JP6076772B2 - Si-based alloy negative electrode material for power storage device and electrode using the same - Google Patents

Description

  The present invention relates to a Si-based alloy negative electrode material that is excellent in conductivity of an electricity storage device that involves movement of lithium ions during charge and discharge, such as a lithium ion secondary battery, a hybrid capacitor, and an all solid lithium ion secondary battery, and an electrode using the same Is.

  In recent years, with the spread of portable devices, development of high-performance secondary batteries centering on lithium-ion batteries has been actively conducted. Furthermore, lithium-ion secondary batteries and hybrid capacitors using the reaction mechanism of the lithium ion secondary battery as a negative electrode as active storage devices for automobiles and households have been actively developed. As a negative electrode material for these electricity storage devices, carbonaceous materials such as natural graphite, artificial graphite, and coke that can occlude and release lithium ions are used. However, since these carbonaceous materials insert lithium ions between the carbon surfaces, the theoretical capacity when used for the negative electrode is limited to 372 mAh / g, which is a new material that replaces carbonaceous materials for the purpose of increasing capacity. The search for is being actively conducted.

On the other hand, Si has attracted attention as a material that can replace carbonaceous materials. The reason is that Si can form a compound represented by Li ₂₂ Si ₅ and occlude a large amount of lithium, so that the capacity of the negative electrode can be greatly increased compared to the case of using a carbonaceous material. As a result, there is a possibility that the storage capacity of the lithium ion secondary battery, the hybrid capacitor, or the all solid state battery can be increased.

  However, when Si is used alone as a negative electrode material, the Si phase is pulverized by repetition of expansion when alloying with lithium during charging and contraction when dealloying with lithium during discharging. There is a problem that the life as an electricity storage device is extremely short because problems such as the Si phase dropping off from the electrode substrate during use or the electrical conductivity between the Si phases being lost can occur.

  In addition, Si has poor electrical conductivity compared to carbonaceous materials and metal-based materials, and the efficient movement of electrons associated with charge / discharge is limited. Therefore, as a negative electrode material, a material that supplements conductivity, such as a carbonaceous material. However, even in that case, initial charge / discharge characteristics and charge / discharge characteristics with high efficiency are also problems.

  As a method for solving the drawbacks of using such a Si phase as a negative electrode, a material in which at least part of a parent lithium phase such as Si is surrounded by an intermetallic compound of Si and a metal typified by a transition metal, The manufacturing method is proposed by Unexamined-Japanese-Patent No. 2001-297757 (patent document 1) and Unexamined-Japanese-Patent No. 10-31804 (patent document 2), for example.

  As another solution, an electrode in which a phase of an active material containing a Si phase is coated with a conductive material such as Cu that is not alloyed with lithium and a method for manufacturing the same are disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-228059 (Patent Document). 3) and Japanese Patent Application Laid-Open No. 2005-44672 (Patent Document 4).

JP 2001-297757 A JP 10-31804 A JP 2004-228059 A JP 2005-44672 A

However, in the above-described method of coating the active material phase with a conductive material such as Cu, it is necessary to coat the active material containing the Si phase with a method such as Cu plating before or after the step of forming the active material on the electrode. Further, there is a problem that it takes time and labor from the industrial point of view, such as control of the coating film thickness.
A material in which at least a part of a parent lithium phase such as Si is surrounded by an intermetallic compound is an industrially preferable process because a parent lithium phase and an intermetallic compound are formed during the solidification process after melting. , There is a problem that sufficient charge / discharge cycle characteristics cannot be obtained.

  Therefore, the problem to be solved by the present invention is to control the chemical composition, structure, structure size, etc. of the Si phase or intermetallic compound phase in the Si-based alloy at a high level, thereby enabling the lithium ion secondary battery or hybrid to be controlled. It is to propose a Si-based alloy negative electrode material that is excellent in charge / discharge characteristics with respect to an electricity storage device that moves lithium ions during charge / discharge, such as a capacitor and an all solid state battery.

  In order to solve the problems as described above, the inventors have intensively developed, and as a result, refinement of the structure, excellent ion conductivity and electron conductivity, control of the component system that enhances the stress relaxation effect, Si phase and The present inventors have found a Si-based alloy negative electrode material capable of obtaining excellent battery characteristics by controlling the crystallite size of the intermetallic compound phase.

Therefore, as means for solving the problems of the present invention,
According to the first aspect of the present invention, a negative electrode material made of a Si-based alloy for an electricity storage device accompanied by movement of lithium ions during charge / discharge, wherein the negative electrode material made of the Si-based alloy is composed of Si main phase made of Si, Si and Si has a compound phase composed of one or more elements other than the compound phase, Si of Si and Cu _X Cu _Y have the (X <Y) comprising a compound phase phase, the Si major phase Si A negative electrode material comprising a Si-based alloy for an electricity storage device, wherein the crystallite size is 30 nm or less and the crystallite size of a compound phase comprising Si and Cu is 40 nm or less.

  According to a second aspect of the present invention, in the negative electrode material comprising the Si-based alloy for an electricity storage device according to the first aspect, the Cu content in the alloy is 30 to 80 at. %, A negative electrode material made of a Si-based alloy for power storage devices.

  According to the third aspect of the present invention, the compound phase of the negative electrode material made of the Si-based alloy for an electricity storage device according to any one of the first to second aspects is added to Cr, Ti, V, Mn, Fe, Ni, Nb, Zn, Al, Co. , Zr, Pd, Bi, In, Sb, Sn, at least one element selected from the group consisting of 0.05 at. % To 5 at. %, A negative electrode material made of a Si-based alloy for power storage devices.

In the alloy of the present invention, Cu is effective for forming a fine eutectic structure with the Si phase, and in addition to controlling the chemical component of the Si-based alloy negative electrode material for the electricity storage device, the Si phase has a crystallite size of 30 nm or less, When the crystallite size of the compound phase of Si and Cu is 40 nm or less, it plays the role of mitigating stress caused by volume expansion at the time of occlusion / release of lithium to Si, and preventing electrical isolation due to Si pulverization. Excellent charge / discharge cycle characteristics can be obtained.

  Furthermore, by controlling the chemical component of the Si-based alloy negative electrode material for an electricity storage device, excellent charge / discharge cycle characteristics can be obtained. Cu content is 30 to 80 at. % Is particularly effective.

Also, Cr, Ti, V, Mn, Si and Cu samples of Si-based alloy negative electrode material for electricity storage devices,
One or more additive elements such as Fe, Ni, Nb, Pd, Zn, Al, Co, Zr, Pd, Bi, In, Sb, and Sn, and the total amount is 0.05 at. % To 5 at. By controlling the crystallite size, the compound phase surrounds the periphery of the fine Si phase, and mitigates the stress caused by the pulverization of Si and the volume expansion at the time of insertion and extraction of lithium into and from the Si. It plays a role in preventing collapse and electrical isolation of Si .

As described above, the present invention has an extremely excellent effect of providing a Si-based alloy negative electrode material for an electricity storage device having a high capacity and excellent cycle characteristics during repeated charge / discharge.

It is a figure which shows the phase diagram of the binary system of Si-Cu.

The present invention is described in detail below.
The charge / discharge capacity of a lithium ion secondary battery is determined by the amount of lithium transferred. There is a need for a material that can occlude and release large amounts of lithium. Therefore, although lithium metal is most effective when used as the negative electrode material, there are safety problems such as battery ignition caused by the formation of dendrites during charging and discharging. Therefore, studies on alloys that can occlude and release more lithium are currently underway, and among these alloys, Si is promising as a substance that can occlude and release lithium in large quantities. Therefore, Si is adopted as the main phase of the alloy phase.

  However, since Si causes volume expansion of about 400% when lithium is occluded / released, Si is peeled off or dropped from the electrode, or Si cannot maintain contact with the current collector. A sudden drop in capacity occurs. Also, if the Si phase size is too large, Si does not react with lithium up to the internal Si phase, but expands from the surface layer that easily reacts with lithium of Si, cracks occur, and then the internal unreacted Si phase expands. In addition, the Si is pulverized repeatedly such that cracks occur. As a result, Si peels off from the electrode, or Si cannot maintain contact with the current collector, resulting in a rapid decrease in charge / discharge capacity associated with the cycle.

FIG. 1 shows a phase diagram of the Si—Cu binary system. As shown in this figure, when the Si—Cu alloy melt is cooled, Si is precipitated as the primary crystal when the liquidus temperature is reached (eg, 1200 ° C. in the case of Si: 64 atomic% —Cu: 36 atomic%). Begin to. This primary crystal precipitates as a granular crystal if the cooling rate is high as in the liquid quenching method or the atomizing method, and when the temperature reaches the solidus temperature (802 ° C.), a eutectic reaction between Si and SiCu ₃ occurs and solidification is completed. To do. Thus, in the phase diagram on the Si rich side, it is a eutectic reaction between the Si phase and the SiCu ₃ phase, and the Si phase surrounds the SiCu ₃ phase.

On the other hand, as a combination of elements that alloy Si other than Cu, for example, Fe-Si, Ni-Si, Mn-Si, Co-Si, Cr-Si, Si-W, Mo-Si, Nb-Si, Si -Ti, Si-V, etc. are conceivable. However, it will both _{FeSi 2, NiSi 2, CoSi 2} , CrSi 2, WSi 2, MoSi 2, MnSi 2, NbSi 2, TiSi 2, VSi 2 and the Si-rich composition remains than metal elements .

The combination of Si and the transition element described above equilibrates with the Si phase as the only Cu-rich compound (SiCu ₃ ). When the resistance value of this Cu-rich compound (SiCu ₃ is examined, SiCu ₃ : 16.3 × 10 ⁻⁴ Ω · m, similarly, FeSi ₂ : 1000 × 10 ⁻⁴ Ω · m, NiSi ₂ : 50 × 10 It can be seen that ⁻⁴ Ω · m, CoSi ₂ : 18 × 10 ⁻⁴ Ω · m and SiCu ₃ have a lower resistance value than other silicide compounds.

There are two factors that have the lowest resistance value of SiCu ₃ , and the first is that SiCu ₃ has a metal-rich composition compared to other silicide compounds. Secondly, when focusing on the transition metal element of the raw material, Cu: 1.73 × 10 ⁻⁴ Ω · m, Fe: 10 × 10 ⁻⁴ Ω · m, Ni: 11.8 × 10 ⁻⁴ Ω · m , Co: 9.71 × 10 ⁻⁴ Ω · m, and simple substance Cu had a very low resistance value compared to other transition metal elements, and was a combination of Si and the transition metal having the lowest resistance value It is.

As can be seen from the above, the combination of Si and transition metal element having the lowest resistance value among the transition metal silicide compounds is Si and Cu. This is because Si and Cu, which are raw materials of transition metal silicide compounds, have extremely low resistance values compared to other single transition metal elements, and can never be obtained by a combination of transition metal elements of Si phase and Si. This is because a metal-rich compound phase with the element (SixCuy (x <y)), for example, a SiCu ₃ phase can be formed. Thus, since the resistance value is the lowest, SiCu ₃ is an Si-rich intermetallic compound (FeSi ₂ , NiSi ₂ , CoSi ₂ , CrSi ₂ , WSi ₂ , MoSi ₂ , MnSi ₂ , NbSi ₂ , TiSi ₂ , It can be seen that the electric conductivity is higher than that of VSi ₂ ).

From the above, it can be seen that only Cu in the combination of Si and the transition metal element precipitates the Si phase and the metal-rich compound (SiCu ₃ ) phase by eutectic reaction, and this SiCu ₃ is Si—Cu. It is also known from the binary phase diagram that in a Si-rich composition (for example, Si: 64 atom% -Cu: 36 atom%), the Si phase surrounds the SiCu ₃ phase. This allows the SiCu ₃ phase to precipitate around the Si phase, which has a much higher electrical conductivity than the combination of Si and other transition metal elements, so that the SiCu ₃ phase plays a role in supplementing the poor electrical conductivity of Si. He will do it. Furthermore, since the SiCu ₃ phase has a lower hardness than Si, it can also be a phase that relieves stress due to the large volume expansion and contraction of Si caused by the reaction between Si and lithium. Moreover, since there is little Si taken in a compound phase and when Cu is added, since more Si phases remain, it also has the characteristic that the capacity | capacitance per volume is large.

In addition to the eutectic structure of Si and Cu, by controlling the crystallite size, further improvements in lithium ion secondary battery characteristics are expected. If the Si phase size is too large, Si does not react with lithium up to the internal Si phase, but expands from the surface layer that reacts easily with lithium of Si, cracks occur, and then the internal unreacted Si phase expands, Moreover, the pulverization of Si which repeats that a crack arises is caused. As a result, Si peels off from the electrode, or Si cannot maintain contact with the current collector, resulting in a rapid decrease in charge / discharge capacity associated with the cycle. For this reason, it is necessary to make the microstructure to a size that does not cause differentiation, and it is preferable to control the crystallite size of the Si phase of the negative electrode material for a lithium ion secondary battery to 30 nm or less. More preferably, it is 25 nm or less. In particular, it is preferably 10 nm or less.

  Control of the crystallite size of the Si phase is possible by controlling the cooling rate at the time of solidification after dissolving the raw material powder in addition to the control of the components defined above. Examples of the production method include water atomization, single-roll quenching method, twin-roll quenching method, gas atomization method, disk atomization method, and centrifugal atomization, but are not limited thereto. Further, when the cooling effect is insufficient in the above process, mechanical milling or the like can be performed. Examples of the milling method include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibration mill, but are not limited thereto.

Further, the Si crystallite size of the Si main phase can be directly observed by a transmission electron microscope (TEM). Alternatively, it can be confirmed by using powder X-ray diffraction. A CuKα ray having a wavelength of 1.54059 mm is used as an X-ray source, and measurement is performed in a range of 2θ = 20 degrees to 80 degrees. In the obtained diffraction spectrum, a relatively broad diffraction peak is observed as the crystallite size decreases. From the full width at half maximum of the peak obtained by powder X-ray diffraction analysis, it can be determined using the Scherrer equation (D (Å) = (K × λ) / (β × cos θ) D: crystallite size, K : Scherrer's constant, λ: wavelength of X-ray tube used, β: broadening of diffraction line depending on crystallite size, θ: diffraction angle).

In the crystallite size, not only the Si main phase but also the crystallite size of the intermetallic compound phase becomes important. By reducing the crystallite size of the intermetallic compound of Si and Cu, it can be expected to increase the yield stress of the intermetallic compound and improve ductility and toughness. Generation | occurrence | production etc. can be suppressed and favorable ion conductivity and electronic conductivity can be ensured. Further, since the crystallite size of the intermetallic compound is reduced, it is possible to contact the Si phase with a larger specific surface area than to the larger particles, and to efficiently absorb and relax the stress due to the volume expansion and contraction of the Si phase. Furthermore, contact with the Si phase with a larger specific surface area is expected to increase the lithium ion conductivity and the electron conductivity path, and to perform a smoother charge / discharge reaction. Therefore, it is preferable to control the crystallite size to 40 nm or less. More preferably, it is 20 nm or less. In particular, it is preferably 10 nm or less.

The crystallite size of the intermetallic compound can also be directly observed with a transmission electron microscope (TEM). Alternatively, it can be confirmed by using powder X-ray diffraction. A CuKα ray having a wavelength of 1.54059 mm is used as an X-ray source, and measurement is performed in a range of 2θ = 20 degrees to 80 degrees. In the obtained diffraction spectrum, a relatively broad diffraction peak is observed as the crystallite size decreases. From the full width at half maximum of the peak obtained by powder X-ray diffraction analysis, it can be determined using the Scherrer equation (D (Å) = (K × λ) / (β × cos θ) D: crystallite size, K : Scherrer constant, λ: wavelength of X-ray tube used, β: broadening of diffraction line depending on crystallite size, θ: diffraction angle). The crystallite size of the intermetallic compound can be controlled by controlling the cooling rate during solidification after dissolving the raw material powder. Examples of the production method include water atomization, single-roll quenching method, twin-roll quenching method, gas atomization method, disk atomization method, and centrifugal atomization, but are not limited thereto. Further, when the cooling effect is insufficient in the above process, mechanical milling or the like can be performed. Examples of the milling method include a ball mill, a bead mill, a planetary ball mill, an attritor, and a vibration mill, but are not limited thereto.

Although Cu content is not specified, Cu is 30 to 80 at. % Is preferable. Cu is 30 to 80 at. %, The fine Si phase and the SiCu ₃ phase coexist finely and crystallize in a well-balanced manner, and a capacity design suitable as a Si-based load material for an electricity storage device becomes possible. Moreover, in the amount of Cu, a more preferable range is 31 to 60 at. %, More preferably 32 to 40 at. %.

Further, in the SixCuy alloy, which is an alloy of Si and Cu that forms an intermetallic compound, the composition of the SixCuy phase needs to be x <y. For example, FeSi ₂ does not become Fe rich. Since an alloy of Fe element and Si forms a Si-rich compound phase, the electrical conductivity is inferior, and the electrical conductivity between Si phases is prevented from being lowered due to the refinement of Si caused by repeated charge and discharge. Therefore, the composition of the SixCuy phase is set to x <y. Preferably, x = 1 and y = 3.

Moreover, regarding the negative electrode material for a lithium ion secondary battery according to claim 1, a fine Si phase can be obtained by forming a eutectic alloy with Si in addition to Cu, and a flexible intermetallic compound having better conductivity than Si. One or more additive elements such as Cr, Ti, V, Mn, Fe, Ni, Nb, Zn, Al, Co, Zr, Pd, Bi, In, Sb, and Sn can be further included. By controlling the crystallite size of the intermetallic compound by adding these, the compound phase surrounds the periphery of the fine Si phase, relieving the stress caused by volumetric expansion when Si is pulverized and lithium is absorbed into and released from Si. And it plays the role which prevents the collapse of an electrode and the electrical isolation of Si.

  In order to give the effect of reducing the effect of stress relaxation caused by the volume expansion / contraction of Si, Cr, Ti, V, Mn, Fe, Ni, Nb, Pd, Zn, Al, Co, Zr, Pd, Bi, The total content of In, Sb, and Sn is 0.05 at. % Or more is necessary, but 5 at. If it exceeds 50%, the amount of lithium inactive elements increases, which causes a decrease in charge / discharge capacity. For this reason, the total content of additive elements contained at least one of Cr, Ti, V, Mn, Fe, Ni, Nb, Pd, Zn, Al, Co, Zr, Pd, Bi, In, Sb, and Sn is 0. .05 at. % To 5 at. % Is desirable. More preferably, 0.1 at. % To 3 at. %.

By using the above-mentioned lithium ion secondary battery negative electrode material, the battery characteristics are excellent in high capacity, excellent cycle characteristics during repeated charge / discharge, and excellent charge / discharge efficiency in the initial cycle.
In addition, in the electrode using the lithium ion secondary battery negative electrode material, by including a polyimide-based binder having excellent binding properties, the adhesion with a current collector such as Cu is improved, and charging and discharging are performed while maintaining a high capacity. The effect of improving cycle characteristics is expected.

Hereinafter, the present invention will be specifically described with reference to examples.
Negative electrode material powders for lithium ion secondary batteries having the compositions shown in Tables 1 and 2 were prepared by water atomization, single-roll quenching method, twin-roll quenching method, gas atomization method, disk atomization method, centrifugal atomization, and the like described below. For the liquid quenching method, which is a single roll quenching method, a raw material having a predetermined composition is placed in a quartz tube having pores at the bottom, melted at a high frequency in an Ar atmosphere to form a molten metal, and a copper roll that rotates this molten metal. After the hot water was discharged on the surface, a quenching ribbon was prepared in which the crystallite size of the Si phase was refined by the quenching effect of the copper roll. The milled ribbon is then sealed in an Ar atmosphere together with zirconia balls, SUS304 balls, or SUJ2 balls in a zirconia, SUS304, or SUJ2 pot container and milled for the purpose of processing into particles. It was. As for milling, a ball mill, a bead mill, a planetary ball mill, an attritor, a vibration mill, and the like can be given.

  Regarding the gas atomization method, a raw material having a predetermined composition is placed in a quartz crucible having pores at the bottom, heated and melted in a high-frequency induction melting furnace in an Ar gas atmosphere, and then subjected to gas injection in an Ar gas atmosphere and a tapping hot water. Then, gas atomized fine powder was obtained by rapid solidification. In the disk atomization method, a raw material having a predetermined composition is placed in a quartz crucible having pores at the bottom, heated and melted in a high-frequency induction melting furnace in an Ar gas atmosphere, and then in an Ar gas atmosphere, 40000 to 60000 r. p. m. The hot water was discharged onto a rotating disk of No. 1 and rapidly solidified to obtain a disk atomized fine powder. Thereafter, the produced atomized fine powder is sealed in a zirconia or SUS304 / SUJ2 pot container together with zirconia balls, SUS304 balls, or SUJ2 balls in an Ar atmosphere, and powdered by mechanical milling to control the crystallite size. went. As for mechanical milling, a ball mill, a bead mill, a planetary ball mill, an attritor, a vibration mill, and the like can be given. In the processing by mechanical milling, the crystallite size of the atomized powder and the intermetallic compound using rapid solidification can be controlled by setting the milling time and the number of rotations.

Hereinafter, a specific method for preparing a negative electrode will be described.
In order to evaluate the electrode performance of the negative electrode as a single electrode, a so-called bipolar coin-type cell using lithium metal as a counter electrode was used. First, a negative electrode active material (Si-Cu, etc.) and a conductive material (acetylene black ) are weighed with an electronic balance, mixed with a dispersion (N-methylpyrrolidone), and then placed on a current collector (Cu, etc.). It was applied evenly. After coating, the solvent was evaporated by vacuum drying with a vacuum dryer, and then roll-pressed as necessary, and then punched into a shape suitable for the coin cell. Similarly, lithium for the counter electrode was punched into a shape suitable for the coin cell .

The electrolyte used for the lithium ion battery was a 3: 7 mixed solvent of ethylene carbonate and dimethyl carbonate, LiPF ₆ (lithium hexafluorophosphate) was used as the supporting electrolyte, and 1 mol was dissolved in the electrolyte. Since the electrolyte solution must be handled in an inert atmosphere with dew point control, the cells were all assembled in a glove box with an inert atmosphere. The separator was cut out in a shape suitable for a coin cell and then held in the electrolyte for several hours under reduced pressure in order to sufficiently permeate the electrolyte into the separator. Thereafter, the negative electrode punched out in the previous step, the separator, and the counter electrode lithium were combined in this order, and the inside of the battery was sufficiently filled with the electrolytic solution.

The measurement of charge capacity and discharge capacity was performed using the above-mentioned bipolar cell, at a temperature of 25 ° C., and charged at a current density of 0.50 mA / cm ² until the same potential (0 V) as that of the metal lithium electrode. At a current value (0.50 mA / cm ² ), discharging was performed up to 1.5 V, and this charging-discharging was defined as one cycle. In addition, as the cycle life, the above measurement was repeated.

  As shown in Tables 1 and 2, no. Nos. 1 to 30 are examples of the present invention. 31-51 shows a comparative example. These characteristics are determined by the initial discharge capacity and the discharge capacity maintenance rate after 50 cycles. The standard is that it is 1000 mAh / g or more and the cycle life is 60% or more [discharge capacity maintenance ratio (%) after 50 cycles].

No. of the example of the present invention. 1 to 11 include a Si main phase and a phase composed of Si and Cu, a crystallite size of Si satisfies a condition of 30 nm or less, and a crystallite size of a compound phase composed of Si and Cu satisfies a condition of 40 nm or less. In order to satisfy, the conditions of the present invention are satisfied. For example, no. 4 includes a Si main phase, Si, and Cu, the Si crystallite size is 5 nm, and satisfies the condition that the Si crystallite size is 30 nm or less. And the crystallite size of the compound phase which consists of Si and Cu is 33 nm, and satisfies the conditions of 40 nm or less. As described above, the conditions of the present invention were satisfied, the discharge capacity was 1174 mAh / g, the discharge capacity retention rate after 50 cycles was 80%, and both the charge / discharge capacity and the cycle life showed good characteristics.

  No. of the example of the present invention. 12 to 30 include a Si main phase and a phase composed of Si and Cu, a condition that the Si crystallite size of the Si main phase is 30 nm or less, and a condition that the crystallite size of the compound phase composed of Si and Cu is 40 nm or less. Therefore, the conditions of the present invention are satisfied. Further, the total content of additive elements contained in at least one of Cr, Ti, V, Mn, Fe, Ni, Nb, Zn, Al, Co, Zr, Pd, Bi, In, Sb, and Sn is 0.05 at. . % To 5 at. %.

For example, no. 25 includes a Si main phase and a phase composed of Si and Cu, and S of the Si main phase.
The crystallite size of i is 11 nm, the crystallite size of Si is 30 nm or less, the crystallite size of the compound phase composed of Si and Cu is 34 nm, and the crystallite size of the compound phase is 40 nm or less. In order to satisfy the conditions, the conditions of the present invention are satisfied. In addition, 0.01 at. % Cr, 0.01 at. % Ti, 0.12 at. % V, 0.03 at. % Mn, 0.02 at. % Fe, 0.01 at. % Ni, 0.01 at. % Nb, 0.14 at. % Zn, 0.16 at. % Al, 0.11 at. % Co, 0.08 at. % Bi, 0.02 at. % In, 0.01 at. % Sb, 0.03 at. % Sn is included. As described above, the conditions of the present invention were satisfied, the discharge capacity was 1137 mAh / g, the discharge capacity retention rate after 50 cycles was 74%, and both the charge / discharge capacity and the cycle life showed good characteristics.

  Comparative Example No. 31 to 33 and 40 to 42 include a Si main phase and a phase composed of Si and Cu, and satisfy the condition that the crystallite size of the compound phase composed of Si and Cu is 40 nm or less, but the condition that the crystallite size of Si is 30 nm or less Does not satisfy the conditions of the present invention. Comparative Example No. 34 to 36 and 43 to 45 include a Si main phase and a phase composed of Si and Cu and satisfy the condition that the crystallite size of Si is 30 nm or less, but the condition that the crystallite size of the compound phase composed of Si and Cu is 40 nm or less Does not satisfy the conditions of the present invention. Comparative Example No. 37 to 39 and 46 to 48 include a Si main phase and a phase composed of Si and Cu, do not satisfy the condition of the Si crystallite size of 30 nm or less, and satisfy the condition of the crystallite size of the compound phase composed of Si and Cu of 40 nm or less. This does not satisfy the conditions of the present invention.

  Comparative Example No. 49 satisfies the condition that the crystallite size of the compound phase composed of Si and Cu is 40 nm or less, but does not include the Si main phase and the phase composed of Si and Cu and does not satisfy the condition of the crystallite size of Si of 30 nm or less. Does not meet the invention conditions. Comparative Example No. 50 does not include the Si main phase and the phase composed of Si and Cu and satisfies the condition that the crystallite size of Si is 30 nm or less, but does not satisfy the condition of the crystallite size of 40 nm or less of the compound phase composed of Si and Cu. Does not meet the invention conditions. Comparative Example No. 51 does not include the Si main phase and the phase composed of Si and Cu, does not satisfy the condition of the Si crystallite size of 30 nm or less, and does not satisfy the condition of the crystallite size of the compound phase composed of Si and Cu of 40 nm or less. Does not meet the invention conditions.

As described above, refinement of the structure, control of components that enhance the excellent ion conductivity and electron conductivity, stress relaxation effect, control of the Si phase crystallite size, and further control of the crystallite size of the intermetallic compound phase By doing so, a smoother charge / discharge reaction can be performed, and charge / discharge cycle characteristics can be improved .

Claims (3)

A negative electrode material made of a Si-based alloy for an electricity storage device accompanied by movement of lithium ions during charge / discharge, wherein the negative electrode material made of the Si-based alloy is composed of a Si main phase made of Si and one or more elements other than Si and Si. comprising compound has a phase, wherein the compound phase has a _{Si X Cu Y (X <Y} ) comprising a compound phase phase of Si and Cu, the Si is at 30nm or less Si crystallite size of the main phase A negative electrode material comprising a Si-based alloy for an electricity storage device, wherein the crystallite size of the compound phase comprising Si and Cu is 40 nm or less. The negative electrode material which consists of Si type alloy for electrical storage devices described in Claim 1 WHEREIN: Cu content in the said alloy is 30-80 at. % Negative electrode material comprising a Si-based alloy for power storage devices. The compound phase of the negative electrode material comprising the Si-based alloy for an electricity storage device according to claim 1, Cr, Ti, V, Mn, Fe, Ni, Nb, Zn, Al, Co, Zr, Pd, Bi, Including at least one element selected from the group consisting of In, Sb, and Sn, the total content is 0.05 at. % To 5 at. % Negative electrode material comprising a Si-based alloy for power storage devices.