JP2008235249A - Electrode for secondary battery and method for making same, and secondary battery using this electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for secondary batteries that provides a high energy density and a high output density. <P>SOLUTION: An electrode for secondary batteries comprising a positive electrode, a negative electrode and a support electrolyte is used as at least one of the electrodes and comprises a radical compound and a single ion-conducting material. As to a battery reaction in which a radical compound takes part, an instance of a reaction at a positive electrode is illustrated. A radical moiety of a radical compound is oxidized into a cation during a charge, thus taking part in the battery reaction. In the electrode for secondary batteries, a cation dissociates from the single ion-conducting material to generate an anion and the charge of the cation generated from the radical compound is thus compensated, thereby permitting the battery reaction to be continued. The single ion-conducting material is a material having a group of -COOX or SO<SB>3</SB>X wherein X is Li or Na at a terminal end of a molecular structure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a secondary battery that has excellent large current charge / discharge characteristics and high energy density, a secondary battery electrode that can provide such a secondary battery, and a method for manufacturing the same.

  In recent years, with the widespread use of portable electronic devices such as notebook computers and digital cameras, there has been an increasing demand for small high-capacity secondary batteries having high energy density. From the viewpoint of environmental problems, electric vehicles and hybrid vehicles using electric power as 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 an ionization reaction. Therefore, it is possible to pass a larger current than a normal lithium ion battery, the cycle characteristics are excellent, and application to portable electronic devices and electric vehicles is expected.

  By the way, in order to realize 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 included 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 is increased, the ion diffusion rate is decreased, and the conductivity of the electrolytic solution is decreased. 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 is disclosed in which a radical compound is used as a positive electrode active material and the spin concentration of the radical compound is limited (Patent Document 1).
A technique of mixing an anionic material having phosphoric acid, sulfonic acid, carboxylic acid or the like with an electrode having a radical compound has been disclosed (Patent Document 2).
However, in this technology, it is thought that dispersion is insufficient when the solvent of the paste formed by mixing the materials is an organic solvent, and when the solvent is water, the pH of the paste is reduced, corroding the aluminum current collector foil, In any case, there is a high possibility that the output will decrease as a result, and it is not perfect yet.
JP 2002-151084 A JP 2006-324179 A

  The present invention has been completed in view of the above circumstances, and provides a secondary battery in which high energy density and high output density are compatible, a secondary battery electrode capable of constituting such a secondary battery, and a method for manufacturing the same. Is a problem to be solved.

(1) As a result of intensive studies by the present inventors for the purpose of solving the above problems, a single ion conductive material having a functional group of —COOX or —SO ₃ X (X is Li or Na) in the molecular structure. And the knowledge that the characteristic of a radical compound can fully be exhibited by making a radical compound coexist in an electrode was acquired. That is, the single ion conductive material can coexist with the radical compound to realize a high energy density without adding a supporting electrolyte at a high concentration in the electrolytic solution. The following invention has been completed based on this finding.

  That is, the electrode for a secondary battery of the present invention contains a single ion conductive material capable of supplying ions that react with a radical compound (for example, an anion when the electrode is used for a positive electrode) in the electrode having the radical compound. In order to solve the above-mentioned problem, at least one electrode of a secondary battery having a positive electrode, a negative electrode, and a supporting electrolyte, which contains a radical compound and a single ion conductive material. Here, the single ion conductive material is a material in which only one type of anion or cation moves. This secondary battery electrode is preferably applied to the positive electrode.

  The battery reaction involving a radical compound will be described by taking the reaction at the positive electrode as an example. The radical portion of the radical compound is involved in the battery reaction by being oxidized during charging to become a cation and release electrons. In the secondary battery electrode of the present invention, the cation is dissociated from the single ion conductive material to generate an anion, and the battery reaction can be continued by compensating the charge of the cation generated from the radical compound.

  Therefore, since the reaction can be easily advanced by further reducing the distance between the radical compound and the single ion conductive material, (a) the radical compound and the single ion conductive material are mixed together. (B) The radical compound and the single ion conductive material are preferably chemically bonded and include those that form the same molecule.

In addition, the single ion conductive material includes a cation structure (Li ⁺ or Na ⁺ ) that is a partial structure that is desorbed to become a cation, and a remainder after the cation structure is desorbed, and the cation structure is desorbed. is a partial structure for generating anions after releasing an anion structure (-COO ^- or -SO 3 ^_-) it is desirable and a material having a.
Further, when the single ion conductive material is not a polymer (in the case of a monomer), it has —COOX or —SO ₃ X (X is Li or Na) at the end of the molecular structure, and per functional group If the molecular weight of is large, the amount of the single ion conductive material added increases, the amount of active material decreases, and the battery capacity decreases. In particular, the single ion conductive material is a polymer, and in this case, the molecular weight of the monomer as a unit is preferably 300 or less, more preferably 200 or less.

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 0.1M is added to an electrolytic solution containing ethylene carbonate and diethyl carbonate in a ratio of 3: 7, which is a typical electrolytic solution, the electrical conductivity is desirably 0.1 mS / cm or less. More preferably, it is 0.01 mS / cm or less when 0.1 M is added.
In addition, the single ion conductive material desirably has a polymer structure, because the molecular weight increases so that it becomes insoluble in the electrolytic solution. By making the average molecular weight in this polymer structure 100,000 or more, the insolubility in the electrolytic solution is remarkably improved.

For the purpose of promptly giving and receiving electrons generated by the battery reaction that proceeds with the radical compound, (a) a conductive material mixed with the radical compound and the single ion conductive material is contained, or (b) the radical As the compound and / or the single ion conductive material, it is desirable to employ a compound having a conductive partial structure in its molecular structure.
In producing an electrode containing a radical compound and a single ion conductive material, it is important to uniformly disperse the radical compound and the single ion conductive material. Monomer (if not a polymer) is at the end, and in the case of a polymer, the single ion conductive material having —COOX or —SO ₃ X at the end and side chain is mostly water-soluble, so dispersed. In order to improve the property, water can be used as a solvent during electrode preparation.

  (2) The secondary battery of the present invention that solves the above problems is characterized in that the secondary battery electrode described in (1) is used for a positive electrode and / or a negative electrode.

  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 a secondary battery and the secondary battery of the present invention will be described in detail below based on the embodiments.

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

  A single ion conductive material is a material that realizes ion conduction by selectively using one of anions and cations, and is compatible with radical compounds in an environment where the secondary battery electrode is applied to a secondary battery. It is a material from which ions can be desorbed.

By including a single ion conductive material in the main electrode, it is possible to smoothly advance the battery reaction related to the radical compound, and an anion which is a counter ion of the Li ion contained in the electrolytic solution. for example, in the case of LiPF _6, PF 6 ^_- to radical compound which exceed an amount which is contained, PF 6 is insufficient ^_- it is possible to exert effects which react in accordance with the progress of the cell reaction on behalf of.

In other words, the single ion conductive material corresponds to the amount of radical compound present in excess by comparing the number of radicals of the radical compound with the number of anions of the Li salt such as LiPF ₆ and LiBF ₄ in the electrolyte. It is desirable to contain. For example, it can be added in an amount that compensates for the amount of radical compound present excessively, or can be contained in excess even more than the amount of radical compound present excessively.

  In addition to determining the content as described above, based on only the content of the radical compound, and based on the number of radicals in the radical compound contained in the electrode, the ratio of the single ion conductive material is 10% or more and 300% or less. It is desirable to mix, and it is more desirable to mix in the ratio of 50% or more and 300% or less.

  Single ion conductive materials include a cation structure that is a partial structure that becomes a cation upon desorption, and a partial structure that generates an anion after the cation structure is desorbed after the cation structure is desorbed. A material having a certain cationic structure can be exemplified.

  Here, the single ion conductive material is a material in which one kind of ions (here, cations) contributes to conduction. As the single ion conductive material, in particular, it has been found that an organic acid has a structure that is easily adsorbed and desorbed with radicals.

Specifically, it is a material having a functional group of —SO ₃ X or —COOX, and examples thereof include organic acid structures represented by R—SO ₃ X and R—COOX. These organic acid structures have a high dissociation property of X, and the anions R—SO ₃ ⁻ and R—COO ⁻ after the dissociation easily adsorb and desorb with radicals derived from radical compounds.

  Here, X is a partial structure corresponding to the cation structure described above, and is a group capable of forming a monovalent cation. X is preferably Li or Na, and particularly preferably Li having a small molecular weight.

In a single ion conductive material in which X is Li, lithium (Li ⁺ ) is included as a cation (structure), and after lithium is dissociated, substituents such as R—SO ₃ ⁻ and R—COO ⁻ are included as an anion structure. The structure remains. Here, the R moiety is a low molecular weight chemical structure comprising an aromatic hydrocarbon substituent benzene group, a styrene group, an aliphatic hydrocarbon substituent alkyl group, an allyl group, an acrylic group, or other organic substances, and Consists of a high molecular weight chemical structure. Among these, a high molecular weight chemical structure is desirable because it has conductivity, so that it can be expected to exhibit an effect as a conductive material described later. The chemical structure having conductivity can be realized by introducing a general conductive polymer structure such as polyaniline, polypyrrole, polythiophene, polyacetylene, polyacene or the like. In the radical compound described later, it is also desirable that such a chemical structure having conductivity is introduced. A structure in which the R portion is H is not included in this embodiment.

In the case where the R portion has a high molecular weight chemical structure, a structure in which a large number of substituents such as —SO ₃ X and —COOX described above are bonded can also be employed. Further, a radical compound described later may coexist in the R portion. The coexistence of a radical compound means that a structure imparting single ion conductivity, such as —SO ₃ X, R—COOX, and a functional group having a radical (for example, 2 , 2,6,6-tetramethylpiperidinoxy group) to form the same compound.

  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. The properties of single ion conductive materials such as solid state or liquid state, soluble and insoluble can be controlled by appropriately selecting the structure and molecular weight of the R moiety. Here, the form of the single ion conductive material 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.

  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 above-mentioned lithium salts of aliphatic and aromatic organic acids such as polystyrene sulfonate lithium and lithium polyacrylate, polymerized ones are also possible. Specific desirable compounds as a single ion conductive material include lithium salt and sodium salt, fatty acid lithium salt and fatty acid sodium salt such as lithium acetate and sodium acetate, lithium p-styrenesulfonate and sodium p-styrenesulfonate. Lithium salt of aromatic organic acid such as sodium salt of aromatic organic acid, lithium polystyrene sulfonate, sodium polystyrene sulfonate, or polyacrylic acid in which these aliphatic organic acids and aromatic organic acids are polymerized Examples include lithium and sodium polyacrylate. Further, there are those obtained by copolymerizing lithium sulfonate or sodium sulfonate with lithium carboxylate or sodium carboxylate.

  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).

  Specific examples of radical compounds that can be used when applied to a secondary battery employing lithium ions include nitroxyl radical compounds, oxy radical compounds, aryloxy radical compounds, and compounds having an aminotriazine structure. Particularly preferred are nitroxyl radical compounds. Among them, the above-mentioned PTMA can be given as a particularly desirable compound as a radical compound.

  It is desirable that the single ion conductive material and the radical compound are as close as possible. For example, it is desirable that the radical compound and the single ion conductive material are mixed (especially at the molecular level).

  Moreover, it is desirable that the radical compound and the single ion conductive material are chemically bonded and include those that form the same molecule. For example, a compound in which a single ion conductive material and a radical compound are simply bonded as described above, or a compound in which a radical compound and a single ion conductive material are bonded as a side chain of a polymer material can be exemplified.

  The electrode for a secondary battery of 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 intended to improve 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. The conductive material is desirably mixed at a rate of 10% to 50% based on the total mass of the radical compound, the single ion conductive material and the conductive material constituting the positive electrode, and mixed at a rate of 10% to 35%. It is further desirable to do so.

  Specific conductive materials include conductive polymers such as ketjen black, acetylene black, carbon black, graphite, carbon nanotube, amorphous carbon, polyaniline, polypyrrole, polythiophene, polyacetylene, polyacene, and metal materials. it can.

  Furthermore, the secondary battery electrode of the present embodiment can employ a configuration containing an active material related to the battery reaction (such as a compound from which lithium ions are inserted and released) in addition to the radical compound.

Specific examples of the positive electrode active material that can be mixed include a lithium-metal composite oxide having a layered structure or a spinel structure. Specifically, Li _(1-X) NiO ₂ , Li _(1-X) MnO ₂ , Examples include Li _(1-X) Mn ₂ O ₄ , Li _(1-X) CoO ₂ , and Li _(1-X) FeO ₂ . X 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. Among these, at least one lithium-metal composite oxide of a lithium manganese-containing composite oxide, a lithium nickel-containing composite oxide, and a lithium cobalt-containing composite oxide having a layered structure or a spinel structure is preferable.

  Furthermore, the secondary battery electrode of the present embodiment includes a single ion conductive material, a radical compound, a binder that binds an active material, and a current collector that collects electrons generated by the radical compound (such as a metal foil). And the like can be formed.

  The binder is preferably formed of a polymer material, and is desirably a material that is chemically and physically stable in the atmosphere in the secondary battery. Then, when any of the above-mentioned single ion conductive material, radical compound, and conductive material is made of a polymer material, it can be considered that the material exerts an action as a binder.

  The electrode for the secondary battery of the present embodiment includes (a) a current collector formed of a metal foil or the like, and (b) a mixture of a radical compound and a single ion conductive material as essential elements, the positive electrode active material described above, A layer composed of an electrode mixture in which an additive selected from a binder, a conductive material, and other materials as needed is mixed, and an electrode mixture layer formed on the surface of the current collector; It is common to do. Examples of the 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.

When the secondary battery electrode of the present embodiment is a positive electrode, a secondary battery is configured in combination with the negative electrode. However, when the cation supplied by the single ion conductive material is lithium ion, the active property of the combined negative electrode is As the substance, a compound that occludes lithium ions during charging and releases lithium ions during discharging can be used. 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 1-methyl-3-ethylimidazolium cation and dimethylethylmethoxyammonium cation having high conductivity, 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 , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiSbF ₆ , LiSiF ₅ , LiAlF ₄ , LiSCN, LiClO ₄ , LiCl, LiF, LiBr , LiI, LiAlF ₄ , LiAlCl ₄ , NaClO ₄ , NaBF ₄ , NaI, and derivatives thereof. Among these, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiCF ₃ SO ₃ derivatives, LiN (CF ₃ SO ₂ ) it is preferable from the viewpoint of electrical characteristics using one or more salts selected from ₂ derivatives and _LiC (CF 3 _{SO 2)} group consisting of ₃ derivatives.

  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 plays a role of holding 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 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 p-styrenesulfonate as a single ion conductive material, PTMA as a radical compound, carbon black as a conductive material, carboxymethylcellulose sodium salt (CMC), polyethylene oxide (PEO), and water as a dispersion medium 22: It was mixed and dispersed at a mass ratio (parts by mass) of 31: 35: 1: 1: 80. Furthermore, 1 part by mass of polytetrafluoroethylene (PTFE) as a binder was added and dispersed to obtain a slurry-like positive electrode mixture.

  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. Thereafter, the positive electrode plate was cut into a predetermined size, and then the electrode mixture at the portion to be a lead tab weld for extracting current was scraped off to produce a sheet-like positive electrode.

(Preparation of electrolyte)
An organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a mass ratio of 3: 7 was used as an electrolyte as it was. In general lithium secondary batteries, a supporting salt such as LiPF ₆ is often dissolved in this mixed organic solvent.

(Production of triode cell)
A triode cell was prepared for the purpose of evaluating the positive electrode. The prepared positive electrode was directly used for the positive electrode, lithium metal for the negative electrode, and lithium metal for the reference electrode. As the electrolytic solution, the prepared electrolytic solution was used. As the separator, a polyethylene porous film having a thickness of 25 μm was used. By evaluating the electrochemical characteristics of the prepared triode cell, the oxidation-reduction behavior of the positive electrode (radical compound) was evaluated.

[Comparative Example 1]
A positive electrode substantially similar to Example 1 was prepared except that no single ion conductive material was added. As the positive electrode, PTMA, carbon black, CMC, PEO, and water were mixed and dispersed at a mass ratio (parts by mass) of 63: 35: 1: 1: 80. Further, 1 part by mass of PTFE was added and dispersed to prepare a positive electrode mixture to prepare a positive electrode. Using the prepared positive electrode, a triode cell was prepared using the same negative electrode and electrolyte as in Example 1.

[Comparative Example 2]
(Preparation of electrolyte)
EC and DEC were added to a mixed organic solvent having a mass ratio of 3: 7 at a concentration of 1.0 mol / L of lithium p-styrenesulfonate to obtain an electrolytic solution. A tripolar cell was prepared using the same positive electrode and negative electrode as those in Comparative Example 1 except for the electrolyte.

[Comparative Example 3]
(Preparation of electrolyte)
LiPF ₆ was added at a concentration of 1.0 mol / L to a mixed organic solvent having a mass ratio of EC and DEC of 3: 7 to obtain an electrolytic solution. A tripolar cell was prepared using the same positive electrode and negative electrode as those in Comparative Example 1 except for the electrolyte.

[Evaluation]
About each tripolar cell of an Example and a comparative example, the electrochemical evaluation of the oxidation-reduction behavior of a radical compound was performed. The results are shown in Table 1.

As apparent from Table 1, by adding lithium p-styrenesulfonate as a single ion conductive material in the positive electrode, the same as in Comparative Example 3 in which LiPF ₆ was added to the electrolyte corresponding to the prior art. The radical redox peak could be confirmed. That is, it was found that the battery reaction can proceed without dissolving the supporting electrolyte in the electrolytic solution by including the single ion conductive material in the electrode.

  In addition to the tripolar cell of Comparative Example 2 to which lithium p-styrenesulfonate was not added, the radical redox reaction was also carried out in Comparative Example 1 which was not added in the positive electrode but only in the electrolytic solution. From the fact that it does not proceed, it became clear that the single ion conductive material contributes to the oxidation-reduction reaction of the radical only when it exists in the positive electrode where the radical compound is present.

  This contributes to the radical redox reaction by the presence of the p-styrenesulfonate anion, which is an anion group (anion structure) after lithium is dissociated from the lithium p-styrenesulfonate, in the vicinity of the radical of the radical compound. Can be guessed.

  In addition, as a result of the same investigation of lithium polyacrylate as a single ion conductive material other than lithium p-styrene sulfonate, it was added to the positive electrode in the same manner as lithium p-styrene sulfonate. Similar tests have shown that it contributes to the progress of the reaction.

[Example 2]
(Preparation of electrolyte)
A solution obtained by adding LiPF ₆ at a concentration of 0.6 mol / L to a mixed organic solvent having a mass ratio of EC and DEC of 3: 7 was used as 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 sealing and insulation between the positive electrode case 4 and the negative electrode case 5.

Example 3
(Preparation of electrolyte)
LiPF ₆ was added at a concentration of 1.0 mol / L to a mixed organic solvent having a mass ratio of EC and DEC of 3: 7 to obtain an electrolytic solution. A coin-type battery was prepared using the same positive electrode and negative electrode as in Example 2 except for the electrolytic solution.
Example 4
Lithium polyacrylate as a single ion conductive material, PTMA as a radical compound, carbon black as a conductive material, CMC, PEO, and water as a dispersion medium 15.5: 47.5: 35: 1: 1: 80 parts by mass (parts by mass) was mixed and dispersed, and 1 part by mass of PTFE was further added and dispersed as a binder to obtain a slurry-like positive electrode mixture. A coin-type battery was prepared using the same electrolyte as in Example 2.
(Preparation of electrolyte)
A solution obtained by adding LiPF ₆ at a concentration of 0.6 mol / L to a mixed organic solvent having a mass ratio of EC and DEC of 3: 7 was used as an electrolytic solution.
Example 5
(Preparation of electrolyte)
LiPF ₆ was added at a concentration of 1.0 mol / L to a mixed organic solvent having a mass ratio of EC and DEC of 3: 7 to obtain an electrolytic solution. A coin-type battery was prepared using the same positive electrode and negative electrode as in Example 4 except for the electrolytic solution.

[Comparative Example 4]
A coin-type battery was prepared using the positive electrode, negative electrode, and electrolyte solution produced in Comparative Example 3.

[Evaluation]
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 capacity value of each coin battery.
Furthermore, it was placed in a constant temperature bath at 25 ° C., charged with constant current and 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. An IV curve was created from the voltage value after 10 seconds of discharge at each current value to obtain a current value of 3.0 V, and the product of the current value and the voltage value (3.0 V) was used as the output.
The capacity ratio and the output ratio are expressed as a ratio when Comparative Example 4 is 1.0.
The obtained results are shown in Table 2.

As is apparent from Table 2, the batteries of Examples 2 to 5 were able to realize higher capacity and output than the battery of Comparative Example 3. That is, by adding p-styrene sulfonate lithium and lithium polyacrylate, which are single ion conductive materials, in the positive electrode, a capacity equal to or higher than that can be realized even if the concentration of the supporting electrolyte in the electrolytic solution is low, A higher capacity and higher output could be achieved by dissolving a supporting electrolyte of the same concentration.
Furthermore, the coin 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 at a constant current up to 3.0 V at a current value equivalent to 10 C. The capacity was measured.
The capacity ratio is expressed as a ratio when the capacity corresponding to 10 C of Comparative Example 4 is 1.0.
The results are shown in Table 3.
As can be seen from Table 3, even when the discharge current value is increased, a single ion conductive material is added in the positive electrode in the same manner, so that a higher capacity, a higher capacity, and a higher output are obtained as compared with the case of no addition. Was realized.

In other words, a high capacity can be realized even if the indicator electrolyte concentration in the electrolyte is lowered. Therefore, if high ionic conductivity is required, the ionic conductivity can be increased by lowering the supporting electrolyte concentration in the electrolyte. It became clear that it was possible to maintain a high capacity.
In addition, when lithium polyacrylate was used as the single ion conductive material in Examples 2 and 3, the capacity ratio and the output ratio were improved as compared with the case where lithium p-styrenesulfonate was used. This is presumably because the use of water improved the dispersibility between lithium polyacrylate, a single ion conductive material, and radicals.

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 ... Electrolytic solution
4 ... Positive electrode case
5 ... Negative electrode case
6… Gasket
7 ... Separator
10 ... Coin-type non-aqueous electrolyte secondary battery

Claims (14)

It is at least one electrode of a secondary battery having a positive electrode, a negative electrode and a supporting electrolyte, and has a radical compound and a single ion conduction having a functional group of -COOX or -SO ₃ X (X is Li or Na) in the molecular structure An electrode for a secondary battery comprising a functional material.   The electrode for a secondary battery according to claim 1, wherein the radical compound and the single ion conductive material are mixed.   3. The electrode for a secondary battery according to claim 1, wherein the radical compound and the single ion conductive material are chemically bonded to each other to form the same molecule. 4. The single ion conductive material has a cation structure (Li ⁺ or Na ⁺ ) that is a partial structure that is desorbed to become a cation, and a remainder after the cation structure is desorbed, after the cation structure is desorbed. anion structure is a partial structure for generating an anion (-COO ^- or -SO 3 ^_-) and materials a secondary battery electrode according to any of claims 1 to 3 with.   Said X is Li, The electrode for secondary batteries in any one of Claims 1-4. The single ion conductive material is a polymer having a functional group of —COOX or —SO ₃ X (X is Li or Na) in the molecular structure, and the molecular weight of the monomer (monomer) as a unit unit is 300 or less. The electrode for a secondary battery according to claim 1, wherein the electrode is a secondary battery electrode.   The secondary battery electrode according to claim 1, wherein the single ion conductive material has a polymer structure (polymer structure).   The secondary battery electrode according to claim 6 or 7, wherein the single ion conductive material having a polymer structure has an average molecular weight of 100,000 or more.   9. The secondary battery according to claim 1, wherein the secondary battery includes a supporting electrolyte and an electrolytic solution that dissolves the supporting electrolyte, and the single ion conductive material is insoluble in the electrolytic solution. electrode.   The electrode for secondary batteries in any one of Claims 1-9 containing the electrically conductive material mixed with the said radical compound and the said single ion conductive material.   The electrode for a secondary battery according to claim 1, wherein the radical compound and / or the single ion conductive material has a partial structure having conductivity in a molecular structure thereof.   The secondary battery electrode according to claim 1, which is used for a positive electrode. A method for producing an electrode for a secondary battery according to any one of claims 1 to 12, wherein the electrode has a current collector,
Preparing a paste in which the radical compound and the single ion conductive material are dissolved or dispersed in water;
And a step of applying the paste to the surface of the current collector.   A secondary battery, wherein the positive electrode and / or the negative electrode is the electrode for a secondary battery according to claim 1.