JP2011032541A - Nanosize particle, negative electrode material for lithium ion secondary battery containing the nanosize particle, negative electrode for lithium ion secondary battery, lithium ion secondary battery, and method for producing the nanosize particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode material for a lithium ion secondary battery which achieves high volume and satisfactory cycle properties. <P>SOLUTION: A nanosize particle 1 contains an element A-1 and an element A-2 as two kinds of elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn, and has a first phase 3 as the single substance or solid solution of the element A-1 and a second phase 5 as the simple substance or solid solution of the element A-2. Both of the first phase 3 and the second phase 5 are exposed to the outer surfaces, and the outer surfaces of the first phase and the second phase are non-spherical. The negative electrode material for a lithium ion secondary battery uses the nanosize particle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a negative electrode for a lithium ion secondary battery, and more particularly to a negative electrode for a lithium ion secondary battery having a high capacity and a long life.

  Conventionally, lithium ion secondary batteries using graphite as a negative electrode active material have been put into practical use. Also, a negative electrode is formed by kneading a negative electrode active material, a conductive aid such as carbon black, and a resin binder to prepare a slurry, and applying and drying on a copper foil. Yes.

  On the other hand, negative electrodes for lithium ion secondary batteries using metals and alloys having a large theoretical capacity as lithium compounds, particularly silicon and its alloys as negative electrode active materials, have been developed with the aim of increasing the capacity. However, since the volume of silicon that occludes lithium ions expands to about 4 times that of silicon before occlusion, a negative electrode using a silicon-based alloy as a negative electrode active material repeatedly expands and contracts during a charge / discharge cycle. For this reason, the negative electrode active material is peeled off, and there is a problem that the life is extremely short as compared with the conventional graphite electrode.

  Therefore, a negative electrode for a non-aqueous electrolyte secondary battery that grows carbon nanofibers on the surface of a silicon-based active material, relaxes strain due to expansion and contraction of negative electrode active material particles by its elastic action, and improves cycle characteristics. It is disclosed (see, for example, Patent Document 1).

  Moreover, the lithium secondary which consists of the powder of the compound of the component A and the component B obtained by mixing the component A which can occlude Li, such as Si and Sn, and the component B, such as Cu and Fe, by a mechanochemical method A negative electrode material for a battery is disclosed (see Patent Document 2).

JP 2006-244984 A JP 2005-78999 A

  However, a conventional negative electrode in which a negative electrode is formed by applying and drying a slurry of a negative electrode active material, a conductive additive, and a binder, and the negative electrode active material and the current collector are bonded to a resin having low conductivity. The amount of resin used must be minimized so that the internal resistance does not increase, and the bonding force is weak. Therefore, if the volume expansion of the silicon itself is not suppressed, the negative electrode active material is reduced in fineness of the negative electrode active material and peeling of the negative electrode active material, generation of cracks in the negative electrode, and a decrease in conductivity between the negative electrode active materials. Etc. occur and the capacity decreases. Therefore, there are problems that the cycle characteristics are poor and the life of the secondary battery is short.

  In addition, the invention described in Patent Document 1 is insufficient to suppress the volume expansion of silicon itself, and binds the negative electrode active material and the current collector with a resin having insufficient bonding force, The deterioration of cycle characteristics could not be prevented sufficiently. Furthermore, the productivity was poor due to the formation process of carbon nanofibers. In the invention described in Patent Document 2, it is difficult to uniformly disperse each component at the nano-size level, and deterioration of cycle characteristics cannot be prevented sufficiently.

  In particular, silicon, which is expected to be put to practical use as a negative electrode material, has a large volume change during charge and discharge, and therefore active material particles containing silicon are liable to crack, causing deterioration of current collection in the particles, and charging and discharging. There was a problem that the discharge cycle characteristics were poor.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to obtain a negative electrode material for a lithium ion secondary battery that realizes high capacity and good cycle characteristics.

  As a result of intensive studies in order to achieve the above object, the present inventor has preferentially occluded lithium when one phase is provided with a first phase and a second phase having different electrochemical potentials for occlusion of lithium. However, when the one phase expands due to occlusion of lithium, the other phase does not expand relatively, so that the expansion of the entire nanosize particle can be suppressed, and the nanosize particle can be refined during charging and discharging. It was found that can be prevented. The present invention has been made based on this finding.

That is, the present invention provides the following nano-sized particles, negative electrode materials for lithium ion secondary batteries, and the like.
(1) The group consisting of Si (silicon), Sn (tin), Al (aluminum), Pb (lead), Sb (antimony), Bi (bismuth), Ge (germanium), In (indium) and Zn (zinc) A first phase that is a single element or a solid solution of the element A-1, and a single element or a solid solution of the element A-2. A second phase, wherein both the first phase and the second phase are exposed on an outer surface, and the outer surfaces of the first phase and the second phase are spherical. Nano-sized particles characterized by being.
(2) The nano-sized particles according to (1), wherein the average particle size is 2 to 300 nm.
(3) The nano-sized particle according to (1), wherein an interface shape of a joint portion between the first phase and the second phase is a circle or an ellipse.
(4) including element A-1, element A-2, and element A-3, which are three elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn A first phase that is a simple substance or a solid solution of the element A-1, a second phase that is a simple substance or a solid solution of the element A-2, and another second that is a simple substance or a solid solution of the element A-3. And the first phase, the second phase, and the other second phase are all exposed on the outer surface, and the first phase, the second phase, and the other phase are exposed. Nano-sized particles, characterized in that the outer surface of the second phase is spherical.
(5) The nano-sized particles according to (1) or (4), wherein the first phase is silicon to which phosphorus or boron is added (6) Cu (copper), Ag (silver), and Au A third phase which further includes an element M which is at least one element selected from the group consisting of (gold) and which is a compound of the element A-1 and the element M or a simple substance or a solid solution of the element M And all of the first phase, the second phase, and the third phase are exposed on the outer surface, and the outer surface of the first phase, the second phase, and the third phase. The nano-sized particles according to (1), wherein is a spherical shape.
(7) The nanosized particle according to (6), wherein the third phase is a compound of MA-1 _x (x ≦ 1, 3 <x).
(8) The nanosized particle according to (6), wherein an atomic ratio of the element M in a total of the element A-1 and the element M is 0.01 to 60%.
(9) It further includes at least one element M ′ selected from the group consisting of Cu, Ag and Au, and the element M ′ is an element of a different type from the element M constituting the third phase. And having a third phase that is a compound of the element A-1 and the element M ′ or a simple substance or a solid solution of the element M ′, and includes the first phase, the second phase, and the All of the third phase and the other third phase are exposed on the outer surface, and the outer surfaces of the first phase, the second phase, the third phase, and the other third phase are The nano-sized particle according to (6), which has a spherical shape.
(10) Fe (iron), Co (cobalt), Ni (nickel), Ca (calcium), Sc (scandium), Ti (titanium), V (vanadium), Cr (chromium), Mn (manganese), Sr ( Strontium), Y (yttrium), Zr (zirconium), Nb (niobium), Mo (molybdenum), Tc (technetium), Ru (ruthenium), Rh (rhodium), Ba (barium), lanthanoid element (Ce (cerium) And Pm (promethium)), Hf (hafnium), Ta (tantalum), W (tungsten), Re (rhenium), Os (osmium) and Ir (iridium). An element D that is an element, and a fourth phase that is a compound of the element A-1 and the element D (1) or (6), wherein a part or all of the fourth phase is covered with the first phase, and an outer surface of the first phase is spherical. Nano-sized particles. The lanthanoid elements (excluding Ce and Pm) are La (lanthanum), Pr (praseodymium), Nd (neodymium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy. (Dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).
(11) The nanosized particle according to (10), wherein the fourth phase is a compound of DA-1 _y (1 <y ≦ 3).
(12) The nanosize according to (10), wherein an atomic ratio of the element D in a total of the element A-1, the element A-2, and the element D is 0.01 to 30% particle.
(13) Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (excluding Ce and Pm), Hf , Ta, W, Re, Os, and Ir, further including an element D ′ that is at least one element selected from the group consisting of the element D ′ and the element D constituting the fourth phase It further includes another fourth phase that is a different kind of element and is a compound of the element A-1 and the element D ′, and a part or all of the other fourth phase is the first phase. The nano-sized particles according to (10), which are covered with a phase of
(14) A negative electrode material for a lithium ion secondary battery comprising the nano-sized particles according to any one of (1) to (13) as a negative electrode active material.
(15) It further has a conductive assistant, and the conductive assistant is selected from the group consisting of C (carbon), Cu (copper), Sn (tin), Zn (zinc), Ni (nickel), and Ag (silver). (14) The negative electrode material for a lithium ion secondary battery according to (14), wherein the negative electrode material is at least one kind of powder.
(16) The negative electrode material for a lithium ion secondary battery according to (14), wherein the conductive additive contains carbon nanohorn.
(17) A negative electrode for a lithium ion secondary battery using the negative electrode material for a lithium ion secondary battery according to any one of (14) to (16).
(18) In an electrolyte having lithium ion conductivity, comprising a positive electrode capable of inserting and extracting lithium ions, a negative electrode according to (17), and a separator disposed between the positive electrode and the negative electrode. A lithium ion secondary battery comprising the positive electrode, the negative electrode, and the separator.
(19) Supplying a raw material containing at least two elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn into plasma to obtain nano-sized particles. A method for producing nano-sized particles.
(20) At least two elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn and at least one element selected from the group consisting of Cu, Ag and Au A method for producing nano-sized particles, wherein a nano-sized particle is obtained by supplying a raw material comprising:
(21) At least two elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn and at least one element selected from the group consisting of Cu, Ag and Au Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (excluding Ce and Pm), Hf, A method for producing nano-sized particles, characterized in that a raw material containing at least one element selected from the group consisting of Ta, W, Re, Os and Ir is supplied into plasma to obtain nano-sized particles .

  According to the present invention, a negative electrode material for a lithium ion secondary battery that achieves a high capacity and good cycle characteristics can be obtained.

(A), (b) The schematic sectional drawing of the nanosized particle which concerns on 1st Embodiment. (A), (b) The schematic sectional drawing of the nanosized particle which concerns on 2nd Embodiment. (A), (b) The schematic sectional drawing of the nanosized particle which concerns on 3rd Embodiment. (A), (b) Schematic sectional drawing of the nanosized particle which concerns on the other example of 3rd Embodiment. The schematic sectional drawing of the nanosized particle which concerns on the other example of 3rd Embodiment. The schematic sectional drawing of the nanosized particle which concerns on 4th Embodiment. The figure which shows the nanosize particle manufacturing apparatus which concerns on this invention. The figure which shows the mixer used for manufacture of the negative electrode which concerns on this invention. The figure which shows the coater used for manufacture of the negative electrode which concerns on this invention. The binary system phase diagram of Si and Sn. Binary system phase diagram of Al and Si. The binary system phase diagram of Al and Sn. Binary system phase diagram of Cu and Si. The binary system phase diagram of Cu and Sn. The binary system phase diagram of Fe and Si. The binary system phase diagram of Co and Si. The binary system phase diagram of Co and Fe. The binary system phase diagram of Fe and Sn. Binary system phase diagram of Cu and Fe.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1. First embodiment)
(1-1. Configuration of Nano-sized Particle 1)
The nanosize particle 1 according to the first embodiment will be described.
FIG. 1A is a schematic cross-sectional view of the nano-sized particle 1. The nanosized particle 1 has a first phase 3 and a second phase 5, and both the first phase 3 and the second phase 5 are exposed on the outer surface of the nanosized particle 1. The outer surfaces of the first phase 3 and the second phase 5 form a spherical shape, and the first phase 3 and the second phase 5 are joined.

  The first phase 3 is a simple substance of the element A-1, and the element A-1 is one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn. is there. The element A-1 is an element that easily stores lithium. Note that the first phase 3 may be a solid solution containing the element A-1 as a main component. The element that forms a solid solution with the element A-1 may be an element selected from the group capable of selecting the element A-1 or an element not listed in the group. The first phase 3 can occlude lithium.

  The outer surfaces of the first phase 3 and the second phase 5 have a spherical shape means that the first phase 3 and the second phase 5 other than the portion where the first phase 3 and the second phase 5 are in contact with each other. Means a sphere or an ellipsoid. In other words, the surfaces of the first phase 3 and the second phase 5 other than the portion where the first phase 3 and the second phase 5 are in contact are generally smooth. It is composed of simple curved surfaces. The shape of the 1st phase 3 and the 2nd phase 5 is a shape different from the shape which has an angle | corner on the surface as formed by the crushing method. Moreover, the interface shape of the junction part of the 1st phase 3 and the 2nd phase 5 is circular or an ellipse.

  The second phase 5 is a simple substance or a solid solution of the element A-2. The element A-2 is one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn, and is a different element from the element A-1. The element A-2 can occlude Li.

  The first phase 3 is preferably silicon to which phosphorus or boron is added. The conductivity of silicon can be increased by adding phosphorus or boron. Indium or gallium can be used instead of phosphorus, and arsenic can be used instead of boron. By increasing the conductivity of the silicon of the first phase 3, the negative electrode using such nano-sized particles has a small internal resistance, allows a large current to flow, and has a good high-rate characteristic.

  The average particle size of the nano-sized particles 1 is preferably 2 to 300 nm, more preferably 50 to 200 nm. According to Hall Petch's law, if the particle size is small, the yield stress increases. Therefore, if the average particle size of the nano-sized particles 1 is 2 to 300 nm, the particle size is sufficiently small, the yield stress is sufficiently large, and pulverized by charge / discharge. Hateful. When the average particle size is smaller than 2 nm, it becomes difficult to handle the nano-sized particles after synthesis. When the average particle size is larger than 300 nm, the particle size becomes large and the yield stress is not sufficient.

  Since the fine particles are usually present in an aggregated state, the average particle size of the nano-sized particles here refers to the average particle size of the primary particles. For particle measurement, image information of an electron microscope (SEM) and a volume-based median diameter of a dynamic light scattering photometer (DLS) are used in combination. For the average particle size, confirm the particle shape in advance using an SEM image, obtain the particle size by image analysis (for example, “A Image-kun” (registered trademark) manufactured by Asahi Kasei Engineering), or disperse the particles in a solvent to obtain DLS (for example, , OLSKA Electronics DLS-8000). If the fine particles are sufficiently dispersed and not agglomerated, almost the same measurement results can be obtained with SEM and DLS. Even when the shape of the nano-sized particles is a highly developed structure such as acetylene black, the average particle size is defined by the primary particle size here, and the average particle size is obtained by image analysis of the SEM photograph. be able to.

  Further, the nano-sized particle 1 according to the first embodiment has another second phase 9 in addition to the second phase 5 like the nano-sized particle 7 shown in FIG. Also good. The other second phase 9 is a single element or a solid solution of the element A-3, and the element A-3 is selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn. It is a seed element, and is a different kind of element from element A-1 and element A-2. The other second phase 9 has a spherical shape and is exposed on the outer surface of the nano-sized particle 7. For example, there is a second phase 5 at one end of the first phase 3 and another second phase 9 at the other end, and the nano-sized particle 7 has two small spheres joined to the surface of a large sphere. It has a shape like a water molecule. For example, silicon can be used as the element A-1, tin can be used as the element A-2, and aluminum can be used as the element A-3.

  Note that oxygen may be bonded to the outermost surface of the nano-sized particle 1. This is because when the nano-sized particles 1 are taken out into the air, oxygen in the air reacts with elements on the surface of the nano-sized particles 1.

(1-2. Effects of nano-sized particles 1)
According to the first embodiment, volume expansion occurs when the first phase 3 occludes lithium, but expansion also occurs when the second phase 5 occludes lithium. However, since the electrochemical potential for storing lithium differs between the first phase 3 and the second phase 5, when one phase preferentially stores lithium and one phase expands in volume, the other phase The volume expansion of one phase is relatively reduced, and the other phase makes it difficult for one phase to be volume expanded. Therefore, compared with particles having only one phase, the nano-sized particles 1 having the first phase 3 and the second phase 5 are less likely to expand when occlusion of lithium, and the occlusion amount of lithium is suppressed. . Therefore, according to 1st Embodiment, even if the nanosized particle 1 occludes lithium, volume expansion is suppressed and the fall of the discharge capacity at the time of cycling characteristics is suppressed.

  Moreover, according to 1st Embodiment, since the nanosized particle 1 does not expand easily, even if it puts out the nanosized particle 1 in air | atmosphere, it is hard to react with oxygen in air | atmosphere. When nanosized particles having only one phase are left in the atmosphere without surface protection, they react with oxygen from the surface, and oxidation proceeds from the surface to the inside of the particles, so that the entire nanosized particles are oxidized. However, when the nano-sized particles 1 of the present invention are left in the atmosphere, the outermost surface of the particles reacts with oxygen, but since the nano-sized particles are difficult to expand as a whole, oxygen is less likely to enter the interior, It is difficult to oxidize to the center of 1. Therefore, normal metal nanoparticles have a large specific surface area and are likely to oxidize and generate heat and volume expansion, but the nano-sized particles 1 of the present invention do not need to be specially coated with organic substances or metal oxides. It can be handled as powder in the atmosphere. Industrial use value is great.

  In addition, according to the first embodiment, the first phase 3 and the second phase 5 are both composed of an element capable of occluding a larger amount of lithium than carbon. The amount of occlusion of lithium is larger than that of the negative electrode active material.

  In addition, according to the first embodiment, when the second phase 5 has higher conductivity than the first phase 3, the nano-sized particles 1 have a nano-level current collection spot on each nano-sized particle 1. Thus, the nano-sized particles 1 become a negative electrode material with good conductivity, and a negative electrode with good current collecting performance is obtained. In particular, when the first phase 3 is formed of silicon having low conductivity, the second phase 5 is made conductive compared to silicon nanoparticles by using a metal element such as tin or aluminum having higher conductivity than silicon. A negative electrode material with good properties can be obtained.

  The nano-sized particles 7 including both the second phase 5 and the other second phase 9 have the same effect as the nano-sized particles 1, and the number of nano-level current collecting spots is increased. Effectively improve.

(2. Second Embodiment)
(2-1. Configuration of Nano-sized Particle 11)
The nanosize particle 11 according to the second embodiment will be described. In the following embodiment, the same number is attached | subjected to the element which fulfill | performs the same aspect as 1st Embodiment, and the overlapping description is avoided.
FIG. 2A is a schematic cross-sectional view of the nano-sized particle 11. The nano-sized particle 11 has a first phase 3, a second phase 5, and a third phase 13, and all of the first phase 3, the second phase 5, and the third phase 13 are included. Are exposed on the outer surface, the outer surfaces of the first phase 3, the second phase 5 and the third phase 13 are spherical, and the second phase 5 is joined to the first phase 3, The third phase 13 is bonded to the first phase 3.

  The third phase 13 is a compound of the element A-1 and the element M or a simple substance or a solid solution of the element M, and is crystalline. The element M is one element selected from the group consisting of Cu, Ag, and Au. The element M is an element that hardly occludes lithium. The third phase 13 hardly absorbs lithium.

If the element A-1 and the element M are a combination capable of forming a compound, the third phase 13 is formed from MA-1 _x (x ≦ 1, 3 <x) which is a compound of the element A-1 and the element M Is done. On the other hand, if the combination of the element A-1 and the element M does not form a compound, the third phase 13 becomes a simple substance or a solid solution of the element M.

  For example, when the element A-1 is Si and the element M is Cu, the third phase 13 is formed from copper silicide that is a compound of the element M and the element A-1.

  For example, when the element A-1 is Si and the element M is Ag or Au, the third phase 13 is formed from a single element or a solid solution of the element M.

  The atomic ratio of the element M in the total of the element A-1 and the element M is preferably 0.01 to 60%. When the atomic ratio is 0.01 to 60%, when the nano-sized particles 11 are used as a negative electrode material for a lithium ion secondary battery, both cycle characteristics and high capacity can be achieved. On the other hand, if it is less than 0.01%, the volume expansion of the nano-sized particles 11 during occlusion of lithium cannot be sufficiently suppressed, and if it exceeds 60%, the merit of high capacity is particularly lost.

  In particular, it is preferable that the first phase 3 is mainly composed of crystalline silicon and the third phase 13 is crystalline silicide.

  Note that the nano-sized particle 11 according to the second embodiment may have another third phase 17 like the nano-sized particle 15 illustrated in FIG. The other third phase 17 includes an element M ′ selected from the group consisting of Cu, Ag, and Au, and the element M ′ is different in kind from the element M. The other third phase 17 is a compound of the element A-1 and the element M ′ or a simple substance or a solid solution of the element M ′. All of the first phase 3, the third phase 13, and the other third phase 17 are exposed on the outer surface, and the outer surface of the first phase 3, the third phase 13, and the other third phase 17. Is spherical. For example, in the nano-sized particle 15, the second phase 5, the third phase 13, and the other third phase 17 having a small spherical shape are bonded to the surface of the first phase 3 having a large spherical shape. Has a shape. Moreover, it is preferable that the atomic ratio of the total of the element M and the element M 'to the total of the element A-1, the element M, and the element M' is 0.01 to 60%.

(2-2. Effects of nano-sized particles 11)
According to the second embodiment, in addition to the effects obtained in the first embodiment, the nano-sized particles 11 have an effect that even if lithium is occluded, the nano-size particles 11 are more difficult to be pulverized. In the second embodiment, volume expansion occurs when the first phase 3 occludes lithium, but since the third phase 13 does not occlude lithium, the expansion of the first phase 3 in contact with the third phase 13 is It can be suppressed. That is, even if the first phase 3 occludes lithium and expands its volume, the third phase 13 hardly expands, so that the third phase 13 exhibits an effect like a wedge or a pin, and is nanosized. Suppresses the expansion of the entire particle. Therefore, compared with the particle | grains which do not have the 3rd phase 13, the nanosize particle | grains 11 which have the 3rd phase 13 are hard to expand | swell when occlusion of lithium, and the occlusion amount of lithium becomes small. Therefore, the nano-sized particles 11 are not easily pulverized even when lithium is occluded.

  The nano-sized particle 15 including both the third phase 13 and the other third phase 17 has the same effect as the nano-sized particle 11, increases the nano-level current collection spot, and the current collection performance is effective. Improve.

(3. Third embodiment)
(3-1. Configuration of Nano-sized Particle 19)
A nanosize particle 19 according to the third embodiment will be described.
FIG. 3A is a schematic cross-sectional view of the nano-sized particle 19. The nano-sized particle 19 has a first phase 3, a second phase 5, and a fourth phase 21, and both the first phase 3 and the second phase 5 are nano-sized particles 19. It is exposed on the outer surface, and the outer surfaces of the first phase 3 and the second phase 5 form a spherical shape, and the first phase 3 and the second phase 5 are joined. Further, part or all of the fourth phase 21 is covered with the first phase 3.

The fourth phase 21 is a compound of element A and element D. Element D is Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (except for Ce and Pm), Hf , One element selected from the group consisting of Ta, W, Re, Os and Ir. The element D is an element that does not easily store lithium, and can form a compound that is the elements A-1 and DA-1 _y (1 <y ≦ 3). The fourth phase 21 hardly absorbs lithium.

  The atomic ratio of element D in the total of element A-1 and element D is preferably 0.01 to 30%. When the atomic ratio is 0.01 to 30%, when the nano-sized particles 19 are used as a negative electrode material for a lithium ion secondary battery, both cycle characteristics and high capacity can be achieved. On the other hand, if it is less than 0.01%, the pulverization of the nano-sized particles 19 during occlusion of lithium cannot be suppressed, and if it exceeds 30%, the merit of high capacity is particularly lost.

  In FIG. 3A, the plurality of fourth phases 21 are dispersed in the first phase 3, but a single fourth phase 21 may be dispersed.

  Further, a part of the fourth phase 21 may be exposed on the surface of the nano-sized particles 19. That is, it is not always necessary to cover the entire periphery of the fourth phase 21 with the first phase 3, and only a part of the periphery of the fourth phase 21 may be covered with the first phase.

  Further, the nano-sized particles 19 according to the third embodiment may have the crystallites 25 of the element A-1 in the first phase 3 like the nano-sized particles 23 shown in FIG. good. The microcrystal 25 of the element A-1 is likely to be generated when the atomic ratio of the element D in the total of the element A-1 and the element D is small. The smaller the element D, the more the crystal phase of the element A-1.

  Further, the nano-sized particle 19 according to the third embodiment includes the element D and the element D ′ like the nano-sized particle 27 illustrated in FIG. 4A, and the fourth phase 21 is included in the first phase 3. And the other fourth phase 29 may be included. The other fourth phase 29 is a compound of the element A-1 and the element D ′. For example, there is a case where the first phase 3 is silicon, the fourth phase 21 is iron silicide, and the other fourth phase 29 is cobalt silicide. At this time, a solid solution of iron and cobalt may be formed in the first phase 3.

  The element D ′ includes Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, and a lanthanoid element (except for Ce and Pm). , Hf, Ta, W, Re, Os, and Ir, and is an element of a different type from the element D.

  In addition, the nano-sized particles 19 according to the third embodiment include the fourth phase 21 and the other fourth phases in the first phase 3 like the nano-sized particles 31 illustrated in FIG. 29, You may have the microcrystal 25 of the element A-1. The microcrystal 25 of the element A-1 is likely to be generated when the total atomic ratio of the element D and the element D ′ in the total of the element A-1, the element D, and the element D ′ is small. The smaller the sum of the element D and the element D ′, the more the crystal phase of the element A-1.

  Further, as in the nano-sized particles 33 shown in FIG. 5, another fourth phase 34 may be formed in the second phase 5. The other fourth phase 34 is a compound of element D and element A-2. For example, the first phase 3 is silicon, the second phase 5 is tin, the fourth phase 21 is iron silicide, and the other fourth phase 34 is an iron-tin alloy. . The other fourth phase 34 has an effect of suppressing the expansion of the second phase 5 by the same action as the effect of the fourth phase 21 suppressing the expansion of the first phase 3.

(3-2. Effects of nano-sized particles 19)
According to the third embodiment, in addition to the effects obtained in the first embodiment, the nano-sized particles 19 are not easily pulverized even when lithium is occluded. In the third embodiment, when the first phase 3 occludes lithium, the volume expands. However, since the fourth phase 21 does not occlude lithium, the expansion of the first phase 3 in contact with the fourth phase 21 is performed. Is suppressed. That is, even if the first phase 3 occludes lithium and tries to expand its volume, the fourth phase 21 hardly expands, so the interface between the first phase 3 and the fourth phase 21 is difficult to slip, The phase 4 of 4 exhibits an effect like a wedge or a pin and suppresses the expansion of the entire nano-sized particle. Therefore, compared with the particle | grains which do not have the 4th phase 21, the nanosize particle | grains 19 which have the 4th phase 21 are hard to expand | swell when occluding lithium, and the occlusion amount of lithium is suppressed. For this reason, the nano-sized particles 19 are not easily pulverized even when lithium is occluded. The other fourth phase 34 functions in the same manner as the fourth phase 21 with respect to the second phase 5.

(4. Fourth embodiment)
(4-1. Configuration of nano-sized particles 35)
The nanosize particles 35 according to the fourth embodiment will be described.
FIG. 6 is a schematic cross-sectional view of the nano-sized particle 35. The nano-sized particles 35 have a first phase 3, a second phase 5, a third phase 13, and a fourth phase 21, and the first phase 3, the second phase 5, and the third phase 21. All of the phases 13 are exposed on the outer surface of the nano-sized particles 35, and the outer surfaces of the first phase 3, the second phase 5, and the third phase 13 form a spherical shape, The first phase 3 and the second phase 5 are joined, and the first phase 3 and the third phase 13 are joined. Further, part or all of the fourth phase 21 is covered with the first phase 3.

  The nano-sized particle 35 according to the fourth embodiment may have another second phase 9 bonded to the first phase 3 in addition to the configuration of the nano-sized particle 35. The third phase 17 may be bonded to the phase 3, and the microcrystal 25 of the element A-1 may be included inside the first phase 3, and is covered with the first phase 3. The other fourth phase 29 may be included, and the other fourth phase 34 may be included inside the second phase 5.

(4-2. Effects of the nano-sized particles 35)
In the fourth embodiment, in addition to the effects obtained in the first embodiment, the effects of the second embodiment and the effects of the third embodiment are combined, the capacity is large, and lithium is occluded and released. Nano-sized particles that are not easily pulverized and have excellent current collecting properties.

(5. Method for producing nano-sized particles)
A method for producing nano-sized particles will be described.
Nano-sized particles are synthesized by a gas phase synthesis method. In particular, nano-sized particles can be produced by converting the raw material powder into plasma and heating it to the equivalent of 10,000 K, followed by cooling.

  A specific example of a manufacturing apparatus used for manufacturing nano-sized particles will be described with reference to FIG. In the nanosize particle manufacturing apparatus 37 shown in FIG. 7, a high frequency coil 45 for generating plasma is wound around the upper outer wall of the reaction chamber 39. An AC voltage of several MHz is applied to the high frequency coil 45 from the high frequency power supply 47. A preferred frequency is 4 MHz. The upper outer wall around which the high-frequency coil 45 is wound is a cylindrical double tube made of quartz glass or the like, and cooling water is passed through the gap to prevent the quartz glass from melting by plasma.

  In addition, a sheath gas supply port 43 is provided in the upper part of the reaction chamber 39 together with the raw material powder supply port 41. The raw material powder 42 supplied from the raw material powder feeder is supplied into the plasma 49 through the raw material powder supply port 41 together with a carrier gas (rare gas such as helium and argon). The sheath gas 44 is supplied to the reaction chamber 39 through the sheath gas supply port 43. Note that the raw material powder supply port 41 is not necessarily installed above the plasma 49 as shown in FIG. 7, and a nozzle can be installed in the lateral direction of the plasma 49. The raw material powder supply port 41 may be water-cooled with cooling water. In addition, the property of the raw material of the nanosize particles supplied to the plasma is not limited to the powder, and a slurry of the raw material powder or a gaseous raw material may be supplied.

  The reaction chamber 39 plays a role of maintaining the pressure in the plasma reaction part and suppressing the dispersion of the produced fine powder. The reaction chamber 39 is also water-cooled to prevent damage due to plasma. A suction tube is connected to the side of the reaction chamber 39, and a filter 51 for collecting the synthesized fine powder is installed in the middle of the suction tube. The suction pipe connecting the reaction chamber 39 and the filter 51 is also water-cooled with cooling water. The pressure in the reaction chamber 39 is adjusted by the suction capacity of a vacuum pump installed on the downstream side of the filter 51.

  The method for producing nano-sized particles is a bottom-up method in which a nano-sized particle is deposited from plasma to a solid via a gas and a liquid, so that it becomes spherical at the stage of droplets, and the first phase 3 and the second phase are produced. Phase 5 is spherical. On the other hand, in the crushing method and the mechanochemical method, in the top-down method in which large particles are made small, the shape of the particles is rugged and is significantly different from the spherical shape of the nano-sized particles 1.

  In addition, when the mixed powder of each powder of element A-1 and element A-2 is used for raw material powder, the nanosized particle 1 which concerns on 1st Embodiment is obtained. On the other hand, when the mixed powder of each powder of the element A-1, the element A-2, and the element M is used as the raw material powder, the nano-sized particles 11 according to the second embodiment are obtained. Moreover, when the mixed powder of each powder of the element A-1, the element A-2, and the element D is used for raw material powder, the nanosized particle 19 which concerns on 3rd Embodiment is obtained. Moreover, when the mixed powder of each powder of the element A-1, the element A-2, the element M, and the element D is used for raw material powder, the nanosized particle 35 which concerns on 4th Embodiment is obtained.

(6. Production of lithium ion secondary battery)
(6-1. Production of negative electrode for lithium ion secondary battery)
First, the manufacturing method of the negative electrode for lithium ion secondary batteries is demonstrated. As shown in FIG. 8, a slurry raw material 57 is put into a mixer 53 and kneaded to form a slurry 55. The slurry raw material 57 is nano-sized particles, a conductive aid, a binder, a thickener, a solvent, and the like.

  The solid content in the slurry 55 includes 25 to 90% by weight of nano-sized particles, 5 to 70% by weight of a conductive aid, and 1 to 10% by weight of a binder.

  As the mixer 53, a general kneader used for preparing a slurry can be used, and an apparatus capable of preparing a slurry called a kneader, a stirrer, a disperser, a mixer, or the like may be used. Moreover, as a thickener, it is suitable to use polysaccharides, such as carboxymethylcellulose and methylcellulose, as a 1 type, or 2 or more types of mixture. Moreover, water can be used as a solvent. Further, when preparing an organic slurry, N-methyl-2-pyrrolidone can be used as a solvent.

  The conductive assistant is a powder made of at least one conductive material selected from the group consisting of carbon, copper, tin, zinc, nickel, and silver. A single powder of carbon, copper, tin, zinc, nickel, or silver may be used, or a powder of each alloy may be used. For example, general carbon black such as furnace black and acetylene black can be used. In addition, carbon nanohorns can be added as conductive aids. In particular, when the element A-1 of the nano-sized particles is silicon having low conductivity, silicon is exposed on the surface of the nano-sized particles, and the conductivity becomes low. Therefore, carbon nanohorn is added as a conductive aid. It is preferable. Here, the carbon nanohorn (CNH) has a structure in which a graphene sheet is rounded into a conical shape, and the actual form is an aggregate in the form of a radial sea urchin with many CNHs facing the apex to the outside. Exists as. The outer diameter of the CNH sea urchin-like aggregate is about 50 nm to 250 nm. In particular, CNH having an average particle size of about 80 nm is preferable.

  The average particle size of the conductive assistant also refers to the average particle size of the primary particles. Even when the structure shape is highly developed such as acetylene black, the average particle diameter can be defined by the primary particle diameter here, and the average particle diameter can be obtained by image analysis of the SEM photograph.

  Moreover, you may use both a particulate-form conductive support agent and a wire-shaped conductive support agent. The wire-shaped conductive aid is a wire made of a conductive material, and the conductive materials listed in the particulate conductive aid can be used. As the wire-shaped conductive assistant, a linear body having an outer diameter of 300 nm or less, such as carbon fiber, carbon nanotube, copper nanowire, or nickel nanowire, can be used. By using a wire-shaped conductive aid, electrical connection with the negative electrode active material or current collector is easily maintained, and the current collection performance is improved. Cracks are less likely to occur. For example, it is conceivable to use copper powder as the particulate conductive additive and use vapor grown carbon fiber (VGCF) as the wire-shaped conductive aid. In addition, you may use only a wire-shaped conductive support agent, without adding a particulate-form conductive support agent.

  The length of the wire-shaped conductive assistant is preferably 0.1 μm to 2 mm. The outer diameter of the conductive aid is preferably 4 nm to 1000 nm, more preferably 25 nm to 200 nm. If the length of the conductive auxiliary agent is 0.1 μm or more, the length is sufficient to increase the productivity of the conductive auxiliary agent, and if the length is 2 mm or less, application of the slurry is easy. Further, when the outer diameter of the conductive auxiliary agent is larger than 4 nm, the synthesis is easy, and when the outer diameter is thinner than 1000 nm, the slurry is easily kneaded. The measuring method of the outer diameter and length of the conductive material was performed by image analysis using SEM.

  The binder is a resin binder, and a fluororesin such as polyvinylidene fluoride (PVdF) and styrene butadiene rubber (SBR) or a rubber-based organic material can be used.

  Next, as illustrated in FIG. 9, the slurry 55 is applied to one surface of the current collector 61 using, for example, a coater 59. As the coater, a general coating apparatus capable of applying the slurry to the current collector can be used. For example, a coater using a roll coater or a doctor blade, a comma coater, or a die coater.

  The current collector 61 is a foil made of at least one metal selected from the group consisting of copper, nickel, and stainless steel. Each may be used alone or may be an alloy of each. The thickness is preferably 4 μm to 35 μm, and more preferably 8 μm to 18 μm.

  Then, in order to dry at about 50-150 degreeC and adjust thickness, the negative electrode for lithium ion secondary batteries is obtained through a roll press.

(6-2. Production of positive electrode for lithium ion secondary battery)
First, a positive electrode active material, a conductive additive, a binder, and a solvent are mixed to prepare a positive electrode active material composition. The composition of the positive electrode active material is directly applied on a metal current collector such as an aluminum foil and dried to prepare a positive electrode.

Any positive electrode active material can be used as long as it is generally used. For example, LiCoO ₂ , LiMn ₂ O ₄ , LiMnO ₂ , LiNiO ₂ , LiCo _1/3 Ni _1/3 Mn _1/3. And compounds such as LiFePO ₄ .

  For example, carbon black is used as the conductive assistant, polyvinylidene fluoride (PVdF), a water-soluble acrylic binder is used as the binder, and N-methyl-2-pyrrolidone (NMP) is used as the solvent. Use water, etc. At this time, the contents of the positive electrode active material, the conductive additive, the binder, and the solvent are at levels that are normally used in lithium ion secondary batteries.

(6-3. Separator)
Any separator can be used as long as it has a function of insulating electronic conduction between the positive electrode and the negative electrode and is usually used in a lithium ion secondary battery. For example, a microporous polyolefin film can be used.

(6-4. Electrolytic solution / electrolyte)
An organic electrolyte (non-aqueous electrolyte), an inorganic solid electrolyte, a polymer solid electrolyte, or the like can be used as an electrolyte and an electrolyte in a lithium ion secondary battery, a Li polymer battery, or the like.
Specific examples of the solvent for the organic electrolyte include carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate; diethyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di Ethers such as butyl ether and diethylene glycol dimethyl ether; aprotic such as benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethylchlorobenzene, nitrobenzene Solvent, or two or more of these solvents Mixed solvent of thereof.

The electrolyte of the organic electrolyte includes LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAlO ₄ , LiAlCl ₄ , LiSbF ₆ , LiSCN, LiCl, LiCF ₃ SO ₃ , LiCF ₃ CO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) A mixture of one or more electrolytes made of a lithium salt such as ₂ can be used.

  As an additive for the organic electrolyte, it is desirable to add a compound capable of forming an effective solid electrolyte interface coating on the surface of the negative electrode active material. For example, a substance having an unsaturated bond in the molecule and capable of reductive polymerization during charging, such as vinylene carbonate (VC), is added.

  In addition, when a polymer solid electrolyte is used instead of the organic electrolyte, the electrolyte is contained in a polymer made of polyethylene oxide, polypropylene oxide, polyethyleneimine, or the like, which is a polymer having high ion conductivity with respect to lithium ions. A gelled polymer can be used.

Further, lithium nitride, lithium halide, lithium oxyacid _{salt, Li 4 SiO 4, Li 4} SiO 4 -LiI-LiOH, Li 3 PO 4 -Li 4 SiO 4, Li 2 SiS 3, Li 3 PO 4 -Li Inorganic materials such as ₂ S—SiS ₂ and phosphorus sulfide compounds may be used as the inorganic solid electrolyte.

(6-5. Assembly of lithium ion secondary battery)
A separator is disposed between the positive electrode and the negative electrode as described above to form a battery structure. When such a battery structure is wound or folded and placed in a cylindrical battery case or a rectangular battery case, an electrolyte is injected to complete a lithium ion secondary battery.

(6-6. Effect of the lithium ion secondary battery according to the present invention)
The lithium ion secondary battery using the nanosized particles as the negative electrode material according to the present invention has a larger capacity than the conventional lithium ion secondary battery because the nanosized particles use an element having a higher capacity per unit volume than carbon. In addition, cycle characteristics are good because nano-sized particles are difficult to be pulverized.

Hereinafter, the present invention will be specifically described using examples and comparative examples.
[Example 1]
(Production of nano-sized particles)
Ar gas generated in the reaction chamber using the mixed powder obtained by mixing silicon powder and tin powder in a molar ratio of Si: Sn = 3: 1 using the apparatus of FIG. The silicon and tin nano-sized particles were manufactured by continuously supplying the plasma with a carrier gas.

  More specifically, it was produced by the following method. After evacuating the reaction chamber with a vacuum pump, Ar gas was introduced to atmospheric pressure. This exhaustion and Ar gas introduction were repeated three times to exhaust the residual air in the reaction vessel. Thereafter, Ar gas was introduced into the reaction vessel as a plasma gas at a flow rate of 13 L / min, an AC voltage was applied to the high frequency coil, and high frequency plasma was generated by a high frequency electromagnetic field (frequency 4 MHz). The plate power at this time was 20 kW. Ar gas having a flow rate of 1.0 L / min was used as a carrier gas for supplying the raw material powder. The obtained fine powder was collected with a filter.

  The formation process of nano-sized particles according to Example 1 will be considered. FIG. 10 is a binary phase diagram of silicon and tin. Since the silicon powder and the tin powder were mixed at a molar ratio of Si: Sn = 3: 1, mole Sn / (Si + Sn) = 0.25 in the raw material powder. The thick line in FIG. 10 is a line indicating mole Sn / (Si + Sn) = 0.25. Since the plasma generated by the high frequency coil is equivalent to 10,000 K, the temperature is far beyond the temperature range of the phase diagram, and a plasma in which tin atoms and silicon atoms are uniformly mixed is obtained. When the plasma cools, both Si and Sn are deposited. Therefore, when the silicon and tin plasma is cooled, nano-sized particles having Si and Sn are formed. At that time, since Si and Sn have low affinity, it is considered that Si and Sn take a shape in which two particles are joined so as to reduce the area in contact with each other.

(Evaluation of cycle characteristics of nano-sized particles)
(I) Preparation of negative electrode slurry The silicon and tin nano-sized particles according to Example 1 were used. Nanosized particles 45.5 wt% and acetylene black (average particle size 35 nm, manufactured by Denki Kagaku Kogyo Co., Ltd., powdered product) were added to the mixer at a ratio of 47.5 wt%. Furthermore, styrene butadiene rubber (SBR) 40 wt% emulsion (manufactured by Nippon Zeon Co., Ltd., BM400B) as a binder is 2 wt% in terms of solid content, and carboxymethylcellulose sodium (Daicel Chemical Industries) as a thickener to adjust the viscosity of the slurry. Co., Ltd., # 2200) A 1 wt% solution was mixed at a rate of 5 wt% in terms of solid content to prepare a slurry.
(Ii) Production of negative electrode Using the doctor blade of the automatic coating apparatus, the prepared slurry was 15 μm thick on a 10 μm thick electrolytic copper foil for current collector (Furukawa Electric Co., Ltd., NC-WS). And dried at 70 ° C. to produce a negative electrode for a lithium ion secondary battery.
(Iii) Characteristic evaluation A lithium secondary battery is constructed using a negative electrode for a lithium ion secondary battery, an electrolytic solution composed of a mixed solution of ethylene carbonate and diethyl carbonate containing 1 mol / L LiPF ₆ , and a metal Li foil counter electrode. The charge / discharge characteristics were examined. The characteristics were evaluated by measuring the initial discharge capacity and the discharge capacity after 50 cycles of charge / discharge, and calculating the rate of decrease of the discharge capacity. The discharge capacity was calculated on the basis of the weight of active materials Si and Sn effective for lithium insertion / extraction, excluding silicon and tin that do not occlude / release lithium such as formation of silicide. First, in a 25 ° C. environment, charging was performed under constant current and constant voltage conditions until the current value was 0.1 C and the voltage value was 0.02 V, and the charging was stopped when the current value decreased to 0.05 C. Next, discharging was performed under the condition of a current value of 0.1 C until the voltage with respect to the metal Li became 1.5 V, and a 0.1 C initial discharge capacity was measured. 1C is a current value that can be fully charged in one hour. Both charging and discharging were performed in a 25 ° C. environment. Next, the above charge / discharge cycle was repeated 50 cycles at a charge / discharge rate of 0.2C. The ratio of the discharge capacity when charging / discharging was repeated 50 cycles with respect to the 0.2 C initial discharge capacity was obtained as a percentage, and was defined as the capacity maintenance ratio.

[Example 2]
Silicon and tin nano-sized particles according to Example 1 were used. Nanosize particles and carbon nanohorn (manufactured by NEC Corporation, average particle size 80 nm) at a ratio of nanosize particles: CNH = 7: 3 (weight ratio) with a grinder (Mararo, Nara Machinery Co., Ltd.) After precision mixing, the mixture was put into a mixer at a ratio of 65 wt% of the precision mixed product and 28 wt% of acetylene black. Further, the same binder and thickener as in Example 1 were mixed in the same ratio and in the same manner as in Example 1 to prepare a slurry. A lithium ion secondary battery was constructed in the same manner as in Example 1, and the cycle characteristics were measured.

[Example 3]
Using the apparatus of FIG. 7, a silicon powder, a tin powder, and a copper powder were mixed at a molar ratio of Si: Sn: Cu = 3: 3: 2 and dried to obtain a raw powder. Nanosized particles were prepared in the same manner as in Example 1.

  Then, the slurry was produced by the same method as Example 1, the lithium ion secondary battery was comprised, and the cycle characteristic was measured.

[Example 4]
Using the apparatus of FIG. 7, silicon powder, tin powder, and iron powder were mixed at a molar ratio of Si: Sn: Fe = 3: 3: 2 and dried to obtain a raw powder. Nanosized particles were prepared in the same manner as in Example 1.

  Then, the slurry was produced by the same method as Example 1, the lithium ion secondary battery was comprised, and the cycle characteristic was measured.

[Example 5]
Using the apparatus of FIG. 7, silicon powder, tin powder, copper powder and iron powder are mixed at a molar ratio of Si: Sn: Cu: Fe = 9: 9: 6: 2 and dried. Was used as a raw material powder to produce nano-sized particles in the same manner as in Example 1.

  Then, the slurry was produced by the same method as Example 1, the lithium ion secondary battery was comprised, and the cycle characteristic was measured.

[Comparative Example 1]
A lithium ion secondary battery was constructed in the same manner as in Example 1 except that silicon nanoparticles having an average particle size of 60 nm (manufactured by Hefei Kai'er NanoTech) were used instead of the nano-sized particles, and cycle characteristics were measured. .

[Comparative Example 2]
Instead of using nano-sized particles, a mixed product in which silicon nanoparticles having an average particle diameter of 60 nm (made by Hefei Kai'er NanoTech) and tin nanoparticles having an average particle diameter of 100 nm are mixed at a molar ratio of Si: Sn = 3: 1 is used. Constituted a lithium ion secondary battery in the same manner as in Example 1, and measured cycle characteristics.

  Table 1 shows the discharge capacities and capacity retention rates of Examples 1 to 5 and Comparative Examples 1 and 2.

  As shown in Table 1, the capacity retention rate after 50 cycles is 38% in Example 1, while it decreases to 23% in Comparative Example 1. It can be seen that the nano-sized particles according to Example 1 have reduced capacity reduction and good cycle characteristics compared to silicon nanoparticles.

  Moreover, when Example 1 and Comparative Example 2 are compared, Example 1 using nano-sized particles in which silicon and tin are combined is simple in that silicon and tin are used in spite of the same amounts of silicon and tin used. Compared with Comparative Example 2 mixed in the above, the initial discharge capacity and the capacity retention after 50 cycles are excellent.

  Moreover, when Examples 1-5 are compared with Comparative Example 1, all of Examples 1-5 using the nano-sized particles according to the present invention have an initial discharge capacity and 50 cycles after that of Comparative Example 1 using silicon nanoparticles. Excellent in terms of capacity retention.

  Moreover, when Example 1 and Example 2 are compared, it turns out that initial stage discharge capacity becomes high and the capacity | capacitance maintenance factor after 50 cycles improves by adding carbon nanohorn.

  In Example 1, nano-sized particles were prepared using a binary system of silicon and tin. However, the nano-sized particles of the present invention are not limited to a binary system of silicon and tin. For example, in the binary phase diagram of aluminum (Al) and silicon (Si) shown in FIG. 11, when plasma of mole Si / (Al + Si) = 0.75 is cooled, Al and Si are precipitated. It is presumed that nanosized particles obtained by bonding particles and Si particles are obtained. The thick line in FIG. 11 is a line indicating mole Si / (Al + Si) = 0.75.

  Further, in the binary phase diagram of aluminum (Al) and tin (Sn) shown in FIG. 12, when plasma of mole Al / (Sn + Al) = 0.75 is cooled, Al and Sn are precipitated, and Al and Sn Therefore, it is presumed that nano-sized particles obtained by bonding Al particles and Sn particles can be obtained so as to reduce the area where Al and Sn are in contact with each other. The thick line in FIG. 12 is a line indicating mole Al / (Sn + Al) = 0.75.

  In addition to using Si as element A-1 and Sn as element A-2, element A-1 and element A-2 are selected from Si, Sn, Al, Pb, Sb, Bi, Ge, and Zn. In any combination used, a similar binary phase diagram is obtained, in which the element A-1 and the element A-2 do not form a compound, the first phase which is a simple substance or a solid solution of the element A-1, and the element A A second phase that is a simple substance or a solid solution of -2. Therefore, in the combination of the element A-1 and the element A-2, both the first phase and the second phase are exposed on the outer surface, and the first phase and the second phase are joined. It is considered that nano-sized particles can be obtained.

  Consider the formation process of the nano-sized particles 7 according to the first embodiment. When Si is used as the element A-1, Sn is used as the element A-2, and Al is used as the element A-3, when the plasma in which Si, Al, and Sn are mixed is cooled, as shown in FIGS. Since Si, Al, and Sn do not form a compound, Si is precipitated as the first phase 3, Sn as the second phase 5, and Al as the other second phase 9, as a simple substance or a solid solution.

Consider the formation process of the nano-sized particles 11 according to the second embodiment. FIG. 13 is a binary system phase diagram of copper and silicon. When silicon powder and copper powder are mixed so that the molar ratio is Si: Cu = 3: 1, mole Si / (Cu + Si) = 0.75 in the raw material powder is obtained. The thick line in FIG. 13 is a line indicating mole Si / (Cu + Si) = 0.75. Since the plasma generated by the high-frequency coil is equivalent to 10,000 K, the temperature is far beyond the temperature range of the phase diagram, and a plasma in which copper atoms and silicon atoms are uniformly mixed is obtained. When the plasma cools, both Cu ₁₉ Si ₆ (or Cu ₃ Si) and Si are deposited. Therefore, when the silicon and copper plasma is cooled, nano-sized particles having Cu ₁₉ Si ₆ (or Cu ₃ Si) and Si are formed. At that time, since Cu and Si have low affinity, it is considered that Cu ₁₉ Si ₆ (or Cu ₃ Si) and Si take a shape in which two particles are joined so as to reduce the area in contact with each other.

Further, in the binary phase diagram of copper (Cu) and tin (Sn) shown in FIG. 14, when the plasma of mole Sn / (Cu + Sn) = 0.75 is cooled, Cu ₃ Sn and Sn are precipitated, and Cu Since Sn and Sn have low affinity, it is presumed that nano-sized particles in which Cu ₃ Sn particles and Sn particles are bonded so that the area where Cu ₃ Sn and Sn contact each other are reduced are obtained. The thick line in FIG. 14 is a line indicating mole Sn / (Cu + Sn) = 0.75.

In addition to using Si as the element A-1 and Cu as the element M, the element A-1 is selected from Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn, and Cu, Ag and Au In any combination of the elements M selected from the above, a compound of MA-1 _x (x ≦ 1, 3 <x) can be obtained, or the elements A and M do not form a compound, and the element M alone or in solid solution A third phase is obtained. Therefore, in the combination of the above element A-1 and element M, both the first phase and the third phase are exposed on the outer surface, and the nanosize has a configuration in which the first phase and the third phase are joined. It is believed that particles are obtained.

  As described above, when the raw material powder obtained by mixing the powder of the element A-1, the powder of the element A-2, and the powder of the element M is supplied to the nanosize particle manufacturing apparatus, the element A-1 and the element A-2 And a plasma containing the element M are generated. When this plasma cools, a first phase composed of element A-1, a second phase composed of element A-2, and a spherical third phase such as a compound of element A-1 and element M are formed. Thus, nanosized particles having a configuration in which the first phase and the second phase are joined and the third phase and the first phase are joined are obtained.

Consider the formation process of the nano-sized particles 19 according to the third embodiment. FIG. 15 is a binary system phase diagram of iron and silicon. When silicon powder and iron powder are mixed so that the molar ratio is Si: Fe = 3: 1, mole Si / (Fe + Si) = 0.75 in the raw material powder is obtained. The thick line in FIG. 15 is a line indicating mole Si / (Fe + Si) = 0.75. Since the plasma generated by the high-frequency coil is equivalent to 10,000 K, it is far beyond the temperature range of the phase diagram, and a plasma in which iron atoms and silicon atoms are uniformly mixed can be obtained. When the plasma cools, FeSi ₂ and Si are deposited. Therefore, when the silicon and iron plasma is cooled, nano-sized particles having FeSi ₂ and Si are formed in the particles. At that time, since Fe and Si have high affinity, FeSi ₂ is considered to be taken into Si.

The nano-sized particles of the present invention are not limited to the binary system of silicon and iron. For example, in the binary phase diagram of Co (cobalt) and Si (silicon) shown in FIG. 16, when the plasma of mole Si / (Co + Si) = 0.75 is cooled, CoSi ₂ and Si are precipitated. It is presumed that nano-sized particles in which CoSi ₂ is covered with Si are obtained. The thick line in FIG. 16 is a line indicating mole Si / (Co + Si) = 0.75.

In addition to using Si as the element A-1 and Fe as the element D, the element A-1 is selected from Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn, and the element D is Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (excluding Ce and Pm), Hf, Ta, W, In any combination selected from Re, Os and Ir, a binary phase diagram similar to Fe—Si is obtained, and a compound DA-1 _x (1 <x ≦ 3) is obtained. Therefore, in the combination of the above element A-1 and element D, it is considered that nanosized particles having a configuration in which the first phase covers part or all of the fourth phase are obtained.

  As described above, when the raw material powder obtained by mixing the powder of the element A-1, the powder of the element A-2, and the powder of the element D is supplied to the nanosize particle manufacturing apparatus, the element A-1 and the element A-2 Plasma containing element D is generated. When the plasma is cooled, a first phase composed of the element A-1, a second phase composed of the element A-2, and a fourth phase composed of the compound of the element A-1 and the element D are generated. The nano-sized particles having a configuration in which the second phase and the second phase are joined and the fourth phase is covered with the first phase are obtained.

Furthermore, the formation process of the nanosized particle 27 which has another 4th phase 29 is considered regarding 3rd Embodiment. From binary phase diagram of Co (cobalt) and Si (silicon) shown in FIG. 16, the nano-sized particles covering the CoSi ₂ Si is is presumed to be obtained.

FIG. 17 is a binary phase diagram of cobalt and iron. When the mixed powder of cobalt powder and iron powder is cooled from plasma, only cobalt and iron cobalt solid solution, iron alone and iron cobalt solid solution, or only iron cobalt solid solution is deposited. Thus, the plasma containing silicon and iron and cobalt cools, nano-sized particles having FeSi ₂ and CoSi ₂ and Si in the particles are formed. At this time, depending on the contents of silicon, iron, and cobalt, iron-cobalt solid solution may precipitate in the nano-sized particles. At that time, since Fe and Si, Co and Si have high affinity, FeSi ₂ , CoSi ₂ , and iron cobalt solid solution are considered to be taken into Si.

  As described above, when the raw material powder obtained by mixing the powder of the element A-1, the powder of the element A-2, the powder of the element D, and the powder of the element D ′ is supplied to the nanosize particle manufacturing apparatus, the element A− 1, an element A-2, an element D, and an element D ′ are generated. When this plasma cools, the spherical first phase 3 made of the element A-1, the spherical second phase 5 made of the element A-2, and the fourth of the compound of the element A-1 and the element D. Phase 21 and other fourth phase 29 of the compound of element A-1 and element D ′ are formed, first phase 3 and second phase 5 are joined, and fourth phase 21 and the other Nanosized particles 27 having a configuration in which the fourth phase 29 is covered with the first phase are obtained.

In the binary phase diagram of iron (Fe) and tin (Sn) shown in FIG. 18, since iron and tin can form a compound, nanosized particles in which Sn is covered with FeSn ₂ can be obtained. There is. That is, there is a possibility that another fourth phase 34 precipitates in the second phase 5 like the nano-sized particles 33 shown in FIG.

  Considering the formation process of the nano-sized particles 35 according to the fourth embodiment, the raw material powder obtained by mixing the powder of the element A-1, the powder of the element A-2, the powder of the element M, and the powder of the element D is obtained. When supplied to the nano-sized particle manufacturing apparatus, plasma containing the element A-1, the element A-2, the element M, and the element D is generated. When this plasma is cooled, the first phase composed of the element A-1, the second phase composed of the element A-2, the third phase such as the compound of the element A-1 and the element M, the element A- A fourth phase of the compound of 1 and element D is formed, the first phase and the second phase are joined, the third phase and the first phase are joined, and the fourth phase is the first phase Nano-sized particles having a configuration covered with a phase are obtained.

  FIG. 19 is a binary system phase diagram of copper (Cu) and iron (Fe). When the plasma containing copper and iron is cooled, copper and iron do not form a solid solution, and copper and iron are deposited. Therefore, no solid solution of iron and copper is precipitated in the nano-sized particles 35. That is, the compound of the element D and the element M does not precipitate in the first phase 3 or the second phase 5 in the nanosize particles 35.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

1 ......... Nano-sized particles 3 ......... First phase 5 ......... Second phase 7 ......... Nano-sized particles 9 ......... Other second phases 11 ......... Nano-sized particles 13 ... ... Third phase 15 ......... Nano-sized particles 17 ......... Other third phases 19 ......... Nano-sized particles 21 ......... Fourth phase 23 ......... Nano-sized particles 25 ......... Element A -1 microcrystals 27 ......... Nano-sized particles 29 ......... Other fourth phases 31 ......... Nano-sized particles 33 ......... Nano-sized particles 34 ......... Other fourth phases 35 ... …… Nano-sized particles 37 ...... Nano-sized particle manufacturing equipment 39 ......... Reaction chamber 41 ...... Raw powder supply port 42 ...... Raw powder 43 ...... Sheath gas supply port 44 ...... Sheath gas 45 ......... High frequency coil 47 ……… High frequency power supply 49 ……… Plasma 51 ……… Filter 53 ...... mixer 55 ......... slurry 57 ......... slurry material 59 ......... coater 61 ......... collector 63 ......... negative

Claims (21)

Including element A-1 and element A-2, which are two elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn,
A first phase that is a simple substance or a solid solution of the element A-1,
A second phase that is a simple substance or a solid solution of the element A-2,
Both the first phase and the second phase are exposed on the outer surface;
The nanosized particles, wherein outer surfaces of the first phase and the second phase are spherical.   The nano-sized particles according to claim 1, wherein the average particle size is 2 to 300 nm.   2. The nanosized particle according to claim 1, wherein an interface shape of a joint portion between the first phase and the second phase is a circle or an ellipse. Including element A-1, element A-2 and element A-3, which are three elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn,
A first phase that is a simple substance or a solid solution of the element A-1,
A second phase that is a simple substance or a solid solution of the element A-2;
And a second phase which is a simple substance or a solid solution of the element A-3,
All of the first phase, the second phase and the other second phase are exposed on the outer surface;
The nano-sized particles, wherein outer surfaces of the first phase, the second phase, and the other second phase are spherical.   The nano-sized particle according to claim 1 or 4, wherein the first phase is silicon to which phosphorus or boron is added. A third phase that further includes an element M that is at least one element selected from the group consisting of Cu, Ag, and Au, or a compound of the element A-1 and the element M, or a simple substance or a solid solution of the element M Further comprising
All of the first phase, the second phase and the third phase are exposed on the outer surface;
The nano-sized particles according to claim 1, wherein outer surfaces of the first phase, the second phase, and the third phase are spherical. The nano-sized particle according to claim 6, wherein the third phase is a compound of MA-1 _x (x ≦ 1, 3 <x).   The nano-sized particle according to claim 6, wherein an atomic ratio of the element M in a total of the element A-1 and the element M is 0.01 to 60%. Further comprising at least one element M ′ selected from the group consisting of Cu, Ag and Au,
The element M ′ is a different element from the element M constituting the third phase,
A compound of the element A-1 and the element M ′ or another third phase which is a simple substance or a solid solution of the element M ′;
All of the first phase, the second phase, the third phase and the other third phase are exposed on the outer surface;
The nano-sized particles according to claim 6, wherein outer surfaces of the first phase, the second phase, the third phase, and the other third phase are spherical. Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (excluding Ce and Pm), Hf, Ta, An element D that is at least one element selected from the group consisting of W, Re, Os, and Ir;
A fourth phase that is a compound of the element A-1 and the element D;
A part or all of the fourth phase is covered by the first phase;
The nano-sized particle according to claim 1 or 6, wherein an outer surface of the first phase is spherical. 11. The nano-sized particle according to claim 10, wherein the fourth phase is a compound of DA-1 _y (1 <y ≦ 3).   11. The nano-sized particle according to claim 10, wherein an atomic ratio of the element D in a total of the element A-1, the element A-2, and the element D is 0.01 to 30%. Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (excluding Ce and Pm), Hf, Ta, An element D ′ that is at least one element selected from the group consisting of W, Re, Os, and Ir;
The element D ′ is an element of a different type from the element D constituting the fourth phase,
And further comprising a fourth phase that is a compound of the element A-1 and the element D ′,
The nano-sized particle according to claim 10, wherein a part or all of the other fourth phase is covered with the first phase.   A negative electrode material for a lithium ion secondary battery, comprising the nanosized particles according to any one of claims 1 to 13 as a negative electrode active material.   The lithium according to claim 14, further comprising a conductive assistant, wherein the conductive assistant is at least one powder selected from the group consisting of C, Cu, Sn, Zn, Ni, and Ag. Negative electrode material for ion secondary battery.   The negative electrode material for a lithium ion secondary battery according to claim 15, wherein the conductive additive contains carbon nanohorn.   The negative electrode for lithium ion secondary batteries using the negative electrode material for lithium ion secondary batteries of any one of Claims 14 thru | or 16. A positive electrode capable of inserting and extracting lithium ions;
A negative electrode according to claim 17,
Having a separator disposed between the positive electrode and the negative electrode;
A lithium ion secondary battery, wherein the positive electrode, the negative electrode, and the separator are provided in an electrolyte having lithium ion conductivity. A raw material containing at least two elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn,
A method for producing nano-sized particles, characterized in that the nano-sized particles are obtained by supplying them into plasma. At least two elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn; and at least one element selected from the group consisting of Cu, Ag and Au;
Containing raw materials,
A method for producing nano-sized particles, characterized in that the nano-sized particles are obtained by supplying them into plasma. At least two elements selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In and Zn; and at least one element selected from the group consisting of Cu, Ag and Au;
Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (excluding Ce and Pm), Hf, Ta, At least one element selected from the group consisting of W, Re, Os and Ir;
Containing raw materials,
A method for producing nano-sized particles, characterized in that the nano-sized particles are obtained by supplying them into plasma.

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