JP2011048969A - Negative electrode for lithium ion secondary battery and secondary battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a negative electrode for a high capacity lithium ion secondary battery having initial charge/discharge efficiency and cycle characteristics improved by suppressing a volume change of the negative electrode accompanied by doping or dedoping in the negative electrode of the lithium ion secondary battery, and to provide the lithium ion secondary battery using the negative electrode by using a manufacturing method having excellent productivity. <P>SOLUTION: The negative electrode for the lithium ion secondary battery is provided with a negative electrode active material layer formed on a current collector. The negative electrode active material layer includes a negative electrode active material capable of being alloyed with lithium, and a binder. The binder includes a polyamideimide resin having a tensile strength of 100 MPa or larger, a tensile elongation of 30% or larger and a tensile elastic modulus of 2.5 GPa or larger when it is formed into a film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a negative electrode for a high capacity type lithium ion secondary battery using a lithium alloy negative electrode active material and a lithium ion secondary battery using the same.

  In recent years, the demand for secondary batteries has increased due to the rapid development of portable electronic devices, and batteries with high energy density have been demanded as portable electronic devices have become smaller, lighter and more functional. In response to this demand, a battery using lithium metal as a negative electrode active material has been proposed. A lithium ion secondary battery using a carbon-based material and a graphite-based material for the negative electrode has been put into practical use. In the case of graphite, the theoretical capacity is 372 mAh, which is much lower than 4000 mAh of lithium metal, so it is close to lithium metal. A negative electrode material using a lithium alloy having a theoretical capacity as an active material has been studied.

  Examples of the lithium alloy used as the negative electrode active material include a lithium soot alloy, a lithium-zinc alloy, a lithium-bismuth alloy, a lithium-aluminum alloy, a lithium-arsenic alloy, a lithium-silicon alloy, and a lithium-antimony alloy.

  However, when these alloy systems are used as the negative electrode active material, the volume expansion and contraction associated with lithium insertion and desorption reactions are much higher than when carbon-based materials and graphite-based materials are used as the negative electrode active material. However, there was a problem that mechanical degradation of the active material and the electrode occurred, the initial charge / discharge efficiency was low, and the cycle characteristics were poor.

  Document 1 proposes a method of covering the surface of the lithium alloy negative electrode active material with a conductive polymer or carbon in order to solve such drawbacks. However, when such a conductive coating layer is present on the surface, there is a problem that the irreversible reaction cannot be reduced due to decomposition of the solvent or electrolyte in the electrolyte.

  Patent Document 2 proposes a patent that uses a polyimide resin as a negative electrode binder. However, when a polyimide resin is used, a special apparatus is required because it needs to be applied to the current collector in the state of polyamic acid as a precursor, and then subjected to heat treatment and ring closure reaction at a high temperature. In addition, there is a problem in that there is a risk of deterioration of the active material due to water generated when the amic acid left unreacted in the battery manufacturing stage is naturally ring-closed, and thus heat generation and ignition.

JP 2001-135303 A JP 2008-282550 A

  The present invention was devised in view of the current state of the prior art, and its purpose is to suppress the decomposition reaction of the solvent and electrolyte in the electrolyte, and the negative electrode accompanying the doping and dedoping of lithium in the negative electrode of the lithium ion secondary battery By suppressing the volume change, the negative electrode for a lithium ion secondary battery with high capacity, improved initial charge / discharge efficiency and cycle characteristics, and a lithium ion secondary battery using the negative electrode with a highly productive manufacturing method Is to provide.

As a result of intensive studies to solve the above problems, the present inventor has obtained a tensile strength of 100 MPa or more, a tensile elongation of 30% or more, and a tensile elastic modulus as a negative electrode binder for a lithium ion secondary battery. If a polyamideimide resin of 2.5 GPa or more is used, it is possible to suppress the decomposition reaction of the electrolyte while improving the dimensional stability of the electrode material due to charge / discharge, and it is possible to suppress mechanical damage of the electrode material due to volume expansion due to charge / discharge. Therefore, it was found that the initial charge / discharge efficiency and cycle characteristics were excellent, and the present invention was completed.
(1) A negative electrode including a negative electrode active material layer formed on a current collector, wherein the negative electrode active material layer includes a negative electrode active material capable of being alloyed with lithium and a binder, and the binder is formed into a film. A negative electrode for a lithium ion secondary battery comprising a polyamideimide resin having a tensile strength of 100 MPa or more, a tensile elongation of 30% or more, and a tensile elastic modulus of 2.5 GPa or more.
(2) The negative electrode for a lithium ion secondary battery according to (1), wherein the polyamideimide resin has a logarithmic viscosity of 0.5 dl / g or more.
(3) As an acid component of the polyamideimide resin, one or more acid anhydrides selected from the group consisting of pyromellitic acid anhydride, benzophenonetetracarboxylic acid anhydride and biphenyltetracarboxylic acid anhydride, and trimellitic acid anhydride The negative electrode for a lithium ion secondary battery according to (1) or (2), which is a polyamideimide resin containing
(4) The lithium ion secondary battery according to any one of (1) to (3), which is a polyamideimide resin containing naphthalene and / or an o-tolidine residue as an amine component and / or an isocyanate component of the polyamideimide resin. Negative electrode.
(5) The negative electrode active material that can be alloyed with lithium is at least one metal and / or metal compound selected from the group consisting of tin, aluminum, bismuth, arsenic, silicon, lead, zinc, and antimony (1 ) A negative electrode for a lithium ion secondary battery according to any one of (4) to (4).
(6) The negative electrode for a lithium ion secondary battery according to any one of (1) to (5), a positive electrode comprising a positive electrode active material layer formed on a current collector, and the negative electrode for a lithium ion secondary battery, A lithium ion secondary battery comprising a separator made of a porous film and an electrolyte containing an electrolyte between positive electrodes.

  According to the present invention, a polyamideimide resin having a tensile strength of 100 MPa or more, a tensile elongation of 30% or more, and a tensile elastic modulus of 2.5 GPa or more as a negative electrode binder for a lithium ion secondary battery is used. Therefore, it is possible to suppress the decomposition reaction of the electrolyte while improving the dimensional stability of the electrode material due to charge / discharge, and to suppress the mechanical damage of the electrode material due to the volume expansion due to charge / discharge. A negative electrode for a lithium ion secondary battery excellent in cycle characteristics and a lithium ion secondary battery using the same can be easily obtained by a production method excellent in productivity.

The present invention is a negative electrode for a lithium ion secondary battery including a negative electrode active material layer formed on a current collector, and the negative electrode active material layer includes a negative electrode active material capable of being alloyed with lithium and a binder. The binder includes a polyamide-imide resin having a tensile strength of 100 MPa or more, a tensile elongation of 30% or more, and a tensile elastic modulus of 2.5 GPa or more when formed into a film. Therefore, the binder has excellent initial charge and discharge efficiency and cycle durability. An anode for an ion secondary battery and a lithium ion secondary battery using the same can be provided.

1. Polyamideimide resin As the polyamideimide resin used in the present invention, aromatic, aliphatic or alicyclic polyamideimide can be used. Among these, strength, elastic modulus, resistance to electrolytic solution, solvent, Aromatic polyamide-imide resins are preferred from the standpoints of solubility, processability and cost. The polyamideimide resin can be produced by using a solution polymerization method, a melt polymerization method, or the like, and can be produced by a known method such as a diamine method or an isocyanate method.

  In addition to trimellitic acid, its anhydride, and acid chloride, pyromellitic acid, biphenyltetracarboxylic acid, biphenylsulfonetetracarboxylic acid, benzophenonetetracarboxylic acid, and biphenylethertetra are used as acid components for the production of polyamideimide resin. Tetracarboxylic acids such as carboxylic acid, ethylene glycol bisanhydro trimellitate, propylene glycol bisanhydro trimellitate and their anhydrides, oxalic acid, adipic acid, malonic acid, sebacic acid, azelaic acid, dodecanedicarboxylic acid, Aliphatic dicarboxylic acids such as dicarboxypolybutadiene, dicarboxypoly (acrylonitrile-butadiene), dicarboxypoly (styrene-butadiene), 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedica Examples thereof include alicyclic dicarboxylic acids such as boric acid, 4,4′-dicyclohexylmethane dicarboxylic acid and dimer acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, diphenylsulfone dicarboxylic acid, diphenyl ether dicarboxylic acid and naphthalenedicarboxylic acid. Of these, trimellitic anhydride is most preferable from the viewpoints of reactivity and heat resistance, and some of them are replaced by pyromellitic anhydride, benzophenonetetracarboxylic anhydride, and biphenyltetracarboxylic anhydride. Is preferable from the viewpoint of tensile strength, tensile elastic modulus, and resistance to electrolytic solution.

  Diamines (diisocyanates) used for the production of polyamideimide resins include aliphatic diamines such as ethylene diamine, propylene diamine, and hexamethylene diamine, and ethylene disocyanates corresponding thereto, aliphatic diisocyanates such as propylene diisocyanate and hexamethylene diisocyanate, 1, Alicyclic diamines such as 4-cyclohexanediamine, 1,3-cyclohexanediamine, isophoronediamine, 4,4′dicyclohexylmethanediamine, and the corresponding 1,4-cyclohexane diisocyanate, 1,3 cyclohexane diisocyanate, isophorone diisocyanate, 4,4 ′ Alicyclic diisocyanates such as dicyclohexylmethane diisocyanate, m-phenylenediamine, p-phenylenediamine, 4 4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, benzidine, o-tolidine, 2,4-tolylenediamine, 2,6-tolylenediamine, xylylenediamine, naphthalene Aromatic diamines such as diamines and their corresponding m-phenylene diisocyanates, p-phenylene diisocyanates, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyl ether diisocyanate, diphenylsulfone-4,4′-diisocyanate, diphenyl-4 Aromatic dii such as 4'-diisocyanate, o-tolidine diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate Examples include socyanates. Among these, 4,4′-diaminodiphenylmethane or 4,4′-diphenylmethane diisocyanate, 2,4-tolylenediamine or 2,4-tolylenediisocyanate, o-tolidine or o-tolidine because of heat resistance and solubility. Diisocyanate, naphthalene diamine or naphthalene diisocyanate, isophorone diamine or isophorone diisocyanate are preferred. In particular, o-tolidine, o-tolidine diisocyanate, naphthalenediamine or naphthalene diisocyanate is preferable from the viewpoint of tensile strength and tensile modulus.

The polyamide-imide resin used for the negative electrode for lithium ion secondary batteries of the present invention can withstand the expansion and contraction of the negative electrode active material during charge / discharge with its toughness. The polyamideimide resin used in the present invention has a tensile strength of 100 MPa or more, preferably 150 MPa or more, more preferably 200 MPa or more when formed into a film, and a tensile elongation of 30% or more, preferably 50% or more, more preferably The tensile elastic modulus is 2.5 GPa or more, preferably 3.5 GPa or more, more preferably 5 GPa or more. Although there is no particular upper limit, a tensile strength of 400 MPa is sufficient, a tensile elongation of 300% is sufficient, and a tensile elastic modulus of 10 GPa is sufficient. When a polyamide-imide resin having a tensile strength of less than 100 MPa, an elongation of less than 30%, or a tensile elastic modulus of less than 2.5 GPa is used as a binder, Inability to withstand, the active material peels off, and the cycle characteristics are significantly degraded.
Regarding the toughness of the polyamideimide resin, it is preferable to appropriately select the acid component, diamine component and / or diisocyanate component of the polyamideimide resin. As the acid component of the polyamide-imide resin, trimellitic acid anhydride, pyromellitic acid anhydride, benzophenone tetracarboxylic acid anhydride, and biphenyl tetracarboxylic acid anhydride are preferable, and as the amine component and / or isocyanate component, naphthalene and / or o -It preferably has a tolidine residue. In particular, as the acid component of polyamideimide resin, a polyamideimide resin in which trimellitic anhydride is partially replaced with pyromellitic anhydride, benzophenonetetracarboxylic anhydride, biphenyltetracarboxylic anhydride is a lithium ion secondary battery. From the viewpoint of the cycle characteristics. When the total acid component of the polyamide-imide resin is 100 mol%, it is preferable to contain 100 to 20 mol% trimellitic anhydride, preferably 0.1 to 50 mol% benzophenonetetracarboxylic anhydride, It is preferable that 0.1-30 mol% of biphenol tetracarboxylic acid anhydride is included, and it is preferable that 0.1-30 mol% of pyromellitic acid anhydride is included. Increasing the copolymerization ratio of tetracarboxylic anhydrides such as pyromellitic anhydride, benzophenonetetracarboxylic anhydride, biphenyltetracarboxylic anhydride, etc. is preferable because it can increase tensile strength and tensile elastic modulus, but it can be dissolved. There is a tendency for properties and elongation to decrease. When the total diamine component (diisocyanate component) of the polyamide-imide resin is 100 mol%, it is preferable to contain 0.1 to 100 mol% of naphthalene and / or o-tolidine residue, more preferably 50 to 100 mol%. is there. Increasing the proportion of naphthalene and / or o-tolidine residue is preferable because the tensile strength and tensile modulus increase, but the solubility and elongation tend to decrease.
In order to increase the toughness of the polyamide-imide resin, particularly the tensile elongation, the polyamide-imide resin is preferably a high molecular weight substance, and preferably has a logarithmic viscosity of 0.5 dl / g or more, more preferably 0.7 dl / g or more, more preferably 1.0 dl / g or more. Although there is no particular upper limit on the logarithmic viscosity, it is preferably 3.0 dl / g or less, more preferably 2.5 dl / g or less from the viewpoint of workability. When the logarithmic viscosity of the polyamideimide resin is less than 0.5 dl / g, the toughness, particularly the elongation, is insufficient, and the initial charge / discharge efficiency and cycle characteristics tend to be lowered.
The logarithmic viscosity can be adjusted by adjusting the charged molar ratio of the acid component and the diamine (diisocyanate) component. Specifically, the charged molar ratio of the acid component / diamine (diisocyanate) component is preferably 0.85 to 1.15, more preferably 0.95 to 1.05. The adjustment of the charged molar ratio may be performed at the initial stage of the polymerization, or may be performed during the polymerization.

  The polyamideimide resin can be copolymerized with a compound having an ionic group for the purpose of improving the dispersibility of the negative electrode active material and conductive carbon. The compound containing an ionic group copolymerized with the polyamide-imide resin is an acid anhydride, dicarboxylic acid, diisocyanate containing a phenolic hydroxyl group, a sulfonic acid group, a phosphonic acid group, and a metal salt or quaternary ammonium salt thereof. Specifically, trimellitic acid monosodium salt, trimesic acid monopotassium salt, 5-sodium carboxytrimellitic anhydride, 5-sodium sulfoisophthalic acid, 2-carboxyethylphosphonic acid monopotassium salt , 5-sodium hydroxyisophthalic acid, 5-dialkylaminoisophthalic acid and the like. Among these, 5-sodium hydroxyisophthalic acid, 5-hydroxysulfoisophthalic acid and their sodium and potassium salts, ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol from the viewpoint of reactivity, price, etc. And the like. These copolymerization amounts are preferably from 0.1 to 20 mol%, more preferably from 0.5 to 10 mol%, still more preferably from 1 to 7 mol%. If it is less than 0.1 mol%, the effect of improving dispersibility tends to be small. Moreover, even if it exceeds 20 mol%, the dispersibility effect does not change.

For solution polymerization of polyamideimide resin, heating at 60 to 200 ° C. in a polar solvent such as N, N′-dimethylacetamide, N-methyl-2-pyrrolidone, N, N′-dimethylformamide, γ-butyrolactone, etc. It can be easily produced by stirring.
In this case, an organic amine compound such as triethylamine, diethylenetriamine, or diazabicycloundecene, or a metal compound such as potassium fluoride, sodium fluoride, cesium fluoride, or sodium methoxide can be used as a catalyst as necessary.

2. The present invention relates to a negative electrode for a lithium ion secondary battery comprising a negative electrode active material layer formed on a current collector, wherein the negative electrode active material layer can be alloyed with lithium Contains active material and binder. The polyamideimide resin is used for the binder.

The negative electrode active material is made of a metal and / or metal compound that can be alloyed with lithium, specifically, tin (Sn), aluminum (Al), silicon (Si), bismuth (Bi), zinc (Zn), It consists of any one or more metals selected from the group consisting of arsenic (As), antimony (Sb), and lead (Pb), and / or metal compounds such as oxides. Specifically, tin oxide, silicon dioxide A known negative electrode active material can be used. The average particle size of these negative electrode active materials is not particularly limited, but is 0.01 to 10 μm, preferably 0.05 to 5 μm, and more preferably 0.1 to 3 μm.
Alloying of Sn, Al, Si or Pb and lithium is preferable, and further alloying of Si or Sn and lithium is preferable. The composition ratio of the alloy is 30:70 to 60:40, preferably 40:60 to 50:50, in terms of mass ratio of the metal: lithium.

  As the current collector, a metal foil such as copper or aluminum, a mesh-type expanded metal, a punched metal, or the like can be used.

As for the thickness of a negative electrode active material layer, 30-150 micrometers is preferable normally, More preferably, it is 50-100 micrometers. If the thickness of the negative electrode active material layer is less than 30 μm, the active material may be insufficient and the charge / discharge capacity may not be sufficient. If the thickness is 150 μm or more, the electrode layer may be cracked or peeled off from the current collector. It tends to be undesirable.

The negative electrode for a lithium ion secondary battery of the present invention is prepared by directly coating a mixture comprising a dispersion containing a negative electrode active material and a polyamideimide resin on a current collector such as a copper foil, and then, if necessary, a hot roll. Or by pressing with a hot plate. The drying is preferably performed at 50 ° C. or more and 160 ° C. or less, and is preferably performed for about 3 minutes to 30 minutes. Since the polyamide-imide resin has completed the imide ring-closing reaction, it does not require heat treatment at a high temperature unlike a polyimide resin via a polyamic acid. Therefore, conventionally known facilities and methods can be used as the method for producing the negative electrode for a lithium ion secondary battery of the present invention. In addition, since the imide ring-closing reaction is completed, the remaining amic acid does not naturally ring-close, so there is no risk of deterioration of the active material due to water, heat generation, or ignition.

  When manufacturing the negative electrode for lithium ion secondary batteries, a electrically conductive agent can be mix | blended in the mixture applied to a collector. The conductive agent is not particularly limited, but carbon blacks such as ketjen black, acetylene black and graphite, anionic, cationic, nonionic and amphoteric surfactants, and electroconductive polymers such as polythiophene, polyacetylene and polyaniline. Etc. are used. Among these, carbon black and polyaniline, which are less dependent on the humidity of conductivity and are excellent in dispersibility and compatibility with polyamideimide, are preferred. Polyaniline can be dissolved or dispersed in an organic solvent in which an oxidatively polymerized polyaniline derivative is doped with an organic protonic acid dopant such as an inorganic acid or dodecylbenzenesulfonic acid.

The dispersion may include a negative electrode active material that can be alloyed with lithium, a conductive agent, a polyamideimide resin, and an organic solvent. The negative electrode active material, the conductive agent, and the polyamide-imide resin preferably have a weight ratio of 97 to 75, 0 to 5, and 3 to 25, respectively. The solid content concentration of the dispersion is preferably 30% by weight or more, more preferably 40% by weight or more, and preferably 60% by weight or less. As the organic solvent, the solvent used at the time of polymerization of the polyamideimide resin can be used as it is.
These can be blended using a conventional disperser such as a dissolver, a three-roll mill, a sand mill, a ball mill, a planetarium mixer, or an attritor.

The dispersion is a dispersant, inorganic filler, leveling agent, antifoaming agent, polyester, polyamide, polyimide, polyurethane and other resins, silicone release agents, and crosslinking agents as long as the properties of the heat resistant conductive composition are not impaired. Etc. can be blended. Examples of the crosslinking agent include bifunctional or higher functional epoxy resins, melamine resins, and isocyanate compounds.

3. Lithium ion secondary battery The lithium ion secondary battery of the present invention includes the negative electrode for a lithium ion secondary battery, a positive electrode including a positive electrode active material layer formed on a current collector, a negative electrode for a lithium ion secondary battery, The separator which consists of a porous film arrange | positioned between positive electrodes and the electrolyte solution containing an electrolyte are provided.

As the positive electrode active material, lithium composite oxides such as LiCoO ₂ and LiMn ₂ O ₄ are used. In addition to these active materials, the positive electrode can contain a conductive agent, a binder, Li ₂ CO _{3 and the} like. As the binder, the polyamideimide resin or polyimide resin of the present invention, polyvinylidene fluoride, vinylidene fluoride-hexafluoro-hexafluoropropylene copolymer, styrene-butadiene copolymer, or the like can be used.

  As the separator, conventionally used separators can be used. Specifically, polyolefin-based porous films such as polyethylene and polypropylene, highly heat-resistant porous films such as polyimide and polyamideimide, composite films of the polyolefin-based porous film and highly heat-resistant porous film, aromatic polyamide, polyimide, polyamideimide, etc. Non-woven fabrics and the like.

The electrolyte is made of a lithium salt and an electrolyte, and conventionally known electrolytes are used. Examples of the electrolyte include tetrahydrofuran, benzene, toluene, trifluorotoluene, isopropyl alcohol, dimethyl carbonate, ethylene methylene carbonate, diethyl carbonate, methyl propyl carbonate, propylene carbonate, propyl acetate, methyl acetate, ethyl acetate, diglyme, etc. A mixed solution of two or more types can be mentioned.
As the lithium salt, LiPF ₆ , LiSO ₃ CF ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiClO ₄ or a mixture of two or more kinds is used.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. In addition, the measured value in an Example is a value measured with the following method.

-The polyamidoimide resin solution obtained in the logarithmic viscosity synthesis example was put into water, and the precipitated solid was washed with water and then dried 0.5 g into 100 ml of NMP (N-methyl-2-pyrrolidone). The dissolved solution was measured at 30 ° C. using an Ubbelohde viscosity tube.

・ Tensile strength, tensile elongation, tensile modulus Polyamideimide resin solution was applied onto a polyester film so that the dry film thickness was about 25 μm, dried at 100 ° C. for 10 minutes, then peeled off and fixed to a metal frame, Furthermore, using a film dried at 200 ° C. for about 20 hours, the polyamideimide resin film having a measurement width of 10 mm and a measurement length of 40 mm was subjected to a tensile speed of 20 mm / min in a 25 ° C. and 65% RH environment. It measured using.

-Charging / discharging efficiency and cycle durability About each battery created in the Example, the charging / discharging test was performed at 0.2C, and the charging / discharging efficiency at the first time and repeating 50 times was calculated | required.
Charging / discharging efficiency = [(discharge capacity / charge capacity) × 100 (%)]

(Synthesis of polyamideimide resin A)
A four-necked flask equipped with a condenser and a nitrogen gas inlet contains 1 mole of trimellitic anhydride (TMA), 1 mole of diphenylmethane 4,4 ′ diisocyanate (MDI), and 0.01 mole of potassium fluoride in a solid content concentration. After charging with N-methyl-2-pyrrolidone (NMP) so as to be 20%, the temperature was raised to 120 ° C. with stirring and the reaction was carried out for about 3 hours. Then, N was adjusted so that the solid concentration would be 15% while cooling. -Diluted with methyl-2-pyrrolidone. The resulting polyimide resin had a logarithmic viscosity of 0.85 dl / g, a tensile elongation of 78%, a tensile strength of 115 MPa, and a tensile modulus of 2.8 GPa.

(Synthesis of polyamideimide resin B)
Using the same apparatus as in Example 1, 1 mol of TMA, 0.5 mol of o-tolidine diisocyanate, 0.5 mol of 2,4-tolylene diisocyanate, and 0.01 mol of potassium fluoride become a solid content concentration of 20%. The mixture was charged with NMP as described above, reacted at 120 ° C. for about 1 hour with stirring, and then diluted with N-methyl-2-pyrrolidone so that the solid concentration was 15% while cooling. The resulting polyimide resin had a logarithmic viscosity of 1.21 dl / g, a tensile elongation of 59%, a tensile strength of 167 MPa, and a tensile modulus of 3.9 GPa.

(Synthesis of polyamideimide resin C)
In a four-necked flask equipped with a condenser and a nitrogen gas inlet, 0.8 mol of TMA, 0.12 mol of biphenyltetracarboxylic anhydride, 0.08 mol of benzophenone tetracarboxylic anhydride, 1 mol of o-tolidine diisocyanate, dia 0.02 mol of Zabicycloundecene (DBU) was added together with NMP so that the solid concentration was 15%, the temperature was raised to 90 ° C. with stirring and reacted for about 4 hours. It diluted with NMP so that it might become%. The resulting polyimide resin had a logarithmic viscosity of 1.38 dl / g, a tensile elongation of 38%, a tensile strength of 287 MPa, and a tensile modulus of 7.5 GPa.

(Synthesis of polyamideimide resin D)
TMA 0.5 mol, benzophenone tetracarboxylic anhydride 0.3 mol, biphenyl tetracarboxylic anhydride 0.2 mol, o-tolidine diisocyanate 0.5 mol in a four-necked flask with a condenser and a nitrogen gas inlet , 0.5 mol of naphthalene diisocyanate and 0.01 mol of potassium fluoride were added together with N-methyl-2-pyrrolidone so that the solid content concentration was 15%, and the temperature was raised to 90 ° C. with stirring and reacted for about 4 hours. After cooling, the mixture was diluted with N-methyl-2-pyrrolidone so that the solid concentration was 12% while cooling. The resulting polyimide resin had a logarithmic viscosity of 1.44 dl / g, a tensile elongation of 62%, a tensile strength of 234 MPa, and a tensile modulus of 6.6 GPa.

(Production Example of Lithium Ion Secondary Battery Negative Electrode-Examples 1, 2, 3, 4)
Each of the polyamideimide resins A, B, C, and D varnishes synthesized above, SiO ₂ as an active material, and Ketjen black as a conductive agent were mixed with N-methyl-2-pyrrolidone at a ratio of 7: 91: 2 by a ball mill. A negative electrode mixture slurry having a solid content concentration of 40% was produced, and this slurry was applied on a copper foil having a width of 5.1 cm and a thickness of 178 μm so that the dry film thickness was 90 μm. Partial drying was performed to manufacture a negative electrode for a lithium ion secondary battery.

(Production example of positive electrode for lithium ion secondary battery)
Polyvinylidene fluoride (PVDF) as a binder, lithium cobaltate as an active material, and ketjen black as a conductive agent are mixed with N-methyl-2-pyrrolidone at a ratio of 7: 91: 2 in a ball mill, and the solid content concentration is A 40% positive electrode mixture slurry was produced, and this slurry was applied to an aluminum foil having a width of 4.9 cm and a thickness of 147 μm so as to have a dry film thickness of 90 μm. A positive electrode for a secondary battery was prepared.

(Production example of lithium ion secondary battery)
The negative electrode shown in the above example, a polyethylene porous membrane separator in which 1.0 mol of LiPF ₆ was dissolved in a 3: 7 volume ratio solvent of ethylene carbonate and diethyl carbonate, and a positive electrode were stacked. A lithium ion secondary battery was prepared in a case.

(Comparative Example 1)
When the polyamideimide resin B was synthesized, a polyamideimide resin E synthesized by the same method as the polyamideimide resin B was synthesized except that trimellitic anhydride was changed to 1.05 mol. The logarithmic viscosity of this resin was 0.46 dl / g, the tensile elongation was 22%, the tensile strength was 176 MPa, and the tensile elastic modulus was 5.3 GPa. Using this polyamideimide resin E, a lithium ion secondary battery was prepared in the same manner as in the example.

(Comparative Example 2)
0.75 mol of trimellitic anhydride, acrylonitrile-butadiene having a carboxyl group at both ends (CTBN 1300 × 13, molecular weight 3500, manufactured by Ube Industries, Ltd.) 0.25 mol, diphenylmethane 1 mol of diisocyanate and 0.01 mol of potassium fluoride are charged together with N-methyl-2-pyrrolidone so that the solid content concentration becomes 30%, polymerized at 150 ° C. for 5 hours, and the solid content concentration becomes 15% while cooling. Thus, polyamideimide resin F was synthesized by diluting with N-methyl-2-pyrrolidone.
The logarithmic viscosity of this polymer was 0.78 dl / g, the tensile elongation was 250%, the tensile strength was 45 MPa, and the tensile elastic modulus was 0.3 GPa. Using this polyamideimide resin F, a lithium ion secondary battery was prepared in the same manner as in Example 1.

From Table 1, for Examples 1, 2, 3, and 4, the initial value of charge / discharge efficiency and the value after 50 cycles were both high and good, but Comparative Examples 1 and 2 had values after 50 cycles. The result was much lower than the initial value.

According to the present invention, a negative electrode for a lithium ion secondary battery having high capacity, improved initial charge / discharge efficiency and cycle characteristics, and a lithium ion secondary battery using the same are provided by a production method excellent in productivity. The

Claims (6)

A negative electrode comprising a negative electrode active material layer formed on a current collector, wherein the negative electrode active material layer includes a negative electrode active material capable of being alloyed with lithium and a binder, and the binder is a tensile when formed into a film A negative electrode for a lithium ion secondary battery, comprising a polyamideimide resin having a strength of 100 MPa or more, a tensile elongation of 30% or more, and a tensile elastic modulus of 2.5 GPa or more. The negative electrode for a lithium ion secondary battery according to claim 1, wherein the logarithmic viscosity of the polyamideimide resin is 0.5 dl / g or more. Polyamide containing one or more acid anhydrides selected from the group consisting of pyromellitic acid anhydride, benzophenonetetracarboxylic acid anhydride and biphenyltetracarboxylic acid anhydride, and trimellitic acid anhydride as the acid component of the polyamideimide resin The negative electrode for a lithium ion secondary battery according to claim 1, which is an imide resin. The negative electrode for a lithium ion secondary battery according to any one of claims 1 to 3, which is a polyamideimide resin containing naphthalene and / or an o-tolidine residue as an amine component and / or an isocyanate component of the polyamideimide resin. The negative electrode active material that can be alloyed with lithium is one or more metals and / or metal compounds selected from the group consisting of tin, aluminum, bismuth, arsenic, silicon, lead, zinc, and antimony. The negative electrode for lithium ion secondary batteries in any one of. A negative electrode for a lithium ion secondary battery according to any one of claims 1 to 5, a positive electrode comprising a positive electrode active material layer formed on a current collector, and a porous material between the negative electrode for lithium ion secondary battery and the positive electrode A lithium ion secondary battery comprising a separator made of a porous film and an electrolyte solution containing an electrolyte.