JP2019164961A - Alloy, negative electrode active material, negative electrode, and non-aqueous electrolyte storage element - Google Patents

Abstract

To provide a negative electrode active material capable of improving a capacity retention rate in a charge and discharge cycle of a nonaqueous electrolyte storage element, and a negative electrode and a nonaqueous electrolyte storage element including the same.SOLUTION: The negative electrode active material, containing a transition metal element and bismuth, is a negative electrode active material containing an alloy having a crystal structure attributable to a space group P63/mmc, Fm-3m, or Pnma. The negative electrode contains the same. The nonaqueous electrolyte storage element includes the same.SELECTED DRAWING: None

Description

  The present invention relates to an alloy, a negative electrode active material, a negative electrode, and a nonaqueous electrolyte storage element.

  Nonaqueous electrolyte secondary batteries typified by lithium ion secondary batteries are widely used in electronic devices such as personal computers and communication terminals, automobiles and the like because of their high energy density. The nonaqueous electrolyte secondary battery generally has a pair of electrodes electrically isolated by a separator and a nonaqueous electrolyte interposed between the electrodes, and transfers ions between the electrodes. It is comprised so that it may charge / discharge. In addition, capacitors such as lithium ion capacitors and electric double layer capacitors are widely used as nonaqueous electrolyte storage elements other than nonaqueous electrolyte secondary batteries. In the future, non-aqueous electrolyte storage elements will be required to have higher capacities for applications such as electric vehicles (EV) power supplies.

  Conventionally, as the active material contained in the negative electrode of the nonaqueous electrolyte storage element, a carbon material such as graphite has been used, and an active material that exhibits a high capacity for increasing the capacity of the nonaqueous electrolyte storage element is used. Development is underway. For example, bismuth is known as a high-capacity negative electrode active material capable of inserting and desorbing 3 moles of lithium from bismuth. Moreover, in the prior art, it is disclosed that charge / discharge measurement was implemented using bismuth as a negative electrode active material (refer nonpatent literature 1).

C. Park et al, Journal of Power Sources, 2009, 186, 206-210

  However, in the above prior art, the negative electrode active material must be made into nanoparticles in order to obtain good cycle performance, and there is room for improvement. In the future, non-aqueous electrolyte electricity storage elements using bismuth as a negative electrode active material are required to have higher capacity retention ratios in charge / discharge cycles.

  The present invention has been made based on the circumstances as described above, and the object thereof is to have an alloy, a negative electrode active material, and this negative electrode active material that can improve the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element. It is to provide a negative electrode and a non-aqueous electrolyte electricity storage device.

  The negative electrode active material according to one embodiment of the present invention made to solve the above problems includes a transition metal element and bismuth, and has a crystal structure that can be assigned to the space group P63 / mmc, Fm-3m, or Pnma. It is a negative electrode active material containing the alloy which has.

A negative electrode active material according to another embodiment of the present invention is an alloy that includes a transition metal element and bismuth and is crystalline, and is 0.7 to 0.9 V (vs) derived from the alloy during discharge. and electricity a of .Li / Li ^+), the ratio of electricity B of 0.0~2.0V derived from the alloy at the time of discharge ^{(vs.Li/Li +) (a / B} ) is less than 60% It is a negative electrode active material containing the alloy which is.

  A negative electrode according to another embodiment of the present invention contains the negative electrode active material.

  A nonaqueous electrolyte storage element according to another embodiment of the present invention includes the negative electrode.

  The alloy according to another embodiment of the present invention includes nickel and bismuth and can be assigned to space group P63 / mmc or space group Fm-3m, and the content ratio of the nickel and the bismuth is atomic ratio. It is an alloy that is 2: 1 to 9: 1.

  ADVANTAGE OF THE INVENTION According to this invention, it uses for the negative electrode active material which can improve the capacity | capacitance maintenance factor in the charging / discharging cycle of a nonaqueous electrolyte electrical storage element, the negative electrode and nonaqueous electrolyte electrical storage element which have this negative electrode active material, and the negative electrode active material of a nonaqueous electrolyte In this case, it is possible to provide an alloy capable of improving the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element.

1 is an external perspective view showing a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. It is the schematic which shows the electrical storage apparatus comprised by gathering together the nonaqueous electrolyte secondary battery which concerns on one Embodiment of this invention. It is an X-ray diffraction pattern of the alloys of Examples 2-3 and 5-9. 2 is an X-ray diffraction pattern before and after a charge / discharge cycle of the alloy of Example 1. FIG. It is an X-ray diffraction pattern before and after the charge / discharge cycle of the alloy of Example 9.

  A negative electrode active material according to one embodiment of the present invention is a negative electrode active material containing an alloy including a transition metal element and bismuth and having a crystal structure that can be assigned to the space group P63 / mmc, Fm-3m, or Pnma. is there. Since the negative electrode active material contains a transition metal element and bismuth and contains an alloy having the above crystal structure, the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element can be improved. The reason for this is not clear, but the alloy containing the negative electrode active material contains a transition metal element and bismuth, and has a crystal structure that can be assigned to the space group P63 / mmc, Fm-3m, or Pnma. It is presumed that the lithium alloying / dealloying reaction proceeds reversibly without using nanoparticles.

  As the transition metal element, elements of Group 3 to Group 11 of the periodic table excluding rhodium, palladium, silver, iridium, platinum and gold are preferable. When the transition metal element is the above element, the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element can be further improved. Although this reason is not certain, it is presumed that these transition metal elements are metal elements that are difficult to alloy with lithium and do not operate as a negative electrode. That is, when the above alloy contains a transition metal element, the load on the crystal structure is reduced when lithium atoms are desorbed and inserted during charge / discharge, and the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element is reduced. It is estimated that the decrease in Among these transition metal elements, chromium, nickel, and copper are incombustible, and an alloy with bismuth is also incombustible, so that safety can be improved.

  The transition metal element is preferably nickel. When the transition metal element is nickel, the capacity retention ratio in the charge / discharge cycle of the nonaqueous electrolyte storage element can be further improved, and the safety of the alloy with bismuth becomes nonflammable.

  The content ratio of the nickel and bismuth in the alloy is preferably 1: 1 to 9: 1 by atomic ratio. The capacity | capacitance maintenance factor in the charging / discharging cycle of a nonaqueous electrolyte electrical storage element can be improved more because the content rate of the said nickel of the said alloy and the said bismuth is the said range.

The crystal structure can be assigned to the space group P63 / mmc, and the lattice constant is preferably 3.9． ≦ a ≦ 4.3Å and 5.1Å ≦ c ≦ 5.6Å. When the crystal structure can be assigned to the space group P63 / mmc, the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element can be further improved by the lattice constant being in the above range. Note that 1Å = 0.1 nm = 10 ⁻¹⁰ m.

  The crystal structure can be assigned to the space group Fm-3m, and the lattice constant is preferably 3.4Å ≦ a ≦ 3.8Å. When the above-mentioned crystal structure can be assigned to the space group Fm-3m, the capacity constant in the charge / discharge cycle of the nonaqueous electrolyte storage element can be further improved because the lattice constant is in the above range.

A negative electrode active material according to another embodiment of the present invention is an alloy that includes a transition metal element and bismuth and is crystalline, and is 0.7 to 0.9 V (vs) derived from the alloy during discharge. and electricity a of .Li / Li ^+), the ratio of electricity B of 0.0~2.0V derived from the alloy at the time of discharge ^{(vs.Li/Li +) (a / B} ) is less than 60% It is a negative electrode active material containing the alloy which is. When the ratio (A / B) of the amount of electricity A and the amount of electricity B in the alloy is in the above range, the capacity retention rate and the charge / discharge efficiency in the charge / discharge cycle of the nonaqueous electrolyte storage element can be improved. The reason for this is not clear, but in the above alloy, the transition metal and bismuth are in solid solution, and the transition metal is disposed at a position that can affect the electronic state of bismuth, such as the first proximity or the second proximity of bismuth. Therefore, the electronic state of bismuth in the alloy becomes appropriate, so that the capacity maintenance rate in the charge / discharge cycle is further improved, and the charge / discharge efficiency is estimated to be improved.

  The negative electrode according to another embodiment of the present invention is a negative electrode containing the negative electrode active material. Therefore, the said negative electrode can improve the capacity | capacitance maintenance factor in the charging / discharging cycle of a nonaqueous electrolyte electrical storage element.

  A nonaqueous electrolyte storage element according to another embodiment of the present invention includes the negative electrode. Therefore, the nonaqueous electrolyte electricity storage element has an excellent capacity retention rate in the charge / discharge cycle.

  The alloy according to another embodiment of the present invention includes nickel and bismuth and can be assigned to space group P63 / mmc or space group Fm-3m, and the content ratio of the nickel and the bismuth is atomic ratio. It is an alloy that is 2: 1 to 9: 1. When the alloy is used as the negative electrode active material of the nonaqueous electrolyte storage element, the capacity retention rate and charge / discharge efficiency in the charge / discharge cycle of the nonaqueous electrolyte storage element can be improved.

  Hereinafter, an alloy, a negative electrode active material, a negative electrode, and a nonaqueous electrolyte storage element according to an embodiment of the present invention will be described in detail.

<Negative electrode active material>
A negative electrode active material according to one embodiment of the present invention includes a transition metal element and bismuth, and a negative electrode active material containing an alloy having a crystal structure that can be assigned to the space group P63 / mmc, Fm-3m, or Pnma ( Hereinafter, it is also referred to as “negative electrode active material”. Since the said negative electrode active material contains the said alloy, the capacity | capacitance maintenance factor in the charging / discharging cycle of a nonaqueous electrolyte electrical storage element can be improved.

(Transition metal element)
As the transition metal element, elements of Group 3 to Group 11 of the periodic table excluding rhodium, palladium, silver, iridium, platinum and gold are preferable. By using these elements as transition metal elements contained in the alloy contained in the negative electrode active material, the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element can be increased. These transition metal elements are not easily alloyed with lithium and do not operate as a negative electrode, so that the load on the crystal structure is reduced when lithium atoms are desorbed and inserted due to charge and discharge, and the nonaqueous electrolyte It is presumed that a decrease in capacity retention rate in the charge / discharge cycle of the storage element can be suppressed.

  Among the above transition metal elements, nickel (Ni), copper (Cu), titanium (Ti), chromium (Cr), zirconium (Zr) from the viewpoint of increasing the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element. Iron (Fe) and molybdenum (Mo) are more preferable. Further, nickel (Ni), copper (Cu), and chromium (Cr) are more preferable from the viewpoint of improving the capacity retention ratio and suppressing bismuth flammability by alloying to improve safety. (Ni) is particularly preferred.

In the above alloy, an electric quantity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge and 0.0 to 2.0 V (vs. The upper limit of the ratio (A / B) of Li / Li ⁺ ) to the amount of electricity B is preferably 70%, more preferably 60%, and sometimes 50%. Electric quantity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge, and 0.0 to 2.0 V (vs. Li ^/ Li from the alloy at the time of discharge) ⁺ ) The ratio (A / B) of the amount of electricity to B (A / B) is in the above range, whereby the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element can be further improved, and the charge / discharge efficiency in the charge / discharge cycle is excellent. Can be. Although it does not specifically limit as a minimum of the said ratio (A / B), 10% is preferable and 20% may be preferable.
Here, the electric quantity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) and the electric quantity B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge. Is a value measured by the following method. First, a nonaqueous electrolyte storage element including a working electrode (negative electrode) containing the above alloy and a metal Li counter electrode is assembled, and the current is 50 mA / g up to 0.0 V (vs. Li / Li ⁺ ) with respect to the mass of the alloy. Charge and perform constant potential charging for 3 hours. After a 10-minute pause, the alloy was discharged to 2.0 V (vs. Li / Li ⁺ ) at a current of 50 mA / g with respect to the mass of the alloy, and 0.0 to 2.0 V (vs. Li / Li ⁺ ). The amount of electricity B is calculated from the discharge capacity in the range, and the amount of electricity A is calculated from the discharge capacity in the range of 0.7 to 0.9 V (vs. Li / Li ⁺ ). In addition, when the working electrode contains a substance that expresses a capacity in the range of 0.0 to 2.0 V (vs. Li / Li ⁺ ) in addition to the alloy, by reducing the discharge capacity due to the substance, The amount of electricity A and the amount of electricity B are calculated. In the present specification, the alloy acts as a negative electrode active material, and “recharges” a reduction reaction in which lithium ions and the like are occluded in the negative electrode active material, and an oxidation reaction in which lithium ions and the like are released from the negative electrode active material. This is called “discharge”.

Electric quantity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge, and 0.0 to 2.0 V (vs. Li ^/ Li from the alloy at the time of discharge) ^The reason why the capacity retention rate and the charge / discharge efficiency in the charge / discharge cycle of the nonaqueous electrolyte storage element can be improved by the ratio (A / B) of ⁺ ) to the electric quantity B being in the above range is not clear, It seems like. Since the reaction potential of the alloy is considered to have a correlation with the electronic state of bismuth contributing to the oxidation-reduction reaction, 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge The ratio (A / B) between the amount of electricity A and the amount of electricity B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the above alloy at the time of discharge corresponds to the electronic state of bismuth. Change. In the alloy, the transition metal and bismuth are in solid solution, and the transition metal is disposed at a position that can affect the electronic state of bismuth, such as the first proximity or the second proximity of bismuth. Therefore, it is presumed that the capacity maintenance rate in the charge / discharge cycle is further improved, and the charge / discharge efficiency is improved.

(Space group P63 / mmc)
The crystal structure that can be assigned to the space group P63 / mmc means that it has a peak that can be assigned to the space group P63 / mmc in the X-ray diffraction pattern.

  When the crystal structure can be assigned to the space group P63 / mmc, the lower limit of the lattice constant is preferably a = 3.9Å and c = 5.1Å, more preferably a = 4.0Å and c = 5.2Å. . Moreover, as this upper limit, a = 4.3? And c = 5.6? Are preferable, and a = 4.2? And c = 5.5? Are more preferable. When the lattice constant is in the above range, the capacity retention rate of the nonaqueous electrolyte storage element using the negative electrode active material can be further increased.

Examples of the alloy having a crystal structure that can be assigned to the space group P63 / mmc include NiBi, Ni ₂ Bi, Ni ₄ Bi, Ni ₅ Bi, and MnBi.

The alloy is composed of any one of Cu ₄ Zn, Ni ₃ Ti, Ni ₃ Zr, Cr ₂ Ti, and Cr ₂ Zr and Bi, and the Bi content is 20% in terms of atomic ratio. An alloy having a crystal structure that can be assigned to the space group P63 / mmc can also be used from the viewpoint of increasing the capacity retention rate of the nonaqueous electrolyte storage element.

(Space group Fm-3m)
The crystal structure that can be assigned to the space group Fm-3m means that it has a peak that can be assigned to the space group Fm-3m in the X-ray diffraction pattern. Note that “−3” in the space group “Fm−3m” represents the target element of the third anti-axis, and is originally described by adding a bar “−” on “3”.

  The lower limit of the lattice constant when the crystal structure can be assigned to the space group Fm-3m is preferably a = 3.4ａ, and more preferably a = 3.5Å. Moreover, as this upper limit, a = 3.8? Is preferable, and a = 3.7? Is more preferable. When the lattice constant is in the above range, the capacity retention rate of the nonaqueous electrolyte storage element using the negative electrode active material can be further increased.

Examples of the alloy having a crystal structure that can be assigned to the space group Fm-3m include Ni ₆ Bi, Ni ₇ Bi, Ni ₈ Bi, Ni ₉ Bi, Mn ₅ Ni ₂ Bi _{4, and the} like.

Further, as the _{alloy, Ni, Cu, FeNi 3,} NiCu, Cu 2 NiZn, Cr 2 Ni 3, Cu 3 Zn, FeCu 4, Cu 3 Mo _and, with any of the _{Cu 3.8} Ni, and Bi And an alloy having a Bi content of less than 20% by atomic ratio and having a crystal structure that can be assigned to the space group Fm-3m also increases the capacity retention rate of the nonaqueous electrolyte storage element. Can be used.

(Space group Pnma)
The crystal structure that can be assigned to the space group Pnma means that it has a peak that can be assigned to the space group Pnma in the X-ray diffraction pattern.

Examples of the alloy having a crystal structure that can be assigned to the space group Pnma include NiBi _{3 and the} like.

X-ray diffraction measurement of the above alloy can be performed by powder X-ray diffraction measurement using “MiniFlex II” manufactured by Rigaku Corporation, an X-ray diffractometer, with a source of CuKα rays, a tube voltage of 30 kV, and a tube current of 15 mA. . At this time, the diffracted X-rays are detected by a high-speed one-dimensional detector D / teX Ultra 2 through a Kβ filter having a thickness of 30 μm. The sampling width is 0.01 °, the scanning speed is 5 ° / min, the divergence slit width is 0.625 °, the light receiving slit width is 13 mm (OPEN), and the scattering slit width is 8 mm. Based on the obtained X-ray diffraction data, the crystal structure can be analyzed by Rietveld analysis using the “Rietan 2000” program (F. Izumi and T. Ikeda, Mater. Sci. Forum, 198 (2000)). it can. The same results can be obtained for the space group and the lattice constant even when using the comprehensive powder X-ray analysis software “PDXL” (manufactured by Rigaku).
The half width of the peak and the crystallite size are obtained by the following method. The obtained X-ray diffraction data is fitted with a split type pseudo-Void function, and the half width of the peak is calculated. The crystallite size of the alloy is obtained from the half width of the peak and the following Scherrer equation.
D = Kλ / βcos (θ)
D: Crystallite size K: Scherrer constant (K = 0.94)
λ: wavelength of CuKα1 line β: FWHM (radian unit)
θ: Bragg angle of diffraction line

  As said space group, P63 / mmc and Fm-3m are preferable in P63 / mmc, Fm-3m, and Pnma from a viewpoint of the capacity maintenance rate improvement of a nonaqueous electrolyte electrical storage element, and Fm-3m is more preferable. The reason why P63 / mmc and Fm-3m are preferable in the space group is not clear, but the change in the crystal structure accompanying charge / discharge of the alloy becomes reversible, and the crystal structure is maintained even after the charge / discharge cycle. Has been. Such a difference in stability of the crystal structure is presumed to affect the capacity retention rate of the nonaqueous electrolyte storage element.

  The lower limit of the crystallite size of the alloy is preferably 20%, more preferably 30%, and even more preferably 40%. The upper limit of the crystallite size of the alloy is preferably 700%, more preferably 600%, further preferably 300%, and still more preferably 200%. When the crystallite size is in the above range, a negative electrode active material having a high discharge capacity and excellent charge / discharge cycle performance can be obtained.

The lower limit of the content ratio of the transition metal and bismuth in the alloy is preferably 1: 3 in terms of atomic ratio, more preferably 1: 1, further preferably 2: 1 and even more preferably 4: 1. When the content ratio of the transition metal and bismuth in the alloy is in the above range, the capacity retention rate in the charge / discharge cycle of the nonaqueous electrolyte storage element can be further improved. Moreover, as an upper limit of the content rate of the transition metal and bismuth of the said alloy, 9: 1 is preferable by atomic ratio, and 8: 1 is more preferable. When the content ratio of the transition metal and bismuth in the alloy is within the above range, the discharge capacity in the charge / discharge cycle of the nonaqueous electrolyte storage element can be further improved.
In addition, when a some element is contained as a transition metal, it is preferable that the total amount of a some transition metal element and the content rate of bismuth are the said range.

The negative electrode active material according to one embodiment of the present invention is an alloy that includes a transition metal element and bismuth and is crystalline, and is 0.7 to 0.9 V (vs. Li) derived from the alloy at the time of discharge. / Li ⁺⁾ and electricity a of the ratio of electricity B of 0.0~2.0V (vs.Li/Li ⁺⁾ derived from the alloy (a / B) is 60% or less at the time of discharge It is a negative electrode active material containing an alloy. Electric quantity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge, and 0.0 to 2.0 V (vs. Li ^/ Li from the alloy at the time of discharge) ^When the ratio (A / B) of ⁺ ) to the amount of electricity B is in the above range, the capacity retention rate and charge / discharge efficiency in the charge / discharge cycle of the nonaqueous electrolyte storage element can be made excellent. Here, the electric quantity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) and the electric quantity B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge. Is a value measured by the method described above.

  When the alloy is crystalline, a plurality of X-ray diffraction peaks derived from the alloy are observed in the X-ray diffraction diagram obtained by the powder X-ray diffraction measurement, and these peaks are any of the seven crystal forms. It can be attributed to. It is preferable that the crystal structure of the alloy can be assigned to the space group P63 / mmc, Fm-3m, or Pnma.

Electric quantity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge, and 0.0 to 2.0 V (vs. Li ^/ Li from the alloy at the time of discharge) ^The reason why the capacity retention rate and the charge / discharge efficiency in the charge / discharge cycle of the nonaqueous electrolyte storage element can be improved by the ratio (A / B) of ⁺ ) to the electric quantity B being in the above range is not clear, It seems like. Since the reaction potential of the alloy is considered to have a correlation with the electronic state of bismuth contributing to the oxidation-reduction reaction, 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge The ratio (A / B) between the amount of electricity A and the amount of electricity B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the above alloy at the time of discharge corresponds to the electronic state of bismuth. Change. In the alloy, the transition metal and bismuth are in solid solution, and the transition metal is disposed at a position that can affect the electronic state of bismuth, such as the first proximity or the second proximity of bismuth. Therefore, it is presumed that the capacity maintenance rate in the charge / discharge cycle is further improved, and the charge / discharge efficiency is improved.

  The alloy may contain a transition metal element and an element other than bismuth as long as the effects of the present invention are not affected. Examples of such other optional elements include metal elements such as zinc, tin, silicon, aluminum, and magnesium.

  The negative electrode active material may be formed of only the above alloy, but may include other negative electrode active materials other than the above alloy. Other negative electrode active materials include, for example, metals or metalloids such as Si and Sn; metal oxides or metalloid oxides such as Si oxide and Sn oxide; polyphosphate compounds; graphite (graphite) and non-graphitic carbon Examples thereof include carbon materials such as (easily graphitizable carbon or non-graphitizable carbon).

  As a content rate of the said alloy in the said negative electrode active material, 80 mass% or more is preferable, 90 mass% or more is more preferable, 95 mass% or more is further more preferable. By increasing the content of the alloy, the capacity retention rate of the nonaqueous electrolyte storage element can be sufficiently improved.

<Alloy>
The alloy according to an embodiment of the present invention includes nickel and bismuth and can be assigned to space group P63 / mmc or space group Fm-3m, and the content ratio of nickel and bismuth is 2 in atomic ratio. : 1-9: 1 alloy. When the alloy is used as a negative electrode active material of a non-aqueous electrolyte storage element, the capacity retention rate and charge / discharge efficiency in the charge / discharge cycle of the non-aqueous electrolyte storage element can be improved.

<Negative electrode>
The negative electrode which concerns on one Embodiment of this invention contains the said negative electrode active material. Since the said negative electrode contains the said negative electrode active material, the capacity | capacitance maintenance factor in the charging / discharging cycle of a nonaqueous electrolyte electrical storage element can be improved.

  The negative electrode includes a negative electrode base material and a negative electrode active material layer disposed on the negative electrode base material directly or via an intermediate layer.

  The negative electrode substrate has conductivity. As a material of the negative electrode base material, a metal such as copper, nickel, stainless steel, nickel-plated steel, aluminum, or an alloy thereof is used, and copper or a copper alloy is preferable. Moreover, foil, a vapor deposition film, etc. are mentioned as a formation form of a negative electrode base material, and foil is preferable from the surface of cost. That is, copper foil is preferable as the negative electrode substrate. Examples of the copper foil include rolled copper foil and electrolytic copper foil.

An intermediate | middle layer is a coating layer of the surface of a negative electrode base material, and reduces the contact resistance of a negative electrode base material and a negative electrode active material layer by including electroconductive particles, such as a carbon particle. The structure of an intermediate | middle layer is not specifically limited, For example, it can form with the composition containing a resin binder and electroconductive particle. “Conductive” means that the volume resistivity measured in accordance with JIS-H-0505 (1975) is 10 ⁷ Ω · cm or less, and “nonconductive” Means that the volume resistivity is more than 10 ⁷ Ω · cm.

  The negative electrode active material layer is formed from a so-called negative electrode mixture containing a negative electrode active material. Moreover, the negative electrode composite material which forms a negative electrode active material layer contains arbitrary components, such as a electrically conductive agent, a binder (binder), a thickener, and a filler as needed.

  The negative electrode active material described above is used as the negative electrode active material. As content of the negative electrode active material in the said negative electrode active material layer, it is 50 mass% or more and 99 mass% or less, for example.

  The conductive agent is not particularly limited as long as it is a conductive material that does not adversely affect battery performance. Examples of such a conductive agent include carbon black such as natural or artificial graphite, furnace black, acetylene black, and ketjen black, metals, and conductive ceramics. Examples of the shape of the conductive agent include powder and fiber.

  Examples of the binder (binder) include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, polyimide; ethylene-propylene-diene rubber (EPDM), Examples thereof include elastomers such as sulfonated EPDM, styrene butadiene rubber (SBR) and fluororubber; polysaccharide polymers.

  Examples of the thickener include polysaccharide polymers such as carboxymethylcellulose (CMC) and methylcellulose. When the thickener has a functional group that reacts with lithium, it is preferable to deactivate this functional group in advance by methylation or the like.

  The filler is not particularly limited as long as it does not adversely affect battery performance. Examples of the main component of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, and carbon.

<Nonaqueous electrolyte storage element>
A nonaqueous electrolyte storage element according to an embodiment of the present invention includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. Hereinafter, a nonaqueous electrolyte secondary battery will be described as an example of a power storage element. The positive electrode and the negative electrode usually form an electrode body that is alternately superposed by stacking or winding via a separator. This electrode body is housed in a case, and the case is filled with a nonaqueous electrolyte. The non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. In addition, as the case, a known metal case that is usually used as a case of a nonaqueous electrolyte secondary battery can be used.

  According to the nonaqueous electrolyte secondary battery (storage element), since the negative electrode containing the negative electrode active material is provided, the capacity retention rate in the charge / discharge cycle is excellent.

(Negative electrode)
As described above, the negative electrode according to an embodiment of the present invention is used for the negative electrode. The details of the negative electrode are as described above.

(Positive electrode)
The positive electrode has a positive electrode base material and a positive electrode active material layer disposed on the positive electrode base material directly or via an intermediate layer. The intermediate layer can have the same structure as the intermediate layer of the negative electrode.

  The positive electrode base material can have the same configuration as the negative electrode base material, but as a material, a metal such as aluminum, titanium, tantalum, stainless steel, or an alloy thereof is used. Among these, aluminum and aluminum alloys are preferable from the balance of potential resistance, high conductivity and cost. Moreover, foil, a vapor deposition film, etc. are mentioned as a formation form of a positive electrode base material, and foil is preferable from the surface of cost. That is, an aluminum foil is preferable as the positive electrode base material. Examples of aluminum or aluminum alloy include A1085P and A3003P defined in JIS-H-4000 (2014).

  The positive electrode active material layer is formed from a so-called positive electrode mixture containing a positive electrode active material. In addition, the positive electrode mixture for forming the positive electrode active material layer contains optional components such as a conductive agent, a binder (binder), a thickener, and a filler as necessary.

Examples of the positive electrode active material include composite oxides represented by Li _x MO _y (M represents at least one transition metal) (Li _x CoO ₂ , Li _x NiO having a layered α-NaFeO ₂ type crystal structure). _{2, Li x MnO 3, Li} x Ni α Co (1-α) O 2, Li x Ni α Mn β Co (1-α-β) O 2 , etc., _Li x _Mn 2 _{O 4} having a spinel type crystal structure , Li _x Ni _α Mn _(2-α) O ₄ ), Li _w Me _x (XO _y ) _z (Me represents at least one transition metal, X represents P, Si, B, V, etc.) And a polyanion compound represented by the formula (LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , LiCoPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , Li ₂ MnSiO ₄ , Li ₂ CoPO ₄ F, etc.). The elements or polyanions in these compounds may be partially substituted with other elements or anion species. In the positive electrode active material layer, one kind of these compounds may be used alone, or two or more kinds may be mixed and used.

  The conductive agent is not particularly limited as long as it is a conductive material that does not adversely affect battery performance. Examples of such a conductive agent include natural or artificial graphite, furnace black, acetylene black, ketjen black and other carbon blacks, metals, conductive ceramics, and the like. Examples of the shape of the conductive agent include powder and fiber.

  Examples of the binder (binder) include fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), thermoplastic resins such as polyethylene, polypropylene, polyimide; ethylene-propylene-diene rubber (EPDM), Examples thereof include elastomers such as sulfonated EPDM, styrene butadiene rubber (SBR) and fluororubber; polysaccharide polymers and the like.

  Examples of the thickener include polysaccharide polymers such as carboxymethylcellulose (CMC) and methylcellulose. When the thickener has a functional group that reacts with lithium, it is preferable to deactivate this functional group in advance by methylation or the like.

  The filler is not particularly limited as long as it does not adversely affect battery performance. Examples of the main component of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, glass, and carbon.

(Separator)
As the material of the separator, for example, a woven fabric, a nonwoven fabric, a porous resin film, or the like is used. Among these, a porous resin film is preferable from the viewpoint of strength, and a nonwoven fabric is preferable from the viewpoint of liquid retention of the nonaqueous electrolyte. The main component of the separator is preferably a polyolefin such as polyethylene or polypropylene from the viewpoint of strength, and is preferably polyimide or aramid from the viewpoint of resistance to oxidative degradation. These resins may be combined.

(Nonaqueous electrolyte)
As said non-aqueous electrolyte, the well-known electrolyte normally used for a non-aqueous electrolyte secondary battery can be used, and what dissolved electrolyte salt in the non-aqueous solvent can be used.

  Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and the like. A chain carbonate etc. can be mentioned.

Examples of the electrolyte salt include lithium salt, sodium salt, potassium salt, magnesium salt, onium salt, and the like, but lithium salt is preferable. Examples of the lithium salt include inorganic lithium salts such as LiPF ₆ , LiPO ₂ F ₂ , LiBF ₄ , LiClO ₄ , LiN (SO ₂ F) ₂ , LiSO ₃ CF ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO Fluorohydrocarbon groups such as ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), LiC (SO ₂ CF ₃ ) ₃ , LiC (SO ₂ C ₂ F ₅ ) ₃ A lithium salt having

  As the non-aqueous electrolyte, a room temperature molten salt, an ionic liquid, a polymer solid electrolyte, or the like can be used.

[Method for producing non-aqueous electrolyte storage element]
The method for producing the nonaqueous electrolyte storage element is not particularly limited. The negative electrode active material is used as the negative electrode active material contained in the negative electrode. The manufacturing method includes, for example, a step of housing a positive electrode and a negative electrode (electrode body) in a case and a step of injecting the nonaqueous electrolyte into the case.

  As the method for producing the negative electrode active material, for example, a material containing a transition metal element and bismuth can be fired or treated by a mechanochemical method. An alloy having a crystal structure that can be assigned to the space group P63 / mmc, Fm-3m, or Pnma can be obtained by treating the active material by firing or mechanochemical method.

  The firing treatment is usually performed in an inert gas atmosphere or a reducing gas atmosphere. As a minimum of baking temperature, 600 degreeC is preferable and 700 degreeC is more preferable. By setting the firing temperature within the above range, firing can proceed sufficiently and an alloy with few impurities can be synthesized. On the other hand, the upper limit of the firing temperature is preferably 1200 ° C, and more preferably 1000 ° C. By making the said baking temperature into the said range, the excessive particle growth of alloy powder can be suppressed and it can be set as a suitable particle diameter. In addition, you may perform the grinding | pulverization process which grind | pulverizes a baked material after a baking process.

  The mechanochemical method (also referred to as mechanochemical treatment) refers to a synthesis method utilizing a mechanochemical reaction. The mechanochemical reaction refers to a chemical reaction such as a crystallization reaction, a solid solution reaction, or a phase transition reaction that uses high energy locally generated by mechanical energy such as friction and compression in the crushing process of a solid substance. Examples of the apparatus for performing the mechanochemical method include ball mills, bead mills, vibration mills, turbo mills, mechano fusions, and disk mills. Among these, a ball mill is preferable.

  The injection can be performed by a known method. After the injection, the non-aqueous electrolyte secondary battery can be obtained by sealing the injection port. The details of each element constituting the nonaqueous electrolyte secondary battery obtained by the above manufacturing method are as described above.

<Other embodiments>
The present invention is not limited to the above-described embodiment, and can be implemented in a mode in which various changes and improvements are made in addition to the above-described mode. For example, the non-aqueous electrolyte storage element has been mainly described in the form of a non-aqueous electrolyte secondary battery, but other storage elements may be used. Examples of other power storage elements include capacitors (electric double layer capacitors, lithium ion capacitors) and the like.

  FIG. 1 shows a schematic view of a rectangular nonaqueous electrolyte secondary battery 1 which is an embodiment of a nonaqueous electrolyte storage element according to the present invention. In the figure, the inside of the container is seen through. In the nonaqueous electrolyte secondary battery 1 shown in FIG. 1, an electrode body 2 is accommodated in a battery container 3. The electrode body 2 is formed by winding a positive electrode including a positive electrode active material and a negative electrode including a negative electrode active material via a separator. The positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode lead 4 ′, and the negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode lead 5 ′. A nonaqueous electrolyte is injected into the battery container 3.

  The configuration of the nonaqueous electrolyte storage element according to the present invention is not particularly limited, and examples thereof include a cylindrical battery, a square battery (rectangular battery), a flat battery, and the like. The present invention can also be realized as a power storage device including a plurality of the above nonaqueous electrolyte power storage elements. One embodiment of a power storage device is shown in FIG. In FIG. 2, the power storage device 30 includes a plurality of power storage units 20. Each power storage unit 20 includes a plurality of nonaqueous electrolyte secondary batteries 1. The power storage device 30 can be mounted as a power source for vehicles such as an electric vehicle (EV), a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

<Creation of negative electrode active material>
[Example 1]
Bi ₂ O ₃ (manufactured by High Purity Chemical Co., Ltd.), NiO (manufactured by High Purity Chemical Co., Ltd.) and C as a reducing agent are weighed so that the molar ratio is Bi ₂ O ₃ : NiO: C = 2: 4: 5. The mixture was heated from room temperature to 800 ° C. in 10 hours in a nitrogen atmosphere, kept at this temperature for 4 hours, and then naturally cooled to room temperature.
The reaction formula of Example 1 is as follows.
2Bi ₂ O ₃ + 4NiO + 5C → 4NiBi + 5CO ₂
After firing, the negative electrode active material of Example 1 containing a nickel bismuth alloy represented by the composition formula NiBi was prepared by grinding in an agate mortar for about 10 minutes.

[Comparative Example 1]
Bi ₂ O ₃ (manufactured by Koyo Chemical Co., Ltd.) and C as a reducing agent were weighed and mixed so that the molar ratio was Bi ₂ O ₃ : C = 2: 3, and then in a nitrogen atmosphere in 10 hours. The temperature was raised from room temperature to 600 ° C., kept at this temperature for 4 hours, and then naturally cooled to room temperature.
The reaction formula of Comparative Example 1 is as follows.
2Bi ₂ O ₃ + 3C → 4Bi + 3CO ₂
After firing, the mixture was pulverized for about 10 minutes in an agate mortar to prepare a negative electrode active material of Comparative Example 1 containing a bismuth metal represented by composition formula Bi.

[Example 2]
Ni (made by Nilaco) and NiBi synthesized in Example 1 were weighed so that the molar ratio of Ni: NiBi was 1: 1. These were put into a tungsten carbide pot having an internal volume of 80 mL containing 250 g (about 250 pieces) of tungsten carbide balls having a diameter of 5 mm, and were covered in a glove box maintained in an argon atmosphere. This was set in a planetary ball mill ("Pulverisete 5" manufactured by FRITSCH), mixed for 10 minutes at a revolution speed of 400 rpm, and then put into a rest for 5 minutes, a total of 12 times.
The reaction formula of Example 2 is as follows.
Ni + NiBi → Ni ₂ Bi
Thus, to produce a negative electrode active material of Example 2 containing nickel bismuth alloy represented by a composition formula Ni 2 _Bi.

[Examples 3 to 9]
The starting materials shown in Table 1 below were weighed so as to have the respective molar ratios shown in Table 1 below. Next, the same operation as in Example 2 was performed using a planetary ball mill. In this way, negative electrode active materials of Examples 3 to 9 containing an alloy represented by the composition formula shown in Table 1 below were prepared.
The reaction formulas of Example 3 to Example 9 are as follows.
(Example 3)
3Ni + NiBi → Ni ₄ Bi
Example 4
4Ni + Bi → Ni ₄ Bi
(Example 5)
4Ni + NiBi → Ni ₅ Bi
(Example 6)
5Ni + NiBi → Ni ₆ Bi
(Example 7)
6Ni + NiBi → Ni ₇ Bi
(Example 8)
7Ni + NiBi → Ni ₈ Bi
Example 9
8Ni + NiBi → Ni ₉ Bi

[Example 10]
Bi ₂ O ₃ (manufactured by High Purity Chemical Co., Ltd.), NiO (manufactured by High Purity Chemical Co., Ltd.) and C as a reducing agent are weighed so that the molar ratio is Bi ₂ O ₃ : NiO: C = 6: 4: 11. The mixture was heated from room temperature to 800 ° C. in 10 hours in a nitrogen atmosphere, kept at this temperature for 4 hours, and then naturally cooled to room temperature.
The reaction formula of Example 10 is as follows.
6Bi ₂ O ₃ + 4NiO + 11C → 4NiBi ₃ + 11CO ₂
After firing, the negative electrode active material of Example 10 containing a nickel bismuth alloy represented by the composition formula NiBi ₃ was prepared by grinding in an agate mortar for about 10 minutes.
[Comparative Example 2]
Bi ₂ O ₃ (manufactured by High Purity Chemical Co., Ltd.), CuO (manufactured by High Purity Chemical Co., Ltd.) and C as a reducing agent are weighed so that the molar ratio is Bi ₂ O ₃ : CuO: C = 2: 4: 5. The mixture was heated from room temperature to 600 ° C. in 10 hours in a nitrogen atmosphere, kept at this temperature for 4 hours, and then naturally cooled to room temperature. 250 g of tungsten carbide balls having a diameter of 5 mm were put into a tungsten carbide pot having an internal volume of 80 mL containing about 250 balls and covered in a glove box maintained in an argon atmosphere. (Pulverisette 5)), mixing for 10 minutes at a revolution speed of 400 rpm, and then putting a pause for 5 minutes was repeated a total of 12 times.
The reaction formula of Comparative Example 2 is as follows.
2Bi ₂ O ₃ + 4CuO + 5C → 4Bi + 4Cu + 5CO ₂
Bi + Cu → CuBi
A negative electrode active material of Comparative Example 2 containing a copper bismuth alloy represented by the composition formula CuBi was prepared.

[Analysis of alloys]
The nickel bismuth alloy, bismuth, and copper bismuth alloy of Examples 1 to 10 and Comparative Examples 1 to 2 were analyzed by the following method. Powder X-ray diffraction measurement was performed using an X-ray diffractometer (“MiniFlex II” manufactured by Rigaku). The radiation source was CuKα ray, the tube voltage was 30 kV, the tube current was 15 mA, and the diffracted X-ray was detected with a high-speed one-dimensional detector (D / teX Ultra2 from Rigaku) through a Kβ filter with a thickness of 30 μm. The sampling width was 0.01 °, the scanning speed was 5 ° / min, the divergence slit width was 0.625 °, the light receiving slit width was 13 mm (OPEN), and the scattering slit width was 8 mm. The X-ray diffraction patterns obtained for the alloys of Examples 2 to 3 and Examples 5 to 9 are shown in FIG. Then, profile fitting was performed on the obtained X-ray diffraction data using the “PDXL” program. For Examples 1 to 10 and Comparative Examples 1 to 2, the peak half width and the crystallite size of the alloy were calculated by the above methods. Space group to which the crystal structure of each alloy obtained by the profile fitting belongs, lattice constant, peak position and full width at half maximum, crystallite size, and the transition metal element and the total content of the transition metal element and bismuth of the transition metal element The content ratio is shown in Table 2 below.

<Preparation of secondary battery (test battery)>
Rechargeable batteries were fabricated in the following manner using the alloys obtained in Examples 1 to 10 and Comparative Examples 1 to 2 as negative electrode active materials. The synthesized alloy powder and acetylene black (AB) were weighed at a mass ratio of 65:20 and mixed in an agate mortar for 5 minutes. This mixed powder, PVDF and NMP are put in a predetermined plastic container, set in a stirring defoaming device (“Shinky Kentaro Awatori”), and thoroughly kneaded at 2000 rpm, so that N-methylpyrrolidone (NMP ) Was used as a dispersion medium. The mass ratio of the negative electrode active material, AB, and PVDF in the slurry is 65:20:15. This slurry was applied to one side of a copper foil substrate having a thickness of 20 μm. This was dried on a hot plate at 80 ° C. for 60 minutes to evaporate the dispersion medium, and then roll-pressed to form a negative electrode mixture layer to obtain a negative electrode.

A test battery was assembled using the negative electrode as a working electrode, and the behavior as a negative electrode was evaluated. For the purpose of accurately observing the single behavior, a counter electrode in which metallic lithium was adhered to a nickel foil base material was used. Here, a sufficient amount of metallic lithium was arranged so that the capacity of the test battery was not limited by the counter electrode. A solution obtained by dissolving LiPF ₆ as an electrolyte in a mixed solvent in which ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) has a volume ratio of 6: 7: 7 so that the concentration becomes 1 mol / L. Was used. As the separator, a polypropylene microporous film whose surface was modified with polyacrylate was used. A metal resin composite film made of polyethylene terephthalate (thickness 15 μm) / aluminum foil (thickness 50 μm) / metal-adhesive polypropylene film (thickness 50 μm) is used for the exterior body, and the working electrode (negative electrode) terminal and counter electrode terminal The electrode was stored so that the open end was exposed to the outside. Subsequently, the fusion allowance in which the inner surfaces of the metal resin composite film face each other was hermetically sealed except for a portion serving as a liquid injection hole, and the liquid injection hole was sealed after pouring the electrolytic solution.

<Evaluation>
[Charge / discharge test (0.0-2.0V)]
The obtained secondary battery was charged and discharged in a thermostat set at 25 ° C. Charging was constant current constant voltage (CCCV) charging, the charging lower limit potential was 0.0 V (vs. Li ^/ Li ⁺ ), and the charge termination condition was the time when 3 hours had passed since reaching the charging lower limit potential. The discharge was a constant current (CC) discharge, and the discharge end potential was 2.0 V (vs. Li ^/ Li ⁺ ). The constant current value for charging and discharging was 50 mA / g with respect to the mass of the negative electrode active material contained in the negative electrode. In each cycle, a pause time of 10 minutes was set after charging and discharging. This cycle was carried out for 8 cycles for Example 1, Example 10, Comparative Example 1 and Comparative Example 2, and 45 cycles for Examples 2-9.

  In this charge / discharge cycle test, the discharge capacity after 6 cycles to the discharge capacity after 2 cycles, the discharge capacity after 8 cycles with respect to the discharge capacity after 2 cycles, and the ratio of the discharge capacity after 45 cycles with respect to the discharge capacity after 2 cycles Is shown in Table 2 as the capacity retention rate (%) in the charge / discharge cycle.

[Ratio of electricity B of 0.0-2.0V during discharging electricity A of 0.7-0.9V (vs.Li/Li ⁺⁾ during the discharge (vs.Li/Li ⁺⁾ (A / B)]
The discharge capacity of 0.7-0.9 V (vs. Li / Li ⁺ ) in the second cycle discharge of the charge / discharge test, and 0.0-2.0 V (vs. Li / Li in the second cycle discharge). ⁺ ) Discharge capacity was calculated.
The working electrode (negative electrode) according to the above Examples and Comparative Examples contains acetylene black (AB). Therefore, since the observed charge / discharge behavior includes the contribution of AB, it is necessary to consider the contribution. Therefore, a test battery (hereinafter referred to as “AB battery”) was prepared in the same manner as in Example 1 except that electrochemically inactive Al ₂ O ₃ was used instead of the nickel bismuth alloy, and the same. The charge / discharge test was conducted under the conditions of The amount of electricity of 0.7-0.9 V (vs. Li / Li ⁺ ) at the time of the second cycle discharge in the AB battery is 5 mAh / g per ₃ mass of Al ₂ O, and is 0.0-2.0 V ( vs. Li / Li ⁺ ) was 72 mAh / g per ₃ mass of Al ₂ O. Above, the discharge capacity of 0.7-0.9V in the discharge (vs.Li/Li ^+), and the discharge capacity of 0.0-2.0V (vs.Li/Li ⁺⁾ in the second cycle of the discharge The value obtained by subtracting the discharge capacity per ₃ mass of Al ₂ O of the AB battery, which is the contribution of AB, was obtained as the discharge capacity excluding the contribution of AB, and was defined as the electric quantity A and the electric quantity B, respectively. The ratio (A / B) was calculated by dividing the amount of electricity A by the amount of electricity B. Electricity B and the ratio of electricity A of 0.7~0.9V during discharge (vs.Li/Li ^+), 0.0-2.0V during discharge (vs.Li/Li ⁺⁾ (A / B) is shown in Table 2.

As shown in Table 2, Examples 1 to 10 containing alloys containing a transition metal element Ni and bismuth and having a crystal structure that can be assigned to the space group P63 / mmc, Fm-3m, or Pnma. The negative battery containing the negative electrode active material of Comparative Examples 1 and 2 containing a negative electrode active material containing an alloy having a crystal structure that can be assigned to the space group R-3m. Compared to the secondary battery, the capacity retention rate in the charge / discharge cycle was excellent. Further, the negative electrode active material contains a transition metal element Ni and bismuth, is crystalline, and has an electric quantity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge. And secondary of Examples 5 to 9 containing an alloy having a ratio (A / B) of electric quantity B of 0.0-2.0 V (vs. Li / Li ⁺ ) at the time of discharge of 60% or less. The battery was particularly excellent in capacity retention rate in the charge / discharge cycle.

[Powder X-ray diffraction measurement after charge / discharge cycle test]
About the secondary battery using each alloy of Example 1 and Example 9, the powder X-ray-diffraction measurement of the negative mix was performed after the charge / discharge test of 10 cycles. The negative electrode was taken out from the secondary battery according to Example 1, washed with DMC, and dried, and then the negative electrode mixture layer was peeled from the copper foil base material. Except that the peeled negative electrode mixture layer was installed in a dedicated device (general purpose atmosphere separator) (manufactured by Rigaku) for maintaining an argon atmosphere and the scan speed was 2 ° / min, the above [alloy analysis ] Powder X-ray diffraction measurement was carried out in the same manner as above. The negative electrode was taken out from the secondary battery according to Example 9, washed with DMC, and dried, and then the negative electrode mixture layer was peeled from the copper foil base material. Powder X-ray diffraction measurement was performed in the same manner as in the above [Analysis of Alloy] except that the peeled negative electrode mixture layer was placed on a glass holder and the scan speed was 2 ° / min. The X-ray diffraction pattern before and after 10 cycles of the charge / discharge test of Example 1 is shown in FIG. 4, and the X-ray diffraction pattern before and after the 10th cycle of Example 9 is shown in FIG.

  From the result of the powder X-ray diffraction measurement, it was found that in any of the alloys of Example 1 and Example 9, the crystal structure was maintained after the charge / discharge test. The secondary battery of the example in which the negative electrode active material contains the transition metal element Ni and bismuth and contains an alloy having a crystal structure that can be assigned to the space group P63 / mmc, Fm-3m, or Pnma is a charge / discharge test. By maintaining the crystal structure later, the capacity retention rate in the charge / discharge cycle is excellent as compared with the secondary battery of the comparative example in which the negative electrode active material contains an alloy having a crystal structure that can be assigned to the space group R-3m. Presumed to be.

  The present invention can be applied to electronic devices such as personal computers and communication terminals, non-aqueous electrolyte storage elements used as a power source for automobiles, and electrodes and negative electrode active materials included therein.

DESCRIPTION OF SYMBOLS 1 Nonaqueous electrolyte secondary battery 2 Electrode body 3 Battery container 4 Positive electrode terminal 4 'Positive electrode lead 5 Negative electrode terminal 5' Negative electrode lead 20 Power storage unit 30 Power storage device

Claims (10)

  A negative electrode active material containing an alloy containing a transition metal element and bismuth and having a crystal structure that can be assigned to space group P63 / mmc, Fm-3m, or Pnma.   2. The negative electrode active material according to claim 1, wherein the transition metal element is an element belonging to Group 3 to Group 11 of the periodic table excluding rhodium, palladium, silver, iridium, platinum and gold.   The negative electrode active material according to claim 1, wherein the transition metal element is nickel.   The negative electrode active material according to claim 3, wherein the content ratio of the nickel and the bismuth in the alloy is 1: 1 to 9: 1 by atomic ratio. The crystal structure can be assigned to the space group P63 / mmc,
The negative electrode active material according to any one of claims 1 to 4, wherein a lattice constant is 3.9Å≤a≤4.3Å, 5.1Å≤c≤5.6Å. The crystal structure can be assigned to the space group Fm-3m,
The negative electrode active material according to any one of claims 1 to 4, wherein a lattice constant is 3.4? ≤a? 3.8 ?. An alloy that includes a transition metal element and bismuth and is crystalline, and has an electric quantity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge, and at the time of discharge A negative electrode active material containing an alloy having a ratio (A / B) of an electric quantity B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the above alloy in 60% or less.   The negative electrode containing the negative electrode active material of any one of Claims 1-7.   A nonaqueous electrolyte storage element comprising the negative electrode according to claim 8.   An alloy containing nickel and bismuth, which can be assigned to space group P63 / mmc or space group Fm-3m, and the content ratio of nickel and bismuth is 2: 1 to 9: 1 in atomic ratio.

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