JP7010099B2 - Negative electrode active material, negative electrode and non-aqueous electrolyte power storage element - Google Patents

Description

The present invention relates to alloys, negative electrode active materials, negative electrodes and non-aqueous electrolyte power storage elements.

Non-aqueous electrolyte secondary batteries typified by lithium ion secondary batteries are widely used in personal computers, electronic devices such as communication terminals, automobiles, etc. due to their high energy density. The non-aqueous electrolyte secondary battery generally has a pair of electrodes electrically separated by a separator and a non-aqueous electrolyte interposed between the electrodes, and transfers ions between the two electrodes. It is configured to charge and discharge. In addition, capacitors such as lithium ion capacitors and electric double layer capacitors are also widely used as non-aqueous electrolyte storage elements other than non-aqueous electrolyte secondary batteries. In the future, non-aqueous electrolyte power storage elements will be required to have even higher capacities for applications such as power sources for electric vehicles (EVs).

Conventionally, a carbon material such as graphite has been used as the active material contained in the negative electrode of the non-aqueous electrolyte power storage element, and the active material exhibiting a high capacity for increasing the capacity of the non-aqueous electrolyte power storage element. Development is in progress. For example, bismuth is known as a high-capacity negative electrode active material capable of inserting and removing 3 moles of lithium from bismuth. Further, in the prior art, it is disclosed that charge / discharge measurement was carried out using bismuth as a negative electrode active material (see Non-Patent Document 1).

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

However, in the above-mentioned 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, even in a non-aqueous electrolyte storage element using bismuth as a negative electrode active material, a non-aqueous electrolyte storage element having a higher capacity retention rate in a charge / discharge cycle is required.

The present invention has been made based on the above circumstances, and an object thereof includes an alloy, a negative electrode active material, and this negative electrode active material capable of improving the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element. It is to provide a negative electrode and a non-aqueous electrolyte power storage element.

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

The negative electrode active material according to another aspect of the present invention is a crystalline alloy containing a transition metal element and bismuth, and is 0.7 to 0.9 V (vs) derived from the above alloy at the time of discharge. The ratio (A / B) of the electric amount A of .Li / Li ⁺ ) to the electric amount B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the above alloy at the time of discharge is 60% or less. It is a negative electrode active material containing an alloy.

The negative electrode according to another aspect of the present invention contains the negative electrode active material.

The non-aqueous electrolyte power storage element according to another aspect of the present invention includes the above-mentioned negative electrode.

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

According to the present invention, it is used for a negative electrode active material capable of improving the capacity retention rate in a charge / discharge cycle of a non-aqueous electrolyte power storage element, a negative electrode having this negative electrode active material, a non-aqueous electrolyte power storage element, and a non-aqueous electrolyte negative electrode active material. If so, it is possible to provide an alloy capable of improving the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element.

It is an external perspective view which shows the non-aqueous electrolyte secondary battery which concerns on one Embodiment of this invention. It is a schematic diagram which shows the power storage device which was configured by gathering a plurality of non-aqueous electrolyte secondary batteries which concerns on one Embodiment of this invention. It is an X-ray-diffraction diagram of the alloy of Examples 2 to 3, 5 to 9. It is an X-ray-diffraction diagram before and after the charge / discharge cycle of the alloy of Example 1. FIG. It is an X-ray-diffraction diagram before and after the charge / discharge cycle of the alloy of Example 9. FIG.

The negative electrode active material according to one aspect of the present invention is a negative electrode active material containing an alloy containing a transition metal element and bismuth and having a crystal structure that can be attributed to the space group P63 / mmc, Fm-3m, or Pnma. be. Since the negative electrode active material contains a transition metal element and bismuth and contains an alloy having the above crystal structure, it is possible to improve the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element. The reason for this is not clear, but the alloy contained in the negative electrode active material contains a transition metal element and bismuth, and has a crystal structure that can be attributed to the space group P63 / mmc, Fm-3m, or Pnma. It is presumed that the alloying / dealloying reaction of lithium reversibly proceeds even if it is not made into nanoparticles.

As the transition metal element, the 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 non-aqueous electrolyte power storage element can be further improved. Although the reason for this is not clear, 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, since the alloy contains a transition metal element, the load on the crystal structure is reduced during desorption and insertion of lithium atoms during charge / discharge, and the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element is reduced. It is presumed that the decrease in the amount of water is suppressed. Further, among these transition metal elements, chromium, nickel, and copper are nonflammable, and the alloy with bismuth is also nonflammable, so that safety can be improved.

Nickel is preferable as the transition metal element. When the transition metal element is nickel, the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element can be further improved, and the alloy with bismuth becomes nonflammable, so that the safety can be further improved.

The content ratio of the nickel and the bismuth of the alloy is preferably 1: 1 to 9: 1 in atomic ratio. When the content ratio of the nickel and the bismuth of the alloy is in the above range, the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element can be further improved.

The crystal structure can be attributed to the space group P63 / mmc, and the lattice constant is preferably 3.9 Å ≤ a ≤ 4.3 Å, 5.1 Å ≤ c ≤ 5.6 Å. When the lattice constant in the case where the crystal structure can be assigned to the space group P63 / mmc is in the above range, the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element can be further improved. It should be noted that 1 ^Å = 0.1 nm = 10-10 m.

The crystal structure can be attributed to the space group Fm-3m, and the lattice constant is preferably 3.4 Å ≤ a ≤ 3.8 Å. When the lattice constant in the case where the crystal structure can be assigned to the space group Fm-3m is in the above range, the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element can be further improved.

The negative electrode active material according to another aspect of the present invention is a crystalline alloy containing a transition metal element and bismuth, and is 0.7 to 0.9 V (vs) derived from the above alloy at the time of discharge. The ratio (A / B) of the electric amount A of .Li / Li ⁺ ) to the electric amount B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the above alloy at the time of discharge is 60% or less. It is a negative electrode active material containing an alloy. When the ratio (A / B) of the amount of electricity A to 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 non-aqueous electrolyte power storage element can be improved. The reason for this is not clear, but in the above alloy, the transition metal and bismuth are solid-melted, and the transition metal is placed at a position that can affect the electronic state of bismuth, such as the first proximity or second proximity of bismuth. Therefore, it is presumed that the electronic state of bismuth in the alloy becomes appropriate, so that the capacity retention rate in the charge / discharge cycle is further improved and the charge / discharge efficiency is improved.

The negative electrode according to another aspect of the present invention is a negative electrode containing the negative electrode active material. Therefore, the negative electrode can improve the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element.

The non-aqueous electrolyte power storage element according to another aspect of the present invention includes the negative electrode. Therefore, the non-aqueous electrolyte power storage element has an excellent capacity retention rate in the charge / discharge cycle.

The alloy according to another aspect of the present invention contains nickel and bismuth, and can be assigned to the space group P63 / mmc or the space group Fm-3m, and the content ratio of the nickel and the bismuth is the atomic ratio. It is an alloy of 2: 1 to 9: 1. When the alloy is used as the negative electrode active material of the 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.

Hereinafter, the alloy, the negative electrode active material, the negative electrode, and the non-aqueous electrolyte power storage element according to the embodiment of the present invention will be described in detail.

<Negative electrode active material>
The negative electrode active material according to one aspect of the present invention contains a transition metal element and bismuth, and contains an alloy having a crystal structure that can be attributed to the space group P63 / mmc, Fm-3m, or Pnma (negative electrode active material). Hereinafter, it is also referred to as “negative electrode active material”). Since the negative electrode active material contains the above alloy, the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element can be improved.

(Transition metal element)
As the transition metal element, the 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 the 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 non-aqueous electrolyte power storage element can be increased. Since these transition metal elements are metal elements that are difficult to alloy with lithium and do not operate as a negative electrode, the load on the crystal structure during desorption and insertion of lithium atoms during charge and discharge is reduced, and non-aqueous electrolytes are used. It is presumed that the decrease in the capacity retention rate in the charge / discharge cycle of the power storage element can be suppressed.

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

In the above alloy, an electric amount 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.) Derived from the alloy at the time of discharge. 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%. The amount of electricity 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) derived from the alloy at the time of discharge. When the ratio (A / B) of ⁺ ) to the amount of electricity B is within the above range, the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element can be further improved, and the charge / discharge efficiency in the charge / discharge cycle is excellent. Can be. The lower limit of the ratio (A / B) is not particularly limited, but 10% is preferable, and 20% may be preferable.
Here, an electric amount A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) and an electric amount 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 non-aqueous electrolyte power storage element equipped with a working electrode (negative electrode) containing the above alloy and a metal Li counter electrode is assembled, and the current is 50 mA / g with respect to the mass of the alloy up to 0.0 V (vs. Li / Li ⁺ ). Charge and perform constant potential charging for 3 hours. After a 10 minute rest, discharge to 2.0 V (vs. Li / Li ⁺ ) with a current of 50 mA / g relative to the mass of the alloy to 0.0-2.0 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 ⁺ ). When the working electrode contains a substance having a capacity in the range of 0.0 to 2.0 V (vs. Li / Li ⁺ ) in addition to the alloy, the discharge capacity caused by the substance is reduced. 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 "charges" a reduction reaction in which lithium ions or the like are occluded in the negative electrode active material, and an oxidation reaction in which lithium ions or the like are released from the negative electrode active material. It is called "discharge".

The amount of electricity 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) derived from the alloy at the time of discharge. It is not clear why the ratio (A / B) of ⁺ ) to the amount of electricity B can be improved in the capacity retention rate and charge / discharge efficiency in the charge / discharge cycle of the non-aqueous electrolyte power storage element. It can be thought of as. Since the reaction potential of the alloy is considered to be correlated with the electronic state of bismuth that contributes to the oxidation-reduction reaction, it is 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge. The ratio (A / B) of the amount of electricity A to the amount of electricity B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge corresponds to the electronic state of bismuth. Change. In the above alloy, the transition metal and the bismuth are solidly melted, and the transition metal is arranged at a position that can affect the electronic state of the bismuth, such as the first proximity or the second proximity of the bismuth. It is presumed that the capacity retention rate in the charge / discharge cycle is further improved and the charge / discharge efficiency is improved because the electronic state of the is appropriate.

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

When the crystal structure can be attributed to the space group P63 / mmc, a = 3.9 Å and c = 5.1 Å are preferable, and a = 4.0 Å and c = 5.2 Å are more preferable as the lower limit of the lattice constant. .. Further, as the upper limit, a = 4.3 Å and c = 5.6 Å are preferable, and a = 4.2 Å and c = 5.5 Å are more preferable. When the lattice constant is in the above range, the capacity retention rate of the non-aqueous electrolyte power storage element using the negative electrode active material can be further increased.

Examples of the alloy having a crystal structure that can be attributed to the space group P63 / mmc include NiBi, _Ni2Bi , _Ni4Bi , _Ni5Bi , MnBi and the like.

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 ratio is 20% in atomic ratio. Alloys having a crystal structure that can be attributed to the space group P63 / mmc, which are less than or equal to, can also be used from the viewpoint of increasing the capacity retention rate of the non-aqueous electrolyte power storage element.

(Space group Fm-3m)
The crystal structure that can be attributed to the space group Fm-3m means that it has a peak that can be attributed to the space group Fm-3m in the X-ray diffraction pattern. In addition, "-3" in the space group "Fm-3m" represents the target element of the three-fold anti-axis, and is originally described by adding a bar "-" on top of "3".

When the crystal structure can be attributed to the space group Fm-3m, a = 3.4 Å is preferable, and a = 3.5 Å is more preferable as the lower limit of the lattice constant. Further, as the upper limit, a = 3.8 Å is preferable, and a = 3.7 Å is more preferable. When the lattice constant is in the above range, the capacity retention rate of the non-aqueous electrolyte power storage element using the negative electrode active material can be further increased.

Examples of the alloy having a crystal structure that can be attributed 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.

The alloys include Ni, Cu, FeNi ₃ , NiCu, Cu ₂ NiZn, Cr ₂ Ni ₃ , Cu ₃ Zn, FeCu ₄ , Cu ₃ Mo, and Cu _3.8 Ni, and Bi. From the viewpoint of increasing the capacity retention rate of the non-aqueous electrolyte power storage element, an alloy composed of copper and having a Bi content ratio of less than 20% in atomic ratio and having a crystal structure that can be attributed to the space group Fm-3m. Can be used from.

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

Examples of the alloy having a crystal structure that can be attributed to the space group Pnma include NiBi ₃ .

The X-ray diffraction measurement of the above alloy can be performed by powder X-ray diffraction measurement using the X-ray diffractometer Rigaku's "MiniFlex II", with the radiation source being CuKα ray, the tube voltage being 30 kV, and the tube current being 15 mA. .. At this time, the diffracted X-rays pass through a Kβ filter having a thickness of 30 μm and are detected by the high-speed one-dimensional detector D / teX Ultra 2. The sampling width is 0.01 °, the scan speed is 5 ° / min, the divergent 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, Meter. Sci. Forum, 198 (2000).). can. The same results can be obtained by using the comprehensive powder X-ray analysis software "PDXL" (manufactured by Rigaku) for the space group and the lattice constant.
The half width of the peak and the crystallite size can be obtained by the following method. The obtained X-ray diffraction data is fitted by a split-type pseudo Voido function, and the half width of the peak is calculated. The half width of the peak and the crystallite size of the alloy can be obtained from the following Scherrer equation.
D = Kλ / βcos (θ)
D: Crystallite size K: Scheller constant (K = 0.94)
λ: Wavelength of CuKα1 line β: FWHM (radian unit)
θ: Bragg angle of diffraction line

As the space group, P63 / mmc and Fm-3m are preferable among P63 / mmc, Fm-3m and Pnma, and Fm-3m is more preferable, from the viewpoint of improving the capacity retention rate of the non-aqueous electrolyte power storage element. The reason why P63 / mmc and Fm-3m are preferable in the space group is not clear, but the change in the crystal structure due to the charge / discharge of the alloy becomes reversible, and the crystal structure is maintained even after the charge / discharge cycle. Has been done. It is presumed that such a difference in the stability of the crystal structure affects the capacity retention rate of the non-aqueous electrolyte power storage device.

The lower limit of the crystallite size of the alloy is preferably 20 Å, more preferably 30 Å, and even more preferably 40 Å. The upper limit of the crystallite size of the alloy is preferably 700 Å, more preferably 600 Å, still more preferably 300 Å, and even more preferably 200 Å. 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.

As the lower limit of the content ratio of the transition metal and bismuth of the alloy, the atomic ratio is preferably 1: 3, more preferably 1: 1 is more preferably 2: 1 and even more preferably 4: 1. When the content ratio of the transition metal of the alloy and bismuth is within the above range, the capacity retention rate in the charge / discharge cycle of the non-aqueous electrolyte power storage element can be further improved. The upper limit of the content ratio of the transition metal and bismuth of the alloy is preferably 9: 1 in atomic ratio, more preferably 8: 1. When the content ratio of the transition metal of the alloy and bismuth is within the above range, the discharge capacity in the charge / discharge cycle of the non-aqueous electrolyte power storage element can be further improved.
When a plurality of elements are contained as the transition metal, it is preferable that the total amount of the plurality of transition metal elements and the content ratio of bismuth are in the above range.

The negative electrode active material according to one aspect of the present invention is an alloy containing a transition metal element and bismuth and is crystalline, and is derived from the above alloy at the time of discharge of 0.7 to 0.9 V (vs. Li). The ratio (A / B) of the electric amount A of / Li ⁺ ) to the electric amount B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge is 60% or less. It is a negative electrode active material containing an alloy. The amount of electricity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the above alloy at the time of discharge and 0.0 to 2.0 V (vs. Li / Li) derived from the above 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 the charge / discharge efficiency in the charge / discharge cycle of the non-aqueous electrolyte power storage element can be made excellent. Here, an electric amount A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) and an electric amount 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.

The fact that the alloy is crystalline means that 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 in any of the seven crystal forms. It means that it can be attributed to. It is preferable that the crystal structure of the alloy can be attributed to the space group P63 / mmc, Fm-3m, or Pnma.

The amount of electricity 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) derived from the alloy at the time of discharge. It is not clear why the ratio (A / B) of ⁺ ) to the amount of electricity B can be improved in the capacity retention rate and charge / discharge efficiency in the charge / discharge cycle of the non-aqueous electrolyte power storage element. It can be thought of as. Since the reaction potential of the alloy is considered to be correlated with the electronic state of bismuth that contributes to the oxidation-reduction reaction, it is 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge. The ratio (A / B) of the amount of electricity A to the amount of electricity B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the alloy at the time of discharge corresponds to the electronic state of bismuth. Change. In the above alloy, the transition metal and the bismuth are solidly melted, and the transition metal is arranged at a position that can affect the electronic state of the bismuth, such as the first proximity or the second proximity of the bismuth. It is presumed that the capacity retention rate in the charge / discharge cycle is further improved and the charge / discharge efficiency is improved because the electronic state of the is appropriate.

The alloy may contain a transition metal element and an element other than bismuth as long as it does not affect the action and effect of the present invention. 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 only from the above alloy, but may contain other negative electrode active materials other than the above alloy. Other negative electrode active materials include, for example, metals or semi-metals such as Si and Sn; metal oxides or semi-metal oxides such as Si oxide and Sn oxide; polyphosphate compounds; graphite and non-graphitic carbon. Examples thereof include carbon materials such as (easy graphitizable carbon or non-graphitizable carbon).

The content of the alloy in the negative electrode active material is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more. By increasing the content of the alloy, the capacity retention rate of the non-aqueous electrolyte power storage element can be sufficiently improved.

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

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

The negative electrode base material has conductivity. As the material of the negative electrode base material, metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum or alloys thereof are used, and copper or a copper alloy is preferable. In addition, examples of the form of forming the negative electrode base material include foils and thin-film deposition films, and foils are preferable from the viewpoint of cost. That is, a copper foil is preferable as the negative electrode base material. Examples of the copper foil include rolled copper foil and electrolytic copper foil.

The intermediate layer is a coating layer on the surface of the negative electrode base material, and contains conductive particles such as carbon particles to reduce the contact resistance between the negative electrode base material and the negative electrode active material layer. The composition of the intermediate layer is not particularly limited, and can be formed by, for example, a composition containing a resin binder and conductive particles. In addition, having "conductive" means that the volume resistivity measured according to JIS-H-0505 (1975) is ¹⁰⁷ Ω · cm or less, and is referred to as "non-conductive". Means that the volume resistivity is more than ¹⁰⁷ Ω · cm.

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

As the negative electrode active material, the above-mentioned negative electrode active material is used. The content of the negative electrode active material in the negative electrode active material layer can be, for example, 50% by mass or more and 99% by mass or less.

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

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

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

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

<Non-water electrolyte power storage element>
The non-aqueous electrolyte power storage element according to the embodiment of the present invention has a positive electrode, a negative electrode, and a non-aqueous electrolyte. Hereinafter, a non-aqueous electrolyte secondary battery will be described as an example of the power storage element. The positive electrode and the negative electrode usually form an electrode body that is alternately superposed by laminating or winding through a separator. The electrode body is housed in a case, and the case is filled with a non-aqueous electrolyte. The non-aqueous electrolyte is interposed between the positive electrode and the negative electrode. Further, as the above case, a known metal case or the like which is usually used as a case of a non-aqueous electrolyte secondary battery can be used.

According to the non-aqueous 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 the negative electrode, as described above, the negative electrode according to the embodiment of the present invention is used. 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 arranged directly on the positive electrode base material or via an intermediate layer. The intermediate layer may have the same structure as the intermediate layer of the negative electrode.

The positive electrode base material may have the same structure as the negative electrode base material, but as the material, a metal such as aluminum, titanium, tantalum, or stainless steel or an alloy thereof is used. Among these, aluminum and aluminum alloys are preferable from the viewpoint of the balance between potential resistance, high conductivity and cost. Further, examples of the formation form of the positive electrode base material include foil, a vapor-deposited film, and the like, and foil is preferable from the viewpoint of cost. That is, aluminum foil is preferable as the positive electrode base material. Examples of aluminum or aluminum alloy include A1085P and A3003P specified 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. Further, the positive electrode mixture forming the positive electrode active material layer contains optional components such as a conductive agent, a binder (binder), a thickener, and a filler, if necessary.

Examples of the positive electrode active material include composite oxides represented by Li _x MO _y (M represents at least one kind of transition metal) (Li _x CoO ₂ and Li _x NiO having a layered α-NaFeO type ₂ 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 etc.), Li _w Me _x ( _Xoy ) _z (Me represents at least one kind of transition metal, and X represents, for example, P, Si, B, V, etc.) Examples thereof include polyanionic compounds represented by (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 of these compounds may be used alone, or two or more thereof 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 the battery performance. Examples of such a conductive agent include natural or artificial graphite, carbon black such as furnace black, acetylene black, and Ketjen black, metals, conductive ceramics, and the like. Examples of the shape of the conductive agent include powder and fibrous.

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

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

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

(Separator)
As the material of the separator, for example, a woven fabric, a non-woven 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 non-woven fabric is preferable from the viewpoint of liquid retention of a non-aqueous electrolyte. As the main component of the separator, polyolefins such as polyethylene and polypropylene are preferable from the viewpoint of strength, and polyimide and aramid are preferable from the viewpoint of oxidative decomposition resistance. Moreover, you may combine these resins.

(Non-water electrolyte)
As the non-aqueous electrolyte, a known electrolyte usually used for a non-aqueous electrolyte secondary battery can be used, and one in which an electrolyte salt is dissolved in a 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. Chain carbonate and the like 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 , and LiN (SO). 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 and other fluorinated hydrocarbon groups Can be mentioned, such as a lithium salt having.

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

[Manufacturing method of non-aqueous electrolyte power storage element]
The method for manufacturing the non-aqueous electrolyte power 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 accommodating a positive electrode and a negative electrode (electrode body) in a case and a step of injecting the non-aqueous electrolyte into the case.

As a 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. By treating the active material material by calcination or mechanochemical method, an alloy having a crystal structure that can be attributed to the space group P63 / mmc, Fm-3m, or Pnma can be obtained.

The firing treatment is usually performed in an inert gas atmosphere or a reducing gas atmosphere. The lower limit of the firing temperature is preferably 600 ° C, more preferably 700 ° C. 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, more preferably 1000 ° C. By setting the firing temperature in the above range, excessive particle growth of the alloy powder can be suppressed, and an appropriate particle size can be obtained. After the firing treatment, a crushing treatment for crushing the fired product may be performed.

The mechanochemical method (also referred to as mechanochemical treatment) is a synthetic method using 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 utilizes high energy locally generated by mechanical energy such as friction and compression in the crushing process of a solid substance. Examples of devices that perform the mechanochemical method include crushers / dispersers such as ball mills, bead mills, vibration mills, turbo mills, mechanofusions, and disc mills. Of these, a ball mill is preferable.

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

<Other embodiments>
The present invention is not limited to the above embodiment, and can be implemented in various modifications and improvements in addition to the above embodiment. For example, although the embodiment in which the non-aqueous electrolyte power storage element is a non-water electrolyte secondary battery has been mainly described, other power 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 non-aqueous electrolyte secondary battery 1 which is an embodiment of the non-aqueous electrolyte power storage element according to the present invention. The figure is a perspective view of the inside of the container. In the non-aqueous electrolyte secondary battery 1 shown in FIG. 1, the electrode body 2 is housed in the battery container 3. The electrode body 2 is formed by winding a positive electrode having a positive electrode active material and a negative electrode having 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'. Further, a non-aqueous electrolyte is injected into the battery container 3.

The configuration of the non-aqueous electrolyte power storage element according to the present invention is not particularly limited, and examples thereof include a cylindrical battery, a square battery (rectangular battery), and a flat battery. The present invention can also be realized as a power storage device including a plurality of the above-mentioned non-aqueous electrolyte power storage elements. An embodiment of the 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 non-aqueous electrolyte secondary batteries 1. The power storage device 30 can be mounted as a power source for an electric vehicle (EV), a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but 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 as to have a molar ratio of Bi ₂ O ₃ : NiO: C = 2: 4: 5. After mixing, the temperature was raised from room temperature to 800 ° C. in a nitrogen atmosphere for 10 hours, maintained at this temperature for 4 hours, and then naturally cooled to room temperature.
The reaction formula of Example 1 is as follows.
2Bi _{2O 3} + 4NiO + 5C → 4NiBi + 5CO ₂
After firing, it was pulverized in an agate mortar for about 10 minutes to prepare a negative electrode active material of Example 1 containing a nickel bismuth alloy represented by the composition formula NiBi.

[Comparative Example 1]
Bi ₂ O ₃ (manufactured by High Purity Chemical Co., Ltd.) and C as a reducing agent were weighed and mixed so as to have a molar ratio of Bi ₂ O ₃ : C = 2: 3, and then mixed in a nitrogen atmosphere for 10 hours. The temperature was raised from room temperature to 600 ° C., maintained 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, it was pulverized in an agate mortar for about 10 minutes to prepare a negative electrode active material of Comparative Example 1 containing a bismuth metal represented by the composition formula Bi.

[Example 2]
Ni (manufactured by Niraco Co., Ltd.) and NiBi synthesized in Example 1 were weighed so that the molar ratio of Ni: NiBi was 1: 1. These were placed in a tungsten carbide pot having an internal volume of 80 mL and containing 250 g (about 250) of tungsten carbide balls having a diameter of 5 mm, and covered in a glove box maintaining an argon atmosphere. This was set in a planetary ball mill (“pulveristte 5” manufactured by FRITSCH), and the operation of mixing for 10 minutes at a revolution speed of 400 rpm and then putting a rest for 5 minutes was repeated 12 times in total.
The reaction formula of Example 2 is as follows.
Ni + NiBi → Ni _2Bi
In this way, the negative electrode active material of Example 2 containing the nickel bismuth alloy represented by the composition formula Ni ₂ Bi was produced.

[Examples 3 to 9]
The starting materials shown in Table 1 below were weighed to 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, the negative electrode active materials of Examples 3 to 9 containing the alloy represented by the composition formula shown in Table 1 below were prepared.
The reaction formulas of Examples 3 to 9 are as follows.
(Example 3)
3Ni ＋ NiBi → Ni _4Bi
(Example 4)
4Ni + Bi → Ni ₄ Bi
(Example 5)
4Ni ＋ NiBi → Ni _5Bi
(Example 6)
5Ni + NiBi → Ni _6Bi
(Example 7)
6Ni ＋ NiBi → Ni ₇ Bi
(Example 8)
7Ni ＋ NiBi → Ni _8Bi
(Example 9)
8Ni ＋ NiBi → Ni _9Bi

[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 as to have a molar ratio of Bi ₂ O ₃ : NiO: C = 6: 4: 11. After mixing, the temperature was raised from room temperature to 800 ° C. in a nitrogen atmosphere for 10 hours, maintained 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, it was pulverized in an agate mortar for about 10 minutes to prepare a negative electrode active material of Example 10 containing a nickel bismuth alloy represented by the composition formula NiBi ₃ .
[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 as to have a molar ratio of Bi ₂ O ₃ : CuO: C = 2: 4: 5. After mixing, the temperature was raised from room temperature to 600 ° C. in 10 hours under a nitrogen atmosphere, maintained at this temperature for 4 hours, and then naturally cooled to room temperature. 250 g of tungsten carbide balls with a diameter of 5 mm (about 250 pieces were placed in a tungsten carbide pot with an internal volume of 80 mL and covered in a glove box that maintained an argon atmosphere. This was placed in a planetary ball mill (FRITSCH). The operation was repeated 12 times in total, in which the mixture was set in "pulveristte 5"), mixed at a revolution speed of 400 rpm for 10 minutes, and then paused for 5 minutes.
The reaction formula of Comparative Example 2 is as follows.
2Bi _{2O 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.

[Alloy analysis]
The nickel bismuth alloys, bismuth and copper bismuth alloys of Examples 1 to 10 and Comparative Examples 1 to 2 were analyzed by the following methods. Powder X-ray diffraction measurement was performed using an X-ray diffractometer (“MiniFlexII” 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 by a high-speed one-dimensional detector (D / teX Ultra2 manufactured by Rigaku) through a Kβ filter having a thickness of 30 μm. The sampling width was 0.01 °, the scan speed was 5 ° / min, the divergent 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 above-mentioned "PDXL" program. Further, for Examples 1 to 10 and Comparative Examples 1 to 2, the half width of the peak and the crystallite size of the alloy were calculated by the above method. The space group to which the crystal structure of each alloy obtained by the profile fitting belongs, the lattice constant, the peak position and half-value width, the crystallite size, and the transition metal element with respect to the total content of the transition metal element and bismuth. The content ratios are shown in Table 2 below.

<Manufacturing of secondary battery (test battery)>
Using the alloys obtained in Examples 1 to 10 and Comparative Examples 1 to 2 as the negative electrode active material, a secondary battery was produced in the following manner. The powder of each of the synthesized alloys and acetylene black (AB) were weighed at a mass ratio of 65:20, and mixed in an agate mortar for 5 minutes. Put this mixed powder, PVDF and NMP in a predetermined plastic container, set it in a stirring defoaming device (Shinky's "Awatori Kentarou"), and knead it sufficiently at 2000 rpm to obtain N-methylpyrrolidone (NMP). ) Was used as a dispersion medium to prepare a slurry. 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 a roll press was performed to form a negative electrode mixture layer to obtain a negative electrode.

A test battery was assembled with the negative electrode as the working electrode, and the behavior as the negative electrode was evaluated. For the purpose of accurately observing the single behavior, a metal lithium was used as the counter electrode in close contact with the nickel foil base material. Here, a sufficient amount of metallic lithium was arranged so that the capacity of the test battery was not limited by the counter electrode. As an electrolyte, a solution in which LiPF ₆ is dissolved in a mixed solvent having an ethylene carbonate (EC): ethylmethyl carbonate (EMC): dimethyl carbonate (DMC) volume ratio of 6: 7: 7 so as to have a concentration of 1 mol / L. Was used. As a separator, a polypropylene micropore membrane surface-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 are used. The electrodes were housed so that the open end was exposed to the outside. Next, the fusion allowance in which the inner surfaces of the metal resin composite film faced each other was hermetically sealed except for the portion to be the injection hole, the electrolytic solution was injected, and then the injection hole was sealed.

<Evaluation>
[Charging / discharging test (0.0-2.0V)]
The obtained secondary battery was charged and discharged in a constant temperature bath set at 25 ° C. Charging was constant current constant voltage (CCCV) charging, the lower limit potential of charging was 0.0 V (vs. Li / Li ⁺ ), and the charging termination condition was the time when 3 hours had passed after reaching the lower limit potential of charging. The discharge was a constant current (CC) discharge, and the discharge end potential was 2.0 V (vs. Li / Li ⁺ ). The constant current values for charging and discharging were set to 50 mA / g with respect to the mass of the negative electrode active material contained in the negative electrode. In each cycle, a rest period 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 to 9.

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

[Ratio of the electric energy A of 0.7-0.9V (vs.Li / Li ⁺ ) at the time of discharge and the electric energy B of 0.0-2.0V (vs.Li / Li ⁺ ) at the time of discharge (A) / B)]
The discharge capacity of 0.7-0.9V (vs. Li / Li ⁺ ) in the second cycle discharge of the above charge / discharge test, and 0.0-2.0 V (vs. Li / Li +) in the second cycle discharge. The discharge capacity of ⁺ ) was calculated respectively.
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 produced by the same procedure as in Example 1 except that the electrochemically inert Al ₂ O ₃ was used instead of the nickel bismuth alloy. The charge / discharge test was performed under the conditions of. The amount of electricity of 0.7-0.9V (vs. Li / Li ⁺ ) at the time of discharging in the _second cycle in the AB battery is 5mAh / g per ₃ mass of Al2O, and 0.0-2.0V ( The amount of electricity of vs. Li / Li ⁺ ) was 72 mAh / g per ₃ mass of _Al2O . From the above-mentioned discharge capacity of 0.7-0.9V (vs.Li / Li ⁺ ) in the discharge and 0.0-2.0V (vs.Li / Li ⁺ ) in the second cycle 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 taken as the amount of electricity A and the amount of electricity B, respectively. The ratio (A / B) was calculated by dividing the amount of electricity A by the amount of electricity B. The amount of electricity A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) at the time of discharge, the amount of electricity B and the ratio (A /) of 0.0-2.0 V (vs. Li / Li ⁺ ) at the time of discharge. B) is shown in Table 2.

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

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

From the results of the powder X-ray diffraction measurement, it was found that the crystal structure was maintained after the charge / discharge test in both the alloys of Example 1 and Example 9. 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 attributed to the space group P63 / mmc, Fm-3m, or Pnma is a charge / discharge test. Since the crystal structure is maintained even after that, the capacity retention rate in the charge / discharge cycle is superior to that of the secondary battery of the comparative example containing the alloy having the crystal structure in which the negative electrode active material can be attributed to the space group R-3m. It is presumed to be.

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

1 Non-aqueous electrolyte secondary battery 2 Electrode body 3 Battery container 4 Positive terminal 4'Positive lead 5 Negative terminal 5'Negative lead 20 Power storage unit 30 Power storage device

Claims (9)

It contains an alloy containing a transition metal element and bismuth and having a crystal structure that can be attributed to the space group P63 / mmc or Fm-3 m .
A negative electrode active material in which the transition metal element is an element of 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 2 , wherein the content ratio of the nickel and the bismuth of the alloy is 1: 1 to 9: 1 in atomic ratio. The above crystal structure can be attributed to the space group P63 / mmc.
The negative electrode active material according to any one of claims 1 to 3 , wherein the lattice constant is 3.9 Å ≤ a ≤ 4.3 Å, 5.1 Å ≤ c ≤ 5.6 Å. The above crystal structure can be attributed to the space group Fm-3m.
The negative electrode active material according to any one of claims 1 to 3 , wherein the lattice constant is 3.4 Å ≤ a ≤ 3.8 Å. An alloy containing a transition metal element and bismuth, which is crystalline, and has an electric amount A of 0.7 to 0.9 V (vs. Li / Li ⁺ ) derived from the above alloy at the time of discharge and an electric amount A at the time of discharge. Contains an alloy in which the ratio (A / B) of the electric amount B of 0.0 to 2.0 V (vs. Li / Li ⁺ ) derived from the above alloy is 60% or less .
The transition metal elements are Group 3 to Group 11 elements of the periodic table excluding rhodium, palladium, silver, iridium, platinum and gold.
A negative electrode active material in which the content ratio of the transition metal element and the bismuth of the alloy is 5 or more in terms of the atomic ratio of the transition metal to the bismuth . It contains an alloy containing nickel and bismuth, which can be assigned to the space group P63 / mmc or the space group Fm-3m, and the content ratio of the nickel and the bismuth is 2: 1 to 9: 1 in atomic ratio. Negative active material . A negative electrode containing the negative electrode active material according to any one of claims 1 to 7. The non-aqueous electrolyte power storage element comprising the negative electrode according to claim 8.

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