KR102220332B1 - Functional electrolyte for lithium-ion battery and lithium-ion battery comprising the same - Google Patents

Abstract

The present invention relates to a functional electrolyte for a lithium ion battery and a lithium ion battery comprising the same, an organic solvent; Lithium (Li) salt; And it relates to a functional electrolyte for a lithium ion battery comprising an additive.
More specifically, according to the present invention, as the additive contained in the functional electrolyte is reduced and decomposed to form a protective film on the surface of the negative electrode, it is possible to reduce decomposition and side reactions of the electrolyte, and form a uniform protective film on the surface of the negative electrode to prevent the electrolyte and By effectively suppressing side reactions with the negative electrode, it is possible to provide a basis for improving the electrochemical life performance of a lithium ion battery composed of a carbon-based and non-carbon-based negative electrode and a layered positive electrode.

Description

Functional electrolyte for lithium-ion battery and lithium-ion battery containing the same {FUNCTIONAL ELECTROLYTE FOR LITHIUM-ION BATTERY AND LITHIUM-ION BATTERY COMPRISING THE SAME}

The present invention relates to a functional electrolyte for a lithium ion battery and a lithium ion battery including the same. More specifically, it relates to a functional electrolyte for a lithium ion battery capable of effectively suppressing side reactions between an electrolyte and a negative electrode and improving the electrochemical performance of a lithium ion battery, and a lithium ion battery including the same.

With the recent development of the information and communication industry, as electronic devices become smaller, lighter, thinner, and portable, the demand for high energy density of batteries used as power sources of such electronic devices is increasing. Lithium-ion batteries are batteries that can best meet these needs, and research on them is currently being actively conducted.

In general, lithium-ion batteries have an operating voltage of 3.6 V or more, which is three times higher than that of nickel-cadmium batteries or nickel-hydrogen batteries, and the market is rapidly increasing in terms of high energy density and lifespan characteristics. Currently, it is widely used in portable electronic devices such as mobile phones, laptops, digital cameras, camcorders, etc., and through the application of high-capacity lithium-ion batteries, research is actively conducted in fields such as electric vehicles, hybrid vehicles, robots, space and aviation. Is in progress.

Lithium-ion batteries include a positive electrode containing a lithium-containing metal oxide, a negative electrode containing a carbon material capable of intercalation or deintercalation of lithium, an electrolyte providing a migration path for lithium ions, and between the positive electrode and the negative electrode. A battery comprising a separator that prevents short circuits, and generates electrical energy through oxidation and reduction reactions when lithium ions are killed/desorbed from the positive and negative electrodes.

In order to overcome the limiting capacity of a carbon material used as a negative electrode of a commercially available lithium-ion battery, research is actively being conducted to apply a silicon-based material having a high theoretical capacity (4200mAh/g) to the negative electrode.

However, since the high-capacity silicon-based negative electrode material is accompanied by severe volume expansion due to the formation of a chemical bond with lithium, there is a problem that it destroys the percolation route of electron transfer in the electrode, thereby hindering smooth electrical communication between the current collector and the active material. .

In addition, there is a problem that silicon active material particles are mechanically disintegrated by electrochemical charging and discharging accompanied by severe volume expansion and contraction, resulting in an irreversible decomposition reaction of the electrolyte, resulting in a new resistive film. If such a reaction continues to occur, it induces depletion of the electrolyte in the battery, resulting in a problem that the battery does not operate.

Recently, research and development to realize a high capacity of the negative electrode by combining silicon, which is a high-capacity metal-based negative electrode material with graphite used in commercial negative electrodes, is in progress.However, these composite negative electrodes are in two types: silicon-electrolyte interface and graphite-electrolyte interface. Since the interface exists, there is a problem that the design of the electrolyte additive is complicated unlike in a single interface.

(Patent Document 1) KR 10-0863887 B1

An object of the present invention is to provide a functional electrolyte for a lithium ion battery and a lithium ion battery including the same.

Another object of the present invention is to provide a functional electrolyte for a lithium ion battery capable of reducing decomposition and side reactions of the electrolyte by reducing and decomposing the additive contained in the functional electrolyte to form a protective film on the surface of the negative electrode, and to provide a lithium ion battery comprising the same. Is to do.

Another object of the present invention is to provide a functional electrolyte for a lithium ion battery with improved electrochemical performance, and a lithium ion battery including the same, by using a silicon-based high-capacity metal anode due to the formation of a negative music protective film in the electrolyte.

In order to achieve the above object, the functional electrolyte for a lithium ion battery according to an embodiment of the present invention includes an organic solvent; Lithium (Li) salt; And an additive selected from the group consisting of a compound consisting of the following Formula 1, a compound consisting of the following Formula 2, a compound consisting of the following Formula 3, and a mixture thereof:

[Formula 1]

[Formula 2]

[Formula 3]

here,

n and m are the same as or different from each other, each independently an integer of 0 to 2,

R ₁ and R ₂ are the same as or different from each other, and each independently from the group consisting of an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, and an aryloxy group having 6 to 20 carbon atoms Is selected,

R ₃ to R ₆ are the same or different from each other, and each independently from the group consisting of an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, and an aryloxy group having 6 to 20 carbon atoms Is selected,

The _{alkyl group, aryl group, alkyloxy group and aryloxy group of R 1} to R ₆ are hydrogen, deuterium, halogen group, alkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms, alkynyl group having 2 to 10 carbon atoms, carbon number A cycloalkyl group of 3 to 10, a heterocycloalkyl group of 3 to 10 nuclear atoms, an aryl group of 6 to 20 carbon atoms, a heteroaryl group of 5 to 20 nuclear atoms, a fluorene group, a spiro fluorene group, 1 to 30 carbon atoms Unsubstituted or substituted with one or more substituents selected from the group consisting of an alkylsilyl group, an arylsilyl group having 6 to 60 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, and an aryloxy group having 6 to 20 carbon atoms.

The lithium (Li) salt may be selected from the group consisting _{of LiPF 6} , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ , LiBOB, LiFOB, LiDFBP, LiTFOP, LiPO ₂ F _{2 and mixtures thereof.}

The organic solvent may be selected from the group consisting of carbonate-based, ester-based, ether-based, ketone-based, and mixtures thereof.

The lithium (Li) salt has a concentration of 0.1 to 3M.

The additive may be included in an amount of 0.1 to 10% by weight based on the weight of the electrolyte.

A lithium ion battery according to another embodiment of the present invention includes a positive electrode including a positive electrode active material capable of reversibly inserting and desorbing battery lithium ions; A negative electrode including a negative active material capable of reversibly inserting and desorbing lithium ions from the battery; A separator coupled between the anode and the cathode to prevent a short circuit; And the electrolyte solution.

The negative active material is a single phase selected from the group consisting of graphite, a silicon-graphite composite, silicon, nickel, germanium, and titanium, or an alloy phase thereof.

The separator may be selected from the group consisting of a polymer membrane of polyethylene, polypropylene, or polyolefin, or a multilayer thereof, a microporous film, a woven fabric, and a nonwoven fabric.

The positive active material may be LiCo _{1 - X} Ni _X O ₂ (0.01<X<1).

In the present invention, the "halogen group" is fluorine, chlorine, bromine or iodine.

In the present invention, “alkyl” refers to a monovalent substituent derived from a linear or branched saturated hydrocarbon having 1 to 40 carbon atoms. Examples thereof include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, iso-amyl, hexyl, and the like.

In the present invention, "alkenyl" refers to a monovalent substituent derived from a straight or branched unsaturated hydrocarbon having 2 to 40 carbon atoms having at least one carbon-carbon double bond. Examples thereof include vinyl (vinyl), allyl (allyl), isopropenyl (isopropenyl), 2-butenyl (2-butenyl), and the like, but is not limited thereto.

In the present invention, "alkynyl" refers to a monovalent substituent derived from a straight or branched unsaturated hydrocarbon having 2 to 40 carbon atoms having at least one carbon-carbon triple bond. Examples thereof include, but are not limited to, ethynyl and 2-propynyl.

In the present invention, "aryl" refers to a monovalent substituent derived from an aromatic hydrocarbon having 6 to 60 carbon atoms in which a single ring or two or more rings are combined. In addition, a form in which two or more rings are simply attached to each other or condensed may be included. Examples of such aryl include phenyl, naphthyl, phenanthryl, anthryl, dimethylfluorenyl, and the like, but are not limited thereto.

In the present invention, "heteroaryl" refers to a monovalent substituent derived from a monoheterocyclic or polyheterocyclic aromatic hydrocarbon having 6 to 30 carbon atoms. At this time, one or more carbons, preferably 1 to 3 carbons in the ring are substituted with heteroatoms such as N, O, S or Se. In addition, a form in which two or more rings are simply attached to each other or condensed may be included, and further, a form condensed with an aryl group may be included. Examples of such heteroaryl include 6-membered monocyclic rings such as pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, and triazinyl, phenoxathienyl, indolizinyl, indolyl ( indolyl), purinyl, quinolyl, benzothiazole, polycyclic rings such as carbazolyl and 2-furanyl, N-imidazolyl, 2-isoxazolyl , 2-pyridinyl, 2-pyrimidinyl, and the like, but are not limited thereto.

In the present invention, “aryloxy” is a monovalent substituent represented by RO-, and R means an aryl having 6 to 60 carbon atoms. Examples of such aryloxy include phenyloxy, naphthyloxy, diphenyloxy, and the like, and may include a structure substituted with a halogen group or an alkyl group substituted with a halogen group, but are not limited thereto.

In the present invention, "alkyloxy" is a monovalent substituent represented by R'O-, wherein R'refers to alkyl having 1 to 40 carbon atoms, and has a linear, branched or cyclic structure It may include. Examples of alkyloxy include methoxy, ethoxy, n-propoxy, 1-propoxy, t-butoxy, n-butoxy, pentoxy, and the like, and substituted with a halogen group or an alkyl group substituted with a halogen group. It may include a structure, but is not limited thereto.

In the present invention, "alkoxy" may be a straight chain, branched chain or cyclic chain. Although the number of carbon atoms of the alkoxy is not particularly limited, it is preferably 1 to 20 carbon atoms. Specifically, methoxy, ethoxy, n-propoxy, isopropoxy, i-propyloxy, n-butoxy, isobutoxy, tert-butoxy, sec-butoxy, n-pentyloxy, neopentyloxy, Isopentyloxy, n-hexyloxy, 3,3-dimethylbutyloxy, 2-ethylbutyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, benzyloxy, p-methylbenzyloxy, etc. May be, but is not limited thereto.

In the present invention, “cycloalkyl” refers to a monovalent substituent derived from a monocyclic or polycyclic non-aromatic hydrocarbon having 3 to 40 carbon atoms. Examples of such cycloalkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, norbornyl, adamantyl, and the like, but are not limited thereto.

In the present invention, "heterocycloalkyl" refers to a monovalent substituent derived from a non-aromatic hydrocarbon having 3 to 40 carbon atoms, and at least one carbon in the ring, preferably 1 to 3 carbons, is N, O, S or Se Is substituted with a hetero atom such as. Examples of such heterocycloalkyl include, but are not limited to, morpholine and piperazine.

In the present invention, “alkylsilyl” refers to silyl substituted with alkyl having 1 to 40 carbon atoms, and “arylsilyl” refers to silyl substituted with aryl having 6 to 60 carbon atoms.

In the present invention, "condensed ring" means a condensed aliphatic ring, a condensed aromatic ring, a condensed heteroaliphatic ring, a condensed heteroaromatic ring, or a combination thereof.

In the present invention, 　“adjacent 　 groups are bonded to each other to form a ring” means 　adjacent 　 groups are bonded to each other to form a substituted or unsubstituted aliphatic hydrocarbon ring; A substituted or unsubstituted aromatic hydrocarbon ring; Substituted or unsubstituted aliphatic heterocycle; Substituted or unsubstituted aromatic heterocycle; Or it means to form a condensed ring of these.

In the present invention, "substitution" means that the hydrogen atom bonded to the carbon atom of the compound is replaced with another substituent, and the position to be substituted is not limited as long as the position at which the hydrogen atom is substituted, that is, the position where the substituent can be substituted, and when two or more are substituted , Two or more substituents may be the same or different from each other.

Hereinafter, the present invention will be described in more detail.

As shown in FIG. 1, the lithium battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2 and the separator 4 described above are wound or folded to be accommodated in the battery case 5. Subsequently, an organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium battery 1. The battery case 5 may be cylindrical, rectangular, thin-film, or the like. For example, the lithium battery 1 may be a thin film type battery. The lithium battery 1 may be a lithium ion battery.

The functional electrolyte for a lithium ion battery according to an embodiment of the present invention includes an organic solvent; Lithium (Li) salt; And an additive selected from the group consisting of a compound consisting of the following Formula 1, a compound consisting of the following Formula 2, a compound consisting of the following Formula 3, and a mixture thereof:

[Formula 1]

[Formula 2]

[Formula 3]

here,

n and m are the same as or different from each other, each independently an integer of 0 to 2,

R ₁ and R ₂ are the same as or different from each other, and each independently from the group consisting of an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, and an aryloxy group having 6 to 20 carbon atoms Is selected,

R ₃ to R ₆ are the same or different from each other, and each independently from the group consisting of an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, and an aryloxy group having 6 to 20 carbon atoms Is selected,

The _{alkyl group, aryl group, alkyloxy group and aryloxy group of R 1} to R ₆ are hydrogen, deuterium, halogen group, alkyl group having 1 to 10 carbon atoms, alkenyl group having 2 to 10 carbon atoms, alkynyl group having 2 to 10 carbon atoms, carbon number A cycloalkyl group of 3 to 10, a heterocycloalkyl group of 3 to 10 nuclear atoms, an aryl group of 6 to 20 carbon atoms, a heteroaryl group of 5 to 20 nuclear atoms, a fluorene group, a spiro fluorene group, 1 to 30 carbon atoms Unsubstituted or substituted with one or more substituents selected from the group consisting of an alkylsilyl group, an arylsilyl group having 6 to 60 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, and an aryloxy group having 6 to 20 carbon atoms.

The additive forms a uniform protective film on the surface of the negative electrode, so that side reactions between the electrolyte and the negative electrode can be effectively suppressed. Due to this effect, it is possible to provide a basis for improving the electrochemical life performance of a lithium ion battery composed of a carbon-based and non-carbon-based negative electrode and a layered positive electrode.

The additive may be more specifically included any one or more from the group consisting of compounds represented by the following formulas 4 to 10:

[Formula 4]

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

[Formula 10]

here,

o, p and q are the same as or different from each other, and each independently an integer of 0 to 10.

The additive may be included in an amount of 0.1 to 10% by weight based on the weight of the electrolyte. If the additive is included in an amount of less than 0.1% by weight, it is difficult to form a protective film on the surface of the negative electrode, and the effect of reducing the decomposition and side reactions of the electrolyte solution is insufficient, and when it exceeds 10% by weight, the additive and the electrolyte solution Impurities generated due to side reactions may deteriorate battery life performance.

The lithium salt is selected from the group consisting of LiPF ₆ , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ , LiBOB, LiFOB, LiDFBP, LiTFOP, LiPO ₂ F ₂ and mixtures thereof, preferably LiPF ₆ However, it is not limited to the above example, and any lithium salt that can be used in the electrolytic solution can be used.

The lithium (Li) salt has a concentration of 0.1 to 3M, and when the concentration range of the lithium salt is less than 0.1 M, the concentration of the electrolyte is low, so that the electrolyte performance is degraded, and when it exceeds 3 M, the viscosity of the electrolyte increases. Mobility may decrease and low-temperature performance may be deteriorated.

The organic solvent is selected from the group consisting of carbonate-based, ester-based, ether-based, ketone-based, and mixtures thereof, preferably carbonate-based organic solvent, more preferably ethylene carbonate (EC), propylene carbonate (PC) , Ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), It may be selected from the group consisting of butylene carbonate (BC) and mixtures thereof, and is not limited to the above example, and any organic solvent that can be easily selected by those skilled in the art may be used.

A lithium ion battery according to another embodiment of the present invention includes a positive electrode including a positive electrode active material capable of reversibly inserting and desorbing battery lithium ions; A negative electrode including a negative active material capable of reversibly inserting and desorbing lithium ions from the battery; A separator coupled between the anode and the cathode to prevent a short circuit; And the electrolyte solution.

The negative electrode active material is a single phase selected from the group consisting of graphite, silicon-graphite composite, silicon, nickel, germanium, and titanium, or an alloy thereof, preferably a silicon-based metal, and more preferably silicon 　 single phase or 　 silicon 　 nano It can be a tube.

At this time, the 　 silicon 　 single phase can easily perform a reversible electrochemical reaction in which an alloy with lithium is formed during charging, and then lithium is released when discharging, and returns to the original 　 silicon 　 single phase.

In addition, since the microstructured 　 silicon 　 nanotube does not have a large change in the volume of the overall 　 cathode 　 active material, the cycle life characteristics of the 　 cathode 　 active material may be improved.

As described above, the 　 cathode 　 active material including the silicon 　 single phase or 　 silicon 　 nanotubes can show more excellent cycle life characteristics or capacity retention by significantly reducing micronization and electrical desorption due to a large volume change of the active material during charge and discharge of a lithium secondary battery .

In addition, the 　 silicon 　 nanotube has a large area in contact with the electrolyte over its inner and outer surfaces due to its structural characteristics, so that lithium insertion and desorption may occur actively over such a large surface area.

The separator is included to prevent a short circuit between the positive electrode and the negative electrode, and more specifically, a polymer film of polyethylene, polypropylene or polyolefin, or a multilayer thereof, a microporous film, may be selected from the group consisting of a woven fabric and a nonwoven fabric. , It is not limited to the above example, and any one of ordinary skill in the art that can easily be used as a separator can be used without limitation.

The positive electrode active material is LiCo _{1 - X} Ni _X O ₂ (0.01<X<1), and more specifically LiCo _0.95 Ni _0.05 O ₂ (LCNO), but is not limited to the above example, and those skilled in the art can easily use it as a positive electrode active material. Anything can be used without limitation.

According to the functional electrolyte for a lithium-ion battery of the present invention, additives included in the functional electrolyte in the lithium-ion battery are reduced and decomposed to form a protective film on the surface of the negative electrode, thereby reducing decomposition and side reactions of the electrolyte.

In addition, by forming a uniform protective film on the surface of the negative electrode, it effectively suppresses side reactions between the electrolyte and the negative electrode, providing a basis for improving the electrochemical life performance of a lithium-ion battery composed of a carbon-based and non-carbon-based negative electrode and a layered positive electrode. can do.

1 is a diagram illustrating the structure of a lithium ion battery.
FIG. 2 relates to room temperature life characteristics of a lithium ion battery composed of an LCNO anode/silicon alloy anode according to Example 1 and Comparative 1 of the present invention.
Figure 3 relates to the room temperature life characteristics of a lithium ion battery composed of an LCNO positive electrode / silicon alloy negative electrode according to Example 2 and Comparative 1 of the present invention.
Figure 4 relates to the room temperature life characteristics of a lithium ion battery composed of an LCNO positive electrode / silicon alloy negative electrode according to Examples 3 to 4 and Comparative 2 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[ Manufacturing example : Preparation of organic electrolyte]

Preparation of reference electrolyte (Ref)

Mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) as an organic solvent in a volume ratio of 2:5:3 (EC:EMC:DEC) One carbonate-based solvent was prepared.

In addition, lithium hexafluorophosphate (LiPF ₆ ) was used as the lithium salt and dissolved so that the molar concentration of the lithium salt in the organic solvent was 1.3 M, thereby preparing a reference electrolyte (Ref).

Manufacture of anode

The positive electrode active material _{(.. LiNi 0 05 Co 0} 95 O 2), the binder (PVDF) and a conductive material to 91.5: 4: 5.5 were mixed at a weight ratio of N- methyl-2-pyrrolidone (n-methyl-2- pyrrolidone, NMP) was added to a solvent and mixed in a mechanical stirrer to prepare a positive electrode active material slurry.

The slurry was evenly coated on an aluminum (Al) current collector, pressed with a roll press, and vacuum dried in a vacuum oven at 110° C. for 2 hours to prepare a positive electrode. The positive electrode had an electrode density of 3.5 g/cc, and a loading amount of ^{15.0 mg/cm 2.}

Fabrication of the cathode

A negative electrode active material (silicon alloy-graphite composite negative electrode material), a binder (SBR+CMC), and a conductive material were mixed in a weight ratio of 96.3:1:2.7, added to distilled water, and mixed in a mechanical stirrer to prepare a negative electrode active material slurry.

The slurry was evenly applied to a copper (Cu) current collector, pressed with a roll press, and vacuum dried in a vacuum oven at 110° C. for 2 hours to prepare a negative electrode. The positive electrode had an electrode density of 1.4 g/cc and a loading amount of ^{7.5 mg/cm 2.}

LCNO /Silicon alloy-graphite composite cathode full cell fabrication

Between the prepared positive electrode and the negative electrode, a separator made of polyethylene was inserted into a battery container, and the reference electrolyte prepared in Preparation Example 1 was injected, and in the form of a 2032 half-cell according to a conventional manufacturing method. A lithium secondary battery was produced.

Example One: VF (One weight% , Chemical formula 4) Preparation of containing electrolyte

Prepared to contain 1% by weight of 4-(4-fluorophenyl)-vinylene carbonate (VF) as an additive for forming a functional negative electrode film, and the balance of the reference electrolyte based on the total weight (100% by weight) of the reference electrolyte I did.

Using each of the organic electrolyte prepared in Example 1 instead of the standard electrolyte, a full cell using an LCNO/silicon-graphite composite cathode was prepared.

Example 2: MH14 (1% by weight, formula 10) Preparation of containing electrolyte

Based on the total weight of the reference electrolyte (100% by weight), (3R,4S,5S,6S)-3,4,5-tris(4-fluorobenzyloxy)-2-((4-fluorobenzyloxy) as an additive for forming a functional cathode film )methyl)-tetrahydro-6-methoxy-2H-pyran (MH14) was prepared to contain 1% by weight and the reference electrolyte as the balance.

A full cell was prepared using an LCNO/silicon-graphite composite cathode in the same manner as in Example 1, except that the organic electrolyte prepared in Example 2 was used instead of the reference electrolyte.

Example 3: AF28 (1 weight% , Chemical formula 9) Preparation of containing electrolyte

Based on the total weight of the reference electrolyte (100% by weight), 1% by weight of 4-methyl-5-((trifluoromethoxy)methyl)-1,3-dioxol-2-one (AF28) as an additive for forming a functional negative electrode film And prepared to include the reference electrolyte as a balance.

Using each of the organic electrolyte prepared in Example 3 instead of the standard electrolyte, a full cell using an LCNO/silicon-graphite composite cathode was prepared.

Example 4: VC+AF28 (VC 0.7 weight% , AF28 0.3 weight% , Chemical formula 9) Preparation of containing electrolyte

With respect to the total weight of the reference electrolyte (100% by weight), vinylene carbonate (VC) as an additive for forming a functional negative electrode film was 0.7% by weight, 4-methyl-5-((trifluoromethoxy)methyl)-1,3-dioxol-2 -one (AF28) was prepared to contain 0.3% by weight, and the reference electrolyte was prepared as a balance.

Using each of the organic electrolyte prepared in Example 4 instead of the reference electrolyte, a full cell using an LCNO/silicon-graphite composite cathode was prepared.

Comparative example One

A full cell was manufactured in the same manner as in Example 1, except that the reference electrolyte was used.

Comparative example 2: VC (1 weight% Preparation of electrolyte containing)

Based on the total weight of the reference electrolyte (100% by weight), 1% by weight of vinylene carbonate (VC) was included as an additive for forming a functional negative electrode film, and the reference electrolyte was prepared to include the balance.

Using the organic electrolyte prepared in Comparative Example 2 instead of the reference electrolyte, a full cell using an LCNO/silicon-graphite composite cathode was prepared.

[ Experimental example : Room temperature lifetime performance evaluation of positive half cell]

For full cells using the LCNO/silicon-graphite composite cathode prepared in Examples 1 to 4 and Comparative Examples 1 to 2, the room temperature lifetime performance after one chemical charge and discharge and one stabilization charge and discharge were evaluated, respectively.

First, during the one-time charging and discharging, the positive half-cell is charged at a constant current at a current of 0.1C at 25°C until a voltage reaches 4.35V (vs. Li), followed by a constant voltage (CV) mode. While maintaining 4.35V at 0.02C current cut-off (cut-off). Subsequently, at the time of discharge, discharge was performed at a constant current of 0.1 C rate until the voltage reached 2.5V (vs. Li) (formation step, 1 ^st cycle).

^{In the full cell using the LCNO/silicon-graphite composite cathode, which passed through the 1 st} cycle of the formation phase, charged at a constant current at a current of 0.2C at 25°C until the voltage reaches 4.35V (vs. Li), and in the constant voltage mode, While maintaining 4.35V, cut-off was performed at a current of 0.1C rate. Subsequently, stabilizing charging and discharging of the cell was performed by applying a current condition of 0.2C- until the voltage reached 2.5V (vs. Li) during discharge.

A full cell using the LCNO/silicon-graphite composite cathode that has undergone the stabilization charge/discharge is charged at a constant current at a current of 1C at 25°C until the voltage reaches 4.35V (vs. Li), and 4.35V is maintained in the constant voltage mode. While doing the cut-off at a current of 0.1C rate. Subsequently, the lifespan performance of the cell was evaluated by setting the current condition as 1C- until the voltage reached 2.5V (vs. Li) during discharge.

Table 1 and Fig. 2 show the evaluation results for the room temperature lifespan according to the presence or absence of the VF additive (Chemical Formula 4).

Capacity after 50 cycles (mAh/g) Coulomb efficiency (%) after 50 cycles Example 1 125.3 98.5 Comparative Example 1 113.2 98.0

Referring to FIG. 2, it can be seen that the room temperature lifetime performance of the lithium secondary battery of Example 1 (1% VF) is similar to that of Comparative Example 1 (Ref).

Referring to Tables 1 and 2, it can be seen that the room temperature lifetime performance of the full cell of Example 1 is improved than that of Comparative Example 1. It can be determined that the negative electrode film-forming additive forms a stable film on the negative electrode surface, suppresses direct contact between the electrolyte and the electrode, effectively suppresses decomposition of the electrolyte, and improves the room temperature lifespan of the battery.

Table 2 and Figure 3 shows the evaluation results for the room temperature life performance according to the presence or absence of the MH14 additive (Chemical Formula 10).

Retention rate after 100 cycles (%) Coulomb efficiency (%) after 100 cycles Example 2 52.9 99.6 Comparative Example 1 35.6 96.7

Referring to FIG. 3, it can be seen that the long-term life stability of the lithium secondary battery of Example 2 (1% MH14) is improved than that of Comparative Example 1 (Ref).

Referring to Tables 2 and 3, it can be seen that the room temperature lifetime performance of the full cell of Example 2 was improved compared to Comparative Example 1. It can be determined that the negative electrode film-forming additive forms a stable film on the negative electrode surface, suppresses direct contact between the electrolyte and the electrode, effectively suppresses decomposition of the electrolyte, and improves the room temperature life performance of the battery.

The evaluation results for room temperature lifespan performance according to the presence or absence of the AF28 additive (Chemical Formula 4) are shown in Table 3 and FIG. 4 below.

Capacity after 100 cycles (mAh/g) Coulomb efficiency (%) after 100 cycles Example 3 145.1 99.7 Example 4 154.1 99.8 Comparative Example 2 128.1 99.6

Referring to Tables 3 and 4, it can be seen that the room temperature lifetime performance of the full cells of Examples 3 (1% AF28) to 4 (0.7% VC + 0.3% AF28) was improved than that of Comparative Example 2 (1% VC). . It is seen that it is improved over Comparative Example 2 including VC, which is widely used as a cathode film stabilizer. This is because the additive for forming the AF28 cathode film formed a more stable film on the surface of the negative electrode than the film formed by VC, By suppressing direct contact, it can be determined that decomposition of the electrolyte is effectively suppressed, and the room temperature life performance of the battery is improved. In addition, in the case of Example 4, when VC and AF28 are used in combination, it is determined that the stability of the silicon-graphite anode interface is greatly improved due to the synergistic effect of the two additives, so that the room temperature lifetime performance is greatly improved.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention defined in the following claims are also present. It belongs to the scope of rights of

1: lithium battery 2: negative electrode
3: anode 4: separator
5: battery case 6: cap assembly

Claims (9)

Organic solvent;
Lithium (Li) salt; And
Functional electrolyte for lithium ion batteries comprising an additive selected from the group consisting of a compound consisting of the following [Chemical Formula 1], a compound consisting of the following [Chemical Formula 2], a compound consisting of the following [Chemical Formula 3], and mixtures thereof:
[Formula 1]

[Formula 2]

[Formula 3]

here,
n is an integer of 1 or 2, m is 1,
R ₁ is an alkyl group having 1 to 5 carbon atoms or an alkyloxy group having 1 to 10 carbon atoms,
R ₂ is selected from the group consisting of an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, and an aryloxy group having 6 to 20 carbon atoms,
R ₃ to R ₆ are the same or different from each other, and each independently from the group consisting of an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, and an aryloxy group having 6 to 20 carbon atoms Is selected,
The _{alkyl group, aryl group, alkyloxy group and aryloxy group of R 1} and R ₂ are one selected from the group consisting of an alkyloxy group having 1 to 10 carbon atoms substituted with a halogen group and an aryloxy group having 6 to 20 carbon atoms substituted with a halogen group Substituted with more than one substituent,
The _{alkyl group, aryl group, alkyloxy group and aryloxy group of R 3} to R ₆ are in the group consisting of a halogen group, an alkyloxy group having 1 to 10 carbon atoms substituted with a halogen group, and an aryloxy group having 6 to 20 carbon atoms substituted with a halogen group It is substituted with one or more selected substituents. The method of claim 1,
The lithium (Li) salt is for a lithium ion battery selected from the group consisting _{of LiPF 6} , LiClO ₄ , LiBF ₄ , LiFSI, LiTFSI, LiSO ₃ CF ₃ , LiBOB, LiFOB, LiDFBP, LiTFOP, LiPO ₂ F _{2 and mixtures thereof} Functional electrolyte. The method of claim 1,
The organic solvent is a functional electrolyte for a lithium ion battery selected from the group consisting of carbonate-based, ester-based, ether-based, ketone-based, and mixtures thereof. The method of claim 1,
The lithium (Li) salt is a functional electrolyte for a lithium ion battery having a concentration of 0.1 to 3M. The method of claim 1,
The additive is a functional electrolyte for lithium ion batteries contained in an amount of 0.1 to 10% by weight based on the weight of the electrolyte. A positive electrode including a positive electrode active material capable of reversibly inserting and desorbing battery lithium ions;
A negative electrode including a negative active material capable of reversibly inserting and desorbing lithium ions from the battery;
A separator coupled between the anode and the cathode to prevent a short circuit; And
A lithium ion battery comprising the electrolyte according to any one of claims 1 to 5. The method of claim 6,
The negative electrode active material is a single phase selected from the group consisting of graphite, a silicon-graphite composite, silicon, nickel, germanium, and titanium, or an alloy phase thereof. The method of claim 6,
The separator is a lithium ion battery selected from the group consisting of a polymer film of polyethylene, polypropylene, or polyolefin or a multilayer thereof, a microporous film, a woven fabric, and a nonwoven fabric. delete

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