KR20170021091A - Additive for magnesium rechargeable batteries electrolyte, manufacturing method of the same, and magnesium rechargeable batteries including the same - Google Patents

Abstract

The present invention relates to an electrolyte additive for magnesium cells, a production method thereof, and a magnesium cell including the same. More specifically, the present invention relates to an electrolyte additive for magnesium cells, capable of inhibiting and eliminating magnesium oxide films formed on surfaces of negative electrodes. The present invention further relates to a production method thereof and a magnesium cell including the same. According to the present invention, the electrolyte additive for magnesium cells effectively prevents formation of the magnesium oxide films formed on the surfaces of the negative electrodes, and also eliminates the magnesium oxide films, thereby increasing reversibility of deposition and elution of magnesium. Accordingly, the magnesium cells including the electrolyte additive for magnesium cells exhibits improved lifespan properties and charging/discharging properties.

Description

TECHNICAL FIELD [0001] The present invention relates to an electrolyte additive for a magnesium battery, a method for producing the same, and a magnesium battery including the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to an electrolyte additive for a magnesium battery, a method for producing the same, and a magnesium battery including the same, and more particularly, to an electrolyte additive for a magnesium battery capable of inhibiting and removing magnesium oxide film formed on a surface of a negative electrode, And a magnesium battery including the same.

In recent years, there has been a growing interest in materials for electric storage batteries.

The magnesium battery has been actively studied because it is environmentally friendly, has excellent price competitiveness, and has a high energy storage characteristic as compared with conventional lithium batteries, lead batteries, nickel-cadmium batteries, nickel-hydrogen batteries and nickel-zinc batteries.

The magnesium secondary battery uses magnesium metal as a cathode as a basic system. However, magnesium metal surface is strongly covered with MgO oxide film, and since MgO oxide film has no ion conduction characteristic, it is known as a main cause of the magnesium battery cell because it inhibits reversible oxidation / reduction reaction of magnesium.

To improve this, research on Grignard reagent, chloride, and borohydride materials has been conducted since the early 2000s.

The magnesium battery generally includes an anode, a cathode, and an ion conductive electrolyte. As the ion conductive electrolyte, an electrolyte solution of a Grignard magnesium salt (RMgX (R = alkyl group or aryl group, X = Cl or Br) is known. The electrochemical reaction of a magnesium battery in which an electrolytic solution of an iron magnesium salt (RMgX (R = alkyl group or aryl group, X = Cl or Br) is used is, for example, as follows:

Bipolar: Mg ↔ Mg ^{2 +} + 2e-

Anode: Mg _y M + _X ^{2 +} zMg ↔ Mg _y + zM _X + 2e-

That is, during discharging, electrons are emitted from the cathode to an external circuit, and the generated magnesium ions pass through the electrolytic solution (oxidation reaction). During the charging, magnesium ions move to the cathode and are plated with metal, ).

However, the low oxidation potential of such materials makes it difficult to expect the improvement of the energy density of the magnesium secondary battery through the high-voltage cathode active material while restricting the capacity of the cathode active materials of the magnesium secondary battery to 2V or less relative to the magnesium metal. In other words, the oxidation potential of these materials is low, and thus there is a technical limitation that the normal behavior of the magnesium battery is difficult due to the electrochemical side reaction when applied to the high voltage anode material for magnesium (> 2.0 V).

On the other hand, attempts have been made to make magnesium alloys electrochemically using metals such as Bi, Sb and Sn, which can be alloyed with magnesium metal, and utilize them as cathodes. However, due to the characteristics of the alloy metal, application to a magnesium battery is very limited due to the low energy density of the cathode itself due to its high weight and low lifetime characteristics in repeated charging.

Therefore, within the current technical category, the magnesium cathode can not be utilized sufficiently, and therefore, there is a limitation in realizing a magnesium secondary battery having a high energy density.

Disclosure of the Invention An object of the present invention is to provide a new electrolyte additive for a magnesium battery and a method for producing the same, in which MgO on the surface of magnesium is removed and oxidation potential is greatly improved in order to solve the problems of the conventional magnesium anode materials.

Another object of the present invention is to provide a magnesium battery comprising the electrolyte additive for a magnesium battery according to the present invention.

The present invention provides an electrolyte additive for a magnesium battery represented by the following formula (1) to solve the above problems.

???????? L _1x M _1? L _2y M ₂ ?????

(L _1x M ₁ and L _2y M ₂ in the above formula (1) are in a solid phase mixed state,

L ₁ is _{TFSI -, PF 6, BF 4} , SR, B (OR) 4, OH-, CH 3 COO-, (CN) 3 C-, (CN) 4 B-, (CN) 2 N-, CF _{3 COO-, CF 3 SO 3,} ClO 4, FSI, N (CN) 2, and oR (R is a substituted or unsubstituted C1 to C ₂ 0 alkane, alkene, or alkyne of the ring Im), selected from the group consisting of Any one or more of

L ₂ is a ligand selected from the group consisting of F, Cl, Br, I,

M ₁ and M ₂ are any one or more selected from the group consisting of Group 3, Group 4, and Group 5 elements)

FIG. 1 shows the action of the electrolyte additive for a magnesium battery on the surface of a negative electrode according to the present invention. In the electrolyte additive for a magnesium battery according to the present invention, M ₁ and M ₂ are elements having strong binding force with oxygen, and Mg functions to weaken the bond of Mg-O formed by bonding with oxygen, and L ₁ and L ₂ Is a substance having excellent compatibility with Mg and having high solubility in an organic electrolytic solution. It decomposes Mg-O bonds through a chemical reaction with magnesium metal whose binding force is weakened due to M ₁ , and dissolves in the electrolytic solution together with MgO It plays a role.

In addition, L ₁ and L ₂ have an excellent solubility in the organic electrolytic solution and selectively dissolve by-products from which the Mg-O film is removed to clean the magnesium surface, thereby facilitating the deposition / dissolution reaction of reversible magnesium ions.

In the electrolyte additive for a magnesium battery according to the present invention, L ₁ is characterized by being TFSI (bis (trifluoromethanesulfonyl) imide).

In the electrolyte additive for a magnesium battery according to the present invention, L ₂ is selected from the group consisting of F, Cl, Br and I.

In the electrolyte additive for a magnesium battery according to the present invention, M ₁ is Mg and M ₂ is Ti.

In the electrolyte additive for a magnesium battery according to the present invention, the additive for an electrolyte for a magnesium battery has a peak at -50 to -100 ppm, preferably -70.0 to -90.0 ppm in F-NMR measurement.

The present invention also relates to

Dissolving a first compound represented by L _{1 x} M ₁ in a first solvent;

Adding a second compound represented by L _2y M ₂ ;

Stirring the mixture;

Removing the first solvent remaining in the mixture;

Refining and drying; The present invention also provides a method for producing an electrolyte additive according to the present invention.

Fig. 2 schematically shows a process for producing an electrolyte additive according to the present invention.

In the method for producing an electrolyte additive according to the present invention, the first solvent is selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and combinations thereof .

In the method for preparing an electrolyte additive according to the present invention, the second compound is added in an amount of 0 to 1000 parts by weight, preferably 30 to 80 parts by weight, per 100 parts by weight of the first compound do.

In the method for producing an electrolyte additive according to the present invention, the step of stirring the mixture of the first compound and the second compound is characterized by stirring for 24 to 72 hours.

The present invention also provides a magnesium battery comprising the electrolyte additive according to the present invention.

4 is a schematic view of a magnesium battery 1 according to one embodiment. As shown in FIG. 4, the magnesium battery 1 includes an anode 3, a cathode 2, and a separator 4. The positive electrode 3, the negative electrode 2 and the separator 4 described above are wound or folded and accommodated in the battery case 5. Then, an organic electrolytic solution is injected into the battery case 5 and sealed with a cap assembly 6 to complete the magnesium battery 1. The battery case may have a cylindrical shape, a rectangular shape, a thin film shape, or the like. For example, the magnesium battery may be a large-sized thin-film battery. The magnesium battery may be a magnesium ion battery.

The cathode active material may include at least one selected from the group consisting of, for example, an oxide compound of a metal element, a halogen compound, a sulfide compound, a selenium compound, a phosphate compound, a phosphide compound and a diboride compound. The metal element may be at least one selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, And may include at least one selected from the group consisting of lead (Pb), ruthenium (Ru), tungsten (W), zirconium (Zr), nickel (Ni), copper (Cu) and zinc (Zn).

The cathode active material may include, for example, Co ₃ O ₄ , Mn ₂ O ₃ , Mn ₃ O ₄ , MoO ₃ , PbO ₂ , Pb ₃ O ₄ , RuO ₂ , V ₂ O ₅ , WO ₃ , Mg ₂ MnSiO ₄ , TiS ₂ , NiS ₂ , FeS ₂ , VS ₂ , ZrS ₂ , Mo ₃ O ₄ , Mo ₆ S ₈ , Mo ₆ Se ₈ , MoS ₆ Se ₂ , MoB ₂ , TiB ₂ and ZrB ₂ Or more.

In addition to the above-described cathode active material, the cathode may further include a conventional cathode active material or a magnesium composite metal oxide. Examples of the magnesium composite metal oxide include Mg (M1-xAx) O4 (0 = x = 0.5, M is Ni, Co, Mn, Cr, V, Fe, Cu or Ti, A is Al, B, , V, C, Na, K or Mg) may be used.

As the conductive material, a carbon material having a high specific surface area such as carbon black, activated carbon, acetylene black, or a mixture of two or more of graphite fine particles may be used. Further, electroconductive fibers such as fibers produced by carbonizing vapor-grown carbon or pitch (by-products such as petroleum, coal, coal tar and the like) at high temperature and carbon fibers prepared from acrylic fibers (polyacrylonitrile) . Carbon fiber and a carbon material having a high specific surface area can be used simultaneously. The use of the carbon fiber and the carbon material having a high specific surface area simultaneously can further improve the electric conductivity. Further, a metal-based conductive material having a lower electrical resistance than that of the cathode active material can be used as a material which does not dissolve in the charge and discharge range of the anode. For example, a corrosion-resistant metal such as titanium or gold, a carbide such as SiC or WC, or a nitride such as Si ₃ N ₄ or BN can be used, but not limited thereto, and any material that can be used as a conductive material in the related art Do.

Examples of the binder include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, polytetrafluoroethylene and mixtures thereof, and styrene butadiene rubber-based polymers But are not limited thereto and can be used as long as they can be used as binders in the art.

As the solvent, N-methylpyrrolidone, acetone, water or the like may be used, but not limited thereto, and any solvent which can be used in the technical field can be used.

The metal current collector is not limited to a material, a shape, a manufacturing method, and the like, and a stable material can be used electrochemically. The metal current collector may be an aluminum foil having a thickness of 10 to 100 탆, an aluminum punched foil having a thickness of 10 to 100 탆, a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate and the like. As the material of the metal current collector, besides aluminum, stainless steel, titanium and the like can also be used.

The content of the positive electrode active material, the conductive material, the binder and the solvent is a level commonly used in a magnesium battery. One or more of the conductive material, the binder and the solvent may be omitted depending on the use and configuration of the magnesium battery.

In the magnesium battery, the negative electrode may include at least one selected from the group consisting of a magnesium metal, a magnesium metal-based alloy, a magnesium intercalating compound, and a carbon-based material. However, the present invention is not necessarily limited to these, and any material which can be used as an anode active material in the technical field includes magnesium or can absorb / release magnesium.

Since the negative electrode determines the capacity of the magnesium battery, the negative electrode may be, for example, magnesium metal. Examples of the magnesium-based alloy include alloys of aluminum, tin, indium, calcium, titanium, vanadium, and the like and magnesium.

For example, the negative electrode may be used in a variety of forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, and the like.

The oxidation potential of the magnesium salt contained in the electrolyte solution impregnated between the positive electrode and the negative electrode may have a range of 2.5V to 4.5V (vs. Mg / Mg2 +). For example, the oxidation potential of the magnesium salt contained in the electrolytic solution may range from 2.8V to 3.3V (vs. Mg / Mg2 +). The magnesium salt has a wide range of oxidation potential, thereby enhancing the reversibility of the deposition / elution of magnesium and improving lifetime characteristics.

A separator may be additionally disposed between the anode and the cathode.

The separator is not limited as long as it can withstand the use environment of the magnesium battery. For example, the separator may be formed of a nonwoven fabric made of polypropylene material or a nonwoven fabric made of polyphenylene sulfide material, a porous nonwoven fabric made of an olefin resin such as polyethylene or polypropylene Film may be exemplified, and two or more kinds of these may be used in combination.

In addition, the separator may have a low resistance to ion movement of the electrolyte and an excellent ability to impregnate the electrolyte. For example, glass fiber, polyester, Teflon, polytetrafluoroethylene (PTFE), or a combination thereof, and may be nonwoven fabric or woven fabric.

For example, the separator may be produced according to the following method.

A polymer resin, a filler and a solvent are mixed to prepare a separator composition. The separator composition may be directly coated on the anode active material layer and dried to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled off from the support may be laminated on the negative active material layer to form a separator.

The polymer resin used in the production of the separator is not particularly limited, and any material used for the binder of the electrode plate may be used. For example, polyethylene, polypropylene, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate or mixtures thereof may be used. As the filler used in the production of the separator, inorganic particles and the like can be used, and the solvent is capable of dissolving the polymer resin and forming pores in the polymer resin upon drying, so long as it is generally used in the related art .

Further, the separator may be separately manufactured by another publicly known method and laminated on the anode active material layer. For example, a dry manufacturing method in which a microporous film is formed by forming a film by melting and extruding polypropylene or polyethylene, annealing at a low temperature to grow a crystal domain, and then stretching in this state to extend an amorphous region Can be used. For example, a film obtained by mixing a low-molecular material such as a hydrocarbon solvent with polypropylene, polyethylene, or the like, and then forming a film, and then a solvent or a small molecule is gathered to form an island phase, A wet production method of forming a microporous membrane by removing a solvent or a low molecular weight using another volatile solvent may be used.

The separator may additionally contain additives such as non-conductive particles, other fillers, and fiber compounds for the purpose of controlling strength, hardness and heat shrinkage. For example, the separator may further include inorganic particles. By further including the inorganic particles, the oxidation resistance of the separator is improved, and deterioration of the battery characteristics can be suppressed. The inorganic particles may be alumina (Al 2 O 3), silica (SiO 2), titania (TiO ₂ ), or the like. The average particle diameter of the inorganic particles may be 10 nm to 5 占 퐉. When the average particle diameter is less than 10 nm, the crystallinity of the inorganic particles is lowered and the effect of addition is insignificant. When the average particle diameter exceeds 5 탆, dispersion of the inorganic particles may be difficult.

The separator may have a multi-layer structure including one or more polymer layers for the purpose of increasing the tear strength and mechanical strength. For example, a polyethylene / polypropylene laminate, a polyethylene / polypropylene / polyethylene laminate, a nonwoven fabric / polyolefin laminate, and the like.

A separator may be disposed between the anode and the cathode to form a battery structure. The battery structure is laminated in a bi-cellular structure, then impregnated with an organic electrolytic solution, and the obtained result is received in a pouch and sealed to complete a magnesium polymer battery.

As shown in FIG. 1, the magnesium battery 1 includes an anode 3, a cathode 2, and a separator 4. The positive electrode 3, the negative electrode 2 and the separator 4 described above are wound or folded and accommodated in the battery case 5. Then, an organic electrolytic solution is injected into the battery case 5 and sealed with a cap assembly 6 to complete the magnesium battery 1. The battery case may have a cylindrical shape, a rectangular shape, a thin film shape, or the like. For example, the magnesium battery may be a large-sized thin-film battery. The magnesium battery may be a magnesium ion battery.

A separator may be disposed between the anode and the cathode to form a battery structure. The battery structure is laminated in a bi-cellular structure, then impregnated with an organic electrolytic solution, and the obtained result is received in a pouch and sealed to complete a magnesium polymer battery.

In addition, a plurality of battery structures may be stacked to form a battery pack, and such a battery pack may be used for all devices requiring a high capacity. For example, a notebook, a smart phone, an electric vehicle, and the like.

In addition, the magnesium battery has excellent storage stability and thermal stability, and thus can be used in an electric storage system (ESS), an electric vehicle (EV), and the like. For example, a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV).

The magnesium additive for magnesium battery according to the present invention effectively inhibits and removes the formation of magnesium oxide on the surface of the negative electrode to increase the reversibility of magnesium deposition / elution, and thus the magnesium battery including the additive for the electrolyte for magnesium battery has a life characteristic and a charge / Can be improved.

1 schematically shows the action of an electrolyte additive for a magnesium battery on the surface of a negative electrode according to the present invention.
2 shows a process for producing an electrolyte additive for a magnesium battery according to the present invention.
3 shows the F-NMR measurement results of the electrolyte additive for a magnesium battery according to the present invention.
4 shows the results of measurement of charge / discharge characteristics of a battery including an electrolyte additive for a magnesium battery according to the present invention.

Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited by the following examples.

< Example  1>

Mg (TFSI) ₂ and TiCl ₄ dissolved in DME were mixed at a ratio of 3: 1 and stirred at room temperature for 2 weeks. After the reaction, DME was removed through a rotary evaporator to obtain a solid product.

Thereafter, the solid product was purified several times with diethyl ether and ethyl acetate and filtered to obtain a purified solid product, which was dried at room temperature / vacuum to obtain the final product.

< Experimental Example > ¹⁹ Identification of additive chemical structure by F-NMR

The chemical structure of the electrolyte additive for magnesium battery synthesized in Example 1 was confirmed by ¹⁹ F-NMR and the results are shown in FIG.

As can be seen in FIG. 2, a new F-peak appears at -74.4 ppm after 7 days of stirring.

This peak is interpreted as a peak that can identify the electrolyte additive for a magnesium battery synthesized by the present invention as a peak derived from a newly formed additive through the reaction of Mg (TFSI) ₂ and TiCl ₄ .

< Example > Manufacture of magnesium battery

A magnesium battery including the electrolyte additive prepared in Example 1 was prepared.

Mo ₆ S ₈ material having a Shavele structure was used as an anode and Mg (TFSI) ₂ as a magnesium salt in a non-aqueous DME / DGM (1/1) mixed solvent and 0.1 M Were added to prepare a magnesium secondary battery.

< Experimental Example > Manufacture of magnesium battery

A coin cell was fabricated from the prepared electrode plate and electrolyte and electrochemical comparative analysis was performed. As a result of evaluating the characteristics of the battery, it was confirmed that the initial discharge characteristics were exhibited by effectively removing MgO on the magnesium surface in the example including the additive, and then it was confirmed that the charge / discharge behavior was stable based on the excellent oxidation potential.

Claims (10)

An electrolyte additive for a magnesium battery represented by the following formula (1).
???????? L _1x M _1? L _2y M ₂ ?????
(L _1x M ₁ and L _2y M ₂ in the above formula (1) are in a solid phase mixed state,
L ₁ is _{TFSI-, PF 6, BF 4,} SR, B (OR) 4, OH-, CH 3 COO-, (CN) 3 C-, (CN) 4 B-, (CN) 2 N-, CF _{3 COO-, CF 3 SO 3,} ClO 4, FSI, N (CN) 2, and oR (R is a substituted or unsubstituted C1 to C20 of the alkane, alkene, or alkyne Im), which is selected from the group consisting of One or more
L ₂ Is one or more selected from the group consisting of F, Cl, Br and I,
M ₁ , M ₂ Is any one or more selected from the group consisting of Group 3, Group 4, and Group 5 elements)
The method according to claim 1,
The L ₁ Is bis (trifluoromethanesulfonyl) imide (TFSI).
The method according to claim 1,
Wherein M ₁ is Mg and M ₂ is Ti.
The method according to claim 1,
Wherein the electrolyte additive for a magnesium battery has a peak at -50.0 to -100.0 ppm in F-NMR measurement.
The method according to claim 1,
Wherein the electrolyte additive for a magnesium battery has a peak at -70.0 to -90.0 ppm in F-NMR measurement.
A magnesium battery comprising the electrolyte additive according to claim 1.
Dissolving a first compound represented by L _{1 x} M ₁ in a first solvent;
Adding a second compound represented by L _2y M ₂ ;
Stirring the mixture;
Removing the first solvent remaining in the mixture;
Refining and drying; Containing
A method for producing an electrolyte additive according to claim 1.
8. The method of claim 7,
Wherein the first solvent is selected from the group consisting of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or combinations thereof.
A method for producing an electrolyte additive.
8. The method of claim 7,
Adding the second compound at a ratio of 0 to 1000 parts by weight of the second compound per 100 parts by weight of the first compound,
A method for producing an electrolyte additive.
8. The method of claim 7,
And the mixture is stirred for 24 to 72 hours in the step of stirring the mixture
A method for producing an electrolyte additive.

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