JP2019145402A - Lithium ion secondary battery - Google Patents

Abstract

To provide a lithium ion secondary battery with a new silicon material and excellent thermal stability.SOLUTION: A lithium ion secondary battery includes a positive electrode including a positive electrode active material and a lithium dopant, and a negative electrode including an Al-containing silicon material.SELECTED DRAWING: None

Description

  The present invention relates to a lithium ion secondary battery.

  Lithium ion secondary batteries are used as power sources for portable devices such as portable information terminals and vehicles. For the purpose of increasing the capacity of the lithium ion secondary battery, it has been studied to employ a silicon material containing silicon that is excellent in theoretical capacity as the negative electrode active material.

For example, Patent Literature 1 and Patent Literature 2 describe lithium ion secondary batteries in which the negative electrode active material is silicon.
Patent Literature 3 and Patent Literature 4 describe lithium ion secondary batteries in which the negative electrode active material is SiO.

Patent Document 5 describes that CaSi ₂ is reacted with an acid to synthesize a layered polysilane, and that a lithium ion secondary battery including the layered polysilane as a negative electrode active material exhibits a suitable capacity. Has been.

Patent Document 6 discloses that a layered polysilane was synthesized by reacting CaSi ₂ with an acid, and the layered polysilane was heated at 300 ° C. or more to produce a nanosilicon material from which hydrogen was released, and the nanosilicon material. It is described that a lithium ion secondary battery having a negative electrode active material exhibits a suitable capacity retention rate.

JP 2014-203595 A Japanese Patent Laying-Open No. 2015-57767 JP 2015-185509 A JP-A-2015-179625 JP 2011-090806 A International Publication No. 2014/080608

  As described above, research on silicon materials has been conducted eagerly, and the provision of new silicon materials that can be employed as negative electrode active materials for secondary batteries is eagerly desired. Moreover, the lithium ion secondary battery which is excellent in thermal stability is calculated | required from a viewpoint of safety.

  This invention is made | formed in view of this situation, and it aims at providing the lithium ion secondary battery which comprises a new silicon material and is excellent in thermal stability.

  The present inventor has intensively studied through trial and error in order to provide a new silicon material. Since silicon itself is a semiconductor, when the silicon material is used as the negative electrode active material of the secondary battery, the present inventor considered that it is preferable to increase the conductivity of the silicon material by some method. Therefore, when a small amount of Al was added to produce a silicon material and the resistance of a secondary battery comprising the silicon material was measured, the resistance was lower than that of a secondary battery comprising an Al-free silicon material. It was found that it was resistance.

  Further, it is known that irreversible capacity exists in silicon materials. The irreversible capacity means a capacity related to an amount of lithium that is trapped by the negative electrode active material and cannot participate in a normal charge / discharge reaction among lithium transferred from the positive electrode to the negative electrode during the first charge.

  The present inventor has tried a means for attaching a metal lithium foil to the surface of the negative electrode in order to compensate for the amount of lithium corresponding to the irreversible capacity of the silicon material. Such means is the method disclosed in Example 10 of JP-A-6-325765. When the lithium ion secondary battery was actually manufactured using the negative electrode with the metal lithium foil attached and its thermal stability was evaluated, the present inventor found that there was room for improvement in thermal stability.

  The inventor has conceived a means for adding a lithium dopant to the positive electrode as a means for compensating the amount of lithium corresponding to the irreversible capacity of the silicon material. And actually, when the lithium ion secondary battery was manufactured using the positive electrode to which the lithium dopant was added and the thermal stability was evaluated, it was found that the thermal stability was remarkably improved.

  That is, the lithium ion secondary battery of the present invention includes a positive electrode including a positive electrode active material and a lithium dopant, and a negative electrode including an Al-containing silicon material.

  According to the present invention, a lithium ion secondary battery having a new silicon material and excellent in thermal stability can be provided.

It is a phase diagram of substitutional solid solution CaSi _2-x Al _x . It is a graph which shows the result (N = 2) of the capacity | capacitance maintenance factor about the lithium ion secondary battery of Example 2, the comparative example 2, and the comparative example 3. FIG.

  The best mode for carrying out the present invention will be described below. Unless otherwise specified, the numerical range “x to y” described in this specification includes the lower limit x and the upper limit y. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.

  The lithium ion secondary battery of the present invention comprises a positive electrode comprising a positive electrode active material and a lithium dopant, and a negative electrode comprising an Al-containing silicon material (hereinafter sometimes referred to as the Al-containing silicon material of the present invention). It is characterized by providing. By charging the lithium ion secondary battery of the present invention, lithium of the lithium dopant is introduced into the negative electrode.

  The positive electrode includes a positive electrode active material and a lithium dopant. The positive electrode includes a current collector and a positive electrode active material layer containing a positive electrode active material that is bound to the surface of the current collector.

  The current collector refers to a chemically inert electronic conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel, etc. Metal materials can be exemplified. The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector.

  The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm.

  The positive electrode active material layer includes a positive electrode active material and, if necessary, a conductive additive and / or a binder. It is preferable that a lithium dopant is added to the positive electrode active material layer.

As the positive electrode active material, a layered rock salt structure Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu , Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, at least one element, 1.7 ≦ f ≦ 3), Li _a Ni _b Co _c Al _{d De} O _f (0.2 ≦ a ≦ 2, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, Cu, Zn, Ca, Mg, At least one element selected from S, Si, Na, K, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, and La, 1.7 ≦ f ≦ 3), and Li ₂ MnO ₃ . be able to. In addition, as a positive electrode active material, a solid solution composed of a spinel structure compound such as LiMn ₂ O ₄ and a mixture of a spinel structure compound and a layered rock salt structure compound, LiMPO ₄ , LiMVO _4, or Li ₂ MSiO ₄ (formula M in the middle is selected from at least one of Co, Ni, Mn, and Fe). Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as the positive electrode active material may have the above-described composition formula as a basic composition, and those obtained by substituting the metal elements contained in the basic composition with other metal elements can also be used as the positive electrode active material. . Further, as a positive electrode active material, a positive electrode active material that does not contain lithium ions that contribute to charge / discharge, for example, sulfur alone, a compound in which sulfur and carbon are combined, a metal sulfide such as TiS ₂ , V ₂ O ₅ , MnO ₂ and other oxides, polyaniline and anthraquinone, compounds containing these aromatics in the chemical structure, conjugated materials such as conjugated diacetate-based organic substances, and other known materials can also be used. Further, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl, etc. may be adopted as the positive electrode active material.

In _{Li a Ni b Co c Mn d} D e O f or _{Li a Ni b Co c Al d} D e O f in the preceding paragraph, b, c, value of d, 0 <b <1,0 <c <1 , 0 <d <1, and at least one of b, c, d is 30/100 <b <95/100, 1/100 <c <70/100, 1/100 <d. It is preferably in the range of <50/100, more preferably in the range of 50/100 <b <90/100, 5/100 <c <50/100, 1/100 <d <30/100, More preferably, the ranges are 80/100 <b <90/100, 5/100 <c <20/100, and 1/100 <d <10/100.
For a, e and f, preferably 0.5 ≦ a ≦ 1.5, 0 ≦ e <0.2, 1.8 ≦ f ≦ 2.5, more preferably 0.8 ≦ a ≦ 1.3. , 0 ≦ e <0.1, 1.9 ≦ f ≦ 2.1.

As the LiMPO _4, of olivine structure _{Li (Mn x, Fe 1-} x) PO 4 (x is 0 ≦ x <1.) Is particularly preferred. When Li (Mn _x , Fe _1-x ) PO ₄ is present in the positive electrode active material layer of the lithium ion secondary battery, heat generation of the battery can be suppressed to some extent even when the positive electrode and negative electrode of the battery are short-circuited. . In addition, as LiMPO _4, it is preferable to employ a carbon-coated surface.

  The amount of the positive electrode active material in the positive electrode active material layer is preferably in the range of 70 to 97% by mass, more preferably in the range of 75 to 96% by mass, still more preferably in the range of 80 to 95% by mass, A range of 95% by mass is particularly preferable.

  The positive electrode active material may be one type or a plurality of types. For example, when the positive electrode active material includes a first positive electrode active material and a second positive electrode active material having a smaller blending amount than the first positive electrode active material, the blending mass ratio thereof is the first positive electrode active material. : Second positive electrode active material = preferably in the range of 95: 5 to 60:40, more preferably in the range of 90:10 to 65:35, and still more preferably in the range of 85:15 to 70:30.

The first positive electrode active material composed mainly of charging and discharging of the lithium ion secondary _{battery, Li a Ni b Co c Mn} d D e O f or _{Li a Ni b Co c Al d} D e O f is preferably the second As the positive electrode active material, LiMPO ₄ is preferable.

  The conductive assistant is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be any chemically inert electronic high conductor, such as carbon black, graphite, acetylene black, ketjen black (registered trademark), vapor grown carbon fiber (Vapor Grown Carbon). Fiber) and various metal particles. These conductive assistants can be added to the active material layer alone or in combination of two or more.

  The compounding amount of the conductive additive in the positive electrode active material layer is preferably in the range of 0.5 to 10% by mass, more preferably in the range of 1 to 5% by mass, and still more preferably in the range of 1 to 3% by mass. This is because if the amount of the conductive auxiliary is too small, an efficient conductive path cannot be formed, and if the amount of the conductive auxiliary is too large, the formability of the positive electrode active material layer is deteriorated and the energy density of the electrode is lowered.

  The binder plays a role of securing an active material or a conductive auxiliary agent to the surface of the current collector and maintaining a conductive network in the electrode. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, alkoxysilyl group-containing resins, poly ( Poly (meth) acrylic resins including meth) acrylic acid and derivatives thereof, styrene-butadiene rubber (SBR), alginate such as carboxymethylcellulose, sodium alginate, ammonium alginate, water-soluble cellulose ester crosslinked product, starch-acrylic acid A graft polymer can be illustrated. These binders may be used singly or in plural.

  A cross-linked polymer obtained by cross-linking a carboxyl group-containing polymer such as polyacrylic acid or polymethacrylic acid with a polyamine such as diamine disclosed in International Publication No. 2016/063882 may be used as a binder. The crosslinked polymer is an embodiment of a poly (meth) acrylic resin.

  Examples of the diamine used in the crosslinked polymer include alkylene diamines such as ethylene diamine, propylene diamine, and hexamethylene diamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, isophorone diamine, and bis (4-aminocyclohexyl) methane. Saturated carbocyclic diamine, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, bis (4-aminophenyl) sulfone, benzidine, o-tolidine, 2,4- Aromatic diamines such as tolylenediamine, 2,6-tolylenediamine, xylylenediamine, and naphthalenediamine are exemplified.

  The amount of the binder in the positive electrode active material layer is preferably in the range of 0.5 to 10% by mass, more preferably in the range of 1 to 7% by mass, and still more preferably in the range of 2 to 5% by mass. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  The lithium dopant is a substance added to compensate for the amount of lithium corresponding to the irreversible capacity of the Al-containing silicon material of the negative electrode. The lithium dopant releases lithium ions when the lithium ion secondary battery of the present invention is charged for the first time. Then, the released lithium ions are introduced into the negative electrode.

  The lithium dopant may be added to the positive electrode active material layer, and may be disposed on the surface of the positive electrode active material layer together with a binder as a lithium dopant-containing layer. From the viewpoint of shortening the manufacturing process, the lithium dopant is preferably added to the positive electrode active material layer.

The amount of the lithium dopant in the positive electrode is preferably an amount corresponding to the irreversible capacity of the negative electrode. That is, the amount of the lithium dopant in the positive electrode is preferably determined as appropriate according to the irreversible capacity of the negative electrode.
Examples of the amount of the lithium dopant in the positive electrode active material layer include a range of 0.5 to 10% by mass, a range of 1 to 7% by mass, and a range of 2 to 6% by mass.

The lithium dopant is not limited as long as it is a substance that releases lithium ions when the lithium ion secondary battery is initially charged. From the viewpoint of a high ratio of lithium per mole, Li ₅ FeO ₄ , Li ₆ MnO ₄ , Li ₆ CoO ₄ , Li ₆ ZnO ₄ , Li ₅ AlO ₄ and Li ₅ GaO ₄ are preferable as the lithium dopant.

  As a lithium dopant, what is coat | covered with carbon is preferable. Since the conductivity of the lithium dopant is improved due to the carbon coating, the carbon-coated lithium dopant can smoothly release electrons and lithium ions when the lithium ion secondary battery is charged for the first time. The carbon content in the carbon-coated lithium dopant is preferably 0.5 to 8% by mass, more preferably 1 to 6% by mass, and still more preferably 2 to 5% by mass.

  Since the Al-containing silicon material of the present invention has improved conductivity due to the presence of Al, it can be said that it is useful as a negative electrode active material for a low-resistance secondary battery. However, since it is silicon that exchanges charge carriers in the negative electrode including the Al-containing silicon material, an Al-containing silicon material whose Al mass% is too high is not preferable as the negative electrode active material.

In the Al-containing silicon material of the present invention, the Al mass% (W _Al %) preferably satisfies 0 <W _Al <1, more preferably 0 <W _Al ≦ 0.9, 0.01 ≦ W _Al ≦ 0.8 is more preferable, 0.05 ≦ W _Al ≦ 0.7 is more preferable, and 0.1 ≦ W _Al ≦ 0.7 is particularly satisfied. It is preferable that 0.15 ≦ W _Al ≦ 0.7 is satisfied.

It is known that the constituent components of the electrolytic solution are decomposed under the charge / discharge conditions of the lithium ion secondary battery to form a SEI (Solid Electrolyte Interface) film containing oxygen on the surface of the negative electrode active material. Here, when the negative electrode active material is a silicon material containing silicon, there is a concern that silicon of the silicon material is oxidized and deteriorated by oxygen contained in the SEI film.
However, since the Al-containing silicon material of the present invention contains Al, it is considered that oxidative degradation of silicon is suppressed. The reason is that Al is considered to preferentially and stably bond with oxygen because it has a lower electronegativity than silicon, and that the Al—O bond between Al and oxygen is more stable than the Si—O bond. In addition, oxygen that forms stable Al—O bonds is less likely to participate in the oxidation of silicon, which has a higher electronegativity than Al.
Therefore, a lithium ion secondary battery comprising the Al-containing silicon material of the present invention as a negative electrode active material can be expected to have a long life.

In this specification, the silicon material means a material containing silicon as a main component. The Si mass% (W _Si %) in the Al-containing silicon material of the present invention preferably satisfies 60 ≦ W _Si ≦ 90, more preferably satisfies 65 ≦ W _Si ≦ 85, and 67 ≦ W _Si ≦. More preferably, 85 is satisfied.
When Si mass% is too low, since the capacity per unit mass of the Al-containing silicon material of the present invention is low, the ability as a negative electrode active material may be insufficient. If the Si mass% is too high, the degree of expansion and contraction of the Al-containing silicon material of the present invention at the time of charging / discharging becomes too large, and there is a concern that the Al-containing silicon material of the present invention is damaged.

  Other elements may be present in the Al-containing silicon material of the present invention within a range not departing from the gist of the present invention. Examples of other elements include those derived from raw materials and manufacturing processes. Specific examples of other elements include Fe, O, Ca, C, and halogen.

The Fe mass% (W _Fe %) in the Al-containing silicon material of the present invention preferably satisfies 0 ≦ W _Fe ≦ 3, more preferably satisfies 0 ≦ W _Fe ≦ 1, and 0 ≦ W _Fe ≦ more preferably satisfies 0.5, particularly preferably satisfies the 0 ≦ _{W Fe} ≦ 0.3, and most preferably satisfies 0 ≦ _{W Fe} ≦ 0.1. In view of the ease of mixing and removal of Fe, the Fe mass% (W _Fe %) in the Al-containing silicon material of the present invention is assumed to be 0 <W _Fe .
Further, the relationship between Al mass% (W _Al %) and Fe mass% (W _Fe %) preferably satisfies W _Al > W _Fe, and more preferably satisfies W _Al > 2 × W _Fe .

The O mass% (W _O %) in the Al-containing silicon material of the present invention preferably satisfies 5 ≦ W _O ≦ 30, more preferably satisfies 10 ≦ W _O ≦ 25, and 12 ≦ W _O ≦ 22 is more preferable, and 13 ≦ W 2 _O ≦ 21 is particularly preferable.
When the Al-containing silicon material of the present invention contains a certain amount of oxygen, the life of the lithium ion secondary battery including the Al-containing silicon material of the present invention as a negative electrode active material is extended.

The Ca mass% (W _Ca %) in the Al-containing silicon material of the present invention preferably satisfies 0 ≦ W _Ca ≦ 3, more preferably satisfies 0 ≦ W _Ca ≦ 1, and 0 ≦ W _Ca ≦ It is more preferable that 0.5 is satisfied, and it is particularly preferable that 0 ≦ W _Ca ≦ 0.3 is satisfied. Considering the ease of mixing Ca and the difficulty of removal, it is assumed that the Ca mass% (W _Ca %) in the Al-containing silicon material of the present invention satisfies 0 <W _Ca.

The halogen mass% (W _X %) in the Al-containing silicon material of the present invention preferably satisfies 0 ≦ W _X ≦ 3, more preferably satisfies 0 ≦ W _X ≦ 2, and 0 ≦ W _X ≦ 1 is more preferable, and 0 ≦ W _X ≦ 0.5 is particularly preferable. In view of the ease of halogen incorporation and the difficulty of removal, it is assumed that the halogen mass% (W _X %) in the Al-containing silicon material of the present invention is 0 <W _X.

  When the Al-containing silicon material of the present invention is described from the viewpoint of the structure, it is preferable to have a structure in which a plurality of plate-like silicon bodies are laminated in the thickness direction. Considering the use of the Al-containing silicon material of the present invention as an active material of a lithium ion secondary battery, for efficient insertion and desorption reactions of charge carriers such as lithium ions, the plate-like silicon body is The thing with the thickness in the range of 10 nm-100 nm is preferable, and the thing within the range of 20 nm-50 nm is more preferable. The length of the plate-like silicon body in the major axis direction is preferably in the range of 0.1 μm to 50 μm. The plate-like silicon body preferably has a (length in the major axis direction) / (thickness) range of 2 to 1000.

  The Al-containing silicon material of the present invention preferably contains amorphous silicon or silicon crystallites. The size of the silicon crystallite is preferably nano-sized. Specifically, the silicon crystallite size is preferably in the range of 0.5 nm to 300 nm, more preferably in the range of 1 nm to 100 nm, still more preferably in the range of 1 nm to 50 nm, and particularly in the range of 1 nm to 10 nm. preferable. The silicon crystallite size is an X-ray diffraction measurement (XRD measurement) performed on the Al-containing silicon material of the present invention, and Scherrer's formula using the half width of the diffraction peak of the Si (111) plane of the obtained XRD chart. Is calculated from

The Al-containing silicon material of the present invention is preferably particulate. The average particle diameter of the Al-containing silicon material of the present invention is preferably in the range of 1 to 30 μm, more preferably in the range of 2 to 20 μm, and still more preferably in the range of 3 to 10 μm. In the specification, the average particle diameter means D ₅₀ when measured with a general laser diffraction type particle size distribution measuring apparatus.

Next, one aspect of the method for producing an Al-containing silicon material of the present invention will be described.
One aspect of the method for producing an Al-containing silicon material of the present invention is:
a) a step of cooling a molten metal containing Ca, Al and Si to form a solid;
b) reacting the solid with an acid to obtain a precursor of an Al-containing silicon material;
c) heating the precursor at 300 ° C. or higher;
It is characterized by including.

The above production method is suitable for producing an Al-containing silicon material of the present invention having a structure in which a plurality of plate-like silicon bodies are laminated in the thickness direction. An example of a chemical change in the a) step, b) step and c) step of the above production method is shown as an ideal reaction formula ignoring Al.
a) Process: Ca + 2Si → CaSi ₂
b) Step: 3CaSi ₂ + 6HCl → Si ₆ H ₆ + 3CaCl ₂
c) Step: Si ₆ H ₆ → 6Si + 3H ₂ ↑

It is considered that the laminated structure of the Al-containing silicon material of the present invention having a structure in which a plurality of plate-like silicon bodies are laminated in the thickness direction is derived from the Si layer in CaSi ₂ or Si ₆ H ₆ .

a) A process is demonstrated. As Ca, Al, and Si used in the step a), elemental elements or alloys of these elements are preferable. CaSi ₂ may be used as a part of the raw material. The elemental composition ratio of Ca and Si in the molten metal is preferably in the range of 1: 1.5 to 1: 2.5, more preferably in the range of 1: 1.8 to 1: 2.2, and 1: 1. A range of 9 to 1: 2.1 is more preferable.

  The amount of Al in the molten metal may be appropriately determined according to the Al mass ratio in the Al-containing silicon material of the present invention to be manufactured. However, since Al can be dissolved in an acid, the amount of Al in the precursor may decrease in the subsequent step b). Therefore, it is preferable to add a little more Al to the molten metal.

The present inventors have considered that in step a), Al is substituted solid solution _{CaSi 2-x} Al x obtained by replacing the Si of CaSi ₂ is manufactured. Therefore, the phase diagram of the solid solution was calculated using thermodynamic equilibrium calculation software (FactSage, Computational Mechanics Research Center, Inc.). FIG. 1 shows a state diagram.

From the state diagram of FIG. 1, x is in the range of 0 <x <0.16. The composition formula of the substitutional solid solution in the case of x = 0.16 is _{CaSi 2-0.16} Al _0.16 . The mass% of Al with respect to the substitutional solid solution is calculated as 100 × 26.98 × 0.16 / (40.08 + 28.09 × 1.84 + 26.98 × 0.16) = 4.5. However, from the state diagram of FIG. 1, the amount of Al in the composition formula of the substitutional solid solution at room temperature is extremely low.
Therefore, the mass% of Al with respect to the total mass of Ca, Si and Al in the molten metal is preferably less than 4.5%, more preferably in the range of 0.01 to 3%, and in the range of 0.05 to 2%. Is more preferable, and the range of 0.1 to 1% is considered to be particularly preferable. In addition, it is thought that when Al is added excessively, CaAl ₂ Si ₂ is also generated, but CaAl ₂ Si ₂ decomposes and disappears in the next step b).

  The molten metal temperature in the step a) may be any temperature at which a mixture of Ca, Al and Si can become a molten metal. Here, the molten metal means a liquid-like state of a mixture of Ca, Al and Si. The molten metal temperature is preferably in the range of 1050 ° C to 1800 ° C, more preferably in the range of 1100 ° C to 1500 ° C, and still more preferably in the range of 1200 ° C to 1400 ° C.

  As the heating device used in the step a), for example, a high frequency induction heating device, an electric furnace, or a gas furnace can be used. The step a) may be performed under pressure or reduced pressure, or in an inert gas atmosphere such as argon, helium, or nitrogen.

  It is preferable to cool the molten metal at a speed as low as possible. This is because generation of an interstitial solid solution can be expected along with the generation of a substitutional solid solution. As a method of cooling the molten metal, a method of pouring the molten metal into a predetermined mold and leaving it at room temperature may be used, or a cooling method using a rapid cooling device may be used.

  The rapid cooling device described in the present specification does not include a device that cools the molten metal by allowing it to stand, and means a device that forcibly cools the molten metal. Rapid cooling equipment includes cooling means (so-called melt span method, strip cast method, or melt spinning method) that injects molten metal onto a rotating cooling roll, and atomizing method that sprays fluid onto the trickled molten metal. A cooling device using the means can be exemplified. Examples of the atomizing method include a gas atomizing method, a water atomizing method, a centrifugal atomizing method, and a plasma atomizing method. Specific rapid cooling devices include a liquid rapid solidification device, a rapid cooling flake production device, a submerged spinning device, a gas atomizing device, a water atomizing device, a rotating disk device, a rotating electrode method device (above, Nisshin Giken Co., Ltd.), liquid Examples of the quenching device and the gas atomizing device (Makabe Giken Co., Ltd.) An example of a preferable cooling rate is 1000 to 100,000 ° C./second.

Moreover, you may add the annealing process heated while maintaining the solid state of the solid obtained by cooling. From the state diagram of FIG. 1, it is considered that the substitutional solid solution CaSi _2-x Al _x is most easily generated at around 900 ° C. Therefore, the heating temperature in the annealing step is preferably 800 to 1000 ° C, and more preferably 850 to 950 ° C. Examples of the heating time include 1 to 50 hours and 5 to 30 hours. After the annealing step, the solid is naturally cooled.

  The solid obtained by cooling may be pulverized or further classified.

Next, step b) will be described. Step b) is a step in which the solid obtained in step a) is reacted with an acid to obtain a precursor of an Al-containing silicon material. The precursor of the Al-containing silicon material has a layer shape because the basic skeleton of the Si layer is maintained by CaSi _2-x Al _x or CaSi ₂ .

  Acids include hydrofluoric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, methanesulfonic acid, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluoro Examples include arsenic acid, fluoroantimonic acid, hexafluorosilicic acid, hexafluorogermanic acid, hexafluorotin (IV) acid, trifluoroacetic acid, hexafluorotitanic acid, hexafluorozirconic acid, trifluoromethanesulfonic acid, and fluorosulfonic acid The These acids may be used alone or in combination.

In the step b), the acid is preferably used in molar ratio in excess of Ca contained in the solid obtained in the step a). Although this step may be performed without a solvent, it is preferable to employ water as a solvent from the viewpoint of separation of a target product and removal of by-products such as CaCl ₂ . The reaction conditions in this step are preferably reduced pressure conditions such as vacuum or an inert gas atmosphere, and are preferably temperature conditions of room temperature or lower such as an ice bath. What is necessary is just to set the reaction time of the same process suitably.

The step b) is preferably carried out in the presence of water and Si ₆ H ₆ can react with water. Therefore, in the step b), for example, the following reaction is considered to proceed.
Si ₆ H ₆ + 3H ₂ O → Si ₆ H ₃ (OH) ₃ + 3H ₂ ↑
Accordingly, the precursor of the Al-containing silicon material can include oxygen. Moreover, the element derived from the anion of the used acid may be contained.

  Next, step c) will be described. Step c) is a step in which an Al-containing silicon material is obtained by heating a precursor of the Al-containing silicon material at 300 ° C. or higher to release hydrogen, water, and the like.

  The step c) is preferably performed in a non-oxidizing atmosphere having a lower oxygen content than in normal air. Examples of the non-oxidizing atmosphere include a reduced pressure atmosphere including a vacuum and an inert gas atmosphere. The heating temperature is preferably in the range of 350 ° C to 950 ° C, more preferably in the range of 400 ° C to 900 ° C. If the heating temperature is too low, hydrogen may not be released sufficiently, and if the heating temperature is too high, energy is wasted. What is necessary is just to set a heating time suitably according to heating temperature. It is preferable to determine the heating time while measuring the amount of hydrogen or the like that escapes from the reaction system. By appropriately selecting the heating temperature and the heating time, the ratio of amorphous silicon and silicon crystallites contained in the produced Al-containing silicon material and the size of the silicon crystallites can be adjusted. By appropriately selecting the heating temperature and the heating time, the shape of a nano-level layer containing amorphous silicon and silicon crystallites contained in the produced Al-containing silicon material can also be prepared.

  The obtained Al-containing silicon material may be pulverized or further classified.

  The negative electrode has a current collector and a negative electrode active material layer bound to the surface of the current collector. What is necessary is just to employ | adopt suitably what was demonstrated with the positive electrode about a collector. The negative electrode active material layer includes a negative electrode active material and, if necessary, a conductive additive and / or a binder.

  As the negative electrode active material, only the Al-containing silicon material of the present invention may be employed, or the Al-containing silicon material of the present invention and a known negative electrode active material may be used in combination. A material obtained by coating the Al-containing silicon material of the present invention with carbon may be used as the negative electrode active material.

In the carbon-coated Al-containing silicon material which is an embodiment of the Al-containing silicon material of the present invention, C mass% (W _C %) preferably satisfies 0 <W _C ≦ 30, and 1 ≦ W _C ≦ 20. Is more preferable, 2 ≦ W _C ≦ 15 is more preferable, and 5 ≦ W _C ≦ 10 is particularly preferable.

  The amount of the negative electrode active material in the negative electrode active material layer is preferably in the range of 70 to 97% by mass, more preferably in the range of 75 to 93% by mass, and still more preferably in the range of 80 to 90% by mass. The amount of the Al-containing silicon material in the negative electrode active material layer is preferably in the range of 50 to 97% by mass, more preferably in the range of 60 to 93% by mass, and still more preferably in the range of 70 to 90% by mass.

  What is necessary is just to employ | adopt suitably what was demonstrated with the positive electrode about the conductive support agent used for a negative electrode. The compounding amount of the conductive additive in the negative electrode active material layer is preferably in the range of 1 to 20% by mass, more preferably in the range of 3 to 15% by mass, and still more preferably in the range of 5 to 11% by mass.

  What is necessary is just to employ | adopt suitably what was demonstrated with the positive electrode about the binder used for a negative electrode. In view of the result of evaluation example E described later, the negative electrode of the lithium ion secondary battery of the present invention after the initial charge exhibits an effect of suppressing hydrogen generation. Therefore, even if a binder capable of generating hydrogen is selected as the binder used for the negative electrode, it can be said that the generation of hydrogen is suppressed. In view of this point and the strong binding force, it is preferable to select polyamide, polyamideimide, or poly (meth) acrylic resin as the binder for the negative electrode.

  The amount of the binder in the negative electrode active material layer is preferably in the range of 3 to 20% by mass, more preferably in the range of 5 to 15% by mass, and still more preferably in the range of 7 to 13% by mass.

  In order to form an active material layer on the surface of the current collector, a current collecting method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method can be used. An active material may be applied to the surface of the body. Specifically, an active material, a solvent, and, if necessary, a binder and / or a conductive aid are mixed to prepare a slurry. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. The slurry is applied to the surface of the current collector and then dried. In order to increase the electrode density, the dried product may be compressed.

  The electrolytic solution includes a nonaqueous solvent and an electrolyte dissolved in the nonaqueous solvent.

  As the non-aqueous solvent, cyclic carbonates, cyclic esters, chain carbonates, chain esters, ethers and the like can be used. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. Examples of the cyclic ester include gamma butyrolactone, 2-methyl-gammabutyrolactone, acetyl-gammabutyrolactone, and gamma valerolactone. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, and ethyl methyl carbonate. Examples of the chain ester include propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. As the non-aqueous solvent, a compound in which part or all of hydrogen in the chemical structure of the specific solvent is substituted with fluorine may be employed.

Examples of the electrolyte include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (FSO ₂ ) ₂ , and LiN (CF ₃ SO ₂ ) ₂ .

  As an electrolytic solution, a lithium salt was dissolved in a non-aqueous solvent such as fluoroethylene carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, propylene carbonate, and diethyl carbonate at a concentration of about 0.5 mol / L to 3 mol / L. A solution can be illustrated.

From the results of Evaluation Example D described later, it is considered that the generation of LiF on the negative electrode surface is a key element of thermal stability. Therefore, it can be said that the electrolyte solution preferably contains fluorine. As the non-aqueous solvent of the electrolytic solution, one containing fluorine may be selected, or as the electrolyte of the electrolytic solution, a lithium salt containing fluorine may be selected. Since the non-aqueous solvent containing fluorine is likely to be reduced and decomposed, it can be said that it is easily decomposed on the negative electrode surface and charged with fluorine during charging.
Further, as will be discussed in detail in Evaluation Example D, in order to promote the production of LiF, it can be said that the concentration of the lithium salt containing fluorine in the electrolytic solution is preferably high. As a density | concentration of the lithium salt containing the fluorine in electrolyte solution, 1-3 mol / L is preferable, 1.5-2.7 mol / L is more preferable, 2-2.5 mol / L is further more preferable.

  The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit due to contact between the two electrodes. As separators, natural resins such as polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polymer), polyester, polyacrylonitrile and other polysaccharides, cellulose, amylose and other polysaccharides, fibroin, keratin, lignin and suberin Examples thereof include porous bodies, nonwoven fabrics, and woven fabrics using one or more electrically insulating materials such as polymers and ceramics. The separator may have a multilayer structure.

  Next, the manufacturing method of a lithium ion secondary battery is demonstrated.

  A separator is sandwiched between the positive electrode and the negative electrode as necessary to form an electrode body. The electrode body may be either a stacked type in which the positive electrode, the separator and the negative electrode are stacked, or a wound type in which the positive electrode, the separator and the negative electrode are sandwiched. After connecting the current collector of the positive electrode and the current collector of the negative electrode to the positive electrode terminal and the negative electrode terminal that communicate with the outside using a lead for current collection, etc., an electrolyte is added to the electrode body and a lithium ion secondary Use batteries. Moreover, the lithium ion secondary battery of this invention should just be charged / discharged in the voltage range suitable for the kind of active material contained in an electrode.

  The shape of the lithium ion secondary battery of the present invention is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be adopted.

  The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from a lithium ion secondary battery for all or a part of its power source, and may be, for example, an electric vehicle or a hybrid vehicle. When a lithium ion secondary battery is mounted on a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form an assembled battery. Examples of devices equipped with lithium ion secondary batteries include various home appliances driven by batteries such as personal computers and portable communication devices, office devices, and industrial devices in addition to vehicles. Furthermore, the lithium ion secondary battery of the present invention includes wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power supplies for ships and / or auxiliary power supply sources, aircraft, Power supply for spacecraft and / or auxiliary equipment, auxiliary power supply for vehicles that do not use electricity as a power source, power supply for mobile home robots, power supply for system backup, power supply for uninterruptible power supply, You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in the charging station for electric vehicles.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, this invention is not limited by these Examples.

(Example 1)
The Al-containing silicon material and lithium ion secondary battery of Example 1 were manufactured as follows.

a) Process Ca, Al, and Si were weighed in a carbon crucible. The elemental composition ratio of Ca and Si was 1: 2, and the amount of Al added was 1% with respect to the total mass of Ca, Al, and Si. The carbon crucible was heated near 1300 ° C. with a high-frequency induction heating apparatus in an argon gas atmosphere to obtain a molten metal containing Ca, Al, and Si. The molten metal was cooled by pouring into a predetermined mold to obtain a solid. The solid was pulverized into powder and then subjected to step b).

b) Step Under a nitrogen gas atmosphere, the powdered solid obtained in step a) was added to 17 wt% hydrochloric acid at 0 ° C. and stirred. The reaction solution was filtered, the residue was washed with distilled water and methanol, and further dried under reduced pressure at room temperature to obtain a precursor of an Al-containing silicon material.

c) Process The Al-containing silicon material of Example 1 was manufactured by heating a precursor of the Al-containing silicon material at 900 ° C. for 1 hour in a nitrogen gas atmosphere.

  Using the Al-containing silicon material of Example 1, the negative electrode of Example 1 and the lithium ion secondary battery of Example 1 were manufactured as follows.

  A polyacrylic acid having a weight average molecular weight of 800,000 was dissolved in N-methyl-2-pyrrolidone to prepare a polyacrylic acid solution containing 10% by mass of polyacrylic acid. Further, 4,4'-diaminodiphenylmethane 0.2 g (1.0 mmol) was dissolved in 0.4 mL of N-methyl-2-pyrrolidone to prepare a 4,4'-diaminodiphenylmethane solution. Under stirring conditions, the total amount of the 4,4′-diaminodiphenylmethane solution was added dropwise to 7 mL of a polyacrylic acid solution (corresponding to 9.5 mmol in terms of acrylic acid monomer), and the resulting mixture was stirred at room temperature for 30 minutes. Stir. Thereafter, using a Dean Stark apparatus, the mixture was stirred at 130 ° C. for 3 hours to advance the dehydration reaction, thereby producing a binder solution.

  72.5 parts by mass of the Al-containing silicon material of Example 1 as the negative electrode active material, 13.5 parts by mass of acetylene black as the conductive additive, and the above binder solution in an amount such that the solid content is 14 parts by mass as the binder, An appropriate amount of N-methyl-2-pyrrolidone was mixed to prepare a slurry. A copper foil was prepared as a negative electrode current collector. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. The copper foil coated with the slurry was dried at 80 ° C. for 15 minutes to remove N-methyl-2-pyrrolidone. Then, the negative electrode of Example 1 in which the negative electrode active material layer was formed was manufactured by pressing and heating at 180 ° C. for 30 minutes in a reduced pressure atmosphere by a vacuum pump.

96 parts by mass of LiNi _82/100 Co _15/100 Al _3/100 O ₂ as a positive electrode active material, 2 parts by mass of acetylene black as a conductive additive, 2 parts by mass of polyvinylidene fluoride as a binder, and an appropriate amount of N-methyl A slurry was prepared by mixing -2-pyrrolidone. An aluminum foil was prepared as a positive electrode current collector. The slurry was applied to the surface of the aluminum foil using a doctor blade so as to form a film. The aluminum foil coated with the slurry was dried at 80 ° C. for 20 minutes to remove N-methyl-2-pyrrolidone. Then, it pressed and heated by 120 degreeC and 6 hours in the pressure reduction atmosphere by the vacuum pump, and manufactured the positive electrode with which the positive electrode active material layer was formed in the surface of an electrical power collector.

A polyethylene porous membrane was prepared as a separator. Furthermore, fluoroethylene carbonate, and ethyl methyl carbonate in a solvent mixture in a volume ratio eighty-one past seven p.m., a solution obtained by dissolving LiPF ₆ at a concentration of 2 mol / L, and an electrolytic solution.

  The negative electrode, separator, and positive electrode in Example 1 were laminated in this order to obtain a laminate. The laminate and the electrolytic solution were housed in a laminated film bag, and the bag was sealed, whereby the lithium ion secondary battery of Example 1 was manufactured.

(Comparative Example 1)
In the step a), the silicon material of Comparative Example 1, the negative electrode of Comparative Example 1, and the lithium ion secondary battery of Comparative Example 1 were produced in the same manner as in Example 1 except that Al was not added.

(Evaluation example 1)
Elemental analysis of the Al-containing silicon material of Example 1 and the silicon material of Comparative Example 1 was performed using an inductively coupled plasma optical emission analyzer (ICP-AES). As a result of elemental analysis, Al mass% in the Al-containing silicon material of Example 1 is 0.25%, Fe mass% is 0%, Al mass% in the silicon material of Comparative Example 1 is 0%, and Fe mass% is 0%.

(Evaluation example 2)
In the constant temperature layer at 25 ° C., the lithium ion secondary battery of Example 1 was adjusted to 15% of SOC (State of Charge). Then, the lithium ion secondary battery was discharged for 10 seconds at a constant current of 1C rate. Resistance was calculated by dividing the amount of change in voltage before and after discharge by the current value. A similar test was performed on the lithium ion secondary battery of Comparative Example 1.
The resistance of the lithium ion secondary battery of Example 1 was 3.3Ω, and the resistance of the lithium ion secondary battery of Comparative Example 1 was 3.6Ω. It was confirmed that the resistance of the lithium ion secondary battery is reduced by using the Al-containing silicon material.

(Example 2)
The Al-containing silicon material, negative electrode, and lithium ion secondary battery of Example 2 were manufactured as follows.

a) Process Ca, Al, and Si were weighed in a carbon crucible. The elemental composition ratio of Ca and Si was 1: 2, and the amount of Al added was 1% with respect to the total mass of Ca, Al, and Si. The carbon crucible was heated near 1300 ° C. with a high-frequency induction heating apparatus in an argon gas atmosphere to obtain a molten metal containing Ca, Al, and Si. The molten metal was poured into a predetermined mold and cooled to obtain a solid. The solid was pulverized into powder and then subjected to step b).

b) Step Under a nitrogen gas atmosphere, the powdered solid obtained in step a) was added to 17 wt% hydrochloric acid at 0 ° C. and stirred. The reaction solution was filtered, the residue was washed with distilled water and methanol, and further dried under reduced pressure at room temperature to obtain a precursor of an Al-containing silicon material.

c) Step The Al-containing silicon material precursor of Example 2 was manufactured by heating the precursor of the Al-containing silicon material at 900 ° C. for 1 hour in a nitrogen gas atmosphere.

  Using the Al-containing silicon material of Example 2, the negative electrode of Example 2 and the lithium ion secondary battery of Example 2 were manufactured as follows.

  A polyacrylic acid having a weight average molecular weight of 800,000 was dissolved in N-methyl-2-pyrrolidone to prepare a polyacrylic acid solution containing 10% by mass of polyacrylic acid. Further, 4,4'-diaminodiphenylmethane 0.2 g (1.0 mmol) was dissolved in 0.4 mL of N-methyl-2-pyrrolidone to prepare a 4,4'-diaminodiphenylmethane solution. Under stirring conditions, the total amount of the 4,4′-diaminodiphenylmethane solution was added dropwise to 7 mL of a polyacrylic acid solution (corresponding to 9.5 mmol in terms of acrylic acid monomer), and the resulting mixture was stirred at room temperature for 30 minutes. Stir. Thereafter, using a Dean Stark apparatus, the mixture was stirred at 130 ° C. for 3 hours to advance the dehydration reaction, thereby producing a binder solution.

  72.5 parts by mass of the Al-containing silicon material of Example 2 as the negative electrode active material, 13.5 parts by mass of acetylene black as the conductive auxiliary agent, and the above binder solution in an amount such that the solid content is 14 parts by mass as the binder, An appropriate amount of N-methyl-2-pyrrolidone was mixed to prepare a slurry. A copper foil was prepared as a negative electrode current collector. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. The copper foil coated with the slurry was dried at 80 ° C. for 15 minutes to remove N-methyl-2-pyrrolidone. Then, the negative electrode of Example 2 in which the negative electrode active material layer was formed was manufactured by pressing and heating at 180 ° C. for 30 minutes in a reduced pressure atmosphere by a vacuum pump.

The negative electrode of Example 2 was cut into a diameter of 11 mm to obtain an evaluation electrode. A metal lithium foil having a thickness of 500 μm was cut into a diameter of 13 mm to form a counter electrode. As a separator, a glass filter (Hoechst Celanese) and celgard 2400 (Polypore Corporation), which is a single-layer polypropylene, were prepared. The volume ratio of ethylene carbonate and diethyl carbonate 1: LiPF ₆ was prepared the electrolytic solution at a concentration 1 mol / L in a mixed solvent obtained by mixing 1. Two kinds of separators were sandwiched between the counter electrode and the evaluation electrode in the order of the counter electrode, the glass filter, celgard 2400, and the evaluation electrode, thereby forming an electrode body. This electrode body was accommodated in a coin-type battery case CR2032 (Hosen Co., Ltd.), and an electrolyte was further injected to obtain a coin-type battery. This was designated as the lithium ion secondary battery of Example 2.

(Example 3)
The production scale was increased, and the following carbon coating step was added after step c), and the carbon-coated Al-containing silicon material was used as the Al-containing silicon material of Example 3, which was used as the negative electrode active material. Except for this point, the Al-containing silicon material, negative electrode, and lithium ion secondary battery of Example 3 were produced in the same manner as in Example 2.

Carbon coating process c) Al-containing silicon material that has undergone the process is placed in a rotary kiln-type reactor and subjected to thermal CVD under the conditions of 880 ° C. and residence time of 60 minutes under a propane-argon mixed gas flow. An Al-containing silicon material was obtained.

Example 4
Powdered CaSi ₂ containing Al and Fe as impurities was prepared. When elemental analysis of the CaSi ₂ was performed using ICP-AES, it was Ca: 38 mass%, Si: 57 mass%, Fe: 4 mass%, and Al: 1 mass%.
The Al-containing silicon material, negative electrode, and lithium ion secondary battery of Example 4 were manufactured in the same manner as in Example 3 except that the following steps b) and below were performed using the CaSi ₂ .

(Comparative Example 2)
In the step a), a silicon material, a negative electrode, and a lithium ion secondary battery of Comparative Example 2 were produced in the same manner as in Example 2, except that Al was not added.

(Comparative Example 3)
In the step a), the silicon material, the negative electrode, and the lithium ion secondary battery of Comparative Example 3 were manufactured in the same manner as in Example 2 except that Fe was not added and Al was added.
In addition, Fe of the process a) was added in an amount of 4% with respect to the total mass of Ca, Fe and Si.

(Evaluation example 3)
Elemental analysis of the Al-containing silicon materials of Examples 2 to 4 and the silicon materials of Comparative Examples 2 and 3 was performed using a fluorescent X-ray analyzer (XRF). In addition, using an oxygen / nitrogen / hydrogen analyzer, elemental analysis for oxygen was performed on the Al-containing silicon materials of Examples 2 to 4 and the silicon materials of Comparative Examples 2 and 3. It was. Furthermore, the elemental analysis which made carbon the object was performed with respect to Al containing silicon material of Example 3 and Example 4 by which carbon was covered using the carbon and sulfur analyzer.

  The results of these elemental analyzes are shown in Table 1 as mass%. The reason why a slight amount of Fe is present in Example 2, Example 3, and Comparative Example 2 is that Fe was contained as an impurity in the raw material metal. Further, O, Ca, and Cl contained in all silicon materials are derived from the solvent (water), raw materials, acid anions, and the like used in the production.

(Evaluation example 4)
The X-ray diffraction of the Al-containing silicon material of Example 2 was measured with a powder X-ray diffractometer.
As a result, a peak derived from silicon crystallites could be confirmed from the X-ray diffraction chart of the Al-containing silicon material of Example 2.

(Evaluation example 5)
The lithium ion secondary batteries of Examples 2 to 4, Comparative Example 2 and Comparative Example 3 were discharged to 0.01 V at a current of 0.2 mA, and then charged to 0.8 V at a current of 0.2 mA. The first charge and discharge was performed.
Further, the lithium ion secondary batteries of Example 2, Comparative Example 2 and Comparative Example 3 after the first charge / discharge were discharged to 0.01 V at a current of 0.5 mA, and then to 1.0 V at a current of 0.5 mA. The charging / discharging cycle when charging was performed several times.

The initial efficiency and capacity retention rate were calculated by the following formulas.
Initial efficiency (%) = 100 × (initial charge capacity) / (initial discharge capacity)
Capacity maintenance rate (%) = 100 × (charge capacity at each cycle) / (charge capacity at the first cycle)
The results of the initial discharge capacity, initial charge capacity, and initial efficiency are shown in Table 2 together with a part of the results of elemental analysis. Further, the result of the capacity maintenance rate (N = 2) is shown in FIG.

  From the results in Table 2, it can be said that the initial discharge capacity, the initial charge capacity, and the initial efficiency are lowered due to the presence of Fe. From the results of FIG. 2, it can be said that the presence of Al or Fe is preferable from the viewpoint of the capacity retention rate. Considering these results comprehensively, it is considered that in the Al-containing silicon material of the present invention, it is preferable that the Fe content is small and that the Al content is large.

(Example 5)
The Al-containing silicon material, negative electrode, and lithium ion secondary battery of Example 5 were manufactured as follows.

a) Process Ca, Al, and Si were weighed in a carbon crucible. The elemental composition ratio of Ca and Si was 1: 2, and the amount of Al added was 0.1% with respect to the total mass of Ca, Al, and Si. The carbon crucible was heated near 1300 ° C. with a high-frequency induction heating apparatus in an argon gas atmosphere to obtain a molten metal containing Ca, Al, and Si. The molten metal was poured into a predetermined mold and cooled to obtain a solid. The solid was pulverized into powder and then subjected to step b).

b) Step Under a nitrogen gas atmosphere, the powdered solid obtained in step a) was added to 17 wt% hydrochloric acid at 0 ° C. and stirred. The reaction solution was filtered, the residue was washed with distilled water and methanol, and further dried under reduced pressure at room temperature to obtain a precursor of an Al-containing silicon material.

c) Step The Al-containing silicon material precursor of Example 5 was manufactured by heating the precursor of the Al-containing silicon material at 900 ° C. for 1 hour in a nitrogen gas atmosphere.

  Using the Al-containing silicon material of Example 5, the negative electrode of Example 5 and the lithium ion secondary battery of Example 5 were produced as follows.

  A polyacrylic acid having a weight average molecular weight of 800,000 was dissolved in N-methyl-2-pyrrolidone to prepare a polyacrylic acid solution containing 10% by mass of polyacrylic acid. Further, 4,4'-diaminodiphenylmethane 0.2 g (1.0 mmol) was dissolved in 0.4 mL of N-methyl-2-pyrrolidone to prepare a 4,4'-diaminodiphenylmethane solution. Under stirring conditions, the total amount of the 4,4′-diaminodiphenylmethane solution was added dropwise to 7 mL of a polyacrylic acid solution (corresponding to 9.5 mmol in terms of acrylic acid monomer), and the resulting mixture was stirred at room temperature for 30 minutes. Stir. Thereafter, using a Dean Stark apparatus, the mixture was stirred at 130 ° C. for 3 hours to advance the dehydration reaction, thereby producing a binder solution.

  72.5 parts by mass of the Al-containing silicon material of Example 5 as the negative electrode active material, 13.5 parts by mass of acetylene black as the conductive auxiliary agent, and the above binder solution in an amount such that the solid content is 14 parts by mass as the binder, An appropriate amount of N-methyl-2-pyrrolidone was mixed to prepare a slurry. A copper foil was prepared as a negative electrode current collector. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. The copper foil coated with the slurry was dried at 80 ° C. for 15 minutes to remove N-methyl-2-pyrrolidone. Then, the negative electrode of Example 5 with which the negative electrode active material layer was formed was manufactured by pressing and heating at 180 degreeC for 30 minutes in the pressure reduction atmosphere with a vacuum pump.

The negative electrode of Example 5 was cut into a diameter of 11 mm to obtain an evaluation electrode. A metal lithium foil having a thickness of 500 μm was cut into a diameter of 13 mm to form a counter electrode. As a separator, a glass filter (Hoechst Celanese) and celgard 2400 (Polypore Corporation), which is a single-layer polypropylene, were prepared. The volume ratio of ethylene carbonate and diethyl carbonate 1: LiPF ₆ was prepared the electrolytic solution at a concentration 1 mol / L in a mixed solvent obtained by mixing 1. Two kinds of separators were sandwiched between the counter electrode and the evaluation electrode in the order of the counter electrode, the glass filter, celgard 2400, and the evaluation electrode, thereby forming an electrode body. This electrode body was accommodated in a coin-type battery case CR2032 (Hosen Co., Ltd.), and an electrolyte was further injected to obtain a coin-type battery. This was designated as the lithium ion secondary battery of Example 5.

(Example 6)
a) In the process, the Al-containing silicon material and negative electrode of Example 6 were prepared in the same manner as in Example 5 except that the amount of Al added was 0.3% with respect to the total mass of Ca, Al and Si. And the lithium ion secondary battery was manufactured.

(Example 7)
a) In the process, the Al-containing silicon material and negative electrode of Example 7 were prepared in the same manner as in Example 5 except that the addition amount of Al was 0.5% with respect to the total mass of Ca, Al and Si. And the lithium ion secondary battery was manufactured.

(Example 8)
a) In the process, the Al-containing silicon material, negative electrode and lithium of Example 8 were prepared in the same manner as in Example 5 except that the amount of Al added was 1% with respect to the total mass of Ca, Al and Si. An ion secondary battery was manufactured.

Example 9
a) The Al-containing silicon material, negative electrode, and lithium ion secondary battery of Example 9 were produced in the same manner as in Example 8, except that the following annealing process was added to the process.

-Annealing process The solid containing Ca, Al, and Si cooled was heated at 900 degreeC under nitrogen atmosphere for 24 hours, and was cooled after that. After cooling, the solid containing Ca, Al, and Si was pulverized into a powder and then subjected to step b).

(Evaluation example 6)
In the same manner as in Evaluation Example 3, elemental analysis of the Al-containing silicon materials of Examples 5 to 9 was performed. The results of these elemental analyzes are shown in Table 3 as mass%. The reason why a slight amount of Fe is present in the Al-containing silicon material of each example is that Fe was contained as an impurity in the raw material metal. In addition, Cl, Ca, C, and O contained in the Al-containing silicon material of each example are derived from the acid anion, raw material, carbon crucible, solvent (water), and the like used in the production.

From Table 3, it can be confirmed that the Al content in the Al-containing silicon material increases as the amount of Al added in the step a) increases. However, it can be seen that the increase rate of the Al content in the Al-containing silicon material is lower than the increase rate of the Al addition amount in the step a). From these results, it is considered that a part of Al added in the step a) was dissolved and removed in the acid solution in the acid treatment in the step b).
Moreover, it can be seen from the results of Example 8 and Example 9 that the Al content in the Al-containing silicon material is increased by adding an annealing step to the step a). The annealing process, a relatively large amount of Al, in order to form the _{CaSi 2-x} Al _x becomes substitutional solid solution is replaced with Si of CaSi _2, is presumed to have escaped from being removed in the acid treatment in b) step The

(Evaluation example 7)
For the lithium ion secondary batteries of Example 5 to Example 9, discharging to 0.01 V at a current of 0.2 mA, and then charging to 1.0 V at a current of 0.2 mA after the initial charge / discharge went.
Furthermore, for the lithium ion secondary batteries of Examples 5 to 9 after the first charge / discharge, discharging to 0.01 V at a current of 0.5 mA and then charging to 1.0 V at a current of 0.5 mA The charge / discharge cycle was performed 50 times.
In addition, the lithium ion secondary batteries of Examples 5 to 9 were discharged to 0.01 V at a current of 0.2 mA, and then charged to 0.8 V at a current of 0.2 mA. Discharge was performed.

The initial efficiency and capacity retention rate were calculated by the following formulas.
Initial efficiency (%) = 100 × (initial charge capacity) / (initial discharge capacity)
Capacity maintenance rate (%) = 100 × (charge capacity at 50 cycles) / (charge capacity at the first cycle)
The results of the initial discharge capacity, the initial charge capacity (1.0 V and 0.8 V), the initial efficiency (1.0 V and 0.8 V), and the capacity retention ratio are shown in Tables 4 and 5 together with the results of Al mass%.

From Table 4, it can be said that the lithium ion secondary batteries of Examples 7 to 9 exhibited excellent initial charge / discharge capacities. From Table 5, it can be said that the lithium ion secondary batteries of Examples 5 to 9 exhibited the same initial efficiency and the same capacity retention rate. From the viewpoint of the capacity retention rate, it can be said that the lithium ion secondary batteries of Examples 7 to 9 are particularly excellent.
From the above results, it can be said that the Al mass% (W _Al %) in the Al-containing silicon material of the present invention is particularly preferably 0.25% or more.

(Example 10)
The Al-containing silicon material of Example 10 was manufactured as follows.

a) Process Ca, Al, and Si were weighed in a carbon crucible. The elemental composition ratio of Ca and Si was 1: 2, and the amount of Al added was 1% with respect to the total mass of Ca, Al, and Si. The carbon crucible was heated near 1300 ° C. with a high-frequency induction heating apparatus in an argon gas atmosphere to obtain a molten metal containing Ca, Al, and Si. The molten metal was cooled by pouring into a predetermined mold to obtain a solid. The solid was pulverized into powder and then subjected to step b).

b) Step Under a nitrogen gas atmosphere, the powdered solid obtained in step a) was added to 17 wt% hydrochloric acid at 0 ° C. and stirred. The reaction solution was filtered, the residue was washed with distilled water and acetone, and further dried under reduced pressure at room temperature to obtain a precursor of an Al-containing silicon material.

c) Process The precursor of Al containing silicon material was heated at 900 degreeC for 1 hour in nitrogen gas atmosphere, and Al containing silicon material was manufactured.

Carbon coating process c) Al-containing silicon material that has undergone the process is placed in a rotary kiln-type reactor and subjected to thermal CVD under the conditions of 880 ° C. and residence time of 60 minutes under a propane-argon mixed gas flow. An Al-containing silicon material was obtained. This carbon-coated Al-containing silicon material was used as the Al-containing silicon material of Example 10.

  Using the Al-containing silicon material of Example 10, the negative electrode of Example 10 and the lithium ion secondary battery of Example 10 were produced as follows.

  80.8 parts by mass of the Al-containing silicon material of Example 10 as a negative electrode active material, 10.2 parts by mass of acetylene black as a conductive additive, 9 parts by mass of polyamideimide as a binder, and an appropriate amount of N-methyl-2- Pyrrolidone was mixed to produce a slurry. A copper foil was prepared as a negative electrode current collector. The slurry was applied in a film form on the surface of the copper foil using a doctor blade. The copper foil coated with the slurry was dried at 80 ° C. for 15 minutes to remove N-methyl-2-pyrrolidone. Then, the negative electrode of Example 10 in which the negative electrode active material layer was formed was manufactured by pressing and heating at 180 ° C. for 30 minutes in a reduced pressure atmosphere by a vacuum pump.

69 parts by mass of LiNi _82/100 Co _15/100 Al _3/100 O ₂ as a positive electrode active material, 26 parts by mass of LiFePO ₄ as a positive electrode active material, 2 parts by mass of acetylene black as a conductive assistant, polyfluoride as a binder 3 parts by mass of vinylidene and an appropriate amount of N-methyl-2-pyrrolidone were mixed to produce a slurry. An aluminum foil was prepared as a positive electrode current collector. The slurry was applied to the surface of the aluminum foil using a doctor blade so as to form a film. The aluminum foil coated with the slurry was dried at 80 ° C. for 20 minutes to remove N-methyl-2-pyrrolidone. Then, it pressed and heated by 120 degreeC and 6 hours in the pressure reduction atmosphere by the vacuum pump, and manufactured the positive electrode with which the positive electrode active material layer was formed in the surface of an electrical power collector.

A polyethylene porous membrane was prepared as a separator. Further, a solvent mixture of dimethyl carbonate and fluoroethylene carbonate in a volume ratio 81:19, a solution obtained by dissolving LiPF ₆ at a concentration of 2 mol / L, and an electrolytic solution.

  A negative electrode, a separator, and a positive electrode in Example 10 were laminated in this order to obtain a laminate. The laminate and the electrolytic solution were accommodated in a laminated film bag, and the bag was sealed, whereby a lithium ion secondary battery of Example 10 was produced.

(Comparative Example 4)
a) The carbon-coated silicon material of Comparative Example 4, the negative electrode of Comparative Example 4, and the lithium ion secondary battery of Comparative Example 4 were produced in the same manner as in Example 10 except that Al was not added in the step. did.

(Evaluation example 8)
Element analysis of the Al-containing silicon material of Example 10 and the carbon-coated silicon material of Comparative Example 4 was performed in the same manner as in Evaluation Example 3. The results of these elemental analyzes are shown in Table 6 as mass%.

(Evaluation example 9)
The lithium ion secondary battery of Example 10 was charged to a voltage of 4.1V. The lithium ion secondary battery of Example 10 in a charged state at a voltage of 4.1 V was disassembled, and the negative electrode of Example 10 in a charged state was taken out. The negative electrode taken out was washed with dimethyl carbonate and then dried. The above operation was performed in an inert gas atmosphere. While the dried negative electrode was exposed to the atmosphere, it was heated to 550 ° C. at a rate of temperature increase of 10 ° C./min, and the temperature change of the negative electrode was observed.
A similar test was performed on the lithium ion secondary battery of Comparative Example 4.

Regarding the negative electrode of Example 10, a temperature change following the temperature increase at 10 ° C./min was observed. On the other hand, for the negative electrode of Comparative Example 4, when the temperature reached 263 ° C., a rapid temperature increase deviating from the temperature increase at 10 ° C./min was observed.
From the above results, it can be said that the Al-containing silicon material of the present invention is excellent in thermal stability in a charged state due to the presence of Al.

(Example A)
The lithium ion secondary battery of Example A was manufactured as follows.

69 parts by mass of LiNi _82/100 Co _15/100 Al _3/100 O ₂ as a positive electrode active material, 21 parts by mass of LiFe _1/3 Mn _2/3 PO ₄ coated with 3% by mass as a positive electrode active material, 5 parts by mass of Li ₅ FeO ₄ coated with 3% by mass as a lithium dopant, 2 parts by mass of acetylene black as a conductive additive, 3 parts by mass of polyvinylidene fluoride as a binder, and an appropriate amount of N-methyl- 2-Pyrrolidone was mixed to produce a slurry. An aluminum foil was prepared as a positive electrode current collector. The slurry was applied to the surface of the aluminum foil using a doctor blade so as to form a film. The aluminum foil coated with the slurry was dried at 80 ° C. for 20 minutes to remove N-methyl-2-pyrrolidone. Then, it pressed and heated by 120 degreeC and 6 hours in the pressure reduction atmosphere by the vacuum pump, and manufactured the positive electrode with which the positive electrode active material layer was formed in the surface of an electrical power collector.

  The negative electrode of Example 10 was used as the negative electrode.

A polyethylene porous membrane was prepared as a separator. Further, a solvent mixture of dimethyl carbonate and fluoroethylene carbonate in a volume ratio 81:19, a solution obtained by dissolving LiPF ₆ at a concentration of 2 mol / L, and an electrolytic solution.

  A negative electrode, a separator, and a positive electrode in Example 10 were laminated in this order to obtain a laminate. The laminate and the electrolytic solution were accommodated in a laminated film bag, and the bag was sealed, whereby a lithium ion secondary battery of Example A was produced.

(Comparative Example A)
As described below, a lithium ion secondary battery of Comparative Example A was produced in which the positive electrode was not provided with a lithium dopant and a metal lithium foil was attached to the negative electrode surface.

69 parts by mass of LiNi _82/100 Co _15/100 Al _3/100 O ₂ as a positive electrode active material, 26 parts by mass of LiFe _1/3 Mn _2/3 PO ₄ coated with 3% by mass as a positive electrode active material, A slurry was prepared by mixing 2 parts by mass of acetylene black as a conductive additive, 3 parts by mass of polyvinylidene fluoride as a binder, and an appropriate amount of N-methyl-2-pyrrolidone. An aluminum foil was prepared as a positive electrode current collector. The slurry was applied to the surface of the aluminum foil using a doctor blade so as to form a film. The aluminum foil coated with the slurry was dried at 80 ° C. for 20 minutes to remove N-methyl-2-pyrrolidone. Then, it pressed and heated by 120 degreeC and 6 hours in the pressure reduction atmosphere by the vacuum pump, and manufactured the positive electrode with which the positive electrode active material layer was formed in the surface of an electrical power collector.

  A metal lithium foil having a thickness of 5 μm was pasted on the surface of the negative electrode active material layer in the negative electrode of Example 10. The separator and the electrolytic solution were the same as in Example A.

  A negative electrode with a metallic lithium foil attached, a separator, and a positive electrode were laminated in this order to obtain a laminate. The laminate and the electrolytic solution were housed in a laminated film bag, the bag was sealed, and a lithium ion secondary battery of Comparative Example A was produced.

  In addition, in the lithium ion secondary battery of Example A and the lithium ion secondary battery of Comparative Example A, the amount of lithium derived from the lithium dopant and the amount of lithium derived from the metal lithium foil, which are supplemented in the negative electrode, are equivalent. Designed to be

(Comparative Example B)
Lithium of Comparative Example B, which does not have a lithium dopant on the positive electrode and does not have a metallic lithium foil attached to the negative electrode surface, in the same manner as in Comparative Example A, except that the metallic lithium foil was not attached to the negative electrode surface. An ion secondary battery was manufactured.

(Evaluation example A)
The lithium ion secondary batteries of Example A and Comparative Example A were subjected to a nail penetration test as a forced short circuit test by the following method.

  A lithium ion secondary battery was sandwiched between restraining plates having holes with a diameter of 10 mm. Next, the lithium ion secondary battery sandwiched between the restraining plates was charged to a voltage of 4.1V. A charged lithium ion secondary battery sandwiched between restraining plates was placed on a press with a nail attached to the top. Then, the nail was moved from the upper part to the lower part, and the battery was penetrated by the nail. The temperature of the penetrating nail was measured over time. The nail used had a diameter of 5 mm and a tip angle of 60 °, and the temperature of the nail before penetration was 25 ° C.

  The maximum temperature of the nail that penetrated the lithium ion secondary battery of Example A was 29 ° C. On the other hand, the maximum temperature of the nail which penetrated the lithium ion secondary battery of Comparative Example A was 316 ° C. It can be said that the lithium ion secondary battery of Example A shows a remarkable heat generation suppressing effect at the time of forced short circuit.

(Evaluation Example B)
The lithium ion secondary battery of Example A was charged to a voltage of 4.1V. The lithium ion secondary battery of Example A having a voltage of 4.1 V was disassembled, and the negative electrode in a charged state was taken out. The negative electrode taken out was washed with dimethyl carbonate and then dried. The above operation was performed in an inert gas atmosphere. While the dried negative electrode was exposed to the atmosphere, it was heated to 550 ° C. at a rate of temperature increase of 10 ° C./min, and the temperature change of the negative electrode was observed.
A similar test was performed on the lithium ion secondary battery of Comparative Example A.

  Regarding the negative electrode of the lithium ion secondary battery of Example A, a temperature change following the temperature increase at 10 ° C./min was observed. On the other hand, regarding the negative electrode of the lithium ion secondary battery of Comparative Example A, when the temperature reached 350 ° C., a rapid temperature increase deviating from the temperature increase at 10 ° C./min was observed.

(Evaluation Example C)
The lithium ion secondary battery of Example A was charged to a voltage of 4.1V. The lithium ion secondary battery of Example A having a voltage of 4.1 V was disassembled, and the negative electrode in a charged state was taken out. The negative electrode taken out was washed with dimethyl carbonate and then dried. The above operation was performed in an inert gas atmosphere. The negative electrode after drying was subjected to thermal analysis with a differential scanning calorimeter (DSC) as follows.

Under the argon gas atmosphere, the dried negative electrode was placed in a stainless DSC container, and the electrolyte was dropped onto the negative electrode. Then, the DSC container was covered and made airtight. And it heated up at the speed | rate of 5 degree-C / min in nitrogen gas atmosphere, and performed the thermal analysis to 250 degreeC.
A similar test was performed on the lithium ion secondary battery of Comparative Example A.

  As a result of the analysis, the calorific value of the negative electrode and the electrolytic solution of the lithium ion secondary battery of Example A was 2500 J / g, and the calorific value of the negative electrode and the electrolytic solution of the lithium ion secondary battery of Comparative Example A was 2750 J / g. g.

  From the results of Evaluation Example B and Evaluation Example C above, the lithium ion secondary in which lithium is doped from the positive electrode lithium dopant rather than the negative electrode of the lithium ion secondary battery in which lithium is doped from the metal lithium foil on the negative electrode surface. It can be said that the negative electrode of the battery is superior in thermal stability in a charged state.

(Evaluation Example D)
The lithium ion secondary battery of Example A was charged to a voltage of 4.1V. The lithium ion secondary battery of Example A having a voltage of 4.1 V was disassembled, and the negative electrode in a charged state was taken out. The negative electrode taken out was washed with dimethyl carbonate and then dried. The above operation was performed in an inert gas atmosphere. The dried negative electrode was analyzed by X-ray photoelectron spectroscopy (XPS).
A similar test was performed on the lithium ion secondary battery of Comparative Example A.

  As a result, peaks derived from Li—F bonds were observed from the surfaces of both negative electrodes. Moreover, the intensity of the peak was stronger in the negative electrode of the lithium ion secondary battery of Example A. From the above results, it is considered that the presence of LiF on the negative electrode surface contributed to effects such as thermal stability.

It is considered that LiF on the negative electrode surface in the lithium ion secondary batteries of Example A and Comparative Example A was generated due to decomposition of the lithium salt, as shown in the following reaction formula.
Formula 1: LiPF ₆ → Li ⁺ + PF ₆ ⁻
Formula 2: Li ⁺ + PF ₆ ⁻ ← → LiF + PF ₅

Here, in the lithium ion secondary battery of Example A, a large amount of lithium ions is released from the lithium dopant into the electrolyte during the initial charge. Then, since the concentration of Li ⁺ increases, the reaction proceeding to the right side in the equilibrium reaction in Equation 2 is advantageous. Due to this mechanism, it is considered that a large amount of LiF was generated on the negative electrode surface of the lithium ion secondary battery of Example A.

  In the equilibrium reaction in Formula 2, in order to favor the reaction proceeding to the right side, it is advantageous that the lithium salt concentration in the electrolytic solution is high. In view of this point, it is considered preferable that the lithium ion secondary battery of the present invention includes an electrolyte containing a high concentration lithium salt.

(Evaluation Example E)
The lithium ion secondary battery of Example A was charged to a voltage of 4.1V. The lithium ion secondary battery of Example A having a voltage of 4.1 V was disassembled, and the negative electrode in a charged state was taken out. The negative electrode taken out was washed with dimethyl carbonate and then dried. The above operation was performed in an inert gas atmosphere. The dried negative electrode was subjected to a temperature-programmed desorption gas analyzer (TPD-MS) to analyze gas generated between room temperature and 500 ° C.
A similar test was performed on the lithium ion secondary battery of Comparative Example B.

  As a result of analysis, it was found that hydrogen gas was generated from the negative electrodes of the lithium ion secondary batteries of Example A and Comparative Example B during heating. Table 7 shows the amount of hydrogen generated from each negative electrode at 200 ° C. and 500 ° C. by the ionic strength detected by MS.

  It can be seen that the hydrogen generation amount of Example A is smaller than that of Comparative Example B. It is considered that the hydrogen generation source in the negative electrode is mainly polyamideimide as a binder. Since the amount of hydrogen generation in the negative electrode of the lithium ion secondary battery of the present invention could be suppressed, a binder capable of generating hydrogen is preferably used for the negative electrode of the lithium ion secondary battery of the present invention. Can do.

Claims (6)

A positive electrode comprising a positive electrode active material and a lithium dopant;
A negative electrode comprising an Al-containing silicon material;
A lithium ion secondary battery comprising: Lithium-ion secondary battery according to claim 1, wherein the lithium dopant is selected from _{Li 5 FeO 4, Li 6 MnO} 4, Li 6 CoO 4, Li 6 ZnO 4, Li 5 AlO 4 and _Li 5 GaO _4.   The lithium ion secondary battery of Claim 1 or 2 provided with the electrolyte solution containing a fluorine.   The lithium ion secondary battery according to any one of claims 1 to 3, wherein the negative electrode includes polyamide, polyamideimide, or poly (meth) acrylic resin. In the Al-containing silicon material, Al mass% (W _Al %) satisfies 0 <W _Al <1 and Si mass% (W _Si %) satisfies 60 ≦ W _Si ≦ 90. The lithium ion secondary battery according to any one of the above.   A method for producing a lithium ion secondary battery, comprising charging the lithium ion secondary battery according to any one of claims 1 to 5 and introducing lithium of the lithium dopant into the negative electrode.