KR101728826B1 - Electrolyte for magnesium rechargeable battery, and magnesium rechargeable battery including the same - Google Patents

Abstract

The present invention relates to an electrolyte for a magnesium secondary battery, and a magnesium secondary battery including the same. And a functional additive for etching the passivation layer are added to a specific organic solvent; and a magnesium secondary battery comprising the electrolyte.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte for a magnesium secondary battery, and a magnesium secondary battery including the same. BACKGROUND ART Electrolyte for a magnesium secondary battery,

An electrolyte for a magnesium secondary battery, and a magnesium secondary battery containing the same.

The magnesium secondary battery is a secondary battery using magnesium, which is rich in resources and low in cost, and has advantages of safety and price competitiveness.

However, since the magnesium secondary battery studied so far has a disadvantage of low reversibility of charging / discharging, it is necessary to develop a new electrode material and an electrolyte to overcome this.

Specifically, when the magnesium secondary battery continues to be charged and discharged, a passivation layer of magnesium is formed on the surface of the electrode, which hinders dissolution (stripping) of magnesium ions and deteriorates the performance of the battery.

On the other hand, in the case of Grignard reagent (RMgX in tetrahydrofuran (THF), R: alkyl, acryl, X: Cl, Br) widely used as an electrolyte of a magnesium secondary battery, the passivation layer is effectively decomposed which is known to dissociate and allow reversible magnesium migration.

However, such Grignard derivatives have a problem of decomposing at the anode due to a low electrochemical oxidative decomposition potential, and involve the use of a solvent having high volatility such as tetrahydrofuran (THF), thereby causing a problem of long-term reliability and safety of the battery have.

In order to overcome the above-mentioned problems, certain magnesium salts; And a functional additive for etching the passivation layer in a specific organic solvent. The present invention also provides a magnesium secondary battery including the electrolyte.

In one embodiment of the invention, the magnesium salt; An organic solvent containing 1,2-dimethoxyethane and a glyme-based solvent represented by the following formula (1); And an additive represented by the following general formula (2).

[Chemical Formula 1]

(In the formula 1,

Each of R ¹ and R ² is independently a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C6 to C30 aryl group, or a combination thereof ,

And n is an integer of 2 to 5)

???????? M ¹ (M ² H ₄ ) _X

(In the formula (2)

M ¹ is any element selected from the group consisting of Li, Na, Mg, K, and Ca,

M ² is any one element selected from the group consisting of B, Al and Ga, or a combination thereof,

Wherein x is 1 or 2.

Specifically, the content of the additive in the electrolyte for the magnesium secondary battery may be 0.05 to 1.0 M, in terms of the molar concentration of the additive relative to the organic solvent.

At the same time, the content of the magnesium salt in the electrolyte for the magnesium secondary battery may be 0.05 to 1.0 M in terms of the molar concentration of the magnesium salt with respect to the organic solvent.

In Formula 2, M ¹ may be Li, Na, or Mg.

Independently, in the above formula (2), M ² may be B, Al, or Ga.

Specifically, the chemical formula 2 is LiBH ₄ , NaBH ₄ , _{Mg (BH 4) 2, KBH} 4, Ca (BH 4) 2, LiAlH ₄ , NaAlH ₄ , _{Mg (AlH 4) 2, KAlH} 4, Ca (AlH 4) 2, LiGaH 4, NaGaH 4, Mg (GaH ₄₎ may be represented by ₂ or ₄ KGaH.

In Formula 1, R ¹ and R ² each independently represent a substituted or unsubstituted C1 to C20 alkyl group.

The volume ratio of the 1,2-dimethoxyethane to the glyme based solvent may be 10:90 to 90:10.

The glyme-based solvent may be diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or a combination thereof.

The magnesium salt may be at least one selected from the group consisting of magnesium bis (trifluoromethanesulfonyl) limide: Mg (TFSI) ₂ , magnesium bis (hexafluorophosphate) _{6) 2),} magnesium bis (perchlorate) (magnesium bis (perchlorate): Mg (ClO _{4) 2),} magnesium bis (trifluoromethane sulfonyl) imide (magnesium bis (trifluoromethanesulfonyl) imide: Mg (CF ₃ SO ₃ N) _2), magnesium bis (oxalate reyito) borate (magnesium bis (oxalato) borate (Mg (BOB) _2), magnesium bis (tetrafluoroborate) (magnesium bis (tetrafluoroborate): Mg (BF _{4) 2)} , Magnesium bis (perfluoroethanesulfonyl) imide: Mg (BETI) ₂ , or a combination thereof.

In another embodiment of the present invention, cathode; And an electrolyte, wherein the electrolyte is in accordance with any one of the foregoing.

According to one embodiment and another embodiment of the present invention, the magnesium salt; And a passivation layer formed on the surface of the electrode (specifically, the cathode), which is decomposed from the organic solvent, facilitates the dissolution of magnesium ions from the electrode as the functional additive is etched, and ultimately, The electrochemical performance of the battery can be improved.

In addition, the functional additive has an oxidation decomposition potential higher than that of a generally known Grignard derivative, so that it is hardly decomposed in the anode and has an advantage of not involving the use of a highly volatile solvent such as tetrahydrofuran (THF).

1 is a view schematically showing a mechanism of action when an additive is not included, unlike an electrolyte for a magnesium secondary battery according to an embodiment of the present invention
FIG. 2 is a schematic view illustrating an action mechanism of an electrolyte for a magnesium secondary battery including an additive according to an embodiment of the present invention. FIG.
FIG. 3 is a schematic view illustrating an interaction between a glyme-based organic solvent and a magnesium salt in an electrolyte for a magnesium secondary battery according to an embodiment of the present invention.
4 is a graph showing the results of a galvanostatic cycle evaluation for Example 1 and Comparative Example 1 of the present invention.
5 is a graph showing the results of a galvanostatic cycle evaluation for Example 2 and Comparative Example 1 of the present invention.
6 is a graph showing the results of a galvanostatic cycle evaluation for Example 3 and Comparative Example 1 of the present invention.
7 is an SEM photograph of a surface of a negative electrode recovered from a battery in which a constant current cycle evaluation for Example 1 of the present invention has been completed.
8 is an SEM photograph of a surface of a negative electrode recovered from a battery in which a constant current cycle evaluation for Example 2 of the present invention has been completed.
9 is an SEM photograph of a surface of a negative electrode recovered from a battery in which a constant current type cycle evaluation according to Example 3 of the present invention has been completed.
10 is an SEM photograph of a surface of a negative electrode recovered from a battery in which a constant current type cycle evaluation for Comparative Example 1 of the present invention has been completed.

In the present specification, the term "combination thereof" means that two or more substituents are bonded to each other via a linking group or two or more substituents are condensed and bonded.

As used herein, the term "alkyl group" means a saturated aliphatic hydrocarbon group, unless otherwise defined.

The alkyl group may have from 1 to 20 carbon atoms. The alkyl group may be a medium-sized alkyl group having 1 to 10 carbon atoms. The alkyl group may also be a lower alkyl group having 1 to 6 carbon atoms.

For example, the C1 to C4 alkyl groups may have 1 to 4 carbon atoms in the alkyl chain, i.e., the alkyl chain may be optionally substituted with one or more substituents selected from the group consisting of methyl, ethyl, propyl, iso-propyl, n-butyl, Indicating that they are selected from the group.

Typical alkyl groups include methyl Mt, ethyl, Et, propyl, isopropyl, butyl, Bu, isobutyl, t-butyl, pentyl, hexyl, ethenyl, propenyl, butenyl, , Cyclobutyl, cyclopentyl, cyclohexyl, and the like. The term " cycloalkyl "

The alkyl group may be branched, straight-chain or cyclic.

"Aryl group" means an aryl group that contains a carboxyclic aryl (e. G., Phenyl) having at least one ring having a covalent pi electron system. The term includes groups of rings that divide adjacent pairs of carbon atoms (i.e., groups that are monocyclic or fused rings).

The term "substituted" as used herein, unless otherwise defined, includes an alkyl group having 1 to 30 carbon atoms, an alkylsilyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, an aryl group having 2 to 30 carbon atoms A trifluoroalkyl group having 1 to 10 carbon atoms such as an alkoxy group having 1 to 10 carbon atoms, a fluoro group and a trifluoromethyl group, a carbazole group having 12 to 30 carbon atoms, an arylamine group having 6 to 30 carbon atoms, A substituted or unsubstituted aminoaryl group having 6 to 30 carbon atoms, or a cyano group.

As used herein, the term " glyme solvent "means a glycol ether unless otherwise defined, and includes glyme solvents such as 1,2-dimethoxyethane and di And a diglyme type solvent such as ethylene glycol dimethyl ether.

Hereinafter, embodiments of the present invention will be described in detail. However, it should be understood that the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

In one embodiment of the invention, the magnesium salt; An organic solvent containing 1,2-dimethoxyethane and a glyme-based solvent represented by the following formula (1); And an additive represented by the following general formula (2).

[Chemical Formula 1]

(In the formula 1,

Each of R ¹ and R ² is independently a substituted or unsubstituted C1 to C20 alkyl group, a substituted or unsubstituted C3 to C20 cycloalkyl group, a substituted or unsubstituted C6 to C30 aryl group, or a combination thereof ,

And n is an integer of 2 to 5)

???????? M ¹ (M ² H ₄ ) _X

(In the formula (2)

M ¹ is any element selected from the group consisting of Li, Na, Mg, K and Ca,

M ² is any one element selected from the group consisting of B, Al and Ga, or a combination thereof,

Wherein x is 1 or 2.

Specifically, in the electrolyte for a magnesium secondary battery, the magnesium salt; And a passivation layer formed on the surface of the electrode (specifically, the cathode) after being decomposed from the organic solvent comprising the 1,2-dimethoxyethane and the glyme-based solvent represented by the following formula (1) The additive represented by Formula 2 may be etched.

More specifically, the passive film includes magnesium oxide (MgO) and / or magnesium hydroxide (Mg (OH) ₂ ), which prevents dissolution (stripping) of magnesium ions from the negative electrode coating, Lt; / RTI > This is shown in Fig.

In this connection, the additive represented by Formula 2 (hereinafter occasionally referred to as "functional additive ") has a dissolving power capable of effectively etching and removing the passive film. Accordingly, dissociation of the magnesium cation from the electrode (concretely, the negative electrode) can be facilitated, and the initial overvoltage generated at this time can be effectively mitigated, thereby ultimately contributing to the improvement of the electrochemical performance of the magnesium secondary battery. This is shown in Fig.

On the other hand, the functional additive generally has a higher oxidative decomposition potential than a Grignard derivative, which is known to effectively dissolve a passivation layer, so that the functional additive is hardly decomposed in the anode, and tetrahydrofuran (THF) There is an advantage not involving the use of highly volatile solvents.

Hereinafter, the electrolyte for the magnesium secondary battery will be described in more detail.

First, the content of the additive in the electrolyte for the magnesium secondary battery may be 0.05 to 0.6 M in terms of molar concentration of the additive to the organic solvent. When the additive content in the molar concentration range is satisfied, the passive film can be effectively removed by the additive.

More specifically, the content of the additive in the electrolyte for the magnesium secondary battery may be 0.1 to 0.2 M in terms of the molar concentration of the additive with respect to the organic solvent, as in the following embodiments.

However, if the molar concentration is excessively high in excess of 0.6 M, the ionic conductivity of the non-dissociated additive salt may increase and the ionic conductivity may be lowered. On the other hand, if the molar concentration is too low to less than 0.05 M, its effectiveness may be insignificant.

The content of the magnesium salt in the electrolyte for the magnesium secondary battery may be 0.05 to 1.0 M in terms of molar concentration of the magnesium salt with respect to the organic solvent. In this case, the content of the high magnesium ion Conductivity can be obtained.

In Formula 2, M ¹ may be Li, Na, or Mg.

Independently of this, in the formula (2), M ² may be B, Al, or Ga.

More specifically, the chemical formula 2 is LiBH ₄ , NaBH ₄ , _{Mg (BH 4) 2, KBH} 4, Ca (BH 4) 2, LiAlH ₄ , NaAlH ₄ , _{Mg (AlH 4) 2, KAlH} 4, Ca (AlH 4) 2, LiGaH 4, NaGaH 4, Mg (GaH ₄₎ may be represented by ₂ or ₄ KGaH.

In Formula 1, R ¹ and R ² each independently represent a substituted or unsubstituted C1 to C20 alkyl group. In this case, the organic solvent can be oriented so as to easily form a complex with the magnesium cation spatially. As a result, dissociation of magnesium ions can be performed more effectively.

When the organic solvent comprises a glyme solvent such as 1,2-dimethoxyethane and a glyme solvent represented by the above formula (1), the magnesium ion insertion / desorption of the magnesium secondary battery A high-performance and high-safety electrolytic solution capable of efficiently inducing the reaction can be produced.

When such a high performance and high safety electrolyte is included, the magnesium secondary battery can improve the reversibility of the electrochemical oxidation / reduction reaction of the magnesium metal cathode and the performance of the full cell.

Specifically, the effect of the glyme-based solvent represented by Formula 1 will be described with reference to FIG. 3, the glyme-based organic solvent represented by Formula 1 serves as a Lewis base, and magnesium ions derived from the magnesium salt can act as a Lewis acid. Therefore, the Lewis base and the Lewis acid Ligand binding.

At this time, since the ether moiety serves as an electron pair donor in the glyme type solvent represented by Formula 1, the ether moiety capable of ligand bonding increases as the chain of the glary organic solvent becomes longer, The insertion / desorption reaction of magnesium ions can be more effectively performed. Accordingly, the glyme-based solvent has a low viscosity, so that the ion mobility can be smoothly improved.

In the organic solvent, the volume ratio of the 1,2-dimethoxyethane to the glyme-based solvent is in the range of 10:90 to 90:10, more specifically 30:70 to 70:30 . When the mixing ratio of the organic solvent is within the above range, dissociation and migration of magnesium ions are optimized to maximize the reversibility of the electrochemical oxidation / reduction reaction of the magnesium secondary battery.

Specifically, the glyme-based solvent represented by the above formula (1) can be used for diglyceride-based daily.

Specifically, the deglycation solvent is an ether solvent in which an alkylene group, a cycloalkylene group, or an arylene group is connected to an ether group, and examples thereof include diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene Glycol dimethyl ether, or a combination thereof.

The diglycidic solvent has a high boiling point and a high donor number, and has a high boiling point, so that the generation of the internal pressure by the volatile gas is small, so that the cell is excellent in terms of stability and the donor number is high. Can easily dissolve magnesium ions and can stably solubilize the dissolved ions and moves the solved ions to the counter electrode to advantageously perform the reduction reaction at the counter electrode interface .

That is, the process of dissolving magnesium ions from magnesium ions is referred to as stripping. At this time, the resistance (overvoltage) required to oxidize Mg ^{2 +} ions to crystalline Mg-Mg bonds is a voltage drop phenomenon. In order to oxidize Mg ^{2 +} ions by breaking strong bonds between these Mg-Mg ions, solvation (solvation) is required so that Mg ^{2 +} ions can be stably maintained in a state of dissociation of Mg ^{2 +} structure is preferable, and the above deglycation solvent is suitable.

Particularly, when the glial solvent and the deglycation solvent are used in combination, the mixed organic solvent works in a complementary manner to improve the reversibility of the electrochemical oxidation / reduction reaction of magnesium and to secure the safety of the battery have.

On the other hand, the donor number is a measure for measuring the Lewis basicity, that is, the extent to which the solvent dissolves cations or Lewis acids. For example, Lewis base and antimony pentachloride (SbCl ₅ ) - The enthalpy value when forming the adduct in dichloroethane is the reference value. The larger the absolute value of the enthalpy, the higher the donor number. On the other hand, the higher the donor number, the better the ability to dissolve the cation or Lewis acid.

The organic solvent may further include a common organic solvent. Specific examples of the organic solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide , And one or more selected from the group consisting of acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite and tetrahydrofuran But is not limited thereto.

The magnesium salt may be at least one selected from the group consisting of magnesium bis (trifluoromethanesulfonyl) limide: Mg (TFSI) ₂ , magnesium bis (hexafluorophosphate) _{6) 2),} magnesium bis (perchlorate) (magnesium bis (perchlorate): Mg (ClO _{4) 2),} magnesium bis (trifluoromethane sulfonyl) imide (magnesium bis (trifluoromethanesulfonyl) imide: Mg (CF ₃ SO ₃ N) _2), magnesium bis (oxalate reyito) borate (magnesium bis (oxalato) borate (Mg (BOB) _2), magnesium bis (tetrafluoroborate) (magnesium bis (tetrafluoroborate): Mg (BF _{4) 2)} , Magnesium bis (perfluoroethanesulfonyl) imide: Mg (BETI) ₂ , or a combination thereof.

In the case of the magnesium salt exemplified above, a passive film which prevents ion permeation is hardly formed on the surface of the magnesium electrode, and the positive electrode current collector is not corroded.

In another embodiment of the present invention, cathode; And an electrolyte, wherein the electrolyte is in accordance with any one of the foregoing.

Since the electrolyte is in accordance with any one of the above-described ones, a repetitive description will be omitted.

The anode includes a collector, a cathode active material layer, and the cathode active material layer may include a conductive material, a binder, and / or a cathode active material.

The anode can be produced by a production method commonly used in the art. For example, a slurry may be prepared by mixing and stirring a binder and a solvent, and if necessary, a conductive material and a dispersant in a cathode active material, applying the slurry to a current collector, and compressing the anode to produce a cathode.

As the cathode active material, a transition metal compound or a magnesium composite metal oxide which can insert and desorb magnesium ions may be used. Oxides, sulfides or halides of scandium, ruthenium, titanium, vanadium, molybdenum, chromium, manganese, iron, cobalt, nickel, copper and zinc can be used as the transition metal compounds. More specifically, TiS ₂ , ZrS ₂ , RuO ₂ , Co ₃ O ₄ , Mo ₆ S ₈ , V ₂ O ₅ , and the like, but is not limited thereto. Further examples of the magnesium compound the metal oxide is _{Mg (M 1-x A x} ) O 4 (0≤≤x≤≤0.5, M is Ni, Co, Mn, Cr, V, Fe, Cu , or Ti, A is Al , B, Si, Cr, V, C, Na, K or Mg) may be used.

Examples of the binder include vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, Various types of binder polymers may be used.

As the conductive material, conductive carbon may be used. For example, various conductive carbon materials such as graphite, carbon black, acetylene black, caden black, denka black, super-P, and carbon nanotubes may be used.

The negative electrode may include a current collector and / or a negative electrode active material layer. Alternatively, a metal such as magnesium may be used for the counter electrode as the counter electrode.

The negative electrode active material layer may include a conductive material, a binder, and / or a negative electrode active material. The negative electrode active material may be oxidized to generate magnesium ions. The negative electrode active material may include at least one selected from the group consisting of a single substance of magnesium and an alloy containing magnesium. The negative electrode active material and / or the negative electrode may be, for example, magnesium foil.

As another example, the cathode may further include a binder and / or a conductive material that is the same as or similar to that used in the production of the anode.

As the separator, a conventional inorganic separator or an organic separator which is conventionally used as a separator may be used. As the inorganic separation membrane, a glass filter or the like can be used, and as the organic separation membrane, a porous polymer membrane can be used.

The porous polymer film may be formed by using a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer Or they may be laminated and used.

When the positive electrode and the negative electrode are prepared, a magnesium secondary battery can be manufactured by providing an electrolyte between the positive electrode and the negative electrode with a separator interposed therebetween.

The battery case to be used in one embodiment of the present invention may be of any type that is commonly used in the art and is not limited in its outer shape depending on the use of the battery. For example, a cylindrical case, a square type, a pouch ) Type, a coin type, or the like.

Hereinafter, preferred embodiments of the present invention, comparative examples thereof, and evaluation examples in which these are evaluated will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Example  One: LiBH ₄ To Preparation of Electrolyte for Magnesium Secondary Battery Added with Functional Additive

As the gaseous solvent, diethylene glycol dimethyl ether, which is a diglycidic solvent, was used, 1,2-dimethoxyethane was mixed with the diethylene glycol dimethyl ether at a volume ratio of 1: 1, Solvent.

Magnesium salts include Mg (TFSI) ₂ (magnesiumbis (trifluoromethanesulfonyl) imide) was used, and the molar concentration of the magnesium to the prepared organic solvent was adjusted to 0.3 M.

As the additive, LiBH ₄ (Lithium borohydride) was used, and the molar concentration of the additive (LiBH ₄ ) to the prepared organic solvent was adjusted to 0.2 M, and the mixture was added to the electrolyte for the magnesium secondary battery of Example 1 .

Specifically, the amount of the magnesium salt was 14% by weight, the amount of the additive was 0.3% by weight, the amount of the 1,2-dimethoxyethane and the diethylene glycol dimethyl (meth) acrylate based on the total weight of the electrolyte for a magnesium secondary battery of Example 1 The ether-mixed organic solvent is prepared so as to be included as the remainder.

Example  2: NaBH ₄ To Preparation of Electrolyte for Magnesium Secondary Battery Added with Functional Additive

The same organic solvent and magnesium salt as in Example 1 were used, and NaBH ₄ (sodium borohydride) was used instead of LiBH ₄ (Lithium borohydride) as an additive.

Specifically, the respective materials were added to the organic solvent so that the molar concentration of the magnesium salt was 0.3 M, the molar concentration of the additive (NaBH ₄ ) was 0.2 M, and the mixture was mixed to obtain magnesium And was obtained as an electrolyte for a secondary battery.

Specifically, the amount of the magnesium salt was 15 wt%, the amount of the additive was 0.6 wt%, the amount of the 1,2-dimethoxyethane and the diethylene glycol dimethyl (meth) acrylate was changed to the total weight (100 wt%) of the electrolyte for a magnesium secondary battery of Example 2 The ether-mixed organic solvent is prepared so as to be included as the remainder.

Example  3: Mg (BH ₄ ) ₂ To Preparation of Electrolyte for Magnesium Secondary Battery Added with Functional Additive

Mg (BH ₄ ) ₂ (Magnesium borohydride) was used instead of LiBH ₄ (Lithium borohydride) as an additive in the same organic solvent and magnesium salt as in Example 1.

Specifically, the molar concentration of the magnesium salt with respect to the organic solvent was adjusted to 0.3 M, and the respective materials were added so that the molar concentration of the additive (Mg (BH ₄ ) ₂ ) was 0.1 M, Lt; / RTI > was obtained as an electrolyte for a magnesium secondary battery of Example 3.

Specifically, with respect to the total weight (100 wt%) of the electrolyte for a magnesium secondary battery of Example 3, the magnesium salt was 15 wt%, the additive was 0.5 wt%, the 1,2-dimethoxyethane and diethylene glycol dimethyl The ether-mixed organic solvent is prepared so as to be included as the remainder.

Comparative Example  1: Preparation of Electrolyte for Magnesium Secondary Battery without Addition of Functional Additive

An electrolyte for a magnesium secondary battery of Comparative Example 1 was obtained in the same manner as in Example 1 except that the functional additive of Example 1 was not added.

Specifically, the magnesium salt was contained in an amount of 14% by weight based on the total weight (100% by weight) of the electrolyte for the magnesium secondary battery of Comparative Example 1, and the organic solvent in which the 1,2-dimethoxyethane and diethylene glycol dimethyl ether were mixed .

Evaluation example  1: Electrochemical performance evaluation

For each of the electrolytes of Examples 1 to 3 and Comparative Example 1, using each of the electrolytes of Examples 1 to 3 and Comparative Example 1, stainless steel was used as a working electrode and a 2016 coin type half cell Respectively.

Specifically, a magnesium metal disk having a thickness of 1.0 T was used as a counter electrode, and a spacer having a thickness of 0.3 T made of stainless steel was used as a working electrode. A galvanostatic cycle in which magnesium ions were dissolved from the magnesium cathode and deposited on the counter electrode was evaluated.

Specifically, the degree of adsorption of magnesium on stainless steel (Stainless Steel) at a current of 6.5 mAh (1C) under a constant current of 0.1 C was evaluated. The results are shown in FIGS. 4 to 6.

4 to 6, magnesium ions are separated from the magnesium cathode, and the potential at which the deposition reaction to the counter electrode is performed can be grasped.

Specifically, the graphs shown at the top of Figures 4 to 6 are in accordance with any one of Examples 1 to 3, respectively, and each exhibits an overvoltage of 0.4 V. On the other hand, the graph shown at the bottom of Figs. 4 to 6 is according to Comparative Example 1, and exhibits an overvoltage of 2.3 V. Fig.

Thus, unlike Comparative Example 1, the electrolytes of Examples 1 to 3 were prepared by mixing LiBH ₄ (Example 1), NaBH ₄ (Example 2), and Mg (BH ₄ ) ₂ (Example 3), which are functional additives, It is deduced that the passivation film formed on the surface of the negative electrode is etched and removed effectively, thereby facilitating the dissolution of magnesium ions in the negative electrode and lowering the overvoltage of the magnesium secondary battery.

Evaluation example  2: Evaluation example  1 Electrochemical performance evaluation of cathode surface after evaluation

In order to more directly confirm the effect of the additive contained in each of the electrolytes of Examples 1 to 3, after the electrochemical performance evaluation of Evaluation Example 1, the respective cathodes of each of the magnesium secondary batteries of Examples 1 to 3 and Comparative Example 1 SEM photographs were taken of the surface and the results are shown in Figs. 7 (Example 1), Fig. 8 (Example 2), Fig. 9 (Example 3) 10 (Comparative Example 1).

7 to 10, it was understood that the dissociation of magnesium ions occurred smoothly in the negative electrode of Examples 1 to 3, but the dissociation of magnesium ions was relatively small in the negative electrode of Comparative Example 1.

Thus, unlike Comparative Example 1, the electrolytes of Examples 1 to 3 were prepared by mixing LiBH ₄ (Example 1), NaBH ₄ (Example 2), and Mg (BH ₄ ) ₂ (Example 3), which are functional additives, It can be directly confirmed that the passivation film formed on the surface of the negative electrode is etched and removed effectively, thereby enabling the reversible migration of magnesium ions.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. As will be understood by those skilled in the art. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (11)

Magnesium salt;
An organic solvent comprising 1,2-dimethoxyethane and a glyme based solvent; And
An additive;
The magnesium salt may be magnesium bis (trifluoromethanesulfonyl) limide: Mg (TFSI) ₂ , magnesium bis (hexafluorophosphate): Mg (PF ₆ ) _2), magnesium bis (perchlorate) (magnesium bis (perchlorate): Mg (ClO _{4) 2),} magnesium bis (trifluoromethane sulfonyl) imide (magnesium bis (trifluoromethanesulfonyl) imide: Mg (CF ₃ SO ₃ N) _2), magnesium bis (oxalate reyito) borate (magnesium bis (oxalato) borate (Mg (BOB) _2), magnesium bis (tetrafluoroborate) (magnesium bis (tetrafluoroborate): Mg (BF 4) 2), Magnesium bis (perfluoroethanesulfonyl) imide: Mg (BETI) ₂ , or a combination thereof,
The glyme based solvent is diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or a combination thereof,
The additive LiBH _4, NaBH _4, Or Mg (BH ₄ ) ₂ ,
Wherein the molar concentration of the magnesium salt in the electrolyte is 0.3 to 1.0 M and the molar concentration of the additive is 0.3 to 0.6 M. [
Electrolytes for magnesium secondary batteries.
delete delete delete delete delete delete The method according to claim 1,
In the organic solvent,
The volume ratio of the 1,2-dimethoxyethane to the glyme-
10:90 to 90:10,
Electrolytes for magnesium secondary batteries.
delete delete anode;
cathode; And
An electrolyte;
The electrolyte according to claim 1 or 8,
Magnesium secondary battery.

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