JP2017004627A - Ion capturing agent for lithium ion secondary battery and lithium ion secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion capturing agent for a lithium ion secondary battery, highly selectively adsorbing impurities generated from a constitutional material of a lithium ion secondary battery and also high in adsorption ability per unit mass, and to provide a lithium ion secondary battery in which generation of a short circuit due to impurities is suppressed using the ion capturing agent and a long life is achieved.SOLUTION: An ion capturing agent for a lithium ion secondary battery contains at least one of a magnesium-aluminum composite oxide and a dried hydrotalcite compound.SELECTED DRAWING: None

Description

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

  Lithium ion secondary batteries are lightweight and have high input / output characteristics compared to other secondary batteries such as nickel metal hydride batteries and lead storage batteries, so they are used for high input / output used in electric vehicles and hybrid electric vehicles. It is attracting attention as a power source.

However, when impurities (for example, magnetic impurities such as iron, nickel, manganese, and copper) are present in the constituent materials of the battery, lithium metal is deposited on the negative electrode during charge and discharge. And when the lithium dendride deposited on the negative electrode breaks the separator and reaches the positive electrode, it may cause a short circuit.
Further, the use temperature of the lithium ion secondary battery may be 40 to 80 ° C. in a car in summer. At this time, a metal such as manganese is eluted from the lithium-containing metal oxide, which is a constituent material of the positive electrode, and is deposited on the negative electrode, thereby degrading the characteristics (capacity) of the battery.

  For such a problem, for example, Patent Document 1 discloses a lithium ion secondary battery having a trapping substance having a function of trapping impurities, by-products generated inside the lithium ion secondary battery by absorption, binding, or adsorption. As the capture substance, activated carbon, silica gel, zeolite, and the like are mentioned.

  Further, for example, in Patent Document 2, a positive electrode using a lithium compound containing Fe or Mn as a metal element as a constituent element as a positive electrode active material, and a negative electrode using a carbon material capable of occluding and releasing lithium ions as a negative electrode active material, A non-aqueous lithium ion secondary battery arranged separately in a non-aqueous electrolyte, wherein the positive electrode contains 0.5 to 5 wt% zeolite with respect to the positive electrode active material, and the zeolite is effective A non-aqueous lithium ion secondary battery having a pore diameter larger than the ion radius of the metal element and 0.5 nm (5 mm) or less is disclosed.

  Further, Patent Documents 3 to 5 disclose an aluminum silicate having a specific composition and structure, a lithium ion secondary battery using the same, and a member.

JP 2000-77103 A JP 2010-129430 A International Publication No. 2012/124222 JP 2013-105673 A JP 2013-127955 A

However, the ion adsorbents disclosed in Patent Documents 1 to 5 may not be able to adsorb impurities with high selectivity, and the adsorption capacity per unit mass is insufficient, so that the required life characteristics can be obtained. There was no case.
The present invention has been made in view of the above-described problems, and the object thereof is to highly selectively adsorb impurities generated from the constituent materials of the lithium ion secondary battery and to have a high adsorption capacity per unit mass. It is to provide an ion scavenger for a lithium ion secondary battery. Another object of the present invention is to provide a long-life lithium ion secondary battery by using the ion scavenger to suppress the occurrence of short circuits due to impurities.

The present inventor said that the ion scavenger containing at least one of magnesium aluminum based composite oxide and dry hydrotalcite compound adsorbs impurities with high selectivity and has high adsorption performance per unit mass. As a result, the present invention has been completed.
That is, the present invention is as follows.
1. An ion scavenger for a lithium ion secondary battery, comprising at least one of a magnesium aluminum composite oxide and a dried hydrotalcite compound.
2. 2. The ion trap for a lithium ion secondary battery according to 1 above, wherein the magnesium aluminum composite oxide is obtained by firing hydrotalcite at 400 ° C. to 750 ° C. and is a compound represented by the following formula (1): Agent.
Mg _a Al _b O _c (1)
[In Formula (1), a, b, and c are positive numbers of 0.1 or more, satisfy 2a + 3b = 2c, a> b, and the ratio of a to b (a / b) is 9 or less. . ]
3. 2. The dried hydrotalcite compound according to the above 1, which is obtained by drying a hydrotalcite compound represented by the following formula (2) at 200 ° C. to 400 ° C. and removing crystal water. An ion scavenger for lithium ion secondary batteries.
M _1-x Al _x (OH) ₂ A ^n- _{x / n} · mH ₂ O (2)
[In the formula (2), M is a Mg and / or Zn, A ^n-is an n-valent anion, x is a positive number of 0 <x <0.5, m is 0 ≦ m <1 Is a positive number. ]
4). 4. The ion scavenger for a lithium ion secondary battery according to any one of the above 1 to 3, wherein the moisture content is 10% by mass or less.
5). A lithium ion secondary battery comprising a positive electrode, a negative electrode, and an electrolytic solution, wherein the ion scavenger for a lithium ion secondary battery according to any one of the above 1 to 4 is contained in at least one of the constituent materials of the battery. The lithium ion secondary battery characterized by the above-mentioned.
6). 6. The lithium ion secondary battery according to 5 above, further comprising a separator as a constituent material of the lithium ion secondary battery.

  The ion scavenger for a lithium ion secondary battery according to the present invention adsorbs impurities generated from the constituent material of the lithium ion secondary battery with high selectivity and has a high adsorbability per unit mass. Therefore, the lithium ion secondary battery using this ion scavenger can suppress the occurrence of a short circuit due to impurities and can be a long-life lithium ion secondary battery.

  An embodiment of the present invention will be described as follows, but the present invention is not limited thereto. Note that “%” means “% by mass” unless otherwise specified, “parts” means “parts by mass”, and “ppm” means “mass ppm”.

1. Ion scavenger for lithium ion secondary battery The ion scavenger for lithium ion secondary battery according to the present invention (hereinafter, also simply referred to as “ion scavenger”) is a magnesium aluminum composite oxide and a dried hydrotalcite compound. It contains at least one of these.
These ion scavengers have excellent adsorptivity for unnecessary metal ions such as manganese ions (Mn ²⁺ ), nickel ions (Ni ²⁺ ), copper ions (Cu ²⁺ ), and iron ions (Fe ²⁺ ). On the other hand, since the adsorptivity to lithium ions is low, it is possible to efficiently adsorb unnecessary metal ions that may cause a short circuit. The unnecessary metal ions are derived from impurity ions present in the constituent members of the lithium ion secondary battery and metal ions eluted from the positive electrode at a high temperature.

The magnesium aluminum composite oxide and dried hydrotalcite are not ion exchanged, and easily incorporate divalent or trivalent ions such as manganese ions and nickel ions into the skeleton of the compound. Since monovalent ions are not taken in, it is considered to have high selectivity.
Moreover, since these ion trapping agents are inorganic oxides, they are excellent in thermal stability and stability in a solvent. For this reason, when it is made to contain in the component of a lithium ion secondary battery, it can exist stably also during charging / discharging. The magnesium aluminum composite oxide and the dried hydrotalcite compound used in the present invention will be described more specifically.

<Magnesium aluminum composite oxide>
The magnesium aluminum composite oxide that can be used in the present invention is obtained by firing hydrotalcite at 400 ° C. to 750 ° C., and is a compound represented by the following formula (1).
Mg _a Al _b O _c (1)
[In Formula (1), a, b, and c are positive numbers of 0.1 or more, satisfy 2a + 3b = 2c, a> b, and the ratio of a to b (a / b) is 9 or less. . ]

The temperature for firing the hydrotalcite is preferably 400 ° C to 750 ° C, more preferably 450 ° C to 600 ° C. If the calcination temperature is in the range of 400 ° C. to 750 ° C., the OH groups and carbonate ions (CO ₃ ²⁻ ) in the hydrotalcite are easily desorbed, and excellent ion trapping ability is obtained. Moreover, within this temperature range, hydrotalcite is not separated into magnesium oxide and aluminum oxide.

<Dry hydrotalcite compound>
The dry hydrotalcite compound that can be used in the present invention is obtained by drying the hydrotalcite compound represented by the following formula (2) at 200 ° C. to 400 ° C. to remove crystal water. It is.
M _1-x Al _x (OH) ₂ A ^n- _{x / n} · mH ₂ O (2)
[In the formula (2), M is a Mg and / or Zn, A ^n-is an n-valent anion, x is a positive number of 0 <x <0.5, m is 0 ≦ m <1 Is a positive number. ]

  The temperature for drying the hydrotalcite compound is preferably 200 to 400 ° C, more preferably 250 to 350 ° C. If the drying temperature is in the range of 200 to 400 ° C., the water of crystallization of the hydrotalcite compound can be sufficiently removed. Further, within this temperature range, condensation of hydrotalcite does not occur and the hydrotalcite structure can be maintained.

The ion scavenger according to the present invention preferably has a moisture content of 10% by mass or less, and more preferably 5% by mass or less. When a lithium ion secondary battery is configured by having a water content of 10% by mass or less, generation of gas due to water causing electrolysis can be suppressed, and expansion of the battery can be suppressed. Can do.
The water content can be measured by the Karl Fischer method.

  As a method for adjusting the water content to 10% by mass or less, a commonly used drying method can be used without any particular limitation. For example, the method of drying at 100-300 degreeC for about 6 to 24 hours under atmospheric pressure or pressure reduction is mentioned.

2. Lithium-ion secondary battery (1) structure The lithium-ion secondary battery of the present invention comprises a positive electrode, a negative electrode, and an electrolytic solution, which are normal components of a lithium-ion secondary battery. Moreover, you may include other structural members, such as a separator, as needed. Details of each component will be described later.
The structure of the lithium ion secondary battery is not particularly limited. Usually, a positive electrode and a negative electrode, and a separator provided as necessary, are wound into a flat spiral shape to form a wound electrode group, In general, the electrode plates are laminated to form a laminated electrode plate group, and the electrode plate group is enclosed in an exterior body.

The ion scavenger of the present invention is preferably contained in at least one constituent member of the positive electrode, the negative electrode, the electrolytic solution, and the separator, and more preferably contained in at least one of the electrolytic solution and the separator. The reason is considered as follows.
In general, impurity ions and eluted ions that can cause a short circuit are present in the electrolytic solution, and these ions permeate, for example, a separator and move in a bidirectional manner between the positive electrode and the negative electrode in the process of charging and discharging. Therefore, unnecessary metal ions can be adsorbed more effectively by including the ion scavenger in at least one of the electrolytic solution and the separator.

(2) Positive electrode The positive electrode which comprises a lithium ion secondary battery can be obtained, for example by forming a positive electrode material layer in at least one part of the collector surface. As the current collector, a belt-shaped member made of a metal or an alloy such as aluminum, titanium, or stainless steel in a foil shape or a mesh shape can be used.

As a positive electrode material used for the positive electrode material layer, for example, a metal compound, a metal oxide, a metal sulfide, or a conductive polymer material that can be doped or intercalated with lithium ions can be used. Specifically, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and composite materials thereof, and conductive properties such as polyacetylene, polyaniline, polypyrrole, polythiophene, and polyacene Polymers and the like can be used alone or in combination.

  When the positive electrode contains the ion scavenger of the present invention, the positive electrode material, the ion scavenger and the binder are kneaded together with a solvent by a dispersing device such as a stirrer to prepare a positive electrode material slurry, which is applied to the current collector. Thus, a positive electrode material layer can be formed. Alternatively, the paste-like positive electrode material slurry can be formed into a sheet shape, a pellet shape, or the like and integrated with the current collector.

  The concentration of the ion scavenger in the positive electrode material slurry can be appropriately selected as necessary. For example, it can be 0.01-5.0 mass%, and it is preferable that it is 0.1-2.0 mass%.

  Examples of the binder include polymer compounds such as styrene-butadiene copolymer, (meth) acrylic copolymer, polyvinylidene fluoride, polyethylene oxide, polyepichlorohydrin, polyphosphazene, polyimide, and polyamideimide. .

  The content ratio of the binder in the positive electrode material layer is preferably 0.5 to 20 parts by mass, and preferably 1 to 10 parts by mass with respect to 100 parts by mass in total of the positive electrode material, the ion scavenger, and the binder. More preferred. If the content ratio of the binder is in the range of 0.5 to 20 parts by mass, it is possible to sufficiently adhere to the positive electrode material and to prevent the electrode resistance from increasing.

  Examples of the method for applying the positive electrode material slurry to the current collector include a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, and screen printing. Known methods such as the method may be mentioned.

(3) Negative electrode The negative electrode of a lithium ion secondary battery can be obtained by forming a negative electrode material layer on the current collector surface in the same manner as the positive electrode. Examples of the negative electrode material used for the negative electrode material layer include carbon materials capable of doping or intercalating lithium ions, metal compounds, metal oxides, metal sulfides, and conductive polymer materials. For example, natural graphite, artificial graphite, silicon, lithium titanate and the like can be used alone or in admixture of two or more.

  The negative electrode is prepared by kneading a negative electrode material, an ion scavenger and a binder together with a solvent by a dispersing device such as a stirrer, a ball mill, a super sand mill, a pressure kneader, etc. To form a negative electrode material layer. Or it can also obtain by shape | molding paste-form negative electrode material slurry in shapes, such as a sheet form and a pellet form, and integrating this with a collector.

  As the ion scavenger and the binder used for the slurry of the negative electrode material, the same kind as that of the positive electrode can be used, and the content thereof can be the same.

  Moreover, the material and shape of the said collector can use the strip | belt-shaped thing which made aluminum, copper, nickel, titanium, stainless steel etc. into foil shape, mesh shape, etc., for example. Furthermore, porous materials such as foam metal and carbon paper can be used.

  As a method of applying the negative electrode material slurry to the current collector, it can be performed by a known method in the same manner as the positive electrode.

(4) Electrolytic Solution The electrolytic solution used for the lithium ion secondary battery according to the present invention is not particularly limited, and a known one can be used. For example, a non-aqueous lithium ion secondary battery can be manufactured by using an electrolytic solution in which an electrolyte is dissolved in an organic solvent.

As the _{electrolyte, LiPF 6, LiClO 4, LiBF} 4, LiClF 4, LiAsF 6, LiSbF 6, LiAlO 4, LiAlCl 4, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2, LiC Examples thereof include lithium salts that generate anions that are difficult to solvate, such as (CF ₃ SO ₂ ) ₃ , LiCl, and LiI.
The concentration of the electrolyte is, for example, preferably 0.3 to 5 mol of electrolyte, more preferably 0.5 to 3 mol, and 0.8 to 1.5 mol with respect to 1 L of the electrolyte solution. It is particularly preferred.

  Examples of the organic solvent include carbonates (propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, methyl propyl carbonate, butyl methyl carbonate, ethyl propyl carbonate, butyl ethyl carbonate. , Dipropyl carbonate, etc.), lactones (γ-butyrolactone, etc.), esters (methyl acetate, ethyl acetate, etc.), chain ethers (1,2-dimethoxyethane, dimethyl ether, diethyl ether, etc.), cyclic ethers ( Tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, 4-methyldioxolane, etc.), ketones (cyclopentanone, etc.), sulfur Orchids (sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, etc.), sulfoxides (dimethylsulfoxide, etc.), nitriles (acetonitrile, propionitrile, benzonitrile, etc.), amides (N, N-dimethylformamide) N, N-dimethylacetamide), urethanes (3-methyl-1,3-oxazolidine-2-one, etc.), and polyoxyalkylene glycols (diethylene glycol, etc.). it can. These organic solvents may be used alone or as a mixed solvent of two or more.

  The electrolytic solution preferably contains at least one of the above ion scavengers. Examples of the method of adding an ion scavenger to the electrolytic solution include a method of adding and mixing the ion scavenger to the electrolytic solution in a solid state or a dispersion state. Among them, the method of adding in a solid state is preferable.

  When the ion scavenger is added to the electrolyte solution in a dispersion state, the solvent of the dispersion solution is not particularly limited. Of these, the same organic solvent as the electrolyte is preferred. Further, the concentration of the ion scavenger in the dispersion can be appropriately selected as necessary. For example, it can be 0.01-50 mass%, and it is preferable that it is 1-20 mass%.

  As a content rate when electrolyte solution contains an ion-trapping agent, it is preferable that it is 0.01-50 mass% in electrolyte solution from a viewpoint of suppressing generation | occurrence | production of a short circuit and internal resistance, and 0.1-30 mass. % Is more preferable, and 0.5 to 10% by mass is still more preferable.

(5) Separator The separator has a role of separating both electrodes so that the positive electrode and the negative electrode are not short-circuited. Further, when an excessive current flows through the battery, it melts due to heat generation, and the micropores are closed. It cuts off the current and ensures safety. In addition, when it is set as the structure where a positive electrode and a negative electrode do not contact directly, it is not necessary to use a separator.
The separator is not particularly limited as long as it is a porous substrate usually used for a separator. The porous substrate is not particularly limited as long as it has a large number of pores or voids therein and has a porous structure in which these pores are connected to each other. Examples thereof include porous films, nonwoven fabrics, paper sheets, and other sheets having a three-dimensional network structure. Among these, a microporous membrane is preferable from the viewpoint of handling properties and strength. As the material constituting the porous substrate, both organic materials and inorganic materials can be used, but thermoplastic resins such as polyolefin resins are preferable from the viewpoint of obtaining shutdown characteristics.

Examples of the polyolefin resin include polyethylene, polypropylene, polymethylpentene, and the like. Among them, those containing 90% by mass or more of polyethylene are preferable from the viewpoint of obtaining good shutdown characteristics. The polyethylene may be any of low density polyethylene, high density polyethylene and ultra high molecular weight polyethylene. In particular, at least one selected from high-density polyethylene and ultrahigh molecular weight polyethylene is preferable, and polyethylene including a mixture of high density polyethylene and ultrahigh molecular weight polyethylene is more preferable. Such polyethylene is excellent in strength and moldability.
The molecular weight of polyethylene is preferably 100,000 to 10,000,000 in terms of weight average molecular weight, and particularly preferably a polyethylene composition containing at least 1% by mass of ultrahigh molecular weight polyethylene having a weight average molecular weight of 1,000,000 or more.
In addition, the porous substrate may be constituted by mixing other polyolefins such as polypropylene and polymethylpentene in addition to polyethylene, or a laminate of two or more layers of a polyethylene microporous membrane and a polypropylene microporous membrane. You may comprise as a body.

The said separator should just contain at least one among the porous base material which is a separator base material, and the ion trapping agent of this invention, and another structure is not restrict | limited in particular. The separator can be obtained by impregnating a porous substrate with a dispersion containing an ion scavenger, applying a dispersion containing an ion scavenger to a porous substrate, and ion trapping a porous substrate. And kneading agents.
Moreover, after impregnating or apply | coating the dispersion liquid containing an ion trapping agent to a porous base material, you may dry as needed. Thereby, a separator in which a layer containing an ion scavenger is formed on the surface of the porous substrate can be obtained.

  When the layer containing the ion scavenger is formed on the surface of the porous substrate, it may be only one surface of the porous substrate or both surfaces. When forming only on one side of the porous substrate, it may be on either the positive side or the negative side. In view of elution of metal ions from the positive electrode and reduction of metal ions in the negative electrode to deposit metal, it is preferably formed on at least the surface on the positive electrode side, and more preferably on both surfaces.

  The solvent of the dispersion liquid containing the ion scavenger is not particularly limited. Examples thereof include water, 1-methyl-2-pyrrolidone, and alcohols such as methanol, ethanol and 1-propanol.

  Further, the concentration of the ion scavenger in the dispersion can be appropriately selected as necessary. For example, it can be 0.01 mass%-50 mass%, and it is preferable that it is 1 mass%-20 mass%.

  The dispersion preferably further contains a binder. The ion trapping agent is immobilized on the porous substrate by the binder containing the ion trapping agent-containing dispersion. For this reason, since it can exist on the separator surface at the time of charging / discharging, it can adsorb | suck an unnecessary metal ion efficiently, without dropping an ion trapping agent at the time of producing a battery.

  Although it does not restrict | limit especially as a binder contained in the said dispersion liquid, It is preferable that it is the same as that used for a positive electrode material layer and a negative electrode material layer as a binder from a viewpoint of the constituent material of a battery.

It is preferable that the content ratio of the binder in the layer containing the ion scavenger is 0.1 to 15 parts by mass with respect to 100 parts by mass in total of the ion scavenger and the binder, and 0.3 to 10 parts by mass. More preferably.
When the content ratio of the binder is in the range of 0.1 to 15 parts by mass, the ion scavenger is effectively immobilized on the porous substrate, and the effect is continuously obtained. Moreover, the metal adsorption efficiency per mass can be improved.

The content of the ion scavenger in the case where the separator contains an ion scavenger is preferably 0.01 to 50 g / m ² from the viewpoint of suppressing the occurrence of a short circuit, and is 0.1 to 20 g / m ² . More preferably.

  The method for applying the dispersion to the separator is not particularly limited. Known methods such as a metal mask printing method, electrostatic coating method, dip coating method, spray coating method, roll coating method, doctor blade method, gravure coating method, and screen printing method may be used.

  As a specific method for forming a separator using a porous substrate containing an ion scavenger, for example, a method described in JP-A-2008-146963 can be mentioned.

  Next, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited thereto.

1. Evaluation Method (1) Water Content The ion scavenger was vacuum-dried at 150 ° C. for 20 hours and measured by the Karl Fusher method.

(2) Metal ion adsorption ability in water Metal ion adsorption ability was evaluated by ICP emission spectroscopic analysis (ICP emission spectrometer “iCAP7600 DUO” (model name) manufactured by Thermo Fisher Scientific). The specific evaluation method is as follows.
First, for Li ⁺ , Ni ²⁺ or Mn ²⁺ , a 100 ppm metal ion solution was prepared using each metal sulfate and pure water. The ion scavenger was added to the prepared solution so as to be 1.0% by mass, mixed well, and then allowed to stand. Then, each metal ion concentration after addition of the ion scavenger was measured by ICP emission spectroscopic analysis. The results are shown in Table 1.

(3) Metal ion adsorption capacity in model electrolyte Solution assuming the application to a lithium ion secondary battery, metal ion adsorption capacity in model electrolyte solution was evaluated. A solution in which diethyl carbonate (DEC) and ethylene carbonate (EC) were mixed as an organic solvent so that the volume ratio was DEC / EC = 1/1 was used, and nickel tetrafluoroborate was used as the solute in the initial Ni ²⁺ . A model electrolyte solution was prepared by adding an ion concentration of 100 ppm.
30 mL of the model electrolyte was placed in a glass bottle, and 0.3 g of an ion scavenger was added thereto. The solution was stirred for about 1 minute and then allowed to stand for about 20 hours. The concentration after addition of the ion scavenger was measured by the ICP emission spectroscopic analysis. In addition, acid decomposition (microwave method) was performed for the pretreatment of the measurement sample. The results are shown in Table 2.

2. Production of ion scavenger [Example 1]
<Synthesis of magnesium aluminum composite oxide>
A hydrotalcite compound (product name “DHT-4H”, manufactured by Kyowa Chemical Co., Ltd.) represented by a composition formula Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂ O is calcined at 550 ° C. for 2 hours, A magnesium aluminum composite oxide represented by a composition of Mg _4.5 Al ₂ O _7.5 was obtained. The moisture content was 0.5%.

[Example 2]
<Synthesis of dried hydrotalcite compounds>
The hydrotalcite compound whose composition formula is represented by Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂ O is dried at 250 ° C. for 2 hours to remove crystal water, and Mg _4.5 Al ₂ (OH) A dry hydrotalcite compound represented by a composition of ₁₃ CO ₃ was obtained. The moisture content was 0.4%.

[Comparative Example 1]
<Synthesis of aluminum silicate>
To 500 ml of 700 mmol / L aluminum chloride aqueous solution, 500 ml of 350 mmol / L sodium orthosilicate aqueous solution was added and stirred for 30 minutes. To this solution, 330 ml of a 1 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 6.1.
The pH adjusted solution was stirred for 30 minutes and then centrifuged for 5 minutes. After centrifugation, the supernatant solution was discharged, the gel precipitate was redispersed in pure water, and returned to the volume before centrifugation. Such desalting treatment by centrifugation was performed three times.
The solution was then placed in a dryer and heated at 98 ° C. for 48 hours. 188 mL of 1 mol / L sodium hydroxide aqueous solution was added to the solution after heating (aluminum silicate density | concentration 47 g / L), and it adjusted to pH = 9.1. The aluminum silicate in the solution was agglomerated by adjusting the pH, and the agglomerate was precipitated by centrifugation similar to the above, thereby discharging the supernatant. The desalting process of adding pure water to this and returning to the volume before centrifugation was performed 3 times.
The gel-like precipitate obtained after the third desalting of the desalting treatment was dried at 60 ° C. for 16 hours to obtain 30 g of powder. This powder was designated as “aluminum silicate”.

Comparative examples other than the above used the following (Tables 1 and 2). These ion scavengers were used after being dried at 150 ° C. for 20 hours.
Comparative Example 2: Wako Pure Chemical Industries, Ltd., activated carbon (reagent) “crushed, 2 to 5 mm”
Comparative Example 3: Wako Pure Chemical Industries, Ltd. Silica gel (reagent) “Small granular (white)”
Comparative Example 4: Y type zeolite “Mizuka Sieves Y-520” (trade name) manufactured by Mizusawa Chemical
Comparative Example 5: Hydrotalcite “DHT-4H” (trade name) manufactured by Kyowa Chemical Co., Ltd.

It was confirmed that the ion scavengers of Examples 1 and 2 selectively adsorbed Ni ²⁺ and Mn ²⁺ in water and were excellent in ion adsorption ability (Table 1). Also in the test using the model electrolyte, the ion scavengers of Examples 1 and 2 showed high ion adsorption (Table 2). From these results, the ion scavenger of the present invention adsorbs unnecessary Ni ²⁺ and Mn ²⁺ in the lithium ion secondary battery, but does not adsorb Li ⁺ essential for charge and discharge. It is possible to suppress the occurrence of a short circuit without impairing the performance.

  The ion scavenger of this invention can be used for the structural member of a lithium ion secondary battery. The present invention can also be applied to a lithium ion capacitor (hybrid capacitor) in which the anode is an electric double layer and the cathode is a lithium ion secondary battery structure. The lithium ion secondary battery using the ion scavenger of the present invention can be used as a paper-type battery, a button-type battery, a coin-type battery, a laminated battery, a cylindrical battery, a rectangular battery, and the like.

Claims (6)

  An ion scavenger for a lithium ion secondary battery, comprising at least one of a magnesium aluminum composite oxide and a dried hydrotalcite compound. 2. The ion for a lithium ion secondary battery according to claim 1, wherein the magnesium aluminum composite oxide is obtained by firing hydrotalcite at 400 ° C. to 750 ° C. and is a compound represented by the following formula (1): Scavenger.
Mg _a Al _b O _c (1)
[In Formula (1), a, b, and c are positive numbers of 0.1 or more, satisfy 2a + 3b = 2c, a> b, and the ratio of a to b (a / b) is 9 or less. . ] 2. The dried hydrotalcite compound is obtained by drying a hydrotalcite compound represented by the following formula (2) at 200 ° C. to 400 ° C. to remove crystal water. An ion scavenger for lithium ion secondary batteries.
M _1-x Al _x (OH) ₂ A ^n- _{x / n} · mH ₂ O (2)
[In the formula (2), M is a Mg and / or Zn, A ^n-is an n-valent anion, x is a positive number of 0 <x <0.5, m is 0 ≦ m <1 Is a positive number. ]   The ion scavenger for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the moisture content is 10% by mass or less.   It is a lithium ion secondary battery provided with a positive electrode, a negative electrode, and electrolyte solution, Comprising: At least 1 of the constituent material of the said battery WHEREIN: The ion trapping agent for lithium ion secondary batteries of any one of Claims 1-4 A lithium ion secondary battery comprising:   The lithium ion secondary battery according to claim 5, further comprising a separator as a constituent material of the lithium ion secondary battery.