JP2019083121A - Negative electrode - Google Patents

Abstract

To provide a negative electrode with excellent physical strength and battery characteristics.SOLUTION: A negative electrode comprises: Ni-containing current collector foil; and a negative electrode active material layer formed on a front surface of the Ni-containing current collector foil, and including a Si-containing negative electrode active material and a polyamide imide.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a negative electrode used in a power storage device such as a secondary battery.

  In general, a power storage device such as a secondary battery includes a positive electrode, a negative electrode, and an electrolyte as main components. The negative electrode is provided with a current collector and a negative electrode active material involved in charging and discharging. The industry is required to increase the capacity of power storage devices, and various techniques are being considered as a countermeasure. As one of the specific techniques, a technique is known in which a Si-containing negative electrode active material containing Si, which has a high ability to store charge carriers such as lithium, is used as a negative electrode active material of a power storage device.

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

In Patent Document 5, a layered silicon compound mainly composed of a layered polysilane in which CaSi ₂ is reacted with an acid to remove Ca is synthesized, and the layered silicon compound is heated at 300 ° C. or higher to release hydrogen. The lithium ion secondary battery which manufactured the material and equipped with the said silicon material as a negative electrode active material is described.

  In addition, copper foil is generally used as a current collector of a negative electrode of a storage battery such as a secondary battery. In fact, the copper foil is employ | adopted as a collector in any negative electrode of patent documents 1-5.

  The Si-containing negative electrode active material is known to expand and contract during charge and discharge. Therefore, in a negative electrode having the Si-containing negative electrode active material, a binder such as polyamide, polyimide or polyamideimide having a strong binding power is used. It is preferable to adopt. And when binders, such as polyamide, polyimide, and polyamide imide, are adopted, heating at a relatively high temperature is performed to form a negative electrode active material layer.

  In fact, Patent Document 1 discloses that a composition containing a silicon powder as a negative electrode active material and a polyamic acid is applied to a copper foil, and then heated at 300 ° C. to imidate a polyamic acid, thereby making the negative electrode active. It is described that the material layer was formed.

  Patent Document 2 describes that a slurry containing silicon particles as a negative electrode active material and a polyimide precursor is applied to a copper foil and then heated to 372 ° C. to manufacture a negative electrode.

  In Patent Document 3, a slurry containing SiO and polyamideimide as a negative electrode active material was applied to a copper foil, and then compressed and heated at 200 ° C., 300 ° C. or 400 ° C. by a heat press roller to produce a negative electrode. It is described.

  Patent Document 4 describes that a composition containing SiO as a negative electrode active material and a polyimide is applied to a copper foil and then heated at 200 ° C. to manufacture a negative electrode.

  Patent Document 5 describes that a slurry containing a silicon material as a negative electrode active material and a polyamide imide is applied to a copper foil and then heated at 200 ° C. to manufacture a negative electrode.

JP, 2014-203595, A JP, 2015-57767, A JP, 2015-185509, A JP, 2015-179625, A International Publication No. 2014/080608

  The inventors of the present invention conducted intensive studies on a negative electrode in which a negative electrode active material layer containing a Si-containing negative electrode active material and a polyamideimide was formed on a copper foil. According to heating at a relatively high temperature, It has been found that the binding ability of the negative electrode is enhanced, and the performance of the negative electrode is improved due to heating at a relatively high temperature. On the other hand, it was also found that the physical strength of the copper foil decreases due to heating at a relatively high temperature.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a negative electrode which is excellent in physical strength and excellent in performance.

  The present inventor recalled the use of a Ni-containing foil, which is superior in physical strength to copper foil, as a current collector. And when the negative electrode which adopted Ni containing current collector foil was manufactured and various kinds of tests were actually done, Ni containing current collector foil is remarkably high in physical strength compared with copper foil, and the strength by heating It has been demonstrated that almost no decline occurs. Based on the test results, the inventor has completed the present invention.

The negative electrode of the present invention is
Ni-containing current collector foil,
A negative electrode active material layer formed on the surface of the Ni-containing current collector foil and containing a Si-containing negative electrode active material and a polyamideimide;
It is characterized by having.

  The negative electrode of the present invention is excellent in physical strength and excellent in performance.

FIG. 2 is a schematic cross-sectional view of a negative electrode of Example 1; It is a graph which shows the result of evaluation example 1. It is a graph which shows the result of evaluation example 2. 15 is a graph showing the results of Evaluation Example 4;

  Below, the form for implementing this invention is demonstrated. In addition, unless otherwise indicated, the numerical range "ab" described in this specification includes the lower limit a and the upper limit b in the range. And a numerical range can be constituted by combining these arbitrarily including the upper limit and lower limit, and the numerical value listed in the example. Furthermore, numerical values arbitrarily selected from these numerical ranges can be used as new upper and lower numerical values.

  The negative electrode of the present invention is characterized by comprising a Ni-containing current collector foil and a negative electrode active material layer formed on the surface of the Ni-containing current collector foil and containing a Si-containing negative electrode active material and a polyamideimide.

  As the Ni-containing current collector foil, a part of the current collector foil may be made of Ni, or all of the current collector foil may be made of Ni. As content of Ni, 20-100%, 30-90%, 40-80% can be illustrated as mass% or elemental composition%. As constituent elements other than Ni in the Ni-containing current collector foil, various elements such as Group 3 to 15 elements can be exemplified.

  The thickness of the Ni-containing current collector foil is preferably 1 to 100 μm, more preferably 3 to 50 μm, still more preferably 5 to 30 μm, and particularly preferably 7 to 20 μm.

  In addition, in order to take advantage of both the high physical strength of Ni and the high conductivity of Cu, Ni-containing current collector foils include a core layer made of Ni and a Cu sandwiching the core layer made of Ni. It is preferable to employ a three-layered clad foil composed of a metallic layer. The thickness of the core layer made of Ni is preferably in the range of 40 to 90% of the entire Ni-containing current collector foil, and more preferably in the range of 50 to 80%.

  As content of Ni in the core material layer made from Ni, 50-100%, 70-99%, 80-98%, 90-97% can be illustrated as mass% or elemental composition%. As constituent elements other than Ni in the core layer made of Ni, various elements such as Group 3 to Group 15 elements can be exemplified, and more specifically, Group 4 to Group 6 elements can be exemplified. The physical strength of the core layer can be improved by adding a small amount of constituent elements other than Ni to the core layer made of Ni.

  As content of Cu in the metal layer made from Cu, 80-100%, 90-100%, 95-100% can be illustrated as mass% or elemental composition%. Ag, Au, Pt, Pd, Ir, and Hg can be illustrated as constituent elements other than Cu in the metal layer made of Cu.

  As the Si-containing negative electrode active material, a Si-containing material capable of inserting and extracting charge carriers can be used.

As specific examples of the Si-containing material, it is possible to exemplify Si alone or SiO _x (0.3 ≦ x ≦ 1.6) disproportionated into two phases of the Si phase and the silicon oxide phase. The Si phase in SiO _x can occlude and release lithium ions, and changes in volume as the secondary battery charges and discharges. The silicon oxide phase has less change in volume due to charge and discharge as compared to the Si phase. That is, SiO _x as the negative electrode active material realizes a high capacity by the Si phase, and suppresses the volume change of the whole negative electrode active material by having the silicon oxide phase. When x is less than the lower limit value, the ratio of Si becomes excessive, so that the volume change during charge and discharge becomes too large, and the cycle characteristics of the secondary battery deteriorate. On the other hand, when x exceeds the upper limit value, the Si ratio becomes too small and the energy density decreases. The range of x is more preferably 0.5 ≦ x ≦ 1.5, and still more preferably 0.7 ≦ x ≦ 1.2.

  As a specific example of the Si-containing material, a silicon material (hereinafter, simply referred to as "silicon material") disclosed in WO 2014/080608 and the like can be mentioned.

The silicon material has a structure in which a plurality of plate-like silicon bodies are stacked in the thickness direction. For example, a silicon material may be reacted with CaSi ₂ and an acid to synthesize a layered silicon compound containing polysilane as a main component, and further, the layered silicon compound may be heated at 300 ° C. or higher to release hydrogen. It is manufactured.

An ideal reaction formula in the case of using hydrogen chloride as an acid is as follows when a method of manufacturing a silicon material is used.
3CaSi ₂ +6 HCl → Si ₆ H ₆ +3 CaCl ₂
Si ₆ H ₆ → 6Si + 3H ₂ ↑

However, in the upper reaction for synthesizing Si ₆ H ₆ which is polysilane, water is generally used as a reaction solvent from the viewpoint of removal of by-products and impurities. And, since Si ₆ H ₆ can react with water, in the process of synthesizing the layered silicon compound including the reaction in the upper stage, the layered silicon compound is hardly produced as one containing only Si ₆ H ₆ , and the layered silicon compound is layered The silicon compound is represented by Si ₆ H _s (OH) _t X _u (X is an element or group derived from the anion of an acid, s + t + u = 6, 0 <s <6, 0 <t <6, 0 <u <6) Manufactured as In the above chemical formula, unavoidable impurities such as remaining Ca are not taken into consideration. And the silicon material obtained by heating the said layered silicon compound also contains the element derived from the anion of oxygen or an acid.

As described above, the silicon material has a structure in which a plurality of plate-like silicon bodies are stacked in the thickness direction. The plate-like silicon body preferably has a thickness in the range of 10 nm to 100 nm, and more preferably in the range of 20 nm to 50 nm in order to efficiently store and release charge carriers such as lithium ions. The length in the longitudinal direction of the plate-like silicon body is preferably in the range of 0.1 μm to 50 μm. The plate-like silicon body preferably has a (longitudinal length) / (thickness) in the range of 2 to 1000. The layered structure of the plate-like silicon body can be confirmed by observation with a scanning electron microscope or the like. Moreover, this laminated structure is considered to be a remnant of the Si layer in the raw material CaSi ₂ .

  The silicon material preferably includes amorphous silicon and / or silicon crystallites. In particular, in the plate-like silicon body, it is preferable that amorphous silicon be a matrix and silicon crystallites be scattered in the matrix. The size of the silicon crystallite 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 preferably in the range of 1 nm to 10 nm. The size of the silicon crystallite is calculated from the Scheller equation using the half width of the diffraction peak of the Si (111) plane of the obtained X-ray diffraction chart by performing X-ray diffraction measurement on the silicon material. .

  The amount and size of the plate-like silicon body, amorphous silicon and silicon crystallite contained in the silicon material mainly depend on the heating temperature and heating time. The heating temperature is preferably in the range of 350 ° C. to 950 ° C., and more preferably in the range of 400 ° C. to 900 ° C.

  Moreover, you may employ | adopt what coat | covered Si containing material with carbon as Si containing negative electrode active material.

The Si-containing negative electrode active material is preferably in the form of a powder which is an aggregate of particles. The average particle diameter of the Si-containing negative electrode active material is preferably in the range of 1 to 30 μm, and more preferably in the range of 2 to 20 μm. The average particle diameter herein means a D ₅₀ in the case of measuring a sample in a conventional laser diffraction particle size distribution analyzer.

  The Si-containing negative electrode active material is preferably contained in an amount of 60 to 99% by mass, more preferably 70 to 95% by mass, based on the total mass of the negative electrode active material layer. The negative electrode active material layer may contain a known negative electrode active material without departing from the scope of the present invention.

  In addition, when the inventor carefully examined the relationship between the strength of the Ni-containing current collector foil and the amount of the Si-containing negative electrode active material in the negative electrode active material layer, the index P calculated by the following equation (1) is 6 When satisfying ≦ P ≦ 43, it has been found that the negative electrode of the present invention functions favorably as compared with the conventional negative electrode.

Formula (1):
P = (mass% of Si-containing negative electrode active material in negative electrode active material layer) × (Abundance of negative electrode active material layer per unit area in Ni-containing current collector foil (mg / cm ² )) ÷ (Ni-containing current collector foil) Thickness (μm))

In the negative electrode of the present invention, (mass% of Si-containing negative electrode active material in negative electrode active material layer), (negative electrode activity per unit area in Ni-containing current collector foil) so that index P satisfies 6 ≦ P ≦ 43. It is preferable to determine the amount of the substance layer present (mg / cm ² ) and the thickness (μm) of the Ni-containing current collector foil, respectively.

  In the negative electrode active material layer, polyamide imide functions as a binder. Polyamideimide means a compound having two or more amide bonds and two or more imide bonds in the molecule. Polyamideimide is produced by reacting an acid component which is to be a carbonyl moiety in an amide bond and an imide bond, and a diamine component or a diisocyanate component which is to be a nitrogen moiety in an amide bond and an imide bond. In order to obtain a polyamideimide, it may manufacture by the said method, and may purchase a commercially available polyamideimide. Commercially available polyamideimides include HR-11NN, HR-12N2, HR-13NX, HR-14ET, HR-15ET and HR-16NN, which are Viromax (registered trademark) series of Toyobo Co., Ltd., Toray Plastics Seiko Co., Ltd. TPS (registered trademark) TI-5000 series TI-5013, TI-5031, TI-5032, TI-5023 and TI-503-AE3, Solvay's Troon (registered trademark) PAI series Torlon 4203L, Torlon 4275, Torlon 7130 And Torlon 5030 can be exemplified.

  Examples of acid components used for producing polyamideimides include trimellitic acid, pyromellitic acid, biphenyl tetracarboxylic acid, diphenyl sulfone tetracarboxylic acid, benzophenone tetracarboxylic acid, diphenyl ether tetracarboxylic acid, oxalic acid, adipic acid, malonic acid, Sebacic acid, azelaic acid, dodecanedicarboxylic acid, dicarboxypolybutadiene, dicarboxypoly (acrylonitrile-butadiene), dicarboxypoly (styrene-butadiene), cyclohexane-1,4-dicarboxylic acid, cyclohexane-1,3-dicarboxylic acid, Dicyclohexylmethane-4,4'-dicarboxylic acid, terephthalic acid, isophthalic acid, bis (carboxyphenyl) sulfone, bis (carboxyphenyl) ether, naphthalene dicarboxylic acid, and These anhydrides, acid halides, mention may be made of derivatives. As the acid component, the above compounds may be employed singly or in a plurality, but from the viewpoint of forming an imide bond, an acid component or a carboxyl group is present at the adjacent carbon of the carbon to which the carboxyl group is bonded The equivalent is essential. As the acid component, trimellitic anhydride is preferable in terms of reactivity, heat resistance, and the like. In addition to trimellitic anhydride, in addition to trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic acid anhydride, biphenyltetramer as a part of the acid component from the viewpoint of tensile strength, tensile modulus of elasticity and electrolytic solution resistance of polyamideimide. It is preferred to employ a carboxylic acid anhydride.

  As a diamine component used for manufacture of polyamidoimide, alkylene diamines, such as ethylene diamine, propylene diamine, hexamethylene diamine, 1, 4- diamino cyclohexane, 1, 3- diamino cyclohexane, isophorone diamine, bis (4-amino cyclohexyl) methane Saturated carbocyclic ring diamines such as m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, bis (4-aminophenyl) sulfone, benzidine, o-tolidine, 2 And aromatic diamines such as 2,4-tolylenediamine, 2,6-tolylenediamine, xylylenediamine, and naphthalenediamine. From the viewpoint of heat resistance and solubility, 4,4'-diaminodiphenylmethane, 2,4-tolylenediamine, o-tolidine, naphthalenediamine and isophoronediamine are preferable. From the viewpoint of tensile strength and tensile modulus of polyamideimide, o-tolidine and naphthalenediamine are preferred.

  As a diisocyanate component used for manufacture of polyamidoimide, what substituted the amine of the said diamine component by the isocyanate can be mentioned. Then, the diisocyanate component is reacted with the anhydride of the acid component to produce polyamideimide.

  The number average molecular weight (Mn) of the polyamideimide is preferably 5,000 to 1,000,000, more preferably 7,000 to 500,000, still more preferably 10,000 to 100,000, and particularly preferably 1,200 to 50,000.

  As the polyamideimide, those accompanied by changes in physical properties at a heating temperature at which the negative electrode active material is formed and in the vicinity thereof are preferable. The binding strength between the polyamideimide and the Ni-containing current collector foil or the binding between the polyamideimide and the Si-containing negative electrode active material due to the change in physical properties occurring at and near the heating temperature at which the negative electrode active material is formed. It can be expected that the strength will increase.

As a glass transition temperature (Tg) of polyamideimide, 200-450 ° C is preferred, 250-400 ° C is more preferred, and 250-350 ° C is still more preferred. The thermal expansion coefficient (linear expansion coefficient) of the polyamideimide is preferably 1 × 10 ⁻⁵ / ° C. to 10 × 10 ⁻⁵ / ° C., more preferably 2 × 10 ⁻⁵ / ° C. to 7 × 10 ⁻⁵ / ° C. And 3 × 10 ⁻⁵ / ° C. to 6 × 10 ⁻⁵ / ° C. are more preferable.

  1-20 mass% is preferable, as for the mixture ratio of the polyamideimide in a negative electrode active material layer, 3-15 mass% is more preferable, and 5-13 mass% is further more preferable. In the negative electrode active material layer, a known binder other than polyamideimide may be contained without departing from the scope of the present invention.

  The negative electrode active material layer may contain a conductive auxiliary agent or a known additive, if necessary.

  The conductive aid is added to enhance the conductivity of the negative electrode. Therefore, the conductive support agent may be optionally added when the conductivity of the negative electrode is insufficient, and may not be added when the conductivity of the negative electrode is sufficiently excellent. The conductive support agent may be any chemically active high electron conductor, and carbon black fine particles such as carbon black, graphite, vapor grown carbon fiber, and various metal particles are exemplified. Ru. Examples of the carbon black include acetylene black, ketjen black (registered trademark), furnace black, channel black and the like. These conductive assistants can be added to the negative electrode active material layer singly or in combination of two or more.

  1-20 mass% is preferable, as for the mixture ratio of the conductive support agent in a negative electrode active material layer, 3-15 mass% is more preferable, and 5-13 mass% is more preferable. Further, the mass ratio of the Si-containing negative electrode active material to the conductive aid is preferably 99: 1 to 85:15, more preferably 97: 3 to 90:10, still more preferably 95: 5 to 92: 8, and 94: 6 to 93: 7 are particularly preferred.

  In order to form the negative electrode active material layer on the surface of the Ni-containing current collector foil, conventionally known methods such as roll coating method, die coating method, dip coating method, doctor blade method, spray coating method and curtain coating method are used. The material of the Si-containing negative electrode active material and the polyamideimide or the polyamideimide may be applied to the surface of the Ni-containing current collector foil.

  Specifically, a composition such as a slurry is prepared by mixing a Si-containing negative electrode active material, a polyamideimide or a raw material of polyamideimide or polyamideimide, a solvent, and a conductive auxiliary agent if necessary, and then the composition is used as a collector. After coating on the surface, it is heated. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone and water.

  As a heating temperature, 200-450 degreeC is preferable and 250-400 degreeC is more preferable. By heating at 200 to 450 ° C., it can be expected that the binding strength between the negative electrode active material layer and the Ni-containing current collector foil and the binding strength between polyamideimide and the Si-containing negative electrode active material can be increased. It can also be expected that the battery performance of the negative electrode of the invention is improved.

  When the negative electrode of the present invention contains a conductive aid, the conductive network in the negative electrode active material layer formed of polyamideimide and the conductive aid can be made more uniform by heating at 200 to 450 ° C. It can be expected to be formed. As a result, it is possible to reduce the amount of the conductive aid more than that normally required. Then, in the negative electrode active material layer, the reduction amount of the conductive additive can be transferred to the increase of the Si-containing negative electrode active material, so that the capacity of the power storage device can be further increased.

From the above viewpoints, it is preferable to use a polyamideimide having a glass transition temperature (Tg) within the range of heating temperature. Moreover, it can be said that it is preferable to employ | adopt what the peak position originating in the amide | amido in infrared absorption spectrum shifts as a polyamideimide from the result of the evaluation example 2 mentioned later.
More specifically, as the polyamideimide, an absorption peak derived from an amide structure is observed at a wave number W _{200 ° C.} (cm ⁻¹ ) when heated at 200 ° C. in measurement with a thermal scanning-infrared spectrometer. When heating at 350 ° C., it is preferable that the wave number be observed to shift to a wave number W _{350 ° C.} (cm ⁻¹ ). The range of the shift width of the wave number _{W 200 ° C.} from ^{(cm -1)} wavenumber _{W 350 ° C.} to ^{(cm -1), 2~30cm -1,} 4~25cm -1, 6~20cm -1, 8~15cm - ¹ can be illustrated.
Further, as the negative electrode of the present invention, the absorption peak derived from the amide structure of polyamideimide has a wave number W _{350 ° C.} (cm ⁻ ) more than wave number W _{200 ° C.} (cm ⁻¹ ) when measured by an infrared spectrometer. ^It is preferable to be observed with a shift in the direction ¹ ). Such a definition means that the environmental change of polyamideimide during heating in the formation of the negative electrode active material layer is also maintained in the negative electrode of the present invention. Be in the range of the shift width here ^can be exemplified by ^{2~30cm -1, 4~25cm -1, 6~20cm -1} , 8~15cm -1.

Next, a power storage device provided with the negative electrode of the present invention will be described.
As a power storage device, a primary battery, a secondary battery, and a capacitor can be exemplified. Hereinafter, the power storage device of the present invention will be described through the description of a lithium ion secondary battery which is a typical example of the power storage device.

One aspect of the lithium ion secondary battery of the present invention comprises the negative electrode, the positive electrode, the separator and the electrolytic solution of the present invention.
The positive electrode includes a current collector and a positive electrode active material layer formed on the surface of the current collector.

  A current collector refers to a chemically inert electron conductor for keeping current flowing to an electrode during discharge or charge of a secondary battery such as a lithium ion secondary battery. The material of the current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the positive electrode active material used. The material of the current collector is 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. can be exemplified. The current collector may be coated with a known protective layer. What processed the surface of a collector by a well-known method may be used as a collector.

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

  When the potential of the positive electrode is set to 4 V or more based on lithium, it is preferable to use aluminum as a current collector for the positive electrode.

  Specifically, it is preferable to use an aluminum or an aluminum alloy as the positive electrode current collector. Here, aluminum refers to pure aluminum, and aluminum having a purity of 99.0% or more is referred to as pure aluminum. An alloy obtained by adding various elements to pure aluminum is called an aluminum alloy. Examples of aluminum alloys include Al-Cu-based, Al-Mn-based, Al-Fe-based, Al-Si-based, Al-Mg-based, Al-Mg-Si-based and Al-Zn-Mg-based.

  As aluminum or aluminum alloy, specifically, for example, A1000 series alloys (pure aluminum series) such as JIS A1085, A1N30, A3000 series alloys such as JIS A3003, A3004 (Al-Mn series), JIS A8079, A8021 etc. A 8000 series alloy (Al-Fe series) is mentioned.

  The positive electrode active material layer contains a positive electrode active material capable of inserting and extracting a charge carrier such as lithium ion, and, optionally, a binder and a conductive agent. The positive electrode active material layer preferably contains 60 to 99% by mass, and more preferably 70 to 95% by mass of the positive electrode active material with respect to the total mass of the positive electrode active material layer.

As a positive electrode active material, a general formula of 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 W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, La, Zr, Cu, Ca, Ir, Hf, Rh, Fe, Ge, Zn, Ru, At least one element selected from Sc, Sn, In, Y, Bi, S, Si, Na, K, P, V, 1.7 ≦ f ≦ 3), or Li _a Ni _b Co _c Al _d D _{e 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, Zr, Ti, P And at least one element selected from Ga, Ge, V, Mo, Nb, W and La, and represented by 1.7 ≦ f ≦ 3) A lithium mixed metal oxide, Li ₂ MnO ₃ can be mentioned. In addition, as a positive electrode active material, a metal oxide of spinel structure such as LiMn ₂ O ₄ , a solid solution composed of a mixture of a metal oxide of spinel structure and a layered compound, LiMPO ₄ , LiMVO ₄ or Li ₂ MSiO ₄ M is selected from at least one of Co, Ni, Mn, and Fe), and the like. 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 a positive electrode active material may have the above composition formula as a basic composition, and one obtained by replacing the metal element contained in the basic composition with another metal element can also be used. Further, as the positive electrode active material, one not containing charge carriers (for example, lithium ions contributing to charge and discharge) may be used. For example, elemental sulfur, compounds in which sulfur and carbon are complexed, metal sulfides such as TiS ₂ , oxides such as V ₂ O ₅ , MnO ₂ , polyaniline and anthraquinone, and compounds containing these aromatic groups in the chemical structure, conjugated Conjugated materials such as acetic acid-based organic materials and other known materials can also be used. Furthermore, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl or the like may be adopted as the positive electrode active material. In the case of using a positive electrode active material containing no charge carrier such as lithium, the charge carrier needs to be previously added to the positive electrode and / or the negative electrode by a known method. The charge carrier may be added in the form of ions or may be added in the form of non ions such as metals. For example, when the charge carrier is lithium, a lithium foil may be attached to the positive electrode and / or the negative electrode to be integrated.

From the point of being excellent in high capacity and durability, etc., a general formula of layered rock salt structure as a positive electrode active material: 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 W, Mo, Re, Pd, Ba, Cr, B, Sb, Sr, Pb, Ga, Al, Nb, Mg, Ta, Ti, La, Zr, Cu, Ca, Ir, Hf, At least one element selected from Rh, Fe, Ge, Zn, Ru, Sc, Sn, In, Y, Bi, S, Na, K, P, V, 1.7 ≦ f ≦ 3) or Li _a Ni _b Co _c Al _d D _e 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 , At least one selected from Na, K, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La It is preferable to use a lithium mixed metal oxide represented by the following element: 1.7 ≦ f ≦ 3).

  In the above general formula, the values of b, c and d are not particularly limited as long as they satisfy the above conditions, but those with 0 <b <1, 0 <c <1, 0 <d <1 It is preferable that at least one of b, c and d is in the range of 30/100 <b <90/100, 10/100 <c <90/100, 1/100 <d <50/100. The range of 40/100 <b <90/100, 10/100 <c <50/100, 2/100 <d <30/100 is more preferable, and 50/100 <b <90/100, It is more preferable to be in the range of 10/100 <c <30/100 and 2/100 <d <10/100.

  The values of a, e and f may be numerical values within the range defined by the above general formula, preferably 0.5 ≦ a ≦ 1.5, 0 ≦ e <0.2, 1.8 ≦ f ≦ 2. And more preferably 0.8 ≦ a ≦ 1.3, 0 ≦ e <0.1, and 1.9 ≦ f ≦ 2.1, respectively.

As a positive electrode active material, Li _x Mn _2-y A _y O ₄ (A is Ca, Mg, S, Si, Na, K, Al, P, Ga, and so on) from the viewpoint of high capacity and excellent durability And at least one element selected from Ge, and at least one metal element selected from transition metal elements such as Ni, etc. 0 <x ≦ 2.2, 0 ≦ y ≦ 1) can be exemplified. As the range of the value of x, 0.5 ≦ x ≦ 1.8, 0.7 ≦ x ≦ 1.5, 0.9 ≦ x ≦ 1.2 can be exemplified, and as the range of the value of y, 0 ≦ y ≦ 0.8 and 0 ≦ y ≦ 0.6 can be exemplified. As a specific compound of spinel structure, LiMn ₂ O ₄ and LiMn _1.5 Ni _0.5 O ₄ can be exemplified.

Specific examples of the positive electrode active material include LiFePO ₄ , Li ₂ FeSiO ₄ , LiCoPO ₄ , Li ₂ CoPO ₄ , Li ₂ MnPO ₄ , Li ₂ MnSiO ₄ , and Li ₂ CoPO ₄ F. Li ₂ MnO ₃ -LiCoO ₂ can be exemplified as another specific positive electrode active material.

  As the binder, 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 resin, carboxymethyl cellulose Known materials such as styrene butadiene rubber may be employed.

As the conductive additive, those described for the negative electrode may be employed.
The compounding amounts of the binder and the conductive additive in the positive electrode active material layer may be appropriately set as appropriate. Further, in order to form the positive electrode active material layer on the surface of the current collector, a known method may be appropriately adopted appropriately.

  The separator separates the positive electrode and the negative electrode, and allows lithium ions to pass while preventing a short circuit due to the contact of the both electrodes. As the separator, a known one may be employed, and polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamide, polyaramid (Aromatic polyamide), polyester, synthetic resin such as polyacrylonitrile, polysaccharide such as cellulose, amylose, fibroin Examples thereof include porous bodies, non-woven fabrics, and woven fabrics using one or more of electrically insulating materials such as natural polymers and ceramics such as keratin, lignin and suberin. In addition, the separator may have a multilayer structure.

  The electrolytic solution contains a non-aqueous solvent and an electrolyte dissolved in the non-aqueous solvent.

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

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

  As an electrolytic solution, lithium salt is added to a nonaqueous solvent such as fluoroethylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, etc. 0.5 mol / L to about 3 mol / L, preferably 1.5 mol / L to 2 A solution dissolved at a concentration of 5 mol / L can be exemplified.

The specific manufacturing method of the lithium ion secondary battery of this invention is described.
For example, the positive electrode and the negative electrode sandwich a separator to form an electrode body. The electrode body may be any of a laminated type in which a positive electrode, a separator and a negative electrode are stacked, or a wound type in which a laminate of a positive electrode, a separator and a negative electrode is wound. 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 leading to the outside using a current collection lead or the like, an electrolytic solution is added to the electrode body to form a lithium ion secondary battery. Good.

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

  The lithium ion secondary battery of the present invention may be mounted on a vehicle. The vehicle may be a vehicle using electric energy from a lithium ion secondary battery for all or 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 a battery pack. As an apparatus which mounts a lithium ion secondary battery, various household appliances driven by a battery, such as a personal computer and a mobile communication apparatus, as well as a vehicle, an office apparatus, an industrial apparatus and the like can be mentioned. Furthermore, the lithium ion secondary battery of the present invention can be used in wind power generation, solar power generation, hydroelectric power generation, storage devices and power smoothing devices for electric power systems, power sources for power and / or accessories of ships, etc., aircraft, Power supply source for power of spacecraft and / or accessories, auxiliary power supply for vehicles not using electricity as 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 charge station etc. for electric vehicles.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. In the range which does not deviate from the summary of the present invention, it can carry out with various forms which gave change, improvement, etc. which a person skilled in the art can make.

  Hereinafter, the present invention will be described more specifically by showing Examples and Comparative Examples. The present invention is not limited by these examples.

(Evaluation example 1)
A 10 μm thick copper foil and an 8 μm thick Ni-containing current collector foil were prepared.
As a Ni-containing current collector foil, a core material layer (about 5 μm thick) made of a Ni-Nb alloy containing 5% by mass of Nb, and two Cu layers (about 1 to 2 μm thickness sandwiching the core material layer) A three-layer clad foil (made by Hitachi Metals Neomaterials, Ltd .: thickness 8 μm) was adopted.
The tensile strength (breaking strength) of the copper foil and the Ni-containing current collector foil after exposure to heating conditions was measured according to JIS Z 2241. The results are shown in Table 1 and FIG.

  From the results of Table 1 and FIG. 2, it can be seen that the strength of the copper foil is significantly reduced by heating in the range of 200 to 400 ° C. On the other hand, Ni-containing current collector foils show a gradual decrease in strength even when heated within the range of 200 to 400 ° C., and even when heated at 400 ° C., they are significantly stronger than copper foil. Is high.

(Evaluation example 2)
Viromax (registered trademark) HR-11NN (Toyobo Co., Ltd.) was prepared as a polyamideimide.
HR-11NN has a number average molecular weight (Mn) of 15 × 10 ³ , a glass transition temperature (Tg) of 300 ° C., and a thermal expansion coefficient of 4.2 × 10 ⁻⁵ / ° C. It is a polyamideimide of a chemical structure.

The above polyamideimide was subjected to a thermal scanning-infrared spectrometer to analyze changes in IR spectrum under heating conditions.
As a result, for the strong absorption peak observed in the vicinity of 1720 cm ^-1 derived from the amide structure and the imide structure, and the medium intensity absorption peak observed in the vicinity of 1770 cm ^-1 derived from the imide structure No change in wave number was observed. On the other hand, for the medium-intensity absorption peak (hereinafter referred to as “amide peak m”) observed near 1680 cm ⁻¹ derived from the amide structure, a change in wave number due to temperature change was observed. The relationship between the heating temperature and the wave number for the amide peak m is shown in Table 2 and FIG.

From the results of Table 2 and FIG. 3, it can be seen that the amide peak m shifts to the high wave number side at a high temperature of 275 ° C. or higher. Furthermore, it is also understood that there is a linear relationship between the heating temperature of 275 ° C. or higher and the wave number shift of the amide peak m.
From the above results, it is suggested that some environmental change occurred at a temperature of 275 ° C. or more in the amide structure part of polyamideimide.

Example 1
<Manufacture of Si-containing negative electrode active material>
CaSi ₂ was added to a concentrated hydrochloric acid solution at 0 ° C. under stirring conditions, and allowed to react for 1 hour. Water was added to the reaction solution, filtration was performed, and a yellow powder was collected by filtration. The yellow powder was washed with water, further washed with ethanol, and then dried under reduced pressure to obtain a layered silicon compound containing layered polysilane. Then, hydrogen was released by heating the layered silicon compound at 800 ° C. in an argon atmosphere to produce a silicon material. By heating the silicon material at 880 ° C. in a propane gas atmosphere, a carbon-coated silicon material which is a Si-containing negative electrode active material was manufactured.

<Manufacture of negative electrode>
11.5 parts by mass of a carbon-coated silicon material as a Si-containing negative electrode active material, 66 parts by mass of graphite as a negative electrode active material, 10 parts by mass of acetylene black as a conductive additive, 12.5 parts by mass of polyamideimide as a binder, The slurry was prepared by mixing N-methyl-2-pyrrolidone. A Ni-containing current collector foil having a thickness of 8 μm was prepared as a current collector for the negative electrode. The above slurry was applied in a film form on the surface of the Ni-containing current collector foil using a comma coater. The slurry-coated Ni-containing current collector foil was dried under reduced pressure to remove N-methyl-2-pyrrolidone. Subsequently, it pressed and heat-processed at 200 degreeC for 3 minutes, and manufactured the negative electrode of Example 1 in which the negative electrode active material layer was formed.
In addition, as Ni-containing current collector foil, clad foil of 3 layer structure used by evaluation example 1 was adopted, and HR-11NN used by evaluation example 2 was adopted as polyamide imide. In addition, the amount (mg / cm ² ) (hereinafter referred to as the basis weight) of the negative electrode active material layer per unit area in the Ni-containing current collector foil was 3.5 mg / cm ² .

The schematic diagram of the negative electrode of Example 1 is shown in FIG.
The negative electrode 1 of Example 1 includes the Ni-containing current collector foil 2 and the negative electrode active material layer 3 formed on the surface of the Ni-containing current collector foil 2 and containing the Si-containing negative electrode active material 30 and the polyamideimide 31. Do. The Ni-containing current collector foil 2 is a three-layered clad foil composed of a core material layer 20 made of Ni and a metal layer 21 made of Cu sandwiching the core material layer 20 made of Ni.

<Manufacture of positive electrode>
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 conduction aid, 2 parts by mass of polyvinylidene fluoride as a binder, and an appropriate amount of N-methyl The -2-pyrrolidone was mixed to produce a slurry. An aluminum foil was prepared as a positive electrode current collector. The above slurry was applied in a film form on the surface of the aluminum foil using a die coater. The N-methyl-2-pyrrolidone was removed by drying the aluminum foil to which the slurry was applied. Then, it pressed and heat-processed at 120 degreeC, and manufactured the positive electrode by which the positive electrode active material layer was formed in the surface of a positive electrode collector.

An electrolyte containing LiPF ₆ at a concentration of 2 mol / L in a non-aqueous solvent was prepared. As a non-aqueous solvent, what mixed dimethyl carbonate and fluoro ethylene carbonate by the volume ratio 81:19 was used.

  A porous membrane made of polyethylene was prepared as a separator.

<Manufacturing of lithium ion secondary battery>
A separator was sandwiched between the positive electrode and the negative electrode of Example 1 to form an electrode plate group. The electrode plate group was covered with a pair of laminate films, the three sides were sealed, and then an electrolytic solution was injected into the bag-like laminate film. By sealing the remaining one side, the four sides were airtightly sealed to obtain a lithium ion secondary battery in which the electrode plate group and the electrolytic solution were sealed. This battery is referred to as the lithium ion secondary battery of Example 1.

(Example 2)
The negative electrode and lithium ion secondary battery of Example 2 are the same as in Example 1 except that the heat treatment at 200 ° C. for 3 minutes in <Production of negative electrode> is changed to heat treatment for 3 minutes at 350 ° C. Manufactured.

(Example 3)
In the same manner as in Example 1, except that the amount of the carbon-coated silicon material was changed to 17.5 parts by mass and the amount of graphite was changed to 60 parts by mass in <Production of negative electrode>, the negative electrode of Example 3 And a lithium ion secondary battery.

(Example 4)
In <Production of negative electrode>, the amount of carbon-coated silicon material is changed to 77.5 parts by mass, the amount of graphite is changed to 0 parts by mass, and the heat treatment at 200 ° C. for 3 minutes is heated at 350 ° C. for 3 minutes A negative electrode and a lithium ion secondary battery of Example 4 were produced in the same manner as in Example 1 except that the treatment was changed and the weight per unit area was changed to 5.5 mg / cm ² .

(Example 5)
The negative electrode and the lithium ion secondary battery of Example 5 were produced in the same manner as in Example 4, except that the heat treatment at 350 ° C. for 3 minutes was changed to the heat treatment at 400 ° C. for 3 minutes. Manufactured.

(Example 6)
In <Production of negative electrode>, the amount of carbon-coated silicon material was changed to 77.5 parts by mass, the amount of graphite was changed to 0 parts by mass, and the coated weight was further changed to 6 mg / cm ² , except for In the same manner as in Example 1, a negative electrode and a lithium ion secondary battery of Example 6 were produced.

(Comparative Examples 1 to 6)
A negative electrode and a lithium ion secondary battery of Comparative Examples 1 to 6 were manufactured in the same manner as in Examples 1 to 6, except that the Ni-containing current collector foil was changed to a copper foil having a thickness of 10 μm.

A list of the negative electrodes of Examples 1 to 6 and Comparative Examples 1 to 6 is shown in Table 3 together with the index P calculated by the following formula (1).
P = (mass% of Si-containing negative electrode active material in negative electrode active material layer) × (area weight (mg / cm ² )) / (thickness of current collector foil (μm))

(Evaluation example 3)
For the lithium ion secondary battery of Example 1, the expansion coefficient of the length of the current collector foil before and after charge and discharge was measured. The same test was performed on the lithium ion secondary batteries of Examples 2 to 6 and Comparative Examples 1 to 6. The length of the current collector foil is shown in Table 4 with x being 1% or more and x being the other.
The charge and discharge of the lithium ion secondary battery were performed under the condition that the battery was discharged to SOC 0% after being charged to SOC 100%.

From the results of Table 4, in comparison with the negative electrode of the comparative example using copper foil, the negative electrode of the example using Ni-containing current collector foil has almost the strength to endure the expansion and contraction of the Si-containing negative electrode active material I understand that However, as shown in Example 6, even when the Ni-containing current collector foil was used, expansion of the Ni-containing current collector foil was observed when the index P was a large value. Moreover, when the index P is a small value of about 4, it can be said that expansion is suppressed even when using copper foil.
Therefore, in the negative electrode of the present invention, when the index P is in a range satisfying 6 ≦ P ≦ 43, it can be said to exhibit superior strength as compared to the negative electrode using copper foil.

(Example 7)
<Manufacture of negative electrode>
81 parts by mass of a carbon-coated silicon material manufactured by the same method as Example 1 as a Si-containing negative electrode active material, 10 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 10 μm thick Ni-containing current collector foil was prepared as a current collector for the negative electrode. The above slurry was applied in the form of a film on the surface of the Ni-containing current collector foil using a doctor blade. The slurry-coated Ni-containing current collector foil was dried under reduced pressure to remove N-methyl-2-pyrrolidone. Subsequently, it pressed and heat-processed at 200 degreeC for 3 minutes, and manufactured the negative electrode of Example 7 in which the negative electrode active material layer was formed.
In addition, as Ni-containing current collector foil, clad foil of 3 layer structure used by evaluation example 1 was adopted, and HR-11NN used by evaluation example 2 was adopted as polyamide imide.

<Manufacture of positive electrode>
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 conduction aid, 2 parts by mass of polyvinylidene fluoride as a binder, and an appropriate amount of N-methyl The -2-pyrrolidone was mixed to produce a slurry. An aluminum foil was prepared as a positive electrode current collector. The slurry was applied in the form of a film on the surface of the aluminum foil using a doctor blade. The N-methyl-2-pyrrolidone was removed by drying the aluminum foil to which the slurry was applied. Then, it pressed and heat-processed at 120 degreeC, and manufactured the positive electrode by which the positive electrode active material layer was formed in the surface of a positive electrode collector.

Dimethyl carbonate and fluoroethylene carbonate were mixed at a volume ratio of 81:19 to give a mixed organic solvent. LiPF ₆ was dissolved in a mixed organic solvent at a concentration of 2 mol / L to form an electrolyte.

  A porous membrane made of polyethylene was prepared as a separator.

<Manufacturing of lithium ion secondary battery>
The separator was sandwiched between the positive electrode and the negative electrode of Example 7 to form an electrode plate group. The electrode plate group was covered with a pair of laminate films, the three sides were sealed, and then an electrolytic solution was injected into the bag-like laminate film. By sealing the remaining one side, the four sides were airtightly sealed to obtain a lithium ion secondary battery in which the electrode plate group and the electrolytic solution were sealed. This battery was used as a lithium ion secondary battery of Example 7.

(Example 8)
The negative electrode and lithium ion secondary battery of Example 8 were processed in the same manner as in Example 7 except that the heat treatment at 200 ° C for 3 minutes in <Production of negative electrode> was changed to heat treatment for 3 minutes at 250 ° C. Manufactured.

(Example 9)
The negative electrode of Example 9 and a lithium ion secondary battery are the same as in Example 7 except that the heat treatment at 200 ° C. for 3 minutes in <Production of negative electrode> is changed to the heat treatment for 3 minutes at 300 ° C. Manufactured.

(Example 10)
The negative electrode and lithium ion secondary battery of Example 10 were processed in the same manner as in Example 7 except that the heat treatment at 200 ° C for 3 minutes in <Production of negative electrode> was changed to heat treatment for 3 minutes at 350 ° C. Manufactured.

(Example 11)
The negative electrode and lithium ion secondary battery of Example 11 were processed in the same manner as in Example 7 except that the heat treatment at 200 ° C. for 3 minutes in <Production of negative electrode> was changed to heat treatment for 3 minutes at 400 ° C. Manufactured.

(Evaluation example 4)
The peel strength of the negative electrode of Examples 7 to 11 was measured using a tensile tester. The test method conformed to JIS Z 0237. Describing the test method in detail, the negative electrode active material layer side was attached downward to the base with an adhesive tape, and the peel strength was measured by pulling the negative electrode upward in the direction of 90 degrees. The results of peel strength are shown in Table 5 and FIG. 4 together with the heating temperatures of the respective negative electrodes.

  It can be seen from Table 5 and FIG. 4 that when the heating temperature exceeds 250 ° C., the peel strength rises sharply. When the results of Evaluation Example 2 are considered together, it is suggested that the environmental change of the amide structure in the polyamideimide contributes to the improvement of the peel strength of the negative electrode active material layer. In addition, it can be seen that the heating temperature in <production of negative electrode> is most preferably around 350 ° C. from the viewpoint of peel strength.

(Evaluation example 5)
The lithium ion secondary batteries of Example 7, Example 10 and Example 11 were charged at 1 C to an SOC of 100%, and then discharged at an initial charge of 1 C to an SOC of 0%. Then, the initial efficiency was calculated by the following equation.
Initial efficiency (%) = 100 × (first discharge capacity) / (first charge capacity)
In addition, with respect to each lithium ion secondary battery adjusted to SOC 15%, a voltage was measured in the case of discharging at constant current for 10 seconds under the condition of 25 ° C. The measurements were performed under multiple conditions of varying current. From the obtained results, a constant current for which the discharge time up to a voltage of 2.5 V is 10 seconds was calculated for each lithium ion secondary battery of SOC 15%. Then, a value obtained by multiplying the calculated current value by 2.5 V was taken as an output (mW).
The initial efficiency and output results are shown in Table 6.

  From the results in Table 6, the characteristics of the lithium ion secondary battery change due to the heating temperature in <production of negative electrode>, and the heating temperature in <production of negative electrode> is most preferably around 350 ° C. Recognize.

(Example 12)
Negative electrode and lithium ion secondary battery of Example 12 in the same manner as Example 10 except that the composition of the carbon-coated silicon material and acetylene black in <Production of negative electrode> was changed to 83 parts by mass and 8 parts by mass. Manufactured.

(Example 13)
A negative electrode and a lithium ion secondary battery of Example 13 in the same manner as Example 10 except that the composition of the carbon-coated silicon material and acetylene black in <Production of negative electrode> is changed to 85 parts by mass and 6 parts by mass. Manufactured.

(Example 14)
The negative electrode and the lithium ion secondary battery of Example 14 are prepared in the same manner as in Example 10 except that the composition of the carbon-coated silicon material and acetylene black in <Production of negative electrode> is changed to 87 parts by mass and 4 parts by mass. Manufactured.

(Evaluation example 6)
The following tests were performed on the lithium ion secondary batteries of Example 10 and Examples 12 to 14 in which the heating temperature in <Manufacturing of negative electrode> was 350 ° C. in all cases.
With respect to each lithium ion secondary battery adjusted to SOC 15%, the voltage in the case of discharging at constant current for 10 seconds at 25 ° C. was measured. The measurements were performed under multiple conditions of varying current. From the obtained results, a constant current for which the discharge time up to a voltage of 2.5 V is 10 seconds was calculated for each lithium ion secondary battery of SOC 15%. Then, a value obtained by multiplying the calculated current value by 2.5 V was taken as an output (mW).
In addition, with respect to the lithium ion secondary batteries of Example 10 and Examples 12 to 14, the charge and discharge cycle of charging and discharging at 1 C between 90% SOC and 15% SOC was repeated 200 times under the condition of 60 ° C. . The capacity retention rate was calculated by the following equation.
Capacity retention rate (%) = 100 × (discharge capacity at 200 cycles) / (discharge capacity at 1 cycle)
The results of output and capacity retention are shown in Table 7.

From the results of Table 7, it can be said that the lithium ion secondary batteries of Example 10 and Examples 12 to 14 are all excellent in output and capacity retention under severe conditions. By setting the heating temperature in <Production of negative electrode> to 350 ° C., the conductive network in the negative electrode active material layer formed of the polyamideimide and the conductive support is formed more uniformly, so the amount of the conductive support is reduced. It can be said that it became possible to
In particular, it is understood that the lithium ion secondary battery of Example 13 in which the mass ratio of the Si-containing negative electrode active material and the conductive additive is 85: 6 is remarkably excellent in both the output and the capacity retention ratio.

DESCRIPTION OF SYMBOLS 1 negative electrode 2 Ni containing current collector foil 3 negative electrode active material layer 20 Ni core material layer 21 Cu metal layer 30 Si containing negative electrode active material 31 polyamidoimide

Claims (8)

Ni-containing current collector foil,
A negative electrode active material layer formed on the surface of the Ni-containing current collector foil and containing a Si-containing negative electrode active material and a polyamideimide;
A negative electrode comprising: The negative electrode according to claim 1, wherein the index P calculated by the following formula (1) satisfies 6 ≦ P ≦ 43.
Formula (1):
P = (mass% of the Si-containing negative electrode active material in the negative electrode active material layer) x (amount of the negative electrode active material layer per unit area in the Ni-containing current collector foil (mg / cm ² )) Thickness of Ni-containing current collector foil (μm))   The clad foil according to claim 1 or 2, wherein the Ni-containing current collector foil is a three-layer clad foil composed of a core layer made of Ni and a metal layer made of Cu sandwiching the core layer made of Ni. Negative electrode. The absorption peak derived from the amide structure is observed at a wave number W of _{200 ° C.} (cm ⁻¹ ) when heated at 200 ° C. in measurement with a thermal scanning-infrared spectrometer, and the polyamideimide is measured at 350 ° C. It is observed at wave number W _{350 ° C} (cm ^-1 ) at the time of heating,
And, when the negative electrode is measured by an infrared spectrometer, the absorption peak derived from the amide structure of the polyamideimide has a wave number W of _{350 ° C.} (cm ⁻¹ ) than that of the wave number W _{200 ° C.} (cm ⁻¹ ) The negative electrode according to any one of claims 1 to 3, which is observed while being shifted in the direction.   A storage device comprising the negative electrode according to any one of claims 1 to 4. It is a manufacturing method of the negative electrode of any one of Claims 1-4, Comprising:
A method for producing a negative electrode, comprising the steps of applying a composition containing a Si-containing negative electrode active material and a polyamideimide to a Ni-containing current collector foil and then heating the composition at 200 to 450 ° C.   The manufacturing method of the negative electrode of Claim 6 whose heating temperature is 250-400 degreeC.   The manufacturing method of an electrical storage apparatus using the negative electrode manufactured by the manufacturing method of Claim 6 or 7.