JP2019145296A - Electrode for lithium ion secondary battery and lithium ion secondary battery using the same - Google Patents

Abstract

To provide an electrode for a lithium ion secondary battery with improved cycle characteristics and a lithium ion secondary battery using the same.SOLUTION: An electrode for a lithium ion secondary battery includes a current collector and an active material layer provided on the current collector, and the active material layer includes active material particles that occlude and release lithium ions, a binder, and a conductive auxiliary agent. The conductive auxiliary agent is composed of carbon containing carbon stable isotopeC of -35 to -20 with a carbon stable isotope ratio δC, and at least a part of the conductive auxiliary agent is attached to the surface of the active material particles.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrode for a lithium ion secondary battery and a lithium ion secondary battery using the same.

Conventionally, a layered compound such as LiCoO ₂ or LiNi _1/3 Mn _1/3 Co _1/3 O ₂ or a spinel compound such as LiMn ₂ O ₄ has been used as a positive electrode material (positive electrode active material) of a lithium ion secondary battery. Yes. In recent years, a compound having a phosphoric acid skeleton typified by LiFePO ₄ , a compound having a silicic acid or boric acid structure, or a sulfide-based compound has attracted attention as a positive electrode material.

  Since these electrode materials have low electron conductivity, it is a common practice to produce an electrode by adding a conductive aid for imparting electron conductivity. Attempts have been made to improve the cycle characteristics by adding a conductive additive to increase the electron conductivity to express a high capacity or adjusting the ratio of carbon as a conductive additive (Patent Document 1). .

  As the conductive assistant, amorphous carbon such as carbon black, graphite, carbon nanotube, graphene, or the like is used.

  Although the conductivity can be increased by using these carbonaceous materials, these carbonaceous materials are insufficient to improve the cycle characteristics.

JP2014-72062A

  However, the conventional methods still do not satisfy various characteristics, and in particular, improvement of cycle characteristics is required.

  The present invention has been made in view of the problems of the cycle characteristics of the above-described prior art, and provides a lithium ion secondary battery electrode capable of improving the cycle characteristics and a lithium ion secondary battery using the same. For the purpose.

  An electrode for a lithium ion secondary battery according to the present invention includes a current collector and an active material layer provided on the current collector, and the active material layer occludes and releases lithium ions. And a binder and a conductive assistant, wherein the conductive assistant is composed of carbon containing carbon stable isotope 13C at a carbon stable isotope ratio δ13C of −35 to −20 ‰, and at least a part of the conductive assistant. Is attached to the surface of the active material particles.

  Cycle characteristics are improved by using the lithium ion secondary battery electrode according to the present invention.

  A lithium ion secondary battery according to the present invention includes the electrode described above and a counter electrode facing the electrode via a separator, and the separator holds an electrolyte.

  With this configuration, a lithium ion secondary battery having excellent cycle characteristics can be provided.

  By using the electrode for a lithium ion secondary battery according to the present invention and the lithium ion secondary battery using the same, cycle characteristics can be improved.

It is a schematic cross section of a lithium ion secondary battery using an electrode according to the present embodiment.

  Hereinafter, preferred embodiments of the active material of the present invention will be described in detail with reference to the drawings. However, the electrode of the present invention is not limited to the following embodiments. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

FIG. 1 is a schematic cross-sectional view of an electrode according to the present embodiment and a lithium ion secondary battery 100 using the electrode.
The lithium ion secondary battery 100 mainly includes a laminate 30, a case 50 that accommodates the laminate 30 in a sealed state, and a pair of leads 60 and 62 connected to the laminate 30.

  The laminated body 30 is configured such that a pair of the positive electrode 10 and the negative electrode 20 are opposed to each other with the separator 18 interposed therebetween. The positive electrode 10 is obtained by providing a positive electrode active material layer 14 on a plate-like (film-like) positive electrode current collector 12. The negative electrode 20 is obtained by providing a negative electrode active material layer 24 on a plate-like (film-like) negative electrode current collector 22. The positive electrode active material layer 14 and the negative electrode active material layer 24 are in contact with both sides of the separator 18. Leads 62 and 60 are connected to the ends of the positive electrode current collector 12 and the negative electrode current collector 22, respectively, and the ends of the leads 60 and 62 extend to the outside of the case 50.

  Hereinafter, the positive electrode 10 and the negative electrode 20 are collectively referred to as electrodes 10 and 20, and the positive electrode current collector 12 and the negative electrode current collector 22 are collectively referred to as current collectors 12 and 22, and the positive electrode active material layer 14 and the negative electrode The active material layers 24 are collectively referred to as active material layers 14 and 24.

The electrodes 10 and 20 according to the present embodiment include current collectors 12 and 22 and active material layers 14 and 24 including an active material and provided on the current collector. The active material layers 14 and 24 are active material particles that occlude and release lithium ions (hereinafter sometimes referred to as a positive electrode active material or a negative electrode active material. The positive electrode active material and the negative electrode active material are collectively referred to as an active material. .), A binder, and a conductive assistant composed of carbon bound on the surface of the particle by the binder, and the conductive assistant has a stable carbon isotope ratio of ¹³ C and a stable carbon isotope ratio δ ¹³ C. -35 to -20 ‰.

Hereinafter, the electrodes 10 and 20 according to the present embodiment will be specifically described.
(Positive electrode 10)
The positive electrode current collector 12 may be a conductive plate material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used. The positive electrode active material layer 14 includes a positive electrode active material, a conductive additive, and a binder. The binder binds the positive electrode active materials, the conductive assistants, and the positive electrode active material and the conductive assistant, and binds them to the positive electrode current collector 12.

The positive electrode active material is not particularly limited as long as it is a material capable of occluding and releasing lithium ions, and known positive electrode active materials for batteries can be used. Examples of the positive electrode active material include those containing at least one kind of transition metal-containing oxide, phosphoric acid compound, silicic acid compound, boric acid compound, and sulfide. The transition metal-containing oxide is specifically a group consisting of lithium element and Mn, Co, Ni, Al, Ba, Ca, Cu, Fe, Mg, Ti, V, Zn, W, Mo, Nb, Zr. An oxide containing at least one element selected from LiCoO ₂ , LiNi _0.85 Co _0.1 Al _0.05 , LiNi _1/3 Mn _1/3 Co _1/3 Li _1.2 Mn _0.55 Ni _0.3 Co _0.15 O ₂ , LiCo _0.95 Mg _0.05 O ₂ , and the like. Examples of the phosphoric acid compound include LiFePO ₄ , LiVOPO ₄ , and Li ₃ V ₂ (PO ₄ ) ₃ . Examples of the silicate compound include Li ₂ FeSiO ₄ , Li ₂ VOSiO ₄ , LiMnSiO ₄ , Li (FeMn) SiO _{4, and the} like. Examples of the boric acid compound include LiFeBO ₃ , LiMnBO ₃ , LiVOBO _{3, and the} like. Examples of the sulfide include FeS _{2 and the} like.

  The conductive assistant is composed of carbon, and examples thereof include carbon black such as oil furnace, ketjen black, acetylene black, carbon nanotube, graphene, graphite, hard carbon, and soft carbon.

Carbon mainly contains ¹² C and contains stable isotope ¹³ C at a carbon stable isotope ratio δ ¹³ C of −35 to −20 ‰. In the present invention, the carbon stable isotope ratio is measured by an isotope mass spectrometer, and the numerical value is a value calculated by the following formula (1).
σ ¹³ C = ( ¹³ C / ¹² C molar ratio of sample) / ( ¹³ C / ¹² C molar ratio of standard sample−1) × 1000 (1)

In measurement using an isotope mass spectrometer according to the present embodiment, the reference sample is ¹² C is ^98.894% arrows ^{stone, 13} C can be used as a 1.106%.

When the conductive auxiliary agent contains carbon stable isotope ¹³ C in a carbon stable isotope ratio δ ¹³ C of −35 to −20 ‰, the electrode has the following effects.

The stable carbon isotope ¹³ C is considered to have a higher electron density than ¹² C, and the presence of ¹³ C to a certain extent relative to ¹² C will cause polarization in the conductive additive composed of carbon. It is done. In the particles that occlude and release lithium ions, it is considered that polarization occurs in a portion that is unstable due to lattice defects or the like. If the conductive additive bound on the surface of the particles that occlude and release lithium ions contains the carbon stable isotope ¹³ C in a carbon stable isotope ratio δ ¹³ C of −35 ‰ to −20 ‰, it is polarized. In addition, since the conductive auxiliary agent can stabilize the surface of the particles that occlude and release lithium ions, the cycle characteristics are improved.

On the other hand, when the carbon stable isotope ¹³ C is more than −20 ‰ in the carbon stable isotope ratio δ ¹³ C, the proportion of ¹³ C in the carbon constituting the conductive assistant increases, so the degree of polarization of the conductive assistant Becomes weak, the surface of the particles that occlude and release lithium ions cannot be stabilized, and the cycle characteristics deteriorate. If it is less than −35 ‰, the proportion of ¹³ C in the carbon constituting the conductive film is reduced, so that the polarization of the conductive film is reduced and the surface of the particles that occlude and release lithium ions cannot be stabilized. Characteristics are degraded.

From the viewpoint of further suppressing the deterioration of cycle characteristics, the conductive assistant preferably contains the carbon stable isotope ¹³ C in a carbon stable isotope ratio δ ¹³ C of −33 ‰ or more and −22 ‰ or less, and −30 ‰ or more. More preferably, the content is -24 ‰ or less.

The carbon stable isotope ¹³ C is preferably unevenly distributed on the interface side with the active material particles in the conductive additive. ^{Since 13} C is unevenly distributed at the interface between the conductive auxiliary agent and the particles that occlude and release lithium ions, the conductive auxiliary agent having a large polarization may directly act on the particles that occlude and release lithium ions. it can. Thereby, the particle | grain surface which occludes / releases lithium ion is stabilized more, and cycling characteristics improve more.

  The material of the binder is not particularly limited as long as the above-described bonding is possible. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene. -Perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride ( Fluorine resin such as PVF).

  In addition to the above, as the binder, for example, vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-TFE-based) Fluororubber), vinylidene fluoride-pentafluoropropylene-based fluororubber (VDF-PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-PFP-TFE-based fluororubber), vinylidene fluoride Ride-perfluoromethyl vinyl ether-tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine rubber (VDF-CTFE-based fluorine rubber) may be used vinylidene fluoride-based fluorine rubbers such.

    In addition to the above, for example, polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, polyamideimide, cellulose, styrene / butadiene rubber, isoprene rubber, butadiene rubber, ethylene / propylene rubber, and the like may be used as the binder. Also, thermoplastic elastomeric polymers such as styrene / butadiene / styrene block copolymers, hydrogenated products thereof, styrene / ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers, and hydrogenated products thereof. May be used. Furthermore, syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, propylene / α-olefin (carbon number 2 to 12) copolymer, polyacrylic acid, lithium polyacrylate, carboxymethylcellulose, etc. are used. Also good.

  As the binder, an electron conductive conductive polymer or an ion conductive conductive polymer may be used. Examples of the electron conductive conductive polymer include polyacetylene. In this case, since the binder also functions as a conductive material, it is not necessary to add a conductive material.

As the ion-conductive conductive polymer, for example, those having ion conductivity such as lithium ion can be used. For example, polymer compounds (polyether-based polymer compounds such as polyethylene oxide and polypropylene oxide) A crosslinked polymer of a polyether compound, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile, etc.) monomers, and LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, LiBr, Examples thereof include a composite of a lithium salt such as Li (CF ₃ SO ₂ ) ₂ N, LiN (C ₂ F ₅ SO ₂ ) ₂ or an alkali metal salt mainly composed of lithium. Examples of the polymerization initiator used for the combination include a photopolymerization initiator or a thermal polymerization initiator that is compatible with the above-described monomer.

  It is preferable that the content rate of the binder contained in the positive electrode active material layer 14 is 0.5-6 mass% on the basis of the mass of an active material layer. When the binder content is less than 0.5% by mass, the amount of the binder is too small and a tendency to make it difficult to form a strong active material layer increases. Moreover, when the content rate of a binder exceeds 6 mass%, the quantity of the binder which does not contribute to an electrical capacity will increase, and the tendency for it to become difficult to obtain sufficient volume energy density becomes large. In this case, particularly, when the electronic conductivity of the binder is low, the electric resistance of the active material layer is increased, and there is a tendency that a sufficient electric capacity cannot be obtained.

(Negative electrode 20)
The negative electrode current collector 22 may be a conductive plate material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used.

The negative electrode active material is not particularly limited, and a known negative electrode active material for a battery can be used. Examples of the negative electrode active material include graphite, non-graphitizable carbon, graphitizable carbon, and low-temperature calcined carbon that can occlude / release (intercalate / deintercalate, or dope / dedope) lithium ions. Carbon materials, metals that can be combined with lithium such as aluminum, silicon and tin, amorphous compounds mainly composed of oxides such as SiO, SiO ₂ and SnO ₂ , lithium titanate (Li ₄ Ti ₅ O ₁₂ ), Particles containing Fe ₂ O _{3 and the} like. As the binder and the conductive assistant, those similar to the positive electrode can be used.

Next, an example of a method for manufacturing the electrodes 10 and 20 according to the present embodiment will be described.
(Method for manufacturing electrodes 10 and 20)
The manufacturing method of the electrodes 10 and 20 according to the present embodiment includes a step of applying a coating material, which is a raw material of the electrode active material layers 14 and 24, onto the aggregate (hereinafter, also referred to as “application step”), and a collector. And a step of removing the solvent in the paint applied on the electric body (hereinafter, also referred to as “solvent removal step”).

(Coating process)
An application process for applying the paint to the current collectors 12 and 22 will be described. The paint includes the positive electrode active material or the negative electrode active material, the binder, the conductive auxiliary agent, and a solvent. In addition to these components, the coating material may contain, for example, a conductive material for increasing the conductivity of the active material. As the solvent, for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide and the like can be used.

  The mixing method of the components constituting the coating material such as the active material, the binder, the conductive auxiliary agent, and the solvent is not particularly limited, and the mixing order is not particularly limited. For example, first, an active material, a conductive additive, and a binder are mixed, and N-methyl-2-pyrrolidone is added to and mixed with the obtained mixture to prepare a coating material.

  The paint is applied to the current collectors 12 and 22. There is no restriction | limiting in particular as an application | coating method, The method employ | adopted when producing an electrode normally can be used. Examples thereof include a slit die coating method and a doctor blade method.

(Solvent removal step)
Subsequently, the solvent in the paint applied on the current collectors 12 and 22 is removed. The removal method is not particularly limited, and the current collectors 12 and 22 to which the paint is applied may be dried, for example, in an atmosphere of 80 ° C. to 150 ° C.

  Then, the electrodes on which the active material layers 14 and 24 are formed in this way may then be pressed by a roll press device or the like as necessary. The linear pressure of the roll press can be, for example, 10 to 50 kgf / cm.

  The electrode according to this embodiment can be manufactured through the above steps.

  By using the electrode according to the present embodiment for at least one of the positive electrode and the negative electrode, the cycle characteristics are improved.

  Here, another component of the lithium ion secondary battery 100 using the electrode manufactured as described above will be described.

The electrolyte is contained in the positive electrode active material layer 14, the negative electrode active material layer 24, and the separator 18. The electrolyte is not particularly limited, and, for example, in the present embodiment, an electrolyte solution containing a lithium salt (electrolyte aqueous solution, electrolyte solution using an organic solvent) can be used. However, the electrolyte aqueous solution is preferably an electrolyte solution (non-aqueous electrolyte solution) using an organic solvent because the electrochemical decomposition voltage is low, and the withstand voltage during charging is limited to a low level. As the electrolyte solution, a lithium salt dissolved in a non-aqueous solvent (organic solvent) is preferably used. Examples of the lithium salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN Salts such as (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiN (CF ₃ CF ₂ CO) ₂ , LiBOB, LiFSI can be used. In addition, these salts may be used individually by 1 type, and may use 2 or more types together.

  Examples of the organic solvent preferably include propylene carbonate, ethylene carbonate, diethyl carbonate, and the like, or fluoropropylene carbonate, fluoroethylene carbonate, fluorodiethyl carbonate, and the like in which these hydrogen atoms are substituted with fluorine atoms. . These may be used alone or in combination of two or more at any ratio.

  In the present embodiment, the electrolyte may be a gel electrolyte obtained by adding a gelling agent in addition to liquid. Further, instead of the electrolyte solution, a solid electrolyte (a solid polymer electrolyte or an electrolyte made of an ion conductive inorganic material) may be contained.

  The separator 18 is an electrically insulating porous body, for example, a single layer of a film made of polyethylene, polypropylene, polyolefin, polyamide, polyimide, polyamideimide, a stretched film of a laminate or a mixture of the above resins, cellulose, Examples thereof include a fiber nonwoven fabric made of at least one constituent material selected from the group consisting of polyester and polypropylene.

  The case 50 seals the laminate 30 and the electrolyte solution therein. The case 50 is not particularly limited as long as it can prevent leakage of the electrolytic solution to the outside and entry of moisture and the like into the electrochemical device 100 from the outside. For example, as the case 50, as shown in FIG. 1, a metal laminate film in which a metal foil 52 is coated with a polymer film 54 from both sides can be used. For example, an aluminum foil can be used as the metal foil 52 and a film such as polypropylene can be used as the polymer film 54. For example, the material of the outer polymer film 54 is preferably a polymer having a high melting point such as polyethylene terephthalate (PET) or polyamide, and the material of the inner polymer film 54 is polyethylene (PE) or polypropylene (PP). preferable.

  The leads 60 and 62 are made of a conductive material such as aluminum.

  Then, the leads 60 and 62 are welded to the positive electrode current collector 12 and the negative electrode current collector 22 by a known method, respectively, and a separator is provided between the positive electrode active material layer 14 of the positive electrode 10 and the negative electrode active material layer 24 of the negative electrode 20. 18 may be inserted into the case 50 together with the electrolytic solution with the 18 interposed therebetween, and the entrance of the case 50 may be sealed.

  As mentioned above, although the suitable embodiment of the electrode of this invention, the lithium ion secondary battery provided with the said electrode, and those manufacturing methods was described in detail, this invention is not limited to the said embodiment. In this embodiment, an active material, a binder, and a conductive assistant are mixed in a solvent and applied to a current collector. For example, the active material, the binder, and the conductive assistant are mechanically worked by mechanical milling or the like. The conductive auxiliary agent may be bound on the surface of the active material.

  For example, the electrode of the present invention can be used for electrochemical devices other than lithium ion secondary batteries. Electrochemical elements include secondary batteries other than lithium ion secondary batteries such as metallic lithium secondary batteries (using the electrode of the present invention as the cathode and metallic lithium as the anode), and electrochemical such as lithium capacitors. A capacitor etc. are mentioned. These electrochemical elements can be used for power sources such as self-propelled micromachines and IC cards, and distributed power sources arranged on or in a printed circuit board.

(Example 1)
<Preparation of conductive aid>
Reducing the pressure of the tube furnace to 1 Pa, while heating to 700 ° ^{C., 13} C purity of 99% ¹³ C methane gas and ¹² C in a purity of 99.9% of the ¹² mixed gas of C methane gas ^{(12 C / 13} Carbon particles, which are conductive assistants, were obtained by flowing C mixed methane gas).

<Preparation of positive electrode>
LiCoO ₂ was used as active material particles, polyvinylidene fluoride (PVdF) was used as a binder, and carbon particles produced by the above method were used as a conductive additive. The active material, binder and carbon particles are mixed at 96.5% by mass, 1.5% by mass and 2% by mass, respectively, and N-methylpyrrolidone (MNP) is added to form a slurry paint, which is applied to an aluminum foil, dried and rolled. As a result, an electrode (positive electrode) was produced.

<Production of negative electrode>
A mixture of silicon monoxide and graphite having a mass ratio of 1: 9 as active material particles and a mixture of polyamideimide (PAI) and acetylene black as a binder were mixed with N-methyl-2-pyrrolidone (NMP) as a solvent. ) To prepare a slurry. The slurry was prepared so that the mass ratio of the active material, acetylene black, and PAI in the slurry was 90: 2: 8. This slurry was applied onto a copper foil as a current collector, dried, and then rolled to obtain an electrode (negative electrode) on which an active material layer was formed.

<Production of lithium ion secondary battery>
The produced positive and negative electrodes and separator were punched into a predetermined mold. As the separator, a film having a two-layer structure of a polyethylene porous film and a polyamideimide porous layer was used. A negative electrode, a separator, a positive electrode, a separator, and a negative electrode were laminated in this order, and a combination of any one of the positive electrode and the negative electrode and one separator was used as a single layer to produce a six-layer laminate. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ to 1 M in a solvent in which fluoroethylene carbonate (FEC) and diethyl carbonate (DEC) were mixed at a mass ratio of 3: 7 was used as the electrolytic solution. The laminate was placed in an aluminum laminate pack, and an electrolyte was injected into the aluminum laminate pack, followed by vacuum sealing to produce an evaluation cell of Example 1.

(Examples 2-9)
Carbon particles with an adjusted ¹² C / ¹³ C mixing ratio were prepared by changing the mixing ratio of the mixed gas with ¹² C methane gas having a purity of ¹² C of 99.9%, and used as a conductive aid. Other than that was carried out similarly to Example 1, and produced the evaluation cell of Examples 2-9.

(Example 10)
An evaluation cell of Example 6 was produced in the same manner as Example 2 except that LiFePO ₄ was used as the active material particles.

(Example 11)
An evaluation cell of Example 7 was produced in the same manner as Example 2 except that LiVOPO ₄ was used as the active material particles.

(Example 12)
An evaluation cell of Example 8 was produced in the same manner as Example 2 except that LiNi _0.85 Co _0.1 Al _0.05 O ₂ was used as the active material particles.

(Example 13)
An evaluation cell of Example 9 was produced in the same manner as in Example 2 except that LiNi _1/3 Mn _1/3 Co _1/3 O ₂ was used as the active material particles.

(Comparative Examples 1 and 2)
Carbon particles with an adjusted ¹² C / ¹³ C mixing ratio were prepared by changing the mixing ratio of the mixed gas with ¹² C methane gas having a purity of ¹² C of 99.9%, and used as a conductive aid. Otherwise, the evaluation cells of Comparative Examples 1 and 2 were produced in the same manner as in Example 1.

<Measurement of cycle characteristics>
Using the manufactured lithium ion secondary battery, charging was repeated at a charge rate of 0.5 C (current value at which discharge was completed in 2 hours when constant current discharge was performed at 25 ° C.), and a cycle of discharging at 1 C was repeated. The capacity after the first cycle and the capacity after 300 cycles were compared to determine the capacity retention rate.

  DESCRIPTION OF SYMBOLS 10 ... Positive electrode, 20 ... Negative electrode, 12 ... Positive electrode collector, 14 ... Positive electrode active material layer, 18 ... Separator, 22 ... Negative electrode collector, 24 ... Negative electrode Active material layer, 30 ... power generation element, 50 ... case, 60, 62 ... lead, 100 ... lithium ion secondary battery.

Claims (2)

A current collector,
An active material layer provided on the current collector,
The active material layer includes active material particles that occlude and release lithium ions, a binder, and a conductive additive.
The conductive auxiliary agent is composed of carbon containing carbon stable isotope 13C at a carbon stable isotope ratio δ13C of −35 to −20 ‰,
An electrode for a lithium ion secondary battery, wherein at least part of the conductive additive is attached to the surface of the active material particles. A lithium ion secondary battery comprising: the lithium ion secondary battery electrode according to claim 1; a separator; a counter electrode facing the lithium ion secondary battery electrode through the separator; and an electrolyte.

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