Method for manufacturing positive electrode active material for lithium ion secondary battery, electrode for lithium ion secondary battery, and lithium ion secondary battery

Abstract

We will break through the complex manufacturing process of LiVOPO4, the positive electrode active material for lithium-ion secondary batteries, and develop a simple manufacturing process. [Solution] We provide positive electrode active materials, orthorhombic β-LiVOPO4 and its polymorph, triclinic α-LiVOPO4, which exhibit excellent charge-discharge characteristics for lithium-ion secondary batteries, through an inexpensive and simplified manufacturing process characterized by a single raw material mixing step at room temperature and a single heat treatment step, without the need for multiple synthesis steps or the addition of reducing agents.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a positive electrode active material for a lithium ion secondary battery, an electrode for a lithium ion secondary battery, and a lithium ion secondary battery. [Background technology]

[0002] Renewable energy sources such as hydroelectric power, wind power, and solar power are primary energy sources that are free from problems such as depletion, greenhouse gas emissions, and radioactive waste, and building a society that runs on these energies can be said to be one of the most important issues facing humanity. Because this energy has problems such as uneven distribution over a wide area and fluctuations over time, the stable use of this energy requires the improvement of the performance of lithium-ion secondary batteries, which are energy storage devices. The current positive electrode active material, triangular lattice trigonal LiCoO2 and its solid solution system LiCo 1 / 3 Mn 1 / 3 Ni 1 / 3 O2 etc. (hereinafter collectively referred to as LCO type) performance (flat potential approx. 3.8V, charge / discharge capacity approx. 140Ahkg -1 It is extremely important to develop a material that surpasses the conventional material and to establish a manufacturing method that enables its mass production.

[0003] While LCO systems exhibit good charge-discharge characteristics, they have problems such as limited capacity and fire hazards, and the solid solution system requires synthesis at high temperatures of around 1300 K. A candidate positive electrode active material that can solve these problems is a combination of transition metals and polyanions (PO4 3- , SiO4 4- , or SO4 2- It represents a group of materials such as:

[0004] Known vanadium polyanion-based positive electrode active materials include phosphate-based materials such as monoclinic Li3V2(PO4)3, Nasicon-type trigonal Li3V2(PO4)3, trigonal Li9V3(P2O7)3(PO4)2, tavorite-type triclinic LiVFPO4, and tavorite-type orthorhombic β-phase LiVOPO4 (hereinafter referred to as β-LiVOPO4 or simply β-phase) (Non-Patent Document 1). If the vanadium ion state, which takes a valence between trivalent and pentavalent in the chemical formula, is considered to represent the substantial charge / discharge region, Li3V2(PO4)3 and Li9V3(P2O7)3(PO4)2 formally take a valence range of trivalent to 4.5valent and trivalent to pentavalent, respectively. On the other hand, the formal valence ranges of LiVFPO4 and β-LiVOPO4, which have smaller molecular weights than these, are trivalent to tetravalent and trivalent to pentavalent, respectively. In particular, β-LiVOPO4 has the highest capacity (approximately 310 Ahkg) of the vanadium phosphates. -1 ) can be an active material.

[0005] The plateau potential of β-LiVOPO4 between the tetravalent and pentavalent vanadium ions is approximately 4.0V, and the maximum charge / discharge capacity is approximately 150Ahkg -1 Therefore, the performance exceeds that of the LCO system (Non-Patent Document 2).

[0006] In addition to the β phase, LiVOPO4 also has a polymorphic triclinic α phase (hereinafter referred to as α-LiVOPO4 or simply α phase), and its charge / discharge capacity is 10 Ah kg -1 (Non-patent documents 1, 3 and 4).

[0007] Various methods for the preparation of β-LiVOPO4 have been reported. This material was developed by Lii et al., who prepared single-crystal samples by hydrothermal synthesis using Li2O, VO2, and H3PO4 as raw materials (Non-Patent Document 5). On the other hand, powder (polycrystalline) samples have been prepared by impregnation in aqueous solution (Non-Patent Document 3), lithium insertion into β-phase VOPO4 via a non-electrochemical topotactic reaction (Non-Patent Document 6), carbothermal reduction (Non-Patent Document 7), glass-ceramic method (Non-Patent Document 8), sol-gel method (Non-Patent Documents 9 and 10), and microwave sintering (Non-Patent Document 2). Of these, only the glass-ceramic method produced single-phase powder. α-LiVOPO4 was developed by Lavrov et al., and a single crystal sample was first prepared by cooling Li2VOP2O7 from 1173 K in a vacuum (Non-Patent Document 10). On the other hand, powder samples were prepared in a single phase by the infiltration method in an aqueous solution (Non-Patent Document 11), the hydrothermal synthesis method (Non-Patent Document 4), or the solid-state reaction method in a vacuum (Non-Patent Document 12).

[0008] As an alternative to LCO-based materials, olivine-type cubic LiFePO4, which has relatively low raw material costs, has attracted attention. However, in this case, the valence of the iron ions is limited to between divalent and trivalent, so the maximum electrical capacity is about the same as that of LCO-based materials and does not exceed the performance of current secondary batteries. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 5741143 (paragraph numbers 0019~0039) [Patent Document 2] Patent No. 6197540 (paragraph numbers 0039~0049) [Non-patent literature]

[0010] [Non-Patent Document 1] Masashige Onoda, Journal of the Crystallographic Society of Japan 56, 78(2014). [Non-patent document 2] L. Wang, L. Yang, L. Gong, X. Jiang, and Z. Hu, Electrochem. Acta 56, 6906 (2011). [Non-patent document 3] BMAzmi, T. Ishihara, H. Nishiguchi, and Y. Takita, Electrochemistry 71, 1108 (2003). [Non-patent document 4] Y. Yang, H. Fang, J. Zheng, L. Li, G. Li, and G. Yan, J. Solid State Sci. 10, 1292 (2008).

Non - Patent Document 5

Non - Patent Document 6

Non - Patent Document 7

Non - Patent Document 8

Non - Patent Document 9

Non - Patent Document 10

Non - Patent Document 11

Non - Patent Document 12

Summary of the Invention

[0011] The charge-discharge characteristics of β-LiVOPO4 exhibit a high plateau potential and high electric capacity when the vanadium ion valence is between tetravalent and pentavalent. However, its manufacturing method involves complex processes such as hydrothermal synthesis, impregnation in aqueous solution, or the sol-gel method, making mass production difficult and single-phase samples difficult to obtain (Patent Documents 1 and 2, Non-Patent Documents 2, 3, and 5-10). In order to mass-produce and commercialize this substance, it is essential to develop an inexpensive and simplified manufacturing method. The present invention relates to a simplified manufacturing method for β-LiVOPO4 and α-LiVOPO4. [Means for solving the problem]

[0012] As a result of extensive research, the present inventors have discovered a simplified method for producing LiVOPO4 in the orthorhombic β phase and the triclinic α phase.

[0013] The method for producing the composition LiVOPO4 of the present invention is characterized by a solid-state reaction method of a mixture of raw material lithium ions, vanadium ions, and phosphorus ions in a stoichiometric molar ratio.

[0014] The above-mentioned manufacturing method is a manufacturing method that can be completed by only one raw material mixing step at room temperature and one heat treatment step, and does not require multiple heat treatment steps or the addition of a reducing agent.

[0015] In the heat treatment step, the amount of oxygen gas generated from the mixture is adjusted to be zero or greater. [Effects of the Invention]

[0016] By using the manufacturing method of the present invention, it is possible to easily provide an electrode for a lithium ion secondary battery and a lithium ion secondary battery that exhibit high potential and high capacity. [Brief explanation of the drawings]

[0017] [Figure 1(a)]The crystal structure of β-LiVOPO4 projected along the rectangular b-axis by the polyhedron method. The quasi-one-dimensional VOV spin-1 / 2 chain is formed along the a-axis. [Figure 1(b)] The crystal structure of α-LiVOPO4 projected by the polyhedron method along the axis perpendicular to the triclinic (110) plane. Quasi-one-dimensional VOV spin-1 / 2 alternating chains are formed along the b axis. [Figure 2] X-ray powder diffraction patterns (X-ray source: CuKα radiation) of a sample prepared by heat-treating a molar mixture of 2Li2CO3, V2O5, V2O3, and 4NH4H2PO4 in air at temperatures of 833K, 853K, and 913K. The row of check marks below each pattern represents the calculated diffraction angles of the major phases. In the 833K pattern, the empty squares, diamonds, and triangles represent the top five diffraction intensities of the minor phases β-phase VOPO4, γ-phase VO2O5, and γ'-phase VO2O5, respectively. [Figure 3] Dependence of the diffraction intensity ratio of the minor phase to the major phase on the heat treatment temperature of a sample prepared by heat treating a mixture of 2Li2CO3, V2O5, V2O3, and 4NH4H2PO4 in molar ratios. [Figure 4] Dependence of the orthorhombic lattice constant of β-LiVOPO4 on the heat treatment temperature. The dotted line is a guide for the eye. [Figure 5] Dependence of the triclinic lattice constant of α-LiVOPO4 on the heat treatment temperature. The dotted line is a guide for the eye. [Figure 6] Temperature dependence of magnetic susceptibility of β-LiVOPO4. Here, the empty circles represent raw data (χraw), the white circles represent data obtained by adding the orbital susceptibility (χorb) and diamagnetic susceptibility (χdia) to the spin susceptibility (χESR) derived from X-band electron spin resonance (ESR), and the solid circles represent data for a sample prepared using the hydrothermal synthesis method proposed by Lii et al. The solid line shows the calculated value for a spin-1 / 2 antiferromagnetic Heisenberg one-dimensional chain based on the molecular field approximation, which takes into account the effective inter-chain interactions. [Figure 7]X-band electron spin resonance absorption derivative spectrum of β-LiVOPO4 at 298 K. Here, the dots represent experimental data, and the solid line represents the results calculated by considering axially symmetric anisotropy for the g-factor and linewidth W of the Lorentzian resonance lineshape. [Figure 8] Block diagram of electrochemical measurements. [Figure 9] Dependence of output potential on electrical capacity of a lithium-ion secondary battery using LiVOPO4: (a) Charge-discharge characteristics after the start of charging when using the β-phase and α-phase, (b) Discharge-charge characteristics after the start of discharging when using the β-phase. DETAILED DESCRIPTION OF THE INVENTION

[0018] Compositions to which the present invention is applied will be described in detail below with reference to the drawings as appropriate. Note that the drawings used in the following description may show characteristic portions enlarged for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may differ from the actual ones. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and can be appropriately modified and implemented within the scope of the present invention.

[0019] (composition) The composition produced by the manufacturing method of the present invention is represented by LiVOPO4. Figure 1(a) shows the crystal structure of the orthorhombic β-phase of the composition represented by LiVOPO4, projected along the b-axis by the polyhedral method. The structure is represented by VO6 octahedra, which are bridged by PO4 tetrahedra and bonded by sharing O-points to form quasi-one-dimensional spin-1 / 2 chains of -VOV- along the a-axis.

[0020] The composition adopts a triclinic α-phase crystal structure depending on the heat treatment conditions. Figure 1(b) shows the crystal structure of the α-phase of the composition represented by LiVOPO4, projected by the polyhedral method along the axis perpendicular to the triclinic (110) plane. The structure is represented by two crystallographically inequivalent V1O6 and V2O6 octahedra, which are bridged by two types of P1O4 and P2O4 tetrahedra and bonded by shared O-points to form quasi-one-dimensional spin-1 / 2 alternating chains of -VOV- along the b-axis.

[0021] The charge / discharge capacity of LiVOPO4 in the β-phase and α-phase when the vanadium ion valence is between tetravalent and pentavalent is up to 150 Ahkg -1 and 10Ahkg -1 Although they have the same chemical formula, their crystal structures are significantly different, resulting in different electrochemical properties.

[0022] (Lithium-ion secondary battery electrodes and lithium-ion secondary batteries) The β and α phases of the above composition are used to form electrodes for lithium ion secondary batteries. Lithium ion secondary batteries are a type of non-aqueous electrolyte secondary battery in which lithium ions in the electrolyte are responsible for electrical conduction. Generally, lithium metal oxide is used for the positive electrode, and a carbon material such as graphite is used for the negative electrode. If lithium ions are not supplied from the negative electrode when starting discharge, a sacrificial lithium source can be added to the positive electrode. Alternatively, a material containing excess lithium ions can be produced by adding a reducing agent to the positive electrode active material.

[0023] The composition described above can be used as an active material for electrodes of a lithium ion secondary battery. Other components such as an electrolyte solution can be those generally known in the art.

[0024] (Method of producing the composition) The manufacturing method of the present invention consists of a single step of mixing raw materials at room temperature and a single heat treatment step of the resulting mixture. The heat treatment time can be changed as needed, and to adjust the grain size or sample density, the following mixture can be pressurized and shaped into pellets or the like, and similar heat treatment steps can be performed multiple times. Furthermore, the initial heat treatment step can be performed in an environment other than air, as long as it is possible to exhaust gases generated from the mixture.

[0025] The manufacturing method of LiVOPO4 is a solid-state reaction method, which consists of a process of mixing a lithium (Li) source, a vanadium (V) source, and a phosphoric acid (PO4) source, and a process of heat-treating the mixture.

[0026] [Mixing process] In the mixing step, the lithium source, vanadium source, and phosphate source are mixed so that the molar ratio of Li, V, and P is 1:1:1, and a mixture is prepared in which the amount of oxygen gas generated from the mixture in the subsequent heat treatment step is adjusted to be zero or greater.

[0027] The lithium source includes, for example, at least one selected from the group consisting of lithium carbonate (Li2CO3), lithium nitrate (LiNO3), lithium oxide (Li2O), lithium hydroxide (LiOH), lithium chloride (LiCl), and lithium sulfate (Li2SO4).

[0028] The vanadium source includes, for example, at least one selected from the group consisting of vanadium 52 oxide (V2O5), vanadium dioxide (VO2), vanadium 32 oxide (V2O3), and ammonium vanadate (NH4VO3).

[0029] The phosphate source includes, for example, at least one selected from the group consisting of ammonium dihydrogen phosphate (NH4H2PO4), diammonium hydrogen phosphate ((NH4)2HPO4), ammonium phosphate ((NH4)3PO4), phosphoric acid (H3PO4), and lithium phosphate (Li3PO4).

[0030] [Heat treatment process] In the heat treatment step, the mixture obtained in the mixing step is heat treated, for example, in air. The heat treatment temperature is preferably 793 K or higher, and more preferably 833 K or higher. The composition will appear as a β phase or an α phase depending on the heat treatment temperature conditions. If the temperature is 850 K to 900 K, a single β phase can be produced. If the temperature exceeds 900 K, a single α phase can be produced. If the temperature is 910 K or higher but 1173 K or lower, the α phase can be produced more stably. Note that above this temperature, lithium ions are likely to scatter.

[0031] The vanadium ion in LiVOPO4 is tetravalent and 3d 1 Although it is in a reduced state, it is stable in high-temperature air, and the valence of vanadium does not exceed 4 even if excess oxygen gas is generated from the mixture during the heat treatment process.

[0032] Although the preferred embodiment of the present invention has been described above, the present invention is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Example]

[0033] As one example of the present invention, the case where the amount of oxygen gas generated from the mixture in the heat treatment step is adjusted to zero will be described in detail below. However, the present invention is not limited to the following example.

[0034] [Sample synthesis] The reagents used for synthesis are listed in Table 1. Polycrystalline LiVOPO4 samples were prepared by heat-treating a mixture consisting of 2 mol of lithium carbonate (Li2CO3), 1 mol of vanadium pentoxide (VO5), 1 mol of vanadium tetraoxide (VO3), and 4 mol of ammonium dihydrogen phosphate (NH4H2PO4) at a fixed temperature between 793 and 973 K in air for 24 to 72 hours. VO3 was prepared by holding VO5 in a hydrogen and nitrogen gas mixture at 973 K for 24 to 48 hours.

[0035] [Table 1]

[0036] It was revealed that two types of phases (β and α) emerge depending on the heat treatment temperature. Figure 2 shows the X-ray powder diffraction patterns of samples prepared in air at temperatures of 833 K, 853 K, and 913 K. The X-ray source used was CuKα radiation, and the row of check marks below each pattern represents the calculated diffraction angle of the major phase. The empty squares, empty diamonds, and empty triangles in the 833 K pattern represent the top five diffraction intensities of the minor phases: β-phase VOPO4, γ-phase VO2O5, and γ'-phase VO2O5, respectively. Figure 3 shows the heat treatment temperature dependence of the diffraction intensity ratio of the minor phase to the major phase. As shown in this figure, the β phase was present as a single phase in heat treatments above 853 K and below 900 K, while the α phase was present as a single phase in heat treatments above 900 K. Inductively coupled plasma optical emission spectroscopy (ICP) revealed that the cation composition of both phases was stoichiometric within 1% accuracy.

[0037] [Lattice constant] X-ray powder diffraction was performed on samples heated and held in air at temperatures between 783K and 973K for 72 hours using a Rigaku Ultima+ diffractometer. The X-ray source was CuKα radiation. The β phase was orthorhombic and the α phase was triclinic, and the heat treatment temperature dependence of their lattice constants was determined as shown in Figures 4 and 5.

[0038] [Optimal heat treatment temperature for β phase production] The lattice constants of the β phase corresponded to the results of X-ray four-axis diffraction for single crystal samples prepared by hydrothermal synthesis by Lii et al. The systematic change in the lattice constants with heat treatment temperatures between 813 and 893 K is thought to be attributable to the lattice stability of the β phase, and therefore 853 K is the optimal heat treatment temperature for producing the β phase.

[0039] [Optimal heat treatment temperature for α-phase production] The lattice constant of the α phase showed little dependence on the heat treatment temperature in the range of 913K to 973K, and corresponded almost to the lattice constant of the stoichiometric composition.

[0040] (Magnetic properties) [Magnetic susceptibility] Magnetic measurements of β-LiVOPO4 were carried out using a Quantum Design MPMS SQUID magnetometer in the temperature range of 2K to 300K and in the magnetic field range of 0T to 4T. The magnetization at 2K was linear with respect to the magnetic field in the magnetic field range below 4T. Figure 6 shows the temperature dependence of the magnetic susceptibility in a magnetic field of 1T. The open circles in the figure represent the raw data of the magnetic susceptibility (χ raw ) The magnetic susceptibility increases as the temperature decreases from the high temperature side, showing a broad maximum at about 40 K, before increasing again below 10 K. The solid circles in this figure represent the data for samples prepared using the hydrothermal synthesis method by Lii et al. (including diamagnetic susceptibility). The data for both methods corresponded closely.

[0041] Although we will not go into detailed discussion here, all experimental data for a spin-1 / 2 antiferromagnetic Heisenberg one-dimensional chain can be quantitatively explained by the molecular field approximation, which takes into account the effective interactions between chains, as shown by the solid line in Figure 6.

[0042] (Microscopic physical properties) [Electron Spin Resonance] Electron spin resonance (hereinafter referred to as ESR) of β-LiVOPO4 was measured using a JEOL TE-200 spectrometer at an X-band frequency of 9.03 GHz in the temperature range of 9 K to 300 K. The ESR spectrum at 298 K was asymmetric, as shown in Figure 7. Here, the spin paramagnetic susceptibility (χ ESR ) is the orbital magnetic susceptibility (χ orb ) and diamagnetic susceptibility (χ dia ) contribution to the magnetic susceptibility (χ raw ) was almost identical to the calculated values. This means that it was confirmed from a microscopic point of view that the prepared sample was single-phase and pure.

[0043] The asymmetric ESR spectrum in Figure 7 can be explained by considering the axially symmetric anisotropy of the g-factor and linewidth of the Lorentzian resonance lineshape, as shown by the solid line in the figure.

[0044] By applying the perturbation theory of spin-orbit coupling to the g-factor derived from ESR data, the orbital magnetic susceptibility (χ orb ) is 7.3×10 -5 emumol -1 This value was almost identical to the value obtained from the magnetic susceptibility analysis.

[0045] Although we will not go into the details here, the temperature dependence of the linewidth derived from the ESR data qualitatively corresponds to the theoretical results of the temperature-induced Tomonaga-Luttinger liquid phase for a three-dimensional weakly coupled spin-1 / 2 chain.

[0046] [Charge / discharge characteristics] The charge-discharge characteristics of LiVOPO4 were tested. The positive electrode consisted of β-LiVOPO4 (weight = 43.464 mg) or α-LiVOPO4 (weight = 94.240 mg), binder polytetrafluoroethylene (PTFE), conductive additive acetylene black, and carbon. The negative electrode was lithium metal foil. The electrolyte was LiPF6 (molarity 1 mol L -1 The solvent was EC:DEC = 1:1 V / V%). A simple battery cell (Figure 9, Table 2) was assembled using these materials and electrochemical tests were performed (C rate ≒ 1 / 48).

[0047] [Table 2] TIFF0007799921000004.tif38170

[0048] Figure 9 shows the capacitance (Q) dependence on output potential (φ). Figure 9(a) shows the charge-discharge characteristics of β-LiVOPO4 in the range of 1.5 V ≦ φ ≦ 5.1 V when starting from the charging process, and the charge-discharge characteristics of α-LiVOPO4 in the range of 3.0 V ≦ φ ≦ 4.5 V when starting from the discharging process. Figure 9(b) shows the discharge-charge characteristics of β-LiVOPO4 in the range of 1.0 V ≦ φ ≦ 4.5 V when starting from the discharging process. The upper horizontal axis in the figure represents the absolute amount (|Δx|) of change in lithium concentration due to desorption and insertion of lithium ions in the positive electrode.

[0049] The charge-discharge characteristics of β-LiVOPO4 shown in Figure 9(a) show a plateau potential of approximately 4.0 V, confirming the deintercalation-intercalation of approximately 1 mol of lithium ions per 1 mol of β-LiVOPO4. Furthermore, the discharge-charge characteristics shown in Figure 9(b) reveal that approximately 1 mol of lithium ions is intercalated-intercalated per 1 mol of β-LiVOPO4. From these results, it is clear that β-LiVOPO4 exhibits approximately two-electron reactions, and the overall electric capacity is approximately 300 Ahkg. -1 It is expected that even better charge / discharge characteristics can be achieved by further refining the battery assembly.

[0050] The charge-discharge characteristics of α-LiVOPO4 shown in Figure 9(a) show that the electric capacity is approximately 10 Ah kg -1 It was confirmed that the results were in close agreement with known results.

[0051] A brief description will be given below of the case where the amount of oxygen gas generated from the mixture in the heat treatment step is adjusted to be finite.

[0052] [Sample synthesis] Polycrystalline samples of LiVOPO4 were prepared by heat-treating a mixture of 1 mol of lithium carbonate, 1 mol of vanadium oxide, and 2 mol of ammonium dihydrogen phosphate in air at a fixed temperature between 793 K and 973 K for 24 to 72 hours.

[0053] Under these conditions, for example, the X-ray powder diffraction pattern of a sample prepared at 873 K showed that β-LiVOPO4 was the main phase, with a very small amount of β-phase VOPO4 present as an impurity phase, while the pattern of a sample prepared at 973 K showed a single phase of α-LiVOPO4.

[0054] The magnetic susceptibility, electron spin resonance, and charge-discharge characteristics of the β-LiVOPO4 prepared in this manner, as well as the charge-discharge characteristics of the α-LiVOPO4, were almost identical to the results for the β-phase and α-phase when the amount of oxygen gas evolved from the mixture during the heat treatment process was adjusted to zero.

[0055] By using LiVOPO4 in lithium ion secondary batteries, the high potential and high capacity of the β phase and the relatively low capacity of the α phase were demonstrated, and it was confirmed that the various physical properties of the β phase correspond to the physical properties of samples prepared by hydrothermal synthesis. By further elucidating this, the present invention was completed.

Claims

1. A method for producing a positive electrode active material LiVOPO4 for a lithium ion secondary battery, which comprises only one raw material mixing step at room temperature and one heat treatment step of the mixture obtained in the raw material mixing step, wherein in the raw material mixing step, a lithium source, a vanadium source, and a phosphate source are mixed so that the molar ratio of Li, V, and P is 1:1:1, and the raw materials used in the raw material mixing step are only the lithium source, the vanadium source, and the phosphate source, and V2O5 and V2O3 are used in combination as the vanadium source, and the heat treatment temperature in the heat treatment step is 850K or higher and 1173K or lower. ４ Manufacturing method.

2. 2. A method for producing an electrode for a lithium ion secondary battery, comprising the step of producing an electrode for a lithium ion secondary battery using the method according to claim 1.

3. 3. A method for producing a lithium ion secondary battery, comprising the steps of: producing a lithium ion secondary battery using the method according to claim 2;

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