active material is also an active material having an area ratio of the peaks of P _B and P _C of I _PB /I _PC of 0.5 or more. The I _PB /I _PC is, for example, preferably 1.0 or more, and more preferably 1.5 or more. On the other hand, the I _PB /I _PC may be, for example, 10.0 or less, 8.0 or less, or 5.0 or less.
When the area ratio is within the above range, the interatomic distance between Si and Si can be further extended, and the effect of the present invention can be made remarkable. At this time, when a plurality of peaks appear, each peak area is the total area of the plurality of peaks.
Note that peaks due to Si defects may appear at wave numbers of 200 cm ⁻¹ to 420 cm ^−1, and whether or not silicide exists can be examined by an electron diffraction method using a transmission electron microscope (TEM). ..
The above P _B indicates that the tensile strain in the active material particles is relatively large, and represents the state in which the interatomic distance between Si and Si is extended. On the other hand, the P _C indicates that tensile strain in the active material particles is relatively small, indicating a state in which shrinks interatomic distance between Si-Si.

In the active material, the full width at half maximum of the peak P _B is preferably 40 cm ⁻¹ or more, more preferably 45 cm ⁻¹ or more, and even more preferably 50 cm ⁻¹ or more, while 90 cm ⁻¹ or less, Among them, 80 cm ^-1 or less is more preferable.

In order to produce the present active material having the above-mentioned characteristics in the Raman spectrum, for example, the above M is 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.

In the present invention, the “peak” in the Raman spectrum obtained by measurement by Raman spectroscopy means a spectrum having a peak top in the Raman spectrum and a full width at half maximum of 5.0 cm ⁻¹ or more. Therefore, a spectrum having a full width at half maximum of 4.9 cm ⁻¹ or less is regarded as noise.
The full width at half maximum and the peak area can be obtained by setting a baseline for the obtained Raman spectrum and separating the peaks.

_{(D 50)}
The laser diffraction/scattering particle size distribution measuring method is a measuring method in which agglomerated powder particles are regarded as one particle (aggregated particle) and the particle size is calculated. The D ₅₀ according to this measuring method means a diameter corresponding to 50% cumulative from the smallest cumulative percentage of the volume-measured particle size measured values in the volume-based particle size distribution chart.

The D ₅₀ of the active material is preferably less than 4.0 μm, more preferably less than 3.8 μm, particularly preferably less than 3.4 μm, and further preferably less than 3.2 μm. It is more preferably less than 3.0 μm, and further preferably less than 2.8 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.
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 of the active material is preferably D _max less than 25μm by and volume particle size distribution measurement obtained by the measurement by a laser diffraction scattering particle size distribution measuring method, 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 ₅₀ according to this measurement method means a diameter corresponding to 100% cumulative from the smallest cumulative percentage of volume-converted particle size measurement values 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 active material is an aggregate of particles, and can be in the form of powder, lump, or the like. 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, according to the gas atomizing method, it has been confirmed that the particles have a spherical shape, and when they are pulverized by a jet mill or the like, the particles are broken along the grain boundaries and thus have 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 present active material is, for example, preferably less than 140 m ² /g, more preferably less than 60 m ² /g, and particularly preferably less than 30 m ² /g. It is preferably less than 10 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>
The active material is obtained by mixing silicon or a silicon (Si)-containing substance, M or an M-containing substance, and optionally other raw materials, heating and melting to alloy them, and crushing or crushing as necessary. It is preferable to carry out the above-mentioned process and, if necessary, classify it, and then carry out a reforming treatment by using a reforming apparatus 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.

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.

As a method of melting a metal in the present invention, it is preferable not to perform the arc melting step as described in JP 2010-135336A. 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.
Further, when the treatment is carried out by a planetary ball mill, a vibrating ball mill, an attritor, a ball mill, etc., particularly in an active material having a small amount of silicide as in the present application, stronger agglomeration occurs, so that D ₅₀ and D _max are targeted values. Will be bigger than 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, which is unsuitable as a production method for obtaining the object of the present invention.

As the above-mentioned reforming treatment, for example, a treatment device having rotary blades in a reaction tank is used, and the peripheral speed of the rotating blades is set to, for example, 3.0 m/s or more and 20 m/s or less and charged into the reaction tank. As a medium to be used, 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 D _{50 of the} active material.
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, it is preferable that the peripheral speed of the rotary blade is, for example, 4.0 m/s or more or 17 m/s or less, particularly 4.5 m/s or more or 15 m/s or less, and among them 5.0 m/s or more, or It is preferably 12 m/s or less. Even when the size of the stirring blade is changed, the same effect can be obtained by adjusting the peripheral speeds.

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 5 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.

The above-mentioned reforming treatment is preferably carried out in an inert atmosphere such as a nitrogen atmosphere or an argon gas atmosphere, and further, it is preferable to carry out gradual oxidation when collecting the treated product. For example, the inside of the reaction tank at the time of carrying out the reforming treatment is set to the above-mentioned inert atmosphere, and when the treated product is recovered from the reaction tank after the reforming treatment, air or the like is gradually introduced into the reaction tank to gradually remove the treated product. Gradual oxidation, that is, gradual oxidation is preferably performed.

<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 is, for example, a main active material, a binder if necessary, a conductive material if necessary, a solid electrolyte if necessary, and an active material different from the main active material if necessary. It may contain graphite. 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.
In the examples of solid-state batteries to be described later, a pellet obtained by press-molding a dry powder composed of an active material, a conductive material and an electrolyte is used as a negative electrode, and the negative electrode does not include a binder and a current collector.

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.

(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.

(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.

(Graphite)
By adding graphite to the main active material as an active material different from the main active material, it is possible to obtain both high capacity due to silicon and good cycle characteristics due to graphite.
In particular, since the active material does not have a plateau region in the discharge profile as described above, when used in combination with a carbon material (Graphite), it is possible to prevent a step from being formed in the discharge profile, and carbon such as graphite can be prevented. It is preferable because it can be easily controlled when used as a negative electrode active material in combination with a material (Graphite).

(Compound composition)
In the present negative electrode, the content of the binder is preferably 1 to 25 parts by mass, and more preferably 2 parts by mass or more or 20 parts by mass or less based on 100 parts by mass of the active material.
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, a carbon material (an active material different from the present active material (particulate), a binder, a conductive material, an electrolyte if necessary, a solvent, and optionally the present active material ( Graphite) and other materials are mixed to prepare a negative electrode mixture, and the negative electrode mixture is applied to the surface of a current collector made of Cu or the like and dried to form a negative electrode mixture. It can be formed by pressing.
Further, as the present negative electrode for an all-solid-state battery, it is preferable to press-mold a dry powder containing an active material, a conductive material, and an electrolyte, and use the obtained pellet as the negative electrode. At this time, the negative electrode preferably does not include a binder and a current collector.

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 The non-aqueous electrolyte battery may be a primary battery or a secondary battery, but is preferably a secondary battery.

(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, ethylmethyl 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, the same one as the above-mentioned non-aqueous electrolyte battery can be used.

<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>
Silicon (Si) and nickel (Ni) ingots are mixed, heated and melted, and the melt heated to 1700° C. is rapidly cooled using a liquid rapid solidification device (single roll type) to obtain a quenched ribbon alloy. It was 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 ZrO ₂ beads and 50 g of the alloy powder were placed in a container having a volume of 2 L, and the mixture was treated under an argon atmosphere 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: 63 wt% and Ni: 31 wt %.

<Example 2>
Silicon (Si), titanium (Ti), and nickel (Ni) ingots 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) and then rapidly cooled. A 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 "Shimoloyer", equipped with a rotary blade in the reaction device). That is, ₂ kg of ZrO ₂ beads and 50 g of alloy powder were placed in a container having a capacity of 2 L, and treatment was performed at 1500 rpm for 3 hours in an argon atmosphere. 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%, Ti: 20 wt%, Ni: 7 wt%.

<Example 3>
Silicon (Si), titanium (Ti) and cobalt (Co) ingots are heated and melted, and the molten liquid heated to 1700° C. is rapidly cooled using a liquid rapid solidification device (single roll type), and 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 ZrO ₂ beads and 50 g of alloy powder were placed in a container having a volume of 2 L, and treatment was carried out at 1500 rpm for 3 hours in an argon atmosphere. 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 carried out, it was Si: 71 wt %, Ti: 20 wt %, Co: 7 wt %.

<Example 4>
A silicon (Si) and titanium (Ti) ingot was heated and melted, and the melt heated to 1700° C. was rapidly cooled using a liquid rapid solidification device (single roll type) to obtain a quenched ribbon alloy. Other than that, coarse pulverization and grain size adjustment were performed in the same manner as in Example 1 to obtain an alloy powder.

The obtained alloy powder was subjected to a reforming treatment in the same manner as in Example 1 by using a nanoparticle surface reforming device (product name "Shimoloyer", equipped with a rotary blade in the reaction device). The treated alloy powder was crushed or crushed using a wet crusher to adjust the particle size, and then an alloy powder (sample) as a negative electrode active material was obtained.
When chemical analysis of the obtained alloy powder (sample) was performed, Si: 71 wt% and Ti: 22 wt% were found.

<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 crushed for 2 hours in a planetary ball mill using a silicon nitride ball in an argon gas atmosphere to obtain an alloy powder 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 . .. Then, a mixture obtained by mixing 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 electrode material of alloy powder.

<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).

_{(D 50)}
Into a 50 ml beaker, 0.15 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 (Nippon Seiki Seisakusho Co., Ltd. Homogenizer US-150E, 20φ tip was used), the dial level was adjusted so that AMPLITUDE was 80%, and ultrasonic waves were applied for 5 minutes to disperse the sample in the liquid to obtain a dispersion liquid. ..
Next, the dispersion was put into a water-soluble solvent (ion-exchanged water containing 20 vol% of ethanol) using an automatic sample feeder for a laser diffraction particle size distribution measuring device (“Microtorac SDC” manufactured by Microtrac Bell Co., Ltd.). .. Flow rate in 70 mL / sec, and measuring the particle size distribution using a Microtrac Bell Co. laser diffraction particle size distribution measuring instrument "MT3300II", from the chart of the resulting volume-based particle size distribution was determined D _50. 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.

(Raman spectroscopy measurement)
Raman spectra of the alloy powders (samples) obtained in the examples and comparative examples were obtained by Raman spectroscopy under the following conditions using a Raman spectroscope.
When Raman measurement is performed on a powder sample, the smaller the unevenness of the sample surface and the higher the density of particles, the more particles are present in the space in which the excitation light and the Raman light are focused, and the lower laser excitation power is used. High Raman light intensity can be obtained.
Using a mini hydraulic press manufactured by Specac and a pellet forming die having a diameter of 7 mm, the sample powder was pressed into 1 ton to form a pellet.

=Raman spectroscopy measurement conditions=
Device: Raman touch (Nanophoton)
Excitation wavelength: 532nm
Laser current: 100%
Excitation power: 10.0mW
Excitation power density: 1.85kW/cm ²
Grating: 600gr/mm
Slit width: 50 μm
Exposure time: 60 seconds Objective lens: ×20/NA0.45
Measurement area: 420μm×65μm
Measurement mode: XY Averaging(AreaFlash)

In the wave number calibration, Si, which is a standard sample contained in the apparatus body, was measured and calibrated so that the main peak appeared at 520.0 cm ^-1 .
The Raman spectrum was obtained by averaging the spectra measured at four points. If the S/N ratio of the spectrum is poor and it is difficult to determine whether it is a sample-derived peak or noise, the number of measurement points may be increased to average the spectrum. In addition, the spectrum may include peaks due to cosmic rays. It is possible to determine whether or not it is a cosmic ray peak, and it can be determined that the peak is a cosmic ray if the peak does not appear in the wave number with good reproducibility when the measurement is repeated.

In Comparative Example 1, the excitation power was set to 1.0 mW, the exposure time was set to 1 second, and the other conditions were set to the above measurement conditions.
For Comparative Example 2, the exposure time was set to 10 seconds, and the other conditions were measured as described above.
For Comparative Example 3, the exposure time was set to 5 seconds, and the other conditions were measured as above. In Comparative Examples 1 to 3, the peak intensity was too strong to exceed the detection limit when measured with the same excitation power and exposure time as those in Examples, so the measurement was performed under the conditions not exceeding.

=Peak analysis=
The peaks in the Raman spectrum were fitted by "Peak Fitting", which is a peak fitting program of Nanophoton. The parameters of peak wavenumber, full width at half maximum, and area were obtained by peak fitting. The baseline was set to draw a tangent line to the spectrum with a first-order straight line in the range of 200 to 610 cm ⁻¹ .
Function used for ^fitting, the peak of 500 cm -1 ~ 525 cm ^-1 is used Lorentzian ^peak of 450 cm -1 ~ 490 cm ^-1 was used a Gaussian function. For the peak at 200 to 420 cm ^−1, a Lorentz function or a Gaussian function with which the fitting converges was used.

(Calculation of peak area ratio)
The peak peak top exists at a wavenumber ^{450cm -1} ~ 490cm -1 _{P B,} the peak peak top is present in the range of wave number ^{500 cm} -1 ~ 525 cm ^-1 was _{P C.} The area ratio of the peaks of P _B and P _C was _defined as I _PB /I _PC .

A spectrum having a peak top in the Raman spectrum and having a full width at half maximum of 5.0 cm ⁻¹ or more was determined as a “peak”. Therefore, a spectrum having a full width at half maximum of 4.9 cm ⁻¹ or less was regarded as noise.

<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-methyl-2. -Dispersed in pyrrolidone 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 s or 5.0 mV change was satisfied. With such a setting, it is recorded every 300 s in the region where the voltage fluctuation is small and is recorded every 5.0 mV change in the region 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.

(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 addition, in Table 2, it is shown as an index when the numerical value of Comparative Example 3 is 100.
At this time, if the potential changes continuously from the beginning of discharge to the end 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 or the plateau can be reduced. Will be shown.

(High-rate characteristic evaluation)
The discharge rate characteristics were evaluated using the electrochemically evaluated cell TOMCEL (registered trademark) that 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 s or 5.0 mV change was satisfied. With such a setting, it is recorded every 300 s in the region where the voltage fluctuation is small and is recorded every 5.0 mV change in the region 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 addition, in Table 2, it is shown as an index when the numerical value of Comparative Example 3 is 100.

(Cycle characteristic evaluation)
A cell for electrochemical evaluation, TOMCEL (registered trademark), 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.
As described above, using the electrochemical evaluation cell TOMCEL (registered trademark) after the initial activation, a charge/discharge test was performed by the method described below, and the 45° C. cycle characteristics were evaluated. 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 is set to 0.01V-1.0V, charging is performed at 0.1C constant current/constant potential and discharging is performed at 0.1C constant current for 1 cycle, and then 1C is charged/discharged 98 times. After that, one charge/discharge cycle was performed at 0.1C. 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 100th cycle by the discharge capacity at the second cycle was determined as the 45°C cycle characteristic value.
In addition, in Table 2, it is shown as an index when the numerical value of Comparative Example 3 is 100.

<Evaluation of battery characteristics>
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. A foil of In and Li was used as the counter electrode, and a powder represented by the composition formula: Li _5.4 PS _4.4 Cl _0.8 Br _0.8 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 a foil of In and Li, attach the lower electrode again, and screw between the upper electrode and the lower electrode at a torque pressure of 6 N·m at four locations, and 1. 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.

<Battery performance evaluation test>
(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 s or 1 mV change was satisfied. With such a setting, recording is performed every 10 s 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 at the time of linear approximation becomes high and there is no plateau region, or there is a plateau region. Is small.

(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 inventor 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 a semi-metal element other than Si and a metal element), and an active material containing:
The content of M in the active material is more than 5 wt% and less than 38 wt %,
In the Raman spectrum obtained by the Raman spectroscopic measurement method, at least one peak P _A derived from the compound represented by the chemical formula MxSiy is present at a wave number of 200 cm ⁻¹ to 420 cm ⁻¹ , and a wave number of 450 cm has at least one or more peaks _{P B} to ^-1 ~ 490 cm ^-1, and the wave number ^{500 cm} -1 ~ 525 cm ^-1 of at least one manifestation peak _{P C} is the area of the peak of the _{P B} and _{P C} It has been found that an active material having a ratio of I _PB /I _PC of 0.5 or more can enhance the cycle characteristics, reduce or eliminate the plateau region in the discharge profile, and further improve the high rate characteristics. It was

Claims (7)

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 M in the active material is more than 5 wt% and less than 38 wt %,
   In the Raman spectrum obtained by measuring the Raman spectroscopy, has at least one or more peaks _{P A} at a wavenumber ^{200 cm} -1 ~ 420 cm ^-1, at least one at a wavenumber of ^{450cm -1} ~ 490cm -1 of has a peak _{P B,} and the wave number ^{500 cm} -1 ~ 525 cm ^-1 appeared one peak _{P C} is at least, the ratio of peak areas between the _{P B} and the _{P C (I PB / I PC} ) is An active material of 0.5 or more.
2. The active material according to claim 1, wherein the full width at half maximum of the peak P _B is 40 cm ⁻¹ or more.
3. 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. 3. The listed active material.
4. The active material according to any one of claims 1 to 3, which has a specific surface area (SSA) of 3.0 m ² /g or more.
5. The active material according to any one of claims 1 to 4, which is used as a negative electrode active material for a lithium secondary battery.
6. A negative electrode containing the active material according to any one of claims 1 to 5.
7. A solid battery comprising a sulfide solid electrolyte and the active material according to claim 1.
   
   

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