JP5298767B2 - Secondary battery electrode, manufacturing method thereof, and secondary battery employing the electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a secondary battery for balancing high energy density with high output density. <P>SOLUTION: This electrode for a secondary battery is used for a positive electrode of a secondary battery including the positive electrode, a negative electrode and an electrolyte. The electrode for a secondary battery is characterized by containing a single ion conducting material, a radical compound and a lithium compound. This secondary battery using the electrode balances high energy density with high output density. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a secondary battery excellent in high-current charge / discharge characteristics and having a high energy density, and an electrode for a secondary battery capable of providing such a secondary battery.

  In recent years, with the widespread use of portable electronic devices such as notebook computers and digital cameras, there is an increasing demand for small high-capacity secondary batteries having high energy density. From the viewpoint of environmental problems, battery cars and hybrid cars using electric power as a part of power have been put into practical use, and there is a demand for higher performance of secondary batteries as power storage means.

  Development of a lithium ion battery is progressing as a promising candidate for a secondary battery that meets these requirements, and development has been carried out to achieve excellent stability and high energy density.

  However, since the lithium ion battery is accompanied by an insertion / release reaction of lithium ions during charging / discharging, the battery performance deteriorates when a large current of a certain level or more is passed. Therefore, for the purpose of exhibiting high battery performance, it is necessary to limit the discharge rate and the charge rate so as not to exceed a certain level.

  On the other hand, a secondary battery using a radical material typified by poly (2,2,6,6-tetramethylpiperidinoxymethacrylate) (PTMA) as a positive electrode uses an ion adsorption / desorption reaction for the battery reaction. Therefore, it is possible to pass a larger current than a normal lithium ion battery, and it is excellent in cycle characteristics, and is expected to be applied to portable electronic devices and electric vehicles.

  By the way, in a lithium ion battery, since an oxide material containing lithium can be contained in the positive electrode material, it is sufficient to increase the lithium oxide material in the positive electrode material when aiming at higher energy density. It is sufficient that the salt concentration in the electrolytic solution is such that the necessary ionic conductivity can be realized.

  However, in order to achieve a high energy density in a secondary battery using a radical material such as PTMA for the positive electrode, the amount of radicals in the positive electrode is increased and, at the same time, a large number of ion sources that react with the radicals are contained in the electrolyte. It was thought that it was necessary to contain. For example, the supporting electrolyte in the electrolytic solution is set to a high concentration according to the capacity of the secondary battery.

Here, when the concentration of the supporting electrolyte as typified by LiPF ₆ is increased, the viscosity of the electrolytic solution increases, the ion diffusion rate decreases, and the ionic conductivity of the electrolytic solution decreases. As a result, the value of the current that can be taken out from the battery is reduced, causing a reduction in output density.

  Furthermore, it has been found that when a large amount of a supporting electrolyte is added to the electrolytic solution, the wettability of the electrolytic solution with respect to the electrode is deteriorated, the internal resistance is increased, and the output of the battery is reduced.

  That is, in a secondary battery using a radical material, it has been difficult to achieve both high energy density and high output density.

As a conventional technique for increasing the energy density of a secondary battery using a radical compound, a technique in which the positive electrode contains a stable radical compound and holds an electrolyte salt is disclosed. (Patent Document 1)
However, when the electrolyte salt is held in the positive electrode, the electrolyte salt held in the positive electrode is dissolved in the electrolytic solution due to an increase in battery temperature when the vehicle is mounted, and as a result, the viscosity of the electrolytic solution is reduced. There was a possibility that the diffusion rate of ions would increase and decrease.

A technique is shown in which an anionic material having phosphoric acid, sulfonic acid, carboxylic acid, or the like is mixed with an electrode having a radical compound. (Patent Document 2)
However, in this technique, if the solvent of the paste formed by mixing the materials is an organic solvent, the dispersion is considered to be insufficient. As a result, there is a high possibility that the output will be lowered, and it is not perfect.

Further, these techniques have a problem in terms of energy density because only an organic material having a π-conjugated electron cloud or a radical is used as an active material.
JP 2004-259618 A JP 2006-324179 A

  The present invention has been completed in view of the above circumstances, and it should be solved to provide a secondary battery in which high energy density and high output density are compatible, and an electrode for a secondary battery that can constitute such a secondary battery. Let it be an issue. Furthermore, it is an object to be solved to provide a manufacturing method capable of manufacturing such an electrode for a secondary battery.

  As a result of intensive investigations aimed at solving the above-mentioned problems, the inventors of the present invention have a single ion conductive material and a radical compound, and the lithium compound is contained and coexisted so that the characteristics of the radical compound are sufficient. The knowledge that it can be demonstrated was obtained. In other words, the single ion conductive material coexists with the radical compound, so that the characteristics of both the radical material and the lithium compound can be sufficiently exhibited without adding a supporting electrolyte at a high concentration in the electrolytic solution, and a high energy density can be obtained. It can be realized. The following invention has been completed based on this finding.

  The battery reaction involving the radical compound at the positive electrode will be described. The radical part of the radical compound is oxidized during charging to become a cation and participates in the battery reaction by releasing electrons. In the secondary battery electrode of the present invention, the anion portion generated by dissociation of the cation from the single ion conductive material compensates for the charge of the cation generated from the radical compound, so that the battery reaction can be continued.

  Since the reaction can easily proceed by further reducing the distance between the single ion conductive material and the radical material, it is desirable that the single ion conductive material and the radical material are mixed. .

  In particular, it is possible to employ a manufacturing method in which a single ion conductive material and a radical compound are dispersed and then mixed with a lithium compound. Further, by adopting a configuration that can be manufactured by the manufacturing method, the interaction between the single ion conductive material and the radical compound can proceed smoothly, and the internal resistance can be reduced when applied to a battery. .

  Further, when the secondary battery electrode is formed of a current collector and a positive electrode mixture formed on the surface of the current collector, the thickness of the positive electrode mixture is 30 μm or more (particularly 50 μm or more). In some cases, it takes time for the ions in the electrolyte to reach the inside of the electrode, but the single ion conductive material acts as a substitute for the ions in the electrolyte. Even in this case, a sufficiently high output can be achieved. Therefore, even when the thickness of the positive electrode mixture is increased, a high output density can be realized in the concentration range where the electrolyte salt concentration is used in the lithium battery.

This single ion conductive material is a material having a functional group of —COOX, —SO ₃ X (X is H 2, Li or Na) at the end of its molecular structure, and after the cation X is dissociated, —COO ^-, -SO ₃ ^- generate, which it is possible to compensate the charge of the cations generated from radical compounds, such structures it is desirable. Here, X is preferably Li from the viewpoint of improving the energy density.

  Furthermore, so that the single ion conductive material is not dissolved in the electrolytic solution and disappears from the electrode, and the viscosity of the electrolytic solution is not increased by dissolving in the electrolytic solution, The single ion conductive material is preferably insoluble in the electrolytic solution.

  Here, insoluble in the electrolytic solution means that, for example, when a single ion conductive material is added to a standard electrolytic solution used in a lithium battery, an insoluble precipitate is observed. . In particular, when ionic conductivity is 0.1 mS / cm or less when 0.1 M is added to an electrolytic solution containing ethylene carbonate and diethyl carbonate in a ratio of 3: 7, which is a typical electrolytic solution (more Preferably, when 0.1 M is added, it is insoluble at 0.01 mS / cm or less.

  In addition, the single ion conductive material may be a polymer, and the higher the molecular weight, the more insoluble in the electrolyte solution. This single ion conductive material is significantly improved in insolubility in the electrolytic solution by using a polymer having an average molecular weight of 100,000 or more.

  As a specific desirable compound as a single ion conductive material, a lithium salt of an aliphatic organic acid such as lithium acetate or lithium butyrate, a lithium salt of an aromatic organic acid such as lithium p-styrenesulfonate or lithium benzoate, Among the lithium salts of the above aliphatic and aromatic organic acids such as polystyrene sulfonate lithium and lithium polyacrylate, polymerized ones can also be used.

  It is desirable that the radical material has a structure containing a nitroxy radical group in the molecule from the viewpoint of improving the power density by performing adsorption / desorption reaction by oxidation and reduction of the nitroxy radical group.

The lithium compound is desirably a material that can insert and remove Li ⁺ used in a normal lithium battery or the like. Particularly lithium compound, the structural formula _{Li 1-Z} alpha or _{Li 1-Z βPO 4 (Z} is the number of 0 to 1) is shown, the structural formula _{Li 1-Z α Li 1-} Z CoO 2, Li 1 _{-Z MnO 2, Li 1-Z} Mn 2 O 4, a _Li 1-Z NiO _2, the structural formula _{Li 1-Z βPO 4 (β} is Fe or Ni, Mn, is one or more than one Co solid Dissolved material) (Z is a number from 0 to 1), and a material containing at least one of these is desirable.

  Then, for the purpose of quickly giving and receiving electrons generated by the battery reaction that proceeds with the radical compound, a conductive material in which the single ion conductive material, the radical material, and the lithium compound are mixed can be included. Among these, a conductive polymer can be introduced into a part of the conductive material. This is because a high energy density can be expected due to the adsorption and desorption of the anion derived from the single ion conductive material and / or the anion derived from the electrolyte salt to the conductive polymer.

  The electrode for a secondary battery according to the present invention can achieve both high output density and high energy density by having the above configuration. In particular, since a high energy density can be realized even when the concentration of the supporting electrolyte in the electrolyte is low, an increase in the viscosity of the electrolyte caused by dissolving the supporting electrolyte at a high concentration can be suppressed, resulting in a high output density. became.

  The electrode for secondary battery (and the manufacturing method thereof) and the secondary battery of the present invention will be described in detail below based on the embodiments.

  The electrode for a secondary battery of this embodiment can be used as a positive electrode of a secondary battery having a positive electrode, a negative electrode, and a supporting electrolyte. The electrode for secondary batteries of this embodiment has a single ion conductive material and a radical compound, and contains a lithium compound.

  Further, when the positive electrode is formed of a current collector and a positive electrode mixture formed on the surface of the current collector, the thickness of the positive electrode mixture is 30 μm or more (particularly 50 μm or more). The performance improvement of the electrode for secondary batteries becomes remarkable. The positive electrode mixture contains a single ion conductive material, a radical compound, and a lithium compound. However, when the thickness of the positive electrode mixture falls within the above-described range, supply of electrolyte ions necessary for the battery reaction in the positive electrode mixture is prevented. It is not sufficient only from the electrolyte salt in the electrolyte. The shortage can be compensated for by adding a single ion conductive material coexisting with radicals, and the effect of maintaining battery output is strongly exhibited. This effect becomes higher as the positive electrode mixture is thicker, and the higher effect is exhibited particularly when the thickness is 50 μm or more.

  A single ion conductive material forms an anion structure after dissociating cations, and is a material that can desorb ions corresponding to radical compounds in an environment where the secondary battery electrode is applied to a secondary battery. is there.

  The single ion conductive material is desirably mixed at a ratio of 10% to 150% based on the number of moles of radicals.

  The sum of the masses of the single ion conductive material and the radical material is preferably 10% or more and 90% or less (mass basis) based on the mass of the whole positive electrode mixture, and is 10% or more and 60% or less (mass basis). More desirable.

  The single ion conductive material exerts a strong effect in the vicinity of the radical, but does not affect the characteristics of the lithium compound. Therefore, it is desirable to arrange the single ion conductive material as close to the radical material as possible.

  In particular, in order to place a single ion conductive material in the vicinity of the radical material, a radical material is added and mixed in a dispersion prepared by mixing and dispersing only the radical material and the single ion conductive material in advance. A single ion conductive material can be disposed in the vicinity. As a result, the radical material and the single ion conductive material are in close proximity. In particular, when both the radical material and the single ion conductive material are composed of a polymer compound, it is desirable that entanglement occurs between the polymer chains.

  As a specific mixing method, for example, both of them (radical material and single ion conductive material) are mixed by stirring until they are uniformly dissolved in some solvent, and then mixed with a lithium compound ( After mixing in a solvent until uniform, the solvent can be removed and the lithium compound can be mixed in a solid state.The dissolution in the solvent does not matter before and after mixing. In addition, a functional group capable of causing interaction between the single ion conductive material and the radical material can be introduced. Moreover, the method (The method etc. which mix by a mechanochemical effect | action using grinding | pulverization operation etc.) which mixes both in a solid state is mentioned. Furthermore, when the single ion conductive material and the radical material are made of a polymer compound, a method of proceeding in the same reaction system when polymerizing them and entanglement between molecular chains simultaneously with the polymerization reaction can be mentioned.

  The single ion conductive material is desirably in a solid state in the secondary battery, and further desirably not dissolved when a liquid is used as the existence form of the supporting electrolyte. Here, the form of the compound outside the secondary battery (before applying the secondary battery electrode to the secondary battery and before manufacturing the secondary battery electrode) is not particularly limited.

 A radical compound is a compound having a radical in its molecular structure. When the secondary battery electrode of this embodiment is applied to a secondary battery, the oxidation-reduction in the radical in the molecular structure is directly related to the battery reaction. It is a compound. Accordingly, the radical compound can be appropriately selected depending on the type of secondary battery to which the secondary battery electrode is applied (the electrode to be combined, the type of supporting electrolyte, and the target battery performance).

  The electrode for a secondary battery according to the present embodiment can further contain a conductive material for the purpose of smoothly transferring and receiving electrons progressing with the radical compound. The conductive material is blended for the purpose of improving the electrical conductivity between the radical of the radical compound and the current collector that collects the current from the radical compound. It is desirable that they are arranged. Alternatively, a conductive polymer can be used for part of the conductive material. The conductive material is preferably mixed at a rate of 5% to 50%, more preferably 5% to 40%, based on the total mass of the positive electrode mixture.

  Specific examples of the conductive material include ketjen black, acetylene black, carbon black, graphite, carbon nanotube, and amorphous carbon. Examples thereof include conductive polymer polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene.

The lithium compound is a material capable of removing and inserting Li ⁺ , and includes a lithium-metal composite oxide having a layered structure or a spinel structure. Specifically, metal oxide-based materials such as Li _1-Z NiO ₂ , Li _1-Z MnO ₂ , Li _1-Z Mn ₂ O ₄ , and Li _1-Z CoO ₂ . Furthermore, there is Li _1-Z βPO ₄ (β is a material in which one or more of Fe, Ni, Mn, and Co are dissolved), and one or more of them can be included. Z in this illustration shows the number of 0-1. A material obtained by adding or substituting a transition metal such as Li, Mg, Al, or Co, Ti, Nb, or Cr may be used. Moreover, not only these lithium-metal composite oxides are used alone, but also a plurality of them can be mixed and used. In particular, LiFePO ₄ may be mentioned.

  Furthermore, the electrode for the secondary battery of the present embodiment includes a dispersion material that disperses a lithium compound, a radical compound, an active material, and the like, a binder that binds them, and a current collector that collects electrons generated by the radical compound. A body (which can be formed from a metal foil or the like) or the like.

  The dispersion material and the binder are preferably formed from a polymer material, and are desirably materials that are chemically and physically stable in the atmosphere in the secondary battery.

  The electrode for a secondary battery according to the present embodiment includes (a) a current collector formed from a metal foil or the like, and (b) a mixture of a radical compound and a lithium compound as essential elements. It is common to use a layer made of an electrode mixture in which an additive selected from the above materials is mixed as necessary, and having an electrode mixture layer formed on the surface of the current collector . Examples of a method for forming the electrode mixture layer on the surface of the current collector include a method in which the electrode mixture is dispersed or dissolved in an appropriate dispersion medium and then applied to the surface of the current collector and dried.

The secondary battery electrode of the present embodiment is combined with a negative electrode to constitute a secondary battery. As the active material of the combined negative electrode, a compound that absorbs lithium ions during charging and releases them during discharging can be employed. The negative electrode active material is not particularly limited in its material configuration, and known materials and configurations can be used. For example, a lithium metal, a carbon material such as graphite or amorphous carbon, an alloy material containing silicon, tin, or the like, or an oxide material such as Li ₄ Ti ₅ O ₁₂ or Nb ₂ O ₅ .

  Although it does not specifically limit as supporting electrolyte, What melt | dissolved supporting salt in solvent, such as an organic solvent, self-liquid ionic liquid, and what melt | dissolved supporting salt further in the ionic liquid can be illustrated. As an organic solvent, the organic solvent normally used for the electrolyte solution of a lithium secondary battery can be illustrated. For example, carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones, oxolane compounds and the like can be used. In particular, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like, and mixed solvents thereof are suitable.

  Among these organic solvents mentioned in the examples, in particular, by using one or more non-aqueous solvents selected from the group consisting of carbonates and ethers, the solubility of the supporting salt, the dielectric constant and the viscosity are excellent, and the battery The charge / discharge efficiency is also preferable.

An ionic liquid will not be specifically limited if it is an ionic liquid normally used for the electrolyte solution of a lithium secondary battery. For example, examples of the cation component of the ionic liquid include N-methyl-N-propylpiperidinium and dimethylethylmethoxyammonium cation, and examples of the anion component include BF ₄ ⁻ , N (SO ₂ C ₂ F ₅ ). ₂ ^-, and the like.

The supporting salt used in the supporting electrolyte of the present embodiment is not particularly limited. For example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiSbF ₆ , LiSCN, LiClO ₄ , LiAlCl ₄ , NaClO ₄ , BClO ₄ , NaI, and salt compounds such as derivatives thereof. Among these, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiCF ₃ SO ₃ derivative, LiN (CF ₃ From the viewpoint of electrical characteristics, it is preferable to use one or more salts selected from the group consisting of a derivative of SO ₂ ) _{2 and} a derivative of LiC (CF ₃ SO ₂ ) ₃ .

  It is desirable to interpose a separator that is a member that achieves both electrical insulation and ion conduction between the positive electrode and the negative electrode. When the supporting electrolyte is liquid, the separator also serves to hold the liquid supporting electrolyte. Examples of the separator include a porous synthetic resin film, particularly a porous film of a polyolefin polymer (polyethylene or polypropylene). Furthermore, it is preferable that the separator has a larger size than the positive electrode and the negative electrode for the purpose of ensuring the insulation between the positive electrode and the negative electrode.

  In general, the positive electrode, the negative electrode, the supporting electrolyte, the separator, and the like are housed in some case. The case is not particularly limited and can be made of a known material and form.

  The secondary battery electrode and the secondary battery of the present invention will be described in more detail based on the following specific examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

[Example 1]
(Preparation of positive electrode as secondary battery electrode of this example)
Lithium polyacrylate as a single ion conductive material, PTMA as a radical compound, LiNiO ₂ as a lithium compound, carbon black as a conductive material, sodium carboxymethylcellulose (CMC), polyethylene oxide (PEO), water as a dispersion medium Was mixed and dispersed at a mass ratio (parts by mass) of 8: 26: 44: 20: 1: 1: 90. Furthermore, 1 part by mass of polytetrafluoroethylene (PTFE) as a binder was added and dispersed to obtain a slurry-like positive electrode mixture.

  Here, the amount of lithium polyacrylate added was adjusted such that the ratio of the carboxylate anion of lithium polyacrylate to the nitroxy radical present in the radical was 100%.

The obtained slurry was applied to both surfaces of a positive electrode current collector, which is an aluminum thin film, dried, and pressed to obtain a positive electrode plate. The thickness of the positive electrode mixture was adjusted to 20 μm. (Preparation of electrolyte)
LiPF ₆ was added at a concentration of 1.0 mol / L to an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a mass ratio of 3: 7 to obtain an electrolytic solution.

(Production of coin-type battery)
FIG. 1 shows a cross-sectional view of the produced coin-type battery. The positive electrode and negative electrode other than the electrolytic solution were the same as those in Example 1. That is, the prepared positive electrode of Example 1 was used for the positive electrode 1 as it was, and lithium metal was used for the negative electrode 2. As the electrolytic solution 3, the prepared electrolytic solution was used. Separator 7 manufactured a coin type battery using a 25-micrometer-thick polyethylene porous membrane, respectively. The positive electrode 1 has a positive electrode current collector 1a, and the negative electrode 2 has a negative electrode current collector 2a.

  These power generation elements were housed in a stainless steel case (consisting of a positive electrode case 4 and a negative electrode case 5). The positive electrode case 4 and the negative electrode case 5 serve as a positive electrode terminal and a negative electrode terminal. A gasket 6 made of polypropylene is interposed between the positive electrode case 4 and the negative electrode case 5 to ensure the sealing and insulating properties between the positive electrode case 4 and the negative electrode case 5.

[Example 2]
The production situation of the slurry-like positive electrode mixture is the same as in Example 1.
The obtained slurry was applied to both surfaces of a positive electrode current collector, which is an aluminum thin film, dried, and pressed to obtain a positive electrode plate. The thickness of the positive electrode mixture was adjusted to 30 μm.
About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

Example 3
The production situation of the slurry-like positive electrode mixture is the same as in Example 1.
The obtained slurry was applied to both surfaces of a positive electrode current collector, which is an aluminum thin film, dried, and pressed to obtain a positive electrode plate. The thickness of the positive electrode mixture was adjusted to 50 μm.
About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

Example 4
The production situation of the slurry-like positive electrode mixture is the same as in Example 1.
The obtained slurry was applied to both surfaces of a positive electrode current collector, which is an aluminum thin film, dried, and pressed to obtain a positive electrode plate. The thickness of the positive electrode mixture was adjusted to 100 μm.
About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

[Comparative Example 1]
PTMA as a radical compound, LiNiO ₂ as a lithium compound, carbon black as a conductive material, carboxymethylcellulose sodium salt (CMC), polyethylene oxide (PEO), and water as a dispersion medium are 34: 44: 20: 1: 1: It was mixed and dispersed at a mass ratio (parts by mass) of 90. The thickness of the positive electrode mixture was prepared to be 20 μm as in Example 1.
About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

[Comparative Example 2]
The production situation of the slurry-like positive electrode mixture is the same as in Comparative Example 1.
The obtained slurry was applied to both surfaces of a positive electrode current collector, which is an aluminum thin film, dried, and pressed to obtain a positive electrode plate. The thickness of the positive electrode mixture was adjusted to 30 μm.
About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

[Comparative Example 3]
The production situation of the slurry-like positive electrode mixture is the same as in Comparative Example 1.
The obtained slurry was applied to both surfaces of a positive electrode current collector, which is an aluminum thin film, dried, and pressed to obtain a positive electrode plate. The thickness of the positive electrode mixture was adjusted to 50 μm.
About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

[Comparative Example 4]
The production situation of the slurry-like positive electrode mixture is the same as in Comparative Example 1.
The obtained slurry was applied to both surfaces of a positive electrode current collector, which is an aluminum thin film, dried, and pressed to obtain a positive electrode plate. The thickness of the positive electrode mixture was adjusted to 100 μm.
About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

[Coin battery evaluation test method]
[Initial capacity]
The coin-type battery is placed in a constant temperature bath at 25 ° C., and is charged at a constant current of up to 4.1 V at a current value equivalent to 1C (1C is a current value that can discharge the battery capacity in 1 hour). Constant current discharge was performed up to 3.0V. After conducting this test five times, the fifth discharge capacity value was used as the initial capacity value of each coin battery.

(Initial output measurement)
The coin-type battery was placed in a constant temperature bath at 25 ° C., charged at a constant current and a constant voltage up to 4.1 V at a current value equivalent to 0.2 C, and discharged for 10 seconds while changing the current value. After increasing the current value and measuring a current value of 3.0 V after 10 seconds, the product of the current value and the voltage value (3.0 V) was used as the initial output voltage.

  The initial capacity value and the initial output value are expressed as a ratio when Comparative Example 1 is set to 100.

From Table 1, it can be seen that the present example has a larger initial output than the comparative example, although the initial capacity is not much different. It was also confirmed that the thicker the positive electrode composite, the more prominent the effect is. This is because the effects of radical PTMA added in the positive electrode and lithium polyacrylate, which is a single ion conductive material, are large. In the battery, PTMA a radical at the time of charging is PF ₆ of LiPF ₆ in the electrolytic solution becomes cation ^- with adsorption and, LiNiO ₂ which are mixed with radical is performing the reaction by conduction Li ^+. That is, when the battery is charged, the LiPF ₆ concentration in the battery decreases. This decrease in the LiPF ₆ concentration decreases the ionic conductivity of the electrolytic solution, and as a result, it becomes difficult to achieve a high output. However, in this embodiment in which a single ion conductive material is present inside, a part of the single ion conductive material is adsorbed and desorbed with radicals, and suppresses a decrease in ionic conductivity due to a decrease in the salt concentration of the electrolyte, resulting in a high output. It is estimated that That is, it was found that the effect of mixing the single ion conductive material and the radical material is very large. In addition, the thicker the positive electrode mixture, the more prominent the effect is. This is because the thicker the positive electrode mixture, the greater the amount of radicals present in the electrode and the smaller the amount of electrolyte present in the gap of the positive electrode compared to the amount of electrolyte present between the positive and negative electrodes. It is presumed that the effect of high ion concentration due to the active material has appeared strongly.

  In the following, verification is carried out at a positive electrode mixture thickness of 50 μm where the effect of adding a single ion conductive material is exerted strongly.

Example 5
Lithium polyacrylate as a single ion conductive material, PTMA as a radical compound, LiNiO ₂ as a lithium compound, carbon black as a conductive material, sodium carboxymethylcellulose (CMC), polyethylene oxide (PEO), water as a dispersion medium Were mixed and dispersed at a mass ratio (parts by mass) of 4.6: 29.4: 44: 20: 1: 1: 90. Furthermore, 1 part by mass of polytetrafluoroethylene (PTFE) as a binder was added and dispersed to obtain a slurry-like positive electrode mixture.

  Here, the amount of lithium polyacrylate added was adjusted such that the ratio of the carboxylate anion of lithium polyacrylate to the nitroxy radical present in the radical was 50%. About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

Example 6
Lithium polyacrylate as a single ion conductive material, PTMA as a radical compound, LiNiO ₂ as a lithium compound, carbon black as a conductive material, sodium carboxymethylcellulose (CMC), polyethylene oxide (PEO), water as a dispersion medium Was mixed and dispersed at a mass ratio (parts by mass) of 1.0: 33.0: 44: 20: 1: 1: 90. Furthermore, 1 part by mass of polytetrafluoroethylene (PTFE) as a binder was added and dispersed to obtain a slurry-like positive electrode mixture.

  Here, the amount of lithium polyacrylate added was adjusted such that the ratio of the carboxylate anion of lithium polyacrylate to the nitroxy radical present in the radical was 10%. The thickness of the positive electrode mixture was prepared to be 50 μm as in Example 3.

  About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

Example 7
Lithium polyacrylate as a single ion conductive material, PTMA as a radical compound, LiNiO ₂ as a lithium compound, carbon black as a conductive material, sodium carboxymethylcellulose (CMC), polyethylene oxide (PEO), water as a dispersion medium Were mixed and dispersed at a mass ratio (parts by mass) of 10.8: 23.2: 44: 20: 1: 1: 90.

  Here, the amount of lithium polyacrylate added was adjusted such that the ratio of the carboxylate anion of lithium polyacrylate to the nitroxy radical present in the radical was 150%. The thickness of the positive electrode mixture was prepared to be 50 μm as in Example 3.

  About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

[Comparative Example 5]
LiNiO ₂ as a lithium compound, carbon black as a conductive material, carboxymethyl cellulose sodium salt (CMC), polyethylene oxide (PEO), and water as a dispersion medium in a mass ratio (parts by mass) of 77: 20: 1: 1: 90 And mixed and dispersed. The thickness of the positive electrode mixture was prepared to be 50 μm as in Example 1. About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1.

  Table 2 shows the positive electrode compositions of Examples 3 and 5-7 and Comparative Examples 3 and 4.

  Here, it is desirable that both the initial capacity and the initial output are large.

  From Table 3, in this example, by changing the amount of lithium polyacrylate, which is a single ion conductive material, together with the amount of radicals, there was no significant difference in initial capacity, but a large difference in initial output appeared.

As shown in Comparative Examples 1 to 4, the effect is very small by simply mixing LiNiO ₂ and the radical material PTMA, and the amount of lithium polyacrylate added in this example is also present in the radicals. The ratio of the carboxylate anion of the lithium polyacrylate to the nitroxy radical is at least 50%. In addition, there is no problem in the scope of the present embodiment in terms of increasing the amount, but when the amount exceeds 150%, the lithium polyacrylate, which is a single ion conductive material, is an insulator, so the amount of conductive material, etc. It is necessary to increase the amount, and as a result, the amount of active material is decreased and the initial capacity is decreased. Therefore, it is important that the addition amount of lithium polyacrylate is 50% or more and 150% or less with respect to the number of radical addition moles. It has also been confirmed that the thicker the electrode mixture, the stronger the effect of the addition amount of the single ion conductive material.

Example 8
P-Styrene sulfonate lithium as a single ion conductive material, PTMA as a radical compound, LiNiO ₂ as a lithium compound, carbon black as a conductive material, carboxymethylcellulose sodium salt (CMC), polyethylene oxide (PEO), as a dispersion medium Were mixed and dispersed at a mass ratio (parts by mass) of 8: 26: 44: 20: 1: 1: 90. Furthermore, 1 part by mass of polytetrafluoroethylene (PTFE) as a binder was added and dispersed to obtain a slurry-like positive electrode mixture.

  Here, the addition amount of lithium p-styrenesulfonate was adjusted such that the ratio of the sulfonate anion of lithium p-styrenesulfonate to the nitroxy radical present in the radical was 100%. About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1. The thickness of the positive electrode mixture was adjusted to 50 μm.

  From Table 4, even when lithium p-styrene sulfonate having a monomer structure is used as the single ion conductive material, it is possible to realize a high initial output as compared with the system in which the single ion conductive material and the radical material are not added. It became clear.

Example 9
After mixing and dispersing lithium polyacrylate as a single ion conductive material and PTMA as a radical compound in N-methylpyrrolidone, N-methylpyrrolidone is removed, and then LiNiO ₂ as a lithium compound, as a conductive material Carbon black, carboxymethylcellulose sodium salt (CMC), polyethylene oxide (PEO), and water as a dispersion medium were mixed and dispersed at a mass ratio (parts by mass) of 8: 26: 44: 20: 1: 1: 90. Furthermore, 1 part by mass of polytetrafluoroethylene (PTFE) as a binder was added and dispersed to obtain a slurry-like positive electrode mixture.

  Here, the amount of lithium polyacrylate added was adjusted such that the ratio of the carboxylate anion of lithium polyacrylate to the nitroxy radical present in the radical was 100%. About the negative electrode other than the positive electrode and the electrolyte, a coin-type battery was manufactured using the same one as in Example 1. The thickness of the positive electrode mixture was adjusted to 50 μm.

From Table 5, the single ion conductive material can be selectively disposed in the vicinity of PTMA by mixing and dispersing the single ion conductive material with PTMA, which is a radical compound, and then mixing with LiNiO _2. Both initial capacity and high initial output can be realized.

In this example, the verification is performed in the case of lithium polyacrylate as the single ion conductive material. However, when other single ion conductive materials are used, the single ion conductive material and It became clear that the method of dispersing PTMA, which is a radical compound, and then mixing with LiNiO ₂ shows higher performance than the case of mixing three types.

  Even if polyacrylic acid lithium, which is a single ion conductive material, is added as an alternative to the binder to polyethylene oxide (PEO) and polytetrafluoroethylene (PTFE) used in the battery preparation in this example. It has been confirmed that the same effect can be obtained.

Furthermore, in this example, lithium polyacrylate and lithium p-styrene sulfonate were used as the single ion conductive material, and LiNiO ₂ was used as the lithium compound. Have confirmed.

  In this example, lithium metal was used for the negative electrode. However, it has been confirmed that the same effect can be obtained when a carbon negative electrode and an alloy negative electrode are used.

  In other words, as in this example, it was revealed that a high-capacity and high-power battery can be manufactured by using a positive electrode in which a single ion conductive material, a radical material, and a lithium compound are mixed.

It is a longitudinal cross-sectional view which shows roughly the structure of the coin-type battery manufactured in the present Example.

Explanation of symbols

1 ... Positive electrode
1a: positive electrode current collector
2 ... Negative electrode
2a ... Negative electrode current collector
3 ... Electrolyte 4 ... Positive electrode case
5 ... Negative electrode case
6… Gasket
7 ... Separator
10 ... Coin-type non-aqueous electrolyte secondary battery

Claims (15)

A secondary battery electrode used for the positive electrode of a secondary battery having an electrolyte solution in which a supporting salt is dissolved in a positive electrode, a negative electrode, and an organic solvent ,
Containing a single ion conductive material, a radical compound and a lithium compound ,
The electrode for a secondary battery, wherein the single ion conductive material is insoluble in the electrolytic solution .   The secondary battery electrode according to claim 1, wherein the single ion conductive material, the radical compound, and the lithium compound are mixed.   The electrode for a secondary battery according to claim 2, which can be manufactured by dispersing the single ion conductive material and the radical compound and then mixing the lithium compound.   The positive electrode has a thin-film current collector, a positive electrode mixture formed on the surface of the current collector, containing the single ion conductive material, the radical compound, and the lithium compound, and the positive electrode mixture The electrode for a secondary battery according to claim 1, wherein the thickness is 30 μm or more.   The secondary battery electrode according to claim 4, wherein the positive electrode mixture has a thickness of 50 μm or more.   The single ion conductive material includes a partial structure that is desorbed to become a cation, and an anion structure that is a remaining structure after the cation structure is desorbed and generates an anion after the cation structure is desorbed. The electrode for a secondary battery according to any one of claims 1 to 5, which is a material having Said single ion conducting material, -COOX at the end of the molecular structure, (the X H, Li or Na) _-SO 3 X according to any one of claims 1 to 6, which is a material having a functional group Secondary battery electrode.   The secondary battery electrode according to claim 7, wherein X is Li.   The secondary battery electrode according to claim 1, wherein the single ion conductive material is insoluble in an electrolytic solution.   The secondary battery electrode according to claim 1, wherein the radical material contains a nitroxy radical group in a molecule. The electrode for a secondary battery according to claim 1, wherein the lithium compound is a material capable of removing and inserting Li ⁺ . The lithium compound has a structural formula of Li _1-Z α (α is CoO ₂ , MnO ₂ , Mn ₂ O ₄ , NiO ₂ ) or Li _1-Z βPO ₄ (β is one of Fe, Ni, Mn, Co, or The electrode for secondary batteries of any one of Claims 1-11 in which 1 or more types of compounds shown by the material (Z is the number of 0-1) of 1 or more types are contained are contained.   The electrode for a secondary battery according to claim 2, further comprising a conductive material mixed with the single ion conductive material, the radical compound, and the lithium compound. Used for a secondary battery having an electrolyte solution in which a supporting salt is dissolved in a positive electrode, a negative electrode, and an organic solvent,
Containing a single ion conductive material, a radical compound and a lithium compound ,
The single ion conductive material is insoluble in the electrolyte;
A method for producing an electrode for a secondary battery, wherein the single ion conductive material and the radical compound are dispersed and then mixed with the lithium compound. A secondary battery comprising the positive electrode according to any one of claims 1 to 13, a negative electrode, and an electrolyte.

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