JP5520782B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery having a high capacity and excellent cycle characteristics.

  Lithium ion secondary batteries are used mainly in portable devices, and higher capacities are required as the devices used become smaller and more multifunctional. However, carbon materials such as artificial graphite and natural graphite, which are currently used as negative electrode active materials for lithium ion secondary batteries, have a theoretical capacity of 372 mAh / g, and a further increase in capacity cannot be expected.

  Therefore, a negative electrode using a metal material such as silicon (Si) or tin (Sn) having a larger theoretical capacity or an oxide material thereof has been proposed (for example, see Patent Document 1). Shows a very high capacity in the initial few cycles, but the pulverization due to expansion and contraction of the active material occurs due to repeated charge and discharge, and the negative electrode active material falls off the current collector, so the cycle characteristics are very poor. There was a problem.

  Then, the method of suppressing deterioration by a charge / discharge cycle is mixed by mixing the component which can occlude Li, such as Si and Sn, and the components, such as Cu and Fe which do not occlude Li, by a mechanochemical method. (For example, refer to Patent Document 2).

  On the other hand, as a method for producing an electrode, a method of forming a thin film of these materials on a current collector by a CVD method, a sputtering method, a vapor deposition method, or a plating method has been proposed (for example, Patent Document 3). Furthermore, as a method for stabilizing the coating on the electrode surface formed by this method, a method of adding a cyclic carbonate having an unsaturated bond to the electrolytic solution has been proposed (for example, Patent Document 4).

Japanese Patent Application Laid-Open No. 07-29602 JP 2005-78999 A Japanese Patent Laid-Open No. 11-135115 JP 2004-171877 A

  However, in the invention described in Patent Document 2, it is difficult to uniformly disperse each component at the nano-size level. In particular, silicon that is expected to be put into practical use as a negative electrode material has a volume during charge / discharge. Since the change was large, cracking was likely to occur and deterioration of cycle characteristics could not be prevented sufficiently.

  In the inventions described in Patent Document 3 and Patent Document 4, although the negative electrode active material layer is formed by a CVD method, a sputtering method, a vapor deposition method, or a plating method, deterioration in cycle characteristics can be suppressed to some extent. Since only a thin film electrode having a thin negative electrode active material layer can be formed, and the amount of active material is insufficient to constitute a lithium secondary battery, practical application is difficult. Furthermore, the invention described in Patent Document 4 can suppress deterioration of cycle characteristics by forming a strong film on the surface of the active material layer of the thin film electrode and suppressing decomposition of the electrolytic solution. The conventional coating-type electrode in which the active material layer is formed by the method cannot obtain the suppressing effect.

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

  As a result of intensive studies to achieve the above object, the present inventor has found that the pulverization of the negative electrode active material can be suppressed by using a nano-sized negative electrode active material mainly having lithium storage properties. Furthermore, it discovered that the 1st phase which occludes lithium, and the 2nd phase which does not occlude lithium are joined via an interface, and can suppress the volume expansion of the 1st phase by charging / discharging. In addition, when a negative electrode active material layer is formed on an electrode by a coating method using such a nano-sized negative electrode active material, the negative electrode active material layer is obtained by including an organic substance capable of reduction polymerization having an unsaturated bond in the electrolyte. It was found that a stable film was formed on the surface of the film and decomposition of the electrolyte was suppressed. And formation of such a film | membrane is based on the electronic arrangement | positioning of the substance contained in a negative electrode, It came to discover that it was possible to show the form of a more effective and various negative electrode active material. . The present invention has been made based on these findings.

That is, the present invention provides the following inventions.
(1) a positive electrode capable of inserting and extracting lithium ions, a negative electrode capable of inserting and extracting lithium ions, and a separator disposed between the positive electrode and the negative electrode, and having lithium ion conductivity the aqueous electrolyte solution, wherein a non-aqueous electrolyte secondary battery provided with the positive electrode and the negative electrode and the separator, the negative electrode active material of the negative electrode, the first average particle size containing the element X is 2nm~500nm a first particle made of a phase, and a second particle having an average particle diameter containing the element M consists of a second phase of 2Nm～10myuemu, said first phase of said first particles, said The distance between the second phases of the second particles is within 1 μm , and the element X is selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, Zn A seed element, wherein the element M is a group 4-11 transition At least one element selected from the group consisting of metal elements, wherein the first particles are composed of the element X alone or a solid solution containing the element X as a main component, and the second particles are A non-aqueous solution characterized in that it comprises a simple substance or a compound of element M, and the electrolyte contains 0.1 wt% to 10 wt% of an organic substance having an unsaturated bond in the molecule and capable of reduction polymerization. Electrolyte secondary battery.
(2) a positive electrode capable of inserting and extracting lithium ions, a negative electrode capable of inserting and extracting lithium ions, and a separator disposed between the positive electrode and the negative electrode, and non-conductive with lithium ions In the nonaqueous electrolyte secondary battery in which the positive electrode, the negative electrode, and the separator are provided in a water electrolyte, the negative electrode active material of the negative electrode is composed of nano-sized particles containing the element X and the element M, The element X is one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn, and the element M is a transition metal of group 4 to 11 At least one element selected from the group consisting of elements, wherein the nano-sized particles are a single phase of the element X or a solid solution containing the element X as a main component; and a simple element of the element M , Solid solution mainly composed of element M Or at least a second phase that is a compound of the element M, and the nano-sized particles have both the first phase and the second phase exposed to the outer surface, and through the interface. The first phase has a substantially spherical outer surface, the nano-sized particles have an average particle diameter of 2 nm to 500 nm, and the electrolyte has an unsaturated bond in the molecule. A non-aqueous electrolyte secondary battery comprising 0.1% by weight to 10% by weight of an organic substance capable of reduction polymerization.
(3) The nano-sized particles are Cu, Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements ( Further including an element M ′, which is at least one element selected from the group consisting of Hf, Ta, W, Re, Os, and Ir, and the element M ′ includes the second phase. The non-water according to (2), wherein the element M is a different element from the element M and further has another second phase that is a single element or a compound of the element M ′. Electrolyte secondary battery.
(4) The nano-sized particles further include an element X ′ that is at least one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn. The nonaqueous electrolyte secondary battery according to (2) or (3), further comprising a third phase which is a simple substance or a solid solution.
(5) The nonaqueous electrolyte secondary battery according to (4), wherein the third phase is bonded to at least one of the first phase and the second phase via an interface. .
(6) The non-aqueous electrolyte secondary battery according to (1), wherein the first particles are the nano-sized particles according to any one of (2) to (5).
(7) The organic substance having an unsaturated bond in the molecule and capable of reductive polymerization is at least one selected from the group consisting of fluoroethylene carbonate, vinylene carbonate and derivatives thereof, and vinyl ethylene carbonate. The nonaqueous electrolyte secondary battery according to any one of (1) to (6).
(8) The negative electrode is formed by applying a coating liquid containing at least a negative electrode active material, a conductive material, and a binder to a current collector and drying it (1) to (7) The nonaqueous electrolyte secondary battery according to any one of the above.

  According to the present invention, a non-aqueous electrolyte secondary battery that achieves high capacity and good cycle characteristics can be obtained.

The cross-sectional schematic diagram which shows an example of the nonaqueous electrolyte secondary battery which concerns on this invention. The conceptual diagram which shows an example of a structure of the negative electrode active material which concerns on 1st Embodiment. (A)-(c) is a schematic sectional drawing of the nanosized particle which concerns on 2nd Embodiment. (A), (b) is a schematic sectional drawing of the nanosized particle which concerns on 2nd Embodiment. (A), (b) is a schematic sectional drawing of the nanosized particle which concerns on 2nd Embodiment. (A)-(c) is a schematic sectional drawing of the nanosized particle which concerns on 3rd Embodiment. (A), (b) is a schematic sectional drawing of the nanosized particle which concerns on 3rd Embodiment. The figure which shows the manufacturing apparatus of the nanosize particle 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 XRD analysis result of the nanosize particle which concerns on Example 1. FIG. (A) BF-STEM photograph of nano-sized particles according to Example 1, and (b) HAADF-STEM photograph of nano-sized particles according to Example 1. (A) HAADF-STEM photograph in the 1st observation location of the nanosized particle which concerns on Example 1, (b)-(c) EDS map in the same visual field. (A) HAADF-STEM photograph in the 2nd observation location of the nanosized particle which concerns on Example 1, (b)-(c) EDS map in the same visual field. The binary system phase diagram of Fe and Si. The XRD analysis result of the nanosize particle which concerns on Example 2. FIG. (A), (b) The STEM photograph of the nanosized particle which concerns on Example 2. FIG. (A) HAADF-STEM photograph in the 1st observation location of the nanosized particle which concerns on Example 2, (b)-(d) EDS map in the same visual field. (A) HAADF-STEM photograph in the 2nd observation location of the nanosized particle which concerns on Example 2, (b)-(d) EDS map in the same visual field. The XRD analysis result of the nanosize particle which concerns on Example 3. FIG. (A) BF-STEM photograph of nanosized particles according to Example 3, (b) HAADF-STEM photograph in the same field of view. (A)-(c) The high-resolution TEM photograph of the nanosized particle which concerns on Example 3. FIG. (A) HAADF-STEM image of nanosized particles according to Example 3, (b) to (c) EDS map in the same field of view. The XRD analysis result of the nanosize particle which concerns on Example 4. FIG. (A) BF-STEM photograph of nanosized particles according to Example 4, (b) HAADF-STEM photograph of nanosized particles according to Example 4. (A)-(b) The HAADF-STEM photograph of the nanosized particle which concerns on Example 4. FIG. (A) HAADF-STEM photograph of nano-sized particles according to Example 4, (b) to (e) EDS map in the same field of view. (A) EDS map of nano-sized particles according to Example 4, (b) HAADF-STEM photograph in the same field of view. (A) HAADF-STEM photograph of nano-sized particles according to Example 4, (b) EDS analysis result at the first location in (a), (c) EDS at the second location in (a) Analysis results, EDS analysis results at the third location in (d) (a), The figure which shows the relationship between the cycle number of the nonaqueous electrolyte secondary battery which concerns on an Example and a comparative example, and a discharge capacity maintenance factor.

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

(1. Configuration of non-aqueous electrolyte secondary battery)
First, a nonaqueous electrolyte secondary battery according to an embodiment of the present invention will be described with reference to FIG.

  The nonaqueous electrolyte secondary battery 1 of the present invention includes a positive electrode 3 capable of inserting and extracting lithium ions, a negative electrode 5 capable of inserting and extracting lithium ions, and a separator 7 disposed between the positive electrode 3 and the negative electrode 5. The positive electrode 3, the negative electrode 5, and the separator 7 are provided in a non-aqueous electrolyte solution 8 having lithium ion conductivity.

  In the present invention, the negative electrode 5 uses, as an active material, particles made of an element that easily occludes lithium ions having a characteristic configuration, and the electrolyte 8 used corresponding to this negative electrode is unsaturated in the molecule. It contains an organic substance having a bond and capable of reductive polymerization.

(2. Negative electrode)
(2-1. Configuration of the negative electrode active material A according to the first embodiment)
Therefore, a first embodiment of the negative electrode active material according to the present invention will be described with reference to FIG. FIG. 2 is a conceptual diagram showing an example of the configuration of the negative electrode active material. The negative electrode active material includes first particles 9 containing the element X and second particles 10 containing the element M.

  The first particles 9 may be composed of the element X alone or a solid solution containing the element X as a main component. Here, the element X is one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn. The phrase “having element X as the main component” means that the proportion of element X is 50 atomic% or more, more preferably 70 atomic% or more. When the first particle 9 is a solid solution of the element X, the element that forms a solid solution with the element X can be selected from the elements listed in the group of the element X, but is selected from the other elements. be able to. The element X is an element that easily stores lithium, and the first particles 9 can also store lithium. The first particles 9 become amorphous when they are occluded and alloyed once and then desorbed and de-alloyed. In addition, the 1st particle | grains 9 can be made into a substantially spherical shape fundamentally, and the aspect of various other forms is mentioned later.

  In the first particles 9, the element X is preferably Si, more preferably crystalline silicon, from the viewpoint of lithium ion storage characteristics. In this case, the conductivity of silicon can be increased by adding phosphorus or boron to silicon. Indium and gallium can be used instead of phosphorus, and arsenic can be used instead of boron. By increasing the conductivity of silicon of the first particles 9, the internal resistance of the negative electrode 5 is reduced, a large current can be passed, and good high-rate characteristics can be exhibited.

The second particles 10 may be composed of the element M alone or a compound of the element M. Here, the element M is at least one element selected from the group consisting of group 4 to group 11 transition metal elements of the periodic table. For example, among the group 4 to group 11 transition metal elements, the element M is stable. Elements such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, Au, etc. These elements M are elements that do not easily store lithium. The element that forms a compound with the element M is not particularly limited, but may be the element X described above. The second particles 10 hardly exhibit lithium storage characteristics, but the lithium storage characteristics can be adjusted by the ratio of the element M and the elements forming the compound. The compound can include various alloys, intermetallic compounds, oxides, and the like.

  In the present invention, since the second particle 10 is composed of a single element or a compound of the element M, two or more electrons exist in the d electron orbit. For example, the outermost electron configuration of Ti, Fe, and Ni is Ti: 3d [2] 4S [2], Fe: 3d [6] 4S [2], Ni: 3d [8] 4S [2], d The electron orbit has 2, 6, and 8 electrons, respectively. In this way, due to the presence of a large number of d electrons in the negative electrode active material, an organic substance having an unsaturated bond in the molecule and capable of reductive polymerization is contained in the nonaqueous electrolyte solution 8 described later due to its electronic interaction. It is considered that formation of a film that causes polymerization to protect the negative electrode 5 is promoted. Further, for example, it has been confirmed that the use of Fe or Ni as the element M promotes the formation of the film, compared to the case of using Ti, so that the number of electrons in the d electron orbit is larger. It is expected that this is preferable.

  In such a negative electrode active material of the present invention, the first particles 9 and the second particles 10 are the surfaces of the closest first particles 9 and the second particles 10 indicated by A in FIG. The distance is set to be within 1 μm. The distance A within 1 μm is a range in which the interaction of electrons at the interface between the first particle 9 and the second particle 10 reaches, and is a distance of about the thickness of the electric double layer. At the same time as the occlusion of lithium of the element X of the first particle 9, electrons are supplied to the element M of the second particle 10, thereby having an unsaturated bond in the molecule contained in the non-aqueous electrolyte solution 8. An organic polymer is produced that is capable of reductive polymerization. Furthermore, when the distance between the first particle and the second particle is within 1 μm, the first particle is further coated with the reduction product generated on the surface of the first particle and further formed with the second particle. The stable reduction product adsorbs and coats the surface of the first particles, so that the decomposition of the electrolyte can be suppressed.

  The average particle diameter of the first particles 9 is preferably 2 nm to 500 nm, more preferably 2 nm to 300 nm, and further 50 nm to 200 nm. Since the yield stress increases when the particle size is small according to the Hall Petch's law, if the average particle size of the nano-sized particles is about 2 nm to 500 nm, the particle size is small, the yield stress is large, and it is difficult to pulverize by charge / discharge. When the average particle size is smaller than 2 nm, it is difficult to handle nano-sized particles after synthesis. When the average particle size is larger than 500 nm, the particle size is too large to obtain a sufficient yield stress, which is not preferable.

  One second particle 10 does not need to consider the influence of pulverization, so the average particle size can be 2 nm to 10 μm. The lower limit is 2 nm because it is a guide value that is not difficult to handle as in the case of the first particles 9 described above, and the upper limit is 10 μm because the electrode active material is applied to the current collector. This is because the density of the active material is uneven when the cycle characteristics are deteriorated.

  In the negative electrode 5 of the present invention, the ratio of the second particles 10 to the first particles 9 can be arbitrarily set within a range in which a desired lithium occlusion amount can be secured by the first particles 9, As a rough guide, it is preferably 1% to 30%, more preferably 7% to 10%, based on the number of X atoms constituting the first particles 9. If the atomic ratio is less than 1%, the effect of forming a film on the surface of the negative electrode and the effect of suppressing the volume change of the negative electrode due to charge / discharge cannot be sufficiently obtained. When the atomic ratio is more than 30%, a sufficient amount of lithium occlusion may not be ensured.

(2-2. Effect of negative electrode active material A)
According to the negative electrode according to the first embodiment, in addition to the first particles 9 that occlude lithium, the second particles 10 that do not occlude lithium are included, and the negative electrode active material is obtained by the catalytic action of the second particles 10. On the surface of the layer, it is possible to effectively form a stable coating of an organic substance having an unsaturated bond in a molecule contained in a nonaqueous electrolyte solution 8 to be described later and capable of reduction polymerization, stabilizing the negative electrode active material Therefore, it is possible to prevent the electrolyte material from being decomposed and to obtain a negative electrode having excellent cycle characteristics.

  Further, when the negative electrode active material has the second particles 10 containing the element M having a high conductivity in addition to the first particles 9 having a relatively low conductivity, the conductivity of the negative electrode 5 as a whole jumps. Rises. That is, even if there is little conductive auxiliary agent, it is a negative electrode active material which has electroconductivity, can form a high capacity | capacitance electrode, and can become a negative electrode active material excellent in a high rate characteristic. In particular, by using a highly conductive metal element such as Fe or Cu as the second particles 10, a negative electrode active material having better conductivity can be obtained compared to the case of using only silicon nanoparticles.

  Further, as the negative electrode active material, in addition to the first particles 9, the first particles 9 also include second particles. The first particles 9 expand when they occlude lithium, whereas the second particles 10 occlude lithium. Therefore, the volume change as the whole negative electrode can be suppressed. Thereby, even if lithium is occluded, the distortion accompanying the volume expansion of the negative electrode is alleviated, and the reduction of the discharge capacity during the cycle characteristics is suppressed.

(2-3. Configuration of Negative Electrode Active Material B According to Second Embodiment)
Next, a second embodiment of the negative electrode active material according to the present invention will be described. FIG. 3 is a schematic cross-sectional view showing the nano-sized particles 11 constituting the negative electrode active material of the negative electrode 5 of the present invention. The nano-sized particle 11 includes an element X and an element M.

  As in the first embodiment, the element X is one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn. The element X is an element that easily stores lithium.

  The element M is at least one element selected from the group consisting of Group 4 to 11 transition metal elements. For example, among the Group 4 to 11 transition metal elements, the element M is a stable element. Specifically, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, Au, etc. It is. These elements M are elements that do not easily store lithium.

And the nanosized particle 11 in this invention has the 1st phase 13 and the 2nd phase 15 at least.
The first phase 13 may be a single element X or a solid solution containing the element X as a main component. Further, the first phase 13 may be crystalline or amorphous. The element that forms a solid solution with the element X can be selected from elements other than those listed in the group of the element X. The first phase 13 can occlude lithium. The first phase 13 becomes amorphous when occluded by lithium and alloyed and then desorbed and dealloyed.

In addition, the second phase 15 may be a single element M, a solid solution containing the element M as a main component, or a compound of the element M. The second phase 15 hardly absorbs lithium. In addition, since the element M has two or more electrons in the d electron orbit as described above, the formation of a film that protects the negative electrode 5 can be promoted and cycle characteristics can be improved.

As long as the element X and the element M are combinations capable of forming a compound, the second phase 15 may be formed of MX _Y , which is a compound of the element X and the element M, or the like. On the other hand, if the combination of the element X and the element M does not form a compound, the second phase 15 may be a single element or a solid solution of the element M.

For example, when the element X is Si and the element M is Cu, the second phase 15 can be formed of copper silicide that is a compound of the element M and the element X.
For example, when the element X is Si and the element M is Ag or Au, the second phase 15 can be formed of a single element of the element M or a solid solution containing the element M as a main component.

When element X is Si, Si and element M can form a compound represented by MX _Y (1 <Y ≦ 3). Specific examples of such a compound include FeSi ₂ , CoSi ₂ (Y = 2), Rh ₃ Si ₄ (Y = 1.33), Ru ₂ Si ₃ (Y = 1.5), and Sr. Examples include ₃ Si ₅ (Y = 1.67), Mn ₄ Si ₇ , Tc ₄ Si ₇ (Y = 1.75), IrSi ₃ (Y = 3), and the like. Here, the atomic ratio of the element M in the total of Si and the element M is preferably 0.01 to 25%. When the atomic ratio is 0.01 to 25%, both the cycle characteristics and the high capacity can be achieved when the nano-sized particles 11 are used as the negative electrode active material. On the other hand, if it is less than 0.01%, the volume change at the time of occlusion of lithium of the nanosize particles 11 cannot be suppressed, and if it exceeds 25%, the merit of high capacity is particularly lost.

  For example, as shown in FIG. 3, the nano-sized particles 11 are exposed to the outer surface of the nano-sized particles 11 and both the first phase 13 and the second phase 15 are bonded to each other through the interface. doing. The interface between the first phase 13 and the second phase 15 is a flat surface or a curved surface. Further, the interface may be stepped. The first phase 13 has a substantially spherical outer surface. The interface shape of the joint portion between the first phase 13 and the second phase 15 is circular or elliptical. By the presence of the second phase 15 that does not occlude lithium on the first phase 13 that expands due to lithium occlusion, expansion of the first phase 13 due to lithium occlusion can be suppressed.

  Note that the outer surface of the first phase 13 has a substantially spherical shape means that the surface of the first phase 13 other than the interface where the first phase 13 and the second phase 15 are in contact is generally a smooth curved surface. In other words, it means that the first phase 13 has a spherical shape or an elliptical spherical shape except for the point where the first phase 13 and the second phase 15 are in contact with each other. The expression “sphere” or “elliptical sphere” does not mean a geometrically exact sphere or ellipsoid. The shape is different from the shape having a corner on the surface, as represented by the shape of particles formed by the crushing method.

  In addition, as in the nano-sized particles 11 illustrated in FIG. 3B, the second phase 15 that is a single element or a compound of the element M may be dispersed in the first phase 13. The second phase 15 is covered with the first phase 13. Like the second phase 15 exposed on the outer surface, the second phase 15 hardly absorbs lithium. Further, as shown in FIG. 3C, a part of the second phase 15 covered with the first phase 13 may be exposed on the surface. That is, the entire periphery of the second phase 15 is not necessarily covered with the first phase 13, and only a part of the periphery of the second phase 15 may be covered with the first phase 13.

  In FIG. 3B, a plurality of second phases 15 are dispersed in the first phase 13, but a single second phase 15 may be included.

  As in the second phase 15 ′ shown in FIG. 4A, it may have a polyhedral shape due to the influence of the stability of the element M simple substance or compound crystal.

  Further, a plurality of second phases 15 may be provided on the first phase 13 like the nano-sized particles 11 shown in FIG. For example, in the particle manufacturing process, the ratio of the element M is small, the collision frequency between the elements M in the gas state or the liquid state is low, the relationship between the melting points of the first phase 13 and the second phase 15 and wetting. It is conceivable that the second phase 15 is dispersed and joined to the surface of the first phase 13 due to the property, the influence of the cooling rate and the like.

  When the plurality of second phases 15 are provided on the first phase 13, the area of the interface between the first phase 13 and the second phase 15 is widened to further suppress the expansion and contraction of the first phase 13. Can do. In addition, since the second phase 15 has a higher conductivity than the first phase 13, the movement of electrons is promoted by the second phase 15, and the nanosize particles 11 are collected in each nanosize particle 11. It will have an electric spot. Therefore, the nano-sized particles 11 having a plurality of second phases 15 become a negative electrode material having high powder conductivity, can reduce the conductive auxiliary agent, and can form a high capacity negative electrode. Furthermore, a negative electrode having excellent high rate characteristics can be obtained.

When the element M includes two or more elements selected from the group in which the element M can be selected, the second phase 15 that is a compound of one element M and the element X includes another element. M may be contained as a solid solution or a compound. That is, even when two or more elements selected from the group from which the element M can be selected are contained in the nano-sized particles, the other second phase 19 is not formed unlike the element M ′ described later. There is a case. For example, when the element X is Si, one element M is Ni, and the other element M is Fe, Fe may exist in NiSi ₂ as a solid solution. In addition, when observed by EDS, the distribution of Ni and the distribution of Fe may be approximately the same or different, and another element M may be uniformly contained in the second phase 15. For example, it may be partially contained.

  Further, in addition to the element M, the nano-sized particles may include an element M ′. Element M ′ includes Cu, Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (Ce and Pm Except), at least one element selected from the group consisting of Hf, Ta, W, Re, Os, and Ir, and an element of a different type from the element M constituting the second phase.

  5A includes the element M and the element M ′, and has the other second phase 19 in addition to the second phase 15 that is a simple substance or a compound of the element M. For example, there is a second phase 15 at one end of the first phase 13 and another second phase 19 at the other end, and the nano-sized particle 17 has two small spheres joined to the surface of a large sphere. Can have a shape. The other second phase 19 is a simple substance or a compound of the element M ′ and, like the second phase 15, hardly absorbs lithium. The nano-sized particles 17 may include a solid solution (not shown) composed of the element M and the element M ′. For example, the second phase 15 is a compound of Si and Fe, the other second phase 19 is a compound of Si and Co, and the solid solution composed of the elements M and M ′ is a solid solution of Fe and Co. Etc.

  Further, as shown in FIG. 5B, the second phase 15 that is a simple substance or a compound of the element M and another second phase 19 that is a simple substance or a compound of the element M ′ are included in the first phase 13. It may be dispersed in the inside. FIGS. 5A and 5B show an example in which two types of elements are selected from the group of elements from which the element M and the element M ′ can be selected, but even when three or more types of elements are selected. Good.

  Even when two or more kinds of elements are selected from the group of the element M and the element M ′ as described above, the group of the element M and the element M ′ with respect to the total of the elements of the group of the element X, the element M, and the element M ′. The total atomic ratio of these elements is preferably 0.01 to 30%.

  In the present invention, it is preferable that the first phase 13 is mainly crystalline silicon and the second phase 15 is crystalline silicide. The first phase 13 is more preferably Si to which phosphorus or boron is added. The conductivity of silicon can be increased by adding phosphorus or boron. Indium and gallium can be used instead of phosphorus, and arsenic can be used instead of boron. By increasing the conductivity of silicon of the first phase 13, the negative electrode using such nano-sized particles has a low internal resistance, allows a large current to flow, and has a good high-rate characteristic.

  Furthermore, in this invention, the average particle diameter of the nanosize particle | grains 11 and 17 and 21 mentioned later becomes like this. Preferably it is 2-500 nm, More preferably, it is 50-200 nm. According to Hall Petch's law, the yield stress increases when the particle size is small. Therefore, if the average particle size of the nano-sized particles is 2 to 500 nm, the particle size is sufficiently small, the yield stress is sufficiently large, and it is difficult to pulverize by charge / discharge. . When the average particle size is smaller than 2 nm, it is difficult to handle nano-sized particles after synthesis. When the average particle size is larger than 500 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.

  Note that oxygen may be bonded to the outermost surface of the nano-sized particles 11 or 17. This is because when the nano-sized particles are taken out into the air, oxygen in the air reacts with elements on the surface of the nano-sized particles. That is, the outermost surface of the nano-sized particles 11 or 17 may have an amorphous layer having a thickness of about 0.5 to 15 nm. In particular, when the first phase is mainly crystalline silicon, the oxide film layer You may have.

(2-4. Effect of negative electrode active material B)
According to the second embodiment, since the second phase 15 containing the element M is included in addition to the first phase 13 that occludes lithium, the second phase 15 of the second phase 15 is similar to the first embodiment. Due to the catalytic action, a stable organic film can be effectively formed on the surface of the negative electrode active material layer, decomposition of the electrolyte material can be prevented, and cycle characteristics can be improved.

  Further, when the first phase 13 occludes lithium, the volume expands, but the second phase 15 does not occlude lithium, so that the expansion of the first phase 13 in contact with the second phase 15 is suppressed. That is, even if the first phase 13 occludes lithium and tries to expand its volume, the second phase 15 hardly expands, so that the second phase 15 exhibits an effect like a wedge or a pin, and is nanosized. Swelling of the entire particle 11 or 17 is suppressed. Therefore, compared with particles not having the second phase 15, the nano-sized particles 11 or 17 having the second phase 15 are less likely to expand when occlusion of lithium, and the restoring force works when lithium is released. It becomes easy to return to the shape of. Therefore, according to the present invention, even when lithium is occluded in the nano-sized particles 11 or 17, distortion associated with volume expansion is relieved, and a decrease in discharge capacity during cycle characteristics is suppressed.

  Furthermore, according to the second embodiment, since the nano-sized particles 11 or 17 are difficult to expand, even if the nano-sized particles are put out into the atmosphere, they hardly react with oxygen in the atmosphere. On the other hand, 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. Oxidize. However, when the nano-sized particles 11 or 17 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. Oxidation hardly reaches the center of the size particle. Therefore, normal metal nanoparticles have a large specific surface area and are likely to oxidize and generate heat and volume expansion. However, the nano-sized particles 11 or 17 of the present invention need to be specially coated with an organic substance or metal oxide. And can be handled as powder in the atmosphere. Such features have great industrial utility value.

  Further, according to the second embodiment, even if the second phase 15 includes the element M, the conductivity is high and the first phase 13 including the element X having low conductivity is included as the main phase. The conductivity of the nano-sized particles 11 or 17 as a whole increases dramatically. In other words, the nano-sized particles 11 or 17 are equivalent to a structure in which each nano-sized particle has a nano-level current collecting spot, and become a negative electrode material having conductivity even if there is a small amount of conductive auxiliary agent. A capacitor electrode can be formed, and can be a negative electrode active material having excellent high-rate characteristics. In particular, by using a highly conductive metal element such as Fe or Cu for the second phase 15, a negative electrode active material with better conductivity can be obtained as compared to the case of using only silicon nanoparticles.

  In addition, the nano-sized particles 11 including the second phase 15 in the first phase 13 and the nano-sized particles 17 including the second phase 15 and another second phase 19 in the first phase 13 are: More parts of the first phase 13 are in contact with a phase that does not occlude lithium, and the expansion of the first phase 13 is more effectively suppressed. As a result, the nano-sized particles 17 can exhibit the effect of suppressing volume expansion with a small amount of the element M, and can effectively increase the amount of element X such as Si that can occlude lithium, Capacity and cycle characteristics are improved.

  The nano-sized particles 17 having both the second phase 15 exposed to the outer surface and the other second phase 19 have the same effect as described above, and the number of nano-level current collection spots is increased. Effectively improve. Addition of two or more elements M and element M 'group generates two or more compounds, and these compounds are easy to separate from each other, so different compounds are easy to separate, increasing the current collection spot It is easy to do and is more preferable.

(2-5. Configuration of negative electrode active material C according to the third embodiment)
Furthermore, the nanosized particle 21 which concerns on 3rd Embodiment of the negative electrode 5 which concerns on this invention is demonstrated. In the following embodiment, the same number is attached | subjected to the element which fulfill | performs the same aspect as 2nd Embodiment, and the duplicate description is avoided.

  FIG. 6 is a schematic cross-sectional view of the nanosized particles 21 constituting the negative electrode active material of the negative electrode 5 of the present invention. As shown in FIG. 6A, the nano-sized particles 21 have a third phase 23 in addition to the same first phase 13 and second phase 15 as described above. The third phase 23 includes an element X ′ that is at least one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn, and is different from the element X Elements. These elements X ′ are elements that easily store lithium. The third phase 23 may be a single element X ′ or a solid solution containing the element X ′ as a main component. The element that forms a solid solution with the element X ′ may be an element selected from the group capable of selecting the element X ′, or may be an element not listed in the group. The third phase 23 can occlude lithium.

The first phase 13, the second phase 15, and the third phase 23 are all exposed on the outer surface, and the outer surfaces of the first phase 13, the second phase 15, and the third phase 23 are substantially spherical. It may be a shape. The second phase 15 is bonded to the first phase 13, and the third phase 23 is bonded to at least one of the first phase 13 and the second phase 15 through an interface. For example, there is a second phase 15 at one end of the first phase 13, a third phase 23 at the other end, and the nano-sized particle 21 has a shape in which two small spheres are joined to the surface of a large sphere. Can have. The interface between the third phase 23 and the first phase 13 is a flat surface or a curved surface. On the other hand, as shown to Fig.7 (a), the 2nd phase 15 and the 3rd phase 23 may join via the interface.
For such nano-sized particles 21, considering the lithium occlusion characteristics and conductivity as the negative electrode active material, for example, the first phase 13 is Si and the second phase 15 is a compound of Si and Fe. For example, the third phase 23 is Sn.

  6B, the second phase 15 that is a single element or a compound of the element M and the third phase 23 that is a single element or a solid solution of the element X ′ It may be dispersed in the phase 13. Further, a phase (not shown) which is a compound of the element X ′ and the element M may be dispersed. These phases 15 and 23 are covered by the first phase 13, but some of the phases 15 and 23 may be exposed on the surface as shown in FIG. That is, it is not always necessary to cover all of the periphery of the phases 15 and 23 dispersed in the first phase 13 with the first phase 13, and only a part of the periphery is covered with the first phase 13. Also good. Note that a plurality of phases may be dispersed in the first phase 13, for example, any of the second phase 15, the third phase 23, and a phase that is a compound of the element X ′ and the element M. May be dispersed.

  Further, the shape of the surface other than the interface of the third phase 23 may be a spherical surface whose surface is generally smooth like the third phase 23 shown in FIG. 6A, or FIG. As shown in the third phase 23 ′ shown in FIG. The polyhedron shape is formed by peeling after the nano-sized particles 11, 17 or 21 are bonded through the third phase 23.

Moreover, the 1st phase 13 and the 3rd phase 23 can suppress the site | part which reacts with lithium by containing oxygen. When oxygen is included, the capacity decreases, but volume expansion accompanying lithium occlusion can be suppressed. Amount of oxygen z is, for example _XO z, when a X'O _z, 0 <z <1 is preferably in the range. When z is 1 or more, the Li storage sites of the element X and the element X ′ are suppressed, and the capacity is greatly reduced.

  When the nano-sized particles include the element X, the element X ′, the element M, and the element M ′, the atomic ratio of the element M and the element M ′ in the total is 0.01 to 25% for the same reason as described above. It is preferable to set the degree. When the atomic ratio is 0.01 to 25%, both the cycle characteristics and the high capacity can be achieved when the nano-sized particles 21 are used as the negative electrode active material.

  Moreover, various aspects can be considered about the structure of the nanosized particle 21 which concerns on this invention. For example, a plurality of third phases 23 can be provided on the surface of the first phase 13. For example, the nano-sized particle 21 can further contain two or more kinds of elements X ′. For example, the second element X ′ is one element selected from the group of the elements X ′ and is a different kind of element from the first element X ′. For example, silicon can be used as the element X, and tin and aluminum can be used as the element X ′. The element X ′ may form another third phase as a simple substance or a solid solution, or may form a compound with the element M and the element M ′. Similar to the third phase 23, the other third phase has a spherical outer surface and can be exposed on the outer surface of the nano-sized particles 21. Further, a phase that is a compound of the element X ′ and the element M may be dispersed in the first phase 13 or the third phase 23. Further, the nano-sized particles 21 may contain an element M ′ in addition to the element M.

  As described above, the nano-sized particles 21 are composed of various combinations of compounds and solid solutions from various combinations of the elements X and X ′, the elements M, and the elements M ′. Can be included. Such a phase may be exposed on the surface of the nano-sized particle 21 or may be dispersed in the first phase 13 or any other phase.

  Note that oxygen may be bonded to the outermost surface of the nano-sized particles 21. This is because when the nanosize particles 21 are taken out into the air, oxygen in the air reacts with elements on the surface of the nanosize particles 21. That is, the outermost surface of the nano-sized particles 21 may have an amorphous layer having a thickness of about 0.5 to 15 nm, and in particular, when the first phase is mainly crystalline silicon, it has an oxide film layer. You may do it.

(2-6. Effect of negative electrode active material C)
According to the third embodiment, the same effect as that obtained in the second embodiment can be obtained. However, according to the third embodiment, volume expansion occurs when the first phase 13 occludes lithium, and expansion also occurs when the third phase 23 occludes lithium. However, since the electrochemical potential for storing lithium differs between the first phase 13 and the third phase 23, when one phase preferentially occludes lithium and one phase expands in volume, 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 the particle | grains without the 3rd phase 23, the nanosize particle | grains 21 which have the 1st phase 13 and the 3rd phase 23 are hard to expand | swell when occlusion of lithium. Therefore, according to the third embodiment, even if the nanosized particles 21 occlude lithium, volume expansion is suppressed, and a decrease in discharge capacity during cycle characteristics is suppressed.

(2-7. Other aspects of negative electrode active material)
In addition, as the negative electrode active material according to the present invention, as the first particles 9 in the negative electrode active material A, nano-sized particles of the negative electrode active materials B and C may be used. By doing in this way, also in the negative electrode active material A, the effect similar to the negative electrode active materials B and C can be acquired.

  Furthermore, as the negative electrode active material according to the present invention, at least part of the surfaces of the first particles 9 and the nanoparticles 11, 17, and 21 in the negative electrode active materials A to C described above, for example, copper, tin, zinc Those coated with silver, nickel or carbon can also be considered. The thickness of the coating is exemplified as being in the range of 0.01 to 0.5 μm. For example, in such a configuration, in the nanoparticle 17 shown in FIG. 5, Cu is selected as the element M ′, and the other second phase 19 that is a single element M ′ is the surface of the first phase 13. It can also be understood that the first phase 13 and the second phase 15 are present (not shown) instead of being bonded to each other.

  Thus, by covering the surface of the negative electrode active material with a material having good conductivity, the conductivity of the entire negative electrode is improved and cycle characteristics are also improved without using a conductive aid or the like. Further, since the surface of the negative electrode active material is coated, oxidation of silicon or the like can be suppressed. By covering the surface, resistance to volume changes due to charge / discharge is improved.

(2-8. Method for producing nano-sized particles)
Here, a method for producing nano-sized particles will be described.
Nano-sized particles can be 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. 8, 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. 8, 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 into a solid via a gas and a liquid, so that it becomes spherical at the droplet stage, and the first phase 13 and the second phase are formed. The phase 15 has a spherical shape. On the other hand, in the top-down method of reducing large particles, such as the crushing method and the mechanochemical method, the shape of the particles is rugged and is significantly different from the spherical shape of the nano-sized particles 11.

  In addition, when the mixed powder of each powder of the element X and the element M is used for raw material powder, the nanosized particle 11 which concerns on 2nd Embodiment is obtained. On the other hand, when the mixed powder of each powder of the element X, the element M, and the element M ′ is used as the raw material powder, the nano-sized particles 17 according to the second embodiment are obtained. Further, when a mixed powder of each powder of the element X, the element M (and the element M ′), and the element X ′ is used as the raw material powder, the nanosize particles 21 according to the second embodiment are obtained.

  About 1st particle | grains and 2nd particle | grains which concern on 1st Embodiment, it can also manufacture using said nanosize particle | grain manufacturing apparatus and method, and manufacture using well-known various methods. You can also.

  Further, the method for particle surface coating is not particularly limited, and various known methods can be employed. Electroless plating or displacement plating is used for coating the metal, and the surface oxidation of particles such as silicon is small, and electroplating is possible if the particles are conductive. For coating the carbon, a method of heat treatment in an inert or reducing atmosphere after mixing an inorganic carbon source such as carbon black or an organic carbon source such as polyvinyl alcohol can be used. In addition, a thermal decomposition CVD method in which the surface of particles is coated with carbon by heating the hydrocarbon gas to 600 ° C. or higher to be thermally decomposed can also be used.

(2-9. Method for producing negative electrode)
Next, the manufacturing method of the negative electrode for nonaqueous electrolyte secondary batteries is demonstrated. The negative electrode of the present invention can be formed by applying a coating liquid containing at least a negative electrode active material, a conductive material and a binder to a current collector and drying it. For example, as shown in FIG. 9, the coating liquid can be prepared by charging a slurry raw material 57 into a mixer 53 and kneading to form a slurry (coating liquid) 55. The slurry raw material 57 is nano-sized particles, a conductive aid, a binder, a thickener, a solvent, and the like.

  In the solid content in the slurry 55, for example, the blending of nano-sized particles 25 to 90% by weight, conductive auxiliary agent 5 to 70% by weight, binder 1 to 30% by weight, thickener 0 to 25% by weight can do.

  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 X of the nano-sized particles is silicon having low conductivity, silicon is exposed on the surface of the nano-sized particles, and the conductivity is lowered. Therefore, carbon nanohorn may be added as a conductive auxiliary agent. 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. Any one of these materials may be used, or two or more of these materials may be used in combination.

  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 auxiliary agent and to use vapor grown carbon fiber (VGCF) as the wire-shaped conductive auxiliary agent. 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, fluorine resin such as polyvinylidene fluoride (PVdF), synthetic rubber such as styrene butadiene rubber (SBR), acrylic resin, celluloses such as carboxymethyl cellulose, polyimide, polyamide An organic material such as imide can be used. Any one of these materials may be used, or two or more of these materials may be used in combination.

  As the solvent, water, N-methyl-2-pyrrolidone (NMP), or the like can be used.

  Next, as illustrated in FIG. 10, the slurry 55 is applied to one surface of the current collector 61 using, for example, a coater 59. As the coater 59, a general coating apparatus capable of applying the slurry 55 to the current collector 61 can be used. For example, the coater 59 is a coater, a comma coater, or a die coater using a roll coater or a doctor blade.

  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 metal may be used independently and may be used as each alloy. 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 nonaqueous electrolyte secondary batteries can be obtained through a roll press. When polyimide or polyamideimide is used as the binder, it is preferable to perform heat treatment in the range of 250 ° C to 450 ° C.

(3. Positive electrode)
As the positive electrode 3, various positive electrodes capable of inserting and extracting lithium ions can be used. This positive electrode for a lithium ion battery is prepared by mixing a positive electrode active material, a conductive additive, a binder and a solvent to prepare a positive electrode active material composition, which is directly applied onto a metal current collector such as an aluminum foil. -It can be manufactured by drying.

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 O ₂ , compounds such as LiFePO ₄ are exemplified.

  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. Water, etc. can be used. At this time, the contents of the positive electrode active material, the conductive additive, the binder, and the solvent are at levels normally used in non-aqueous electrolyte secondary batteries and the like.

(4. 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 non-aqueous electrolyte secondary battery. For example, a microporous polyolefin film can be used.

(5. Electrolyte / Electrolyte)
As the electrolytic solution and the electrolyte, a non-aqueous organic electrolytic solution having lithium ion conductivity used for a lithium ion secondary battery, a Li polymer battery, or the like can be used.

  Specific examples of the organic electrolyte solvent 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.

  In the present invention, the electrolyte is characterized by containing an organic substance having an unsaturated bond in the molecule and capable of reductive polymerization. By adding such an organic substance to the electrolyte, an effective solid electrolyte interface film can be formed on the surface of the negative electrode active material, and decomposition of the electrolyte material can be suppressed. Examples of the substance having an unsaturated bond in the molecule and capable of undergoing reductive polymerization at the time of charging include, for example, carbonates such as fluoroethylene carbonate, vinylene carbonate (VC), vinyl ethylene carbonate, and derivatives thereof, and unsaturated carboxylic acid esters. , Phosphoric acid esters, boric acid esters, alcohols and the like can be used. Among them, it is shown as a preferable example that vinylene carbonate (VC) is used.

  In order to obtain a stable solid electrolyte interface film, such an organic substance is preferably added in an amount of about 0.1 wt% to 10 wt% of the electrolyte weight. Furthermore, it is more preferable to add about 1 to 5% by weight. When the addition amount is in the range of 0.1% by weight to 10% by weight, it can be reduced during charging to form a stable film on the surface of the negative electrode active material layer, and the decomposition of the electrolyte material can be prevented. . When the addition amount is less than 0.1% by weight, it is difficult to sufficiently form a stable film on the surface of the negative electrode active material, and when the addition amount exceeds 10% by weight, it is reduced. Since the amount increases, the formed solid electrolyte interface film becomes thick, and the impedance of the battery increases, which is not preferable.

(6. Assembly of non-aqueous electrolyte secondary battery)
In the nonaqueous electrolyte secondary battery of the present invention, a separator is disposed between the positive electrode and the negative electrode as described above to form a battery structure. After winding or folding such a battery structure into a cylindrical or rectangular battery case, an electrolyte is injected to complete a lithium ion secondary battery.

  Specifically, as shown in FIG. 1, the non-aqueous electrolyte secondary battery 1 of the present invention has a positive electrode 3 and a negative electrode 5 stacked in the order of separator-negative electrode-separator-positive electrode via a separator 7. Then, the positive electrode 3 is wound so as to be on the inner side to form an electrode plate group, which is inserted into the battery can 25. The positive electrode 3 is connected to the positive electrode terminal 29 via the positive electrode lead 27, and the negative electrode 5 is connected to the battery can 25 via the negative electrode lead 31, and the chemical energy generated inside the nonaqueous electrolyte secondary battery 1 is externally used as electric energy. To be able to take out. Next, after filling the battery can 25 with the non-aqueous electrolyte solution 8 so as to cover the electrode plate group, the upper end (opening portion) of the battery can 25 is composed of a circular lid plate and a positive electrode terminal 29 on the upper portion thereof. The non-aqueous electrolyte secondary battery 1 of the present invention can be manufactured by attaching the sealing body 33 having a built-in safety valve mechanism thereto via an annular insulating gasket.

(7. Effects of the nonaqueous electrolyte secondary battery according to the present invention)
The non-aqueous electrolyte secondary battery according to the present invention uses nano-sized particles containing Si, which has a higher capacity per unit volume than carbon, as a negative electrode active material, and therefore has a larger capacity than a conventional lithium ion secondary battery. In addition, the cycle characteristics are good because the nano-sized particles are not easily pulverized.

  In addition, even when such a nano-sized negative electrode active material is used and a negative electrode is formed by a coating method, the surface of the negative electrode active material layer can be stabilized by including an organic substance capable of reduction polymerization having an unsaturated bond in the electrolyte. Effective film is formed, the negative electrode active material is stabilized, decomposition of the electrolytic solution is suppressed, and cycle characteristics are improved.

Hereinafter, the present invention will be specifically described using examples and comparative examples.
[Example 1]
(Nano-sized particles)
Using the apparatus of FIG. 8, Ar gas generated in the reaction chamber using a mixed powder obtained by mixing silicon powder and iron powder in a molar ratio of Si: Fe = 23: 2 and using the dried mixed powder as a raw material powder. The silicon and iron nano-sized particles were manufactured by continuously supplying the plasma with a carrier gas.

  In detail, it manufactured by the method as follows. 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.

(Evaluation of the composition of nano-sized particles)
Regarding the crystallinity of the nano-sized particles, XRD analysis was performed using RINT-Ultima III manufactured by Rigaku Corporation. FIG. 11 shows an XRD diffraction pattern of the nano-sized particles of Example 1. The nano-sized particles obtained in Example 1 were found to be composed of two components, Si and FeSi ₂ . It was also found that all Fe was present as silicide FeSi ₂ and there was almost no Fe as a single element (valence 0).

  The particle shape of the nano-sized particles was observed using a scanning transmission electron microscope (manufactured by JEOL Ltd., JEM 3100FEF). 12A is a BF-STEM (Bright-Field Scanning Transmission Electron Microscopy) image of the nano-sized particles according to Example 1. FIG. Nano-sized particles in which hemispherical particles are bonded to the substantially spherical particles having a particle diameter of about 80 to 100 nm via the interface are observed, and within the same particles, a relatively dark colored portion is iron containing iron. It is made of silicide, and a relatively light-colored portion is made of silicon. It can also be seen that an amorphous silicon oxide film having a thickness of 2 to 4 nm is formed on the surface of the nano-sized particles. FIG. 12 (b) is a STEM photograph by HAADF-STEM (High-Angle-Annel-Dark-Field-Scanning-Transmission-Electron-Microscopy: high angle scattering dark field-scanning transmission electron microscopy). In HAADF-STEM, a relatively light portion of the same particle is made of iron silicide, and a relatively dark portion is made of silicon.

  Observation and composition analysis of nano-sized particles using a scanning transmission electron microscope (manufactured by JEOL, JEM 3100FEF), observation of particle shape by HAADF-STEM, and EDS (Energy Dispersive Spectroscopy: Energy Dispersive X) Line analysis). Fig. 13 (a) is a HAADF-STEM image of nano-sized particles, Fig. 13 (b) is an EDS map of silicon atoms at the same observation location, and Fig. 13 (c) is at the same observation location. It is an EDS map of an iron atom.

  According to FIG. 13 (a), nano-sized particles having a particle size of about 50 to 150 nm are observed, and each nano-sized particle has a substantially spherical shape. From FIG. 13 (b), it can be seen that silicon atoms are present in the entire nano-sized particles, and from FIG. 13 (c), many iron atoms are detected at the brightly observed positions in FIG. 13 (a). From the above, it can be seen that nano-sized particles have a structure in which a second phase formed of a compound of silicon and iron is bonded to a first phase formed of silicon.

  14A to 14C, the observation of the shape and composition analysis of another nano-sized particle according to Example 1 were similarly performed. 14 also shows that, similarly to FIG. 13, the first phase formed of silicon and the second phase formed of a compound of silicon and iron are joined.

The formation process of the obtained nano-sized particles is considered. FIG. 15 is a binary phase diagram of Si and Fe. Since the silicon powder and the iron powder were mixed at a molar ratio of Si: Fe = 23: 2, mole Si / (Fe + Si) = 0.92 in the raw material powder. The thick line in FIG. 15 is a line indicating mole Si / (Fe + Si) = 0.92. 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 iron atoms and silicon atoms are uniformly mixed is obtained. When the plasma is cooled, spherical droplets grow in the process of changing from plasma to gas and from gas to liquid, and when cooled to about 1470K, both Fe ₃ Si ₇ and Si are deposited. Then, when cooled to about 1220K, _Fe 3 Si ₇ is a phase change to a FeSi ₂ and Si. Therefore, when the plasma of silicon and iron is cooled, nano-sized particles are formed in which FeSi ₂ and Si are bonded via the interface. Since Si and Fe have low affinity, Si and Fe take a shape in which two particles are joined so as to reduce the area in contact with each other.
The average particle size of the obtained nano-sized particles was 100 nm.

(Evaluation of powder conductivity)
In order to evaluate the electronic conductivity in the powder state, the powder conductivity was evaluated using a powder resistance measurement system MCP-PD51 manufactured by Mitsubishi Chemical. The conductivity was determined from the resistance value when the sample powder was compressed at an arbitrary pressure. The data in Table 1 to be described later is a value when measured by compressing the sample powder at 63.7 MPa.

(Evaluation of cycle characteristics of non-aqueous electrolyte secondary batteries)
(I) Preparation of negative electrode slurry After using the Si and Fe nano-sized particles obtained above as the negative electrode active material, acetylene black (produced by Denki Kagaku Kogyo Co., Ltd., powdered product) as a conductive material was charged into the mixer Furthermore, a styrene butadiene rubber (SBR) 40 wt% emulsion as a binder (manufactured by Nippon Zeon Co., Ltd., BM-400B), sodium carboxymethyl cellulose as a thickener for adjusting the viscosity of the slurry (Daicel Chemical Industries, Ltd.) # 2200) 1 wt% solution was mixed to prepare a slurry. The composition of the slurry was 64% by weight of the negative electrode active material, 16% by weight of the conductive material, 5% by weight of the binder (in terms of solid content), and 15% by weight of the thickener (in terms of solid content).

(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). The negative electrode A was manufactured by coating at 70 ° C. for 10 minutes.

(Iii) Evaluation Negative electrode A for test electrode, lithium for counter electrode and reference electrode, microporous membrane made of polyolefin for separator, ethylene carbonate (EC) and ethyl methyl carbonate containing 1.3 mol / L LiPF ₆ for electrolyte An evaluation cell was constructed using an electrolytic solution obtained by adding 1% by weight of vinylene carbonate (VC) to a mixed solution of (EMC) and dimethyl carbonate (DMC), and the charge / discharge characteristics were examined.

  The charge / discharge characteristics were evaluated by measuring the initial discharge capacity and the discharge capacity after 50 cycles of charge / discharge, and determining the ratio of the discharge capacity after 50 cycles of charge / discharge to the initial discharge capacity as a percentage. The maintenance rate. The discharge capacity is the weight of the active material Si (Si and Sn if Sn is included) that is effective for lithium insertion / extraction, excluding silicon and tin that do not occlude / release lithium, such as forming silicide. Calculated as a reference. First, in a 25 ° C. environment, constant current charging was performed at a current of 0.1 C to a voltage of 0.02 V, and constant voltage charging was performed until the current value decreased to 0.05 C. Next, constant current discharge was performed at a current of 0.1 C to a voltage of 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. Next, the above charging / discharging was repeated 50 cycles.

[Example 2]
Using the apparatus of FIG. 8, silicon powder and iron powder were mixed at a molar ratio of Si: Fe = 38: 1, and the dried mixed powder was used as a raw material powder in the same manner as in Example 1, Nano-sized particles having an average particle size of 100 nm were prepared. And using this nanosized particle as a negative electrode active material, the negative electrode B was manufactured by the method similar to Example 1, the cell for evaluation was constructed | assembled, and the charge / discharge characteristic was investigated.

FIG. 16 shows an XRD diffraction pattern of the nano-sized particles according to Example 2. Example 2 was found to be composed of two components of Si and FeSi _2. It was also found that all Fe was present as silicide FeSi ₂ and there was almost no elemental Fe. In comparison with FIG. 9, as compared to the nano-sized particles according to Example 1, small proportions of Fe, a peak derived from FeSi ₂ can not be confirmed only a trace amount.

The observation result by STEM is shown in FIG. According to FIG. 17A, a large number of substantially spherical particles having a diameter of about 50 to 150 nm are observed. In the non-overlapping particles, it is considered that the dark part is iron silicide and the light part is silicon. Further, it is observed that the atoms of the silicon portion are regularly arranged, and it can be seen that the silicon corresponding to the first phase is crystalline. FIG. 17B shows that the surface of the nano-sized particles is covered with an amorphous layer having a thickness of about 1 nm on the silicon portion, and the amorphous layer having a thickness of about 2 nm is covered on the portion of iron silicide. Moreover, by comparing the STEM photographs in FIG. 12 and FIG. 17, the relative sizes of Si and FeSi ₂ can be confirmed, and the FeSi ₂ of the nano-sized particles according to Example ₂ is the same as that of the nano-sized particles according to Example 1. It can be seen that it is smaller than FeSi ₂ .

  The observation of the particle shape by HAADF-STEM and the results of EDS analysis are shown in FIGS. According to FIG. 18 (a), nano-sized particles having a particle size of about 150 to 250 nm are observed, and each nano-sized particle has a substantially spherical shape. From FIG. 18B, it can be seen that silicon atoms are present in the entire nano-sized particle, and from FIG. 18C, a large amount of iron atoms are detected at the bright spots observed in FIG. From FIG. 18 (d), it can be seen that oxygen atoms considered to be due to oxidation are slightly distributed throughout the nano-sized particles.

  Similarly, according to FIG. 19A, substantially spherical nano-sized particles having a particle diameter of about 250 nm are observed, and from FIG. 19B, silicon atoms are present in the entire nano-sized particles, and FIG. From c), it can be seen that many iron atoms are detected in the brightly observed part in FIG. From FIG. 19 (d), it can be seen that oxygen atoms considered to be due to oxidation are slightly distributed throughout the nano-sized particles. From the above, it can be seen that nano-sized particles have a structure in which a second phase formed of a compound of silicon and iron is bonded to a first phase formed of silicon.

[Example 3]
Using the apparatus of FIG. 8, silicon powder and iron powder were mixed at a molar ratio of Si: Ni = 12: 1, and the dried mixed powder was used as a raw material powder in the same manner as in Example 1, Nano-sized particles having an average particle size of 100 nm were prepared. And using this nanosized particle as a negative electrode active material, the negative electrode C was manufactured by the method similar to Example 1, the cell for evaluation was constructed | assembled, and the charge / discharge characteristic was investigated.

FIG. 20 shows an XRD diffraction pattern of the nano-sized particles according to Example 3. Example 3 was found to be composed of two components of Si and NiSi _2. Further, it was found that Ni was present as silicide NiSi ₂ and there was almost no Ni as a single element (valence 0). It can be seen that Si and NiSi ₂ have the same diffraction angle 2θ and almost the same plane spacing.

  FIG. 21A is a BF-STEM image, and FIG. 21B is a HAADF-STEM image with the same field of view. According to FIG. 21, nano-sized particles having a particle size of about 75 to 150 nm are observed. Each nano-sized particle is bonded to a large particle having a substantially spherical shape, and another particle having a substantially hemispherical shape is bonded via an interface. It has a shape like this.

  FIG. 22 is a high-resolution TEM image of nanosized particles according to Example 3. In FIGS. 22A to 22C, lattice images are seen, and the lattice stripes of the silicon phase and the silicide phase substantially coincide, and it can be seen that the silicide has a polyhedral shape. The boundary between the silicon phase and the silicide phase is a straight line, a curve, or a staircase. It can also be seen that the surface of the nano-sized particles is covered with an amorphous layer of silicon having a thickness of about 2 nm.

  In FIG. 23, the HAADF-STEM image of the nanosized particle which concerns on Example 3, and the result of an EDS analysis are shown. According to FIG. 23A, nano-sized particles having a particle size of about 75 to 150 nm are observed. From FIG. 23B, it can be seen that silicon atoms are present in the entire nano-sized particles, and from FIG. 23C, a large amount of nickel atoms are detected at the brightly observed positions in FIG. From the above, it can be seen that the nano-sized particles have a structure in which a second phase formed of a compound of silicon and nickel is bonded to a first phase formed of silicon. Further, FIG. 23 (d) shows that oxygen atoms considered to be oxidized are slightly distributed throughout the nano-sized particles.

[Example 4]
Using the apparatus of FIG. 8, silicon powder and iron powder were mixed at a molar ratio of Si: Fe: Sn = 21: 1: 1, and the dried mixed powder was used as a raw material powder, as in Example 1. By this method, nano-sized particles having an average particle size of 100 nm were prepared. And using this nanosized particle as a negative electrode active material, the negative electrode D was manufactured by the method similar to Example 1, the cell for evaluation was constructed | assembled, and the charge / discharge characteristic was investigated.

FIG. 24 is an X-ray diffraction (XRD) pattern of nano-sized particles according to Example 4. Nano-sized particles according to Example 4 is seen to have a Si, Sn, and FeSi _2.

  The STEM photograph of the nanosized particle which concerns on Example 4 is shown to Fig.25 (a)-(b). Nano-sized particles having a substantially spherical outer surface with a particle size of about 50 to 150 nm were observed. In FIG. 25A, it is considered that the dark part is Sn and the light part is Si.

  The STEM photograph of the nanosized particle which concerns on Example 4 is shown to Fig.26 (a)-(b). Nano-sized particles having a substantially spherical outer surface with a particle size of about 50 to 150 nm were observed. The bright area is mainly composed of Sn, and the dark area is mainly composed of Si.

  According to FIG. 27 (a), nano-sized particles having a particle size of about 100 to 150 nm are observed, and from FIG. 27 (b), many silicon atoms are detected at locations that are darkly observed in FIG. 27 (a). I understand. From FIG. 27 (c), it can be seen that many iron atoms are detected at locations that are observed slightly brighter in FIG. 27 (a). From FIG. 27 (d), it can be seen that many tin atoms are detected at the bright spots observed in FIG. 27 (a). From FIG. 27 (e), it can be seen that oxygen atoms that are thought to be due to oxidation are distributed throughout the nano-sized particles.

  FIG. 28 is a diagram further illustrating the EDS analysis result. FIG. 28 (a) is an EDS map of Fe and Sn and a diagram obtained by superimposing these, and FIG. 28 (b) is a HAADF-STEM image in the same field of view. According to Fig.28 (a), there is little overlap of the detection point of Sn and Fe. In the XRD analysis, no peak derived from the Sn—Fe alloy has been confirmed, and therefore no Sn—Fe alloy is formed on the nanosized particles. Moreover, since Si and Sn do not form an alloy, Sn exists alone.

  FIG. 29 is a diagram showing the EDS analysis results at the first to third locations in the nano-sized particles. In the first part of FIG. 29B, Si was mainly observed and Sn was slightly observed. Si and Sn were observed at the second location in FIG. In the third part of FIG. 29 (d), Si and Fe were mainly observed, and a slight amount of Sn was observed. In addition, the background of Cu derived from the TEM mesh holding the sample during observation is widely observed.

[Comparative Example 1]
As the negative electrode active material, instead of the nano-sized particles, silicon nanoparticles having an average particle size of 100 nm (made by Hefei Kai'er NanoTech) were used, and the negative electrode E was manufactured and evaluated in the same manner as in Example 1. A cell was constructed and the charge / discharge characteristics were examined.

[Comparative Example 2]
The negative electrode A prepared in the same manner as in Example 1 was used as a test electrode, lithium as a counter electrode and a reference electrode, a microporous membrane made of polyolefin as a separator, and ethylene carbonate (EC) containing 1.3 mol / L LiPF ₆ as an electrolyte. ), Ethyl methyl carbonate (EMC), and a mixed solution of dimethyl carbonate (DMC) were used to form an evaluation cell, and the charge / discharge characteristics were examined. That is, vinylene carbonate (VC) was not added to the electrolytic solution.

[Comparative Example 3]
A negative electrode B produced in the same manner as in Example 2 was used as a test electrode, and thereafter, an evaluation cell was constructed in the same manner as in Comparative Example 2, and the charge / discharge characteristics were examined.

[Comparative Example 4]
A negative electrode C prepared in the same manner as in Example 3 was used as a test electrode, and thereafter, an evaluation cell was constructed in the same manner as in Comparative Example 2, and the charge / discharge characteristics were examined.

[Comparative Example 5]
A negative electrode D prepared in the same manner as in Example 4 was used as a test electrode, and thereafter, an evaluation cell was constructed in the same manner as in Comparative Example 2, and the charge / discharge characteristics were examined.

(Evaluation of nano-sized particles)
Table 1 shows the powder conductivity measured for the Si-based nano-sized particles according to Examples 1 to 4 and Comparative Example 1 under the condition that the powder particles were compressed at 63.7 MPa by the method shown in Example 1. .
In Examples 1 to 4, the powder conductivity was 4 × 10 ⁻⁸ [S / cm] or more, and in Comparative Example 1, the powder conductivity was less than 4 × 10 ⁻⁸ [S / cm]. In Comparative Example 1, the measurement limit was less than 1 × 10 ⁻⁸ [S / cm]. When the powder conductivity is high, the blending of the conductive auxiliary agent can be reduced, the capacity per unit volume of the electrode can be increased, and it is advantageous in high rate characteristics.

(Evaluation of nano-sized particles)
Table 1 shows the powder conductivity measured for the Si-based nano-sized particles according to Examples 1 to 4 and Comparative Example 1 under the condition that the powder particles were compressed at 63.7 MPa by the method shown in Example 1. .
In Examples 1 to 4, the powder conductivity was 4 × 10 ⁻⁸ [S / cm] or more, and in Comparative Example 1, the powder conductivity was 4 × 10 ⁻⁸ [S / cm] or less. In Comparative Example 1, the measurement limit was 1 × 10 ⁻⁸ [S / cm] or less. When the powder conductivity is high, the blending of the conductive auxiliary agent can be reduced, the capacity per unit volume of the electrode can be increased, and it is advantageous in high rate characteristics.

  Table 2 shows the discharge capacities and capacity retention rates of Examples 1 to 4 and Comparative Examples 1 to 6. FIG. 30 shows the relationship between the number of cycles of Examples 1 to 4 and Comparative Examples 1 to 6 and the discharge capacity retention rate.

  As is apparent from Table 2 and FIG. 30, when Examples 1 to 4 and Comparative Examples 2 to 5 are compared, the capacity retention rate after 50 cycles is 2 by adding VC to the electrolyte. It can be seen that the non-aqueous electrolyte secondary batteries according to Examples 1 to 4 have reduced capacity reduction and good cycle characteristics.

  Furthermore, paying attention to the results of Comparative Example 1 and Comparative Example 6, the effect of suppressing the decrease in capacity by adding VC to the electrolytic solution can be suitably obtained as described above for the nonaqueous electrolyte secondary battery according to the present invention. However, it can be seen that the non-aqueous electrolyte secondary battery using Si nano-sized particles as the negative electrode active material has no effect at all, but rather has reduced charge / discharge characteristics.

In this example, Fe and Ni were used as the negative electrode active material as an element M that forms a second phase with a compound with Si, and Sn was used as an element A that forms a third phase. However, it can be used in the present invention. The negative electrode active material is not limited to this. Any nano-sized particles including at least a first phase made of Si and a second phase of a compound MSi _X (1 <X ≦ 3) of the elements M and Si may be used. In addition to Fe and Ni, for example, Ti It is presumed that similar results can be obtained even when Co or Co is used.

  In this example, vinylene carbonate was used as an organic substance having an unsaturated bond in the molecule and capable of reductive polymerization, but it has an unsaturated bond in the molecule that can be used in the present invention and can be reductively polymerized. The organic material is not limited to this. It is presumed that the result of the same tendency as in this example can be obtained even if vinyl ethylene carbonate is used, for example, by performing reductive polymerization at the negative electrode charging potential and forming a stable film on the negative electrode active material surface.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to the example which concerns. It is obvious that a person skilled in the art can come up with various changes or modifications within the scope of the technical idea disclosed in the present application, and it is understood that these also belong to the technical scope of the present invention. Is done.

DESCRIPTION OF SYMBOLS 1 ......... Nonaqueous electrolyte secondary battery 3 ......... Positive electrode 5 ......... Negative electrode 7 ......... Separator 8 ...... Nonaqueous electrolyte 9 ......... First particle 10 ......... Second particle 11 ……… Nanosize particles 13 ……… First phase 15 ……… Second phase 17 ……… Nanosize particles 19 ……… Other second phases 21 ……… Nanosize particles 23 ……… 3rd phase 25 .... battery can 27 .... positive electrode lead 29 .... positive electrode terminal 31 .... negative electrode lead 33 .... sealing body 37 .... nano size particle manufacturing apparatus 39 .... reaction chamber 41. ……… Raw powder supply port 42 ……… Raw material 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 raw material 59 ……… Coater 61 ……… Current collector

Claims (8)

A non-aqueous electrolyte having a lithium ion conductivity, having a positive electrode capable of inserting and extracting lithium ions, a negative electrode capable of inserting and extracting lithium ions, and a separator disposed between the positive electrode and the negative electrode A non-aqueous electrolyte secondary battery in which the positive electrode, the negative electrode, and the separator are provided,
The negative electrode active material of the negative electrode comprises first particles comprising a first phase having an average particle diameter of 2 nm to 500 nm containing the element X and second phases having an average particle diameter comprising the element M of 2 nm to 10 μm. A second particle,
It said first phase of said first particles, the distance between the second phase of the second particles is within 1 [mu] m,
The element X is one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn,
The element M is at least one element selected from the group consisting of Group 4 to 11 transition metal elements,
The first particle is composed of the element X alone or a solid solution containing the element X as a main component,
The second particles are composed of a single element or a compound of the element M,
The non-aqueous electrolyte secondary battery, wherein the electrolytic solution contains 0.1 wt% to 10 wt% of an organic substance having an unsaturated bond in a molecule and capable of reduction polymerization. A non-aqueous electrolyte having a lithium ion conductivity, having a positive electrode capable of inserting and extracting lithium ions, a negative electrode capable of inserting and extracting lithium ions, and a separator disposed between the positive electrode and the negative electrode A non-aqueous electrolyte secondary battery in which the positive electrode, the negative electrode, and the separator are provided,
The negative electrode active material of the negative electrode is composed of nano-sized particles containing the element X and the element M,
The element X is one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn,
The element M is at least one element selected from the group consisting of Group 4 to 11 transition metal elements,
The nano-sized particles are a first phase that is a single element of the element X or a solid solution that contains the element X as a main component, and a single solution of the element M, a solid solution that contains the element M as a main component, or a compound of the element M. Two phases, and
The nano-sized particles have both the first phase and the second phase exposed to the outer surface and bonded via an interface, and the outer surface of the first phase is substantially spherical. And
The nano-sized particles have an average particle diameter of 2 nm to 500 nm,
The electrolyte solution contains 0.1 wt% to 10 wt% of an organic substance having an unsaturated bond in the molecule and capable of reductive polymerization. The nano-sized particles are Cu, Fe, Co, Ni, Ca, Sc, Ti, V, Cr, Mn, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ba, lanthanoid elements (Ce and Pm). And an element M ′ that is at least one element selected from the group consisting of Hf, Ta, W, Re, Os, and Ir,
The element M ′ is an element different in kind from the element M constituting the second phase,
The nonaqueous electrolyte secondary battery according to claim 2, further comprising another second phase that is a single element or a compound of the element M ′. The nano-sized particles further include an element X ′ that is at least one element selected from the group consisting of Si, Sn, Al, Pb, Sb, Bi, Ge, In, and Zn,
The nonaqueous electrolyte secondary battery according to claim 2, further comprising a third phase that is a single element or a solid solution of the element X ′.   The nonaqueous electrolyte secondary battery according to claim 4, wherein the third phase is joined to at least one of the first phase and the second phase via an interface.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the first particles are nano-sized particles according to any one of claims 2 to 5.   The organic substance having an unsaturated bond in the molecule and capable of reductive polymerization is at least one selected from the group consisting of fluoroethylene carbonate, vinylene carbonate and derivatives thereof, and vinyl ethylene carbonate. The nonaqueous electrolyte secondary battery according to any one of 1 to 6. The negative electrode is formed by applying a coating liquid containing at least a negative electrode active material, a conductive material, and a binder to a current collector and drying it. The non-aqueous electrolyte secondary battery described in 1.