KR20220023159A - Cyclic ether diol derivatives, nonaqueous electrolyte for lithium secondary battery comprising the same, and lithium secondary battery - Google Patents

Abstract

The present invention relates to an electrolyte additive for a lithium secondary battery, an electrolyte including the additive, and a lithium secondary battery including the electrolyte, wherein the additive includes a cyclic ether diol derivative compound. The present invention can implement a lithium secondary battery with high voltage and high capacity.

Description

Cyclic ether diol derivative, lithium secondary battery electrolyte and lithium secondary battery containing the same

The present invention relates to an electrolyte solution additive for a lithium secondary battery, an electrolyte solution including the additive, and a lithium secondary battery including the electrolyte solution.

Recently, interest in medium and large-capacity lithium secondary batteries for application to power sources for next-generation vehicles and the like is increasing.

In this regard, when a layered oxide containing an excess of lithium (ie, lithium-rich) is used as a cathode active material, the charge driving voltage of the battery can be improved, and a silicon-based material rather than a carbon-based material can be used. Since it can be used as an anode active material, the capacity of the battery can be improved.

On the other hand, in a general lithium secondary battery, lithium salt dissolved in an organic solvent is used as an electrolyte. The over-lithium positive active material creates a high voltage environment while generating oxygen gas during the first charge, and the silicon-based negative active material is used for repeated charging and discharging. Accordingly, serious volume expansion occurs and cracks are formed on the surface thereof, and eventually, a decomposition reaction of the electrolyte solution is commonly induced on the surface of the electrode to which each of the active materials is applied.

As a result, as the electrolyte is gradually depleted, the electrochemical performance of the battery is rapidly deteriorated, and as a thick film acting as a resistance is formed on the surface of each electrode, the electrochemical reaction rate of the battery is lowered, and the decomposition result of the electrolyte is generated The acidic material (eg, HF, etc.) melts each electrode film or damages the positive electrode active material, so there is a problem in that the electrochemical stability of the battery is not guaranteed.

The present invention aims to solve the above-mentioned problems by adding a special additive to an electrolyte solution for a lithium secondary battery.

Specifically, an object of the present invention is to provide an oxidative decomposition additive, which is a material capable of being oxidatively decomposed into an electrolyte additive to form a protective film on the surface of an anode.

In another embodiment of the present invention, it is an object of the present invention to provide a secondary battery electrolyte comprising a reductive decomposition additive, which is a material that is reductively decomposed to form a protective film on the surface of the anode, together with the oxidative decomposition additive.

In addition, the present invention is to provide a lithium secondary battery including the electrolyte.

The present invention provides a secondary battery electrolyte additive comprising at least one selected from the group consisting of cyclic ether diol derivative compounds represented by the following formula (1).

[Formula 1]

In Formula 1, W is O, S, SO, SO2, NR, NCOR, NSO2R, Z is halogen, alkoxy, alkyl substituted B, P, or SO, SO2, CO, R is C1-C4 It is a hydrocarbon or C6~C12 aryl.

Preferably, the present invention provides a secondary battery electrolyte additive, wherein the cyclic ether diol derivative of Formula 1 is at least one compound selected from the following compound group A.

<Compound group A>

The secondary battery electrolyte additive is an oxidative decomposition additive.

The present invention provides a secondary battery electrolyte comprising at least one oxidative decomposition type additive selected from the group consisting of compounds represented by Formula 1 above.

The secondary battery electrolyte may further include a reductive decomposition type additive.

The present invention provides a secondary battery comprising the secondary battery electrolyte.

The present invention relates to a secondary battery electrolyte comprising a cyclic ether diol derivative compound represented by Formula 1, and by adding the additive to the secondary battery electrolyte, the electrochemical performance, reaction rate and stability of the battery can be improved. Specifically, a protective film is formed on the surface of the positive electrode by the oxidative decomposition additive to improve electrochemical performance, reaction rate, and stability of the battery. In addition, the electrolyte solution additive of the present invention has the effect of sufficiently improving the capacity retention rate and lifespan retention rate of the secondary battery.

In addition, it is included in the electrolyte together with a solvent and an electrolyte, so that it is possible to simultaneously apply an overlithium positive active material and a silicon-based negative active material, and as a result, a high voltage and high capacity lithium secondary battery can be realized.

In addition, the protective film is formed on the surface of the anode by the oxidative decomposition additive, the protective film is formed on the surface of the anode by the reductive decomposition additive, and the function of removing the acidic material by the reactive additive can be simultaneously performed.

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

Lithium secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used, and can be classified into cylindrical, prismatic, coin-type, pouch-type, etc. according to the shape. According to the size, it can be divided into a bulk type and a thin film type. Since the structure and manufacturing method of these batteries are well known in the art, a detailed description thereof will be omitted.

A lithium secondary battery is constructed by sequentially stacking a negative electrode, a separator, and a positive electrode, and then storing the negative electrode in a battery container while being wound on a spiral.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative electrode active material. As the negative active material, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide is used as a material capable of reversibly intercalating and deintercalating lithium ions.

Among the negative active materials, a carbon-based material such as graphite is widely known as a material capable of reversibly intercalating and deintercalating lithium ions. Graphite has a low discharge voltage of -0.2V compared to lithium, and a battery using graphite as an anode active material exhibits a high discharge voltage of 3.6V, providing an advantage in terms of energy density of a lithium battery. In addition, secondary batteries using graphite as an anode active material are the most widely used because they guarantee a long lifespan of lithium secondary batteries with excellent reversibility.

However, the graphite active material has a problem with low capacity in terms of energy density per unit volume of the electrode plate due to the low density of graphite (theoretical density 2.2 g/cc) during the manufacture of the electrode plate, and a side reaction with the organic electrolyte used at a high discharge voltage is easy to occur, There is a problem of swelling of the battery and a decrease in capacity accordingly. Therefore, in recent years, as a material capable of doping and de-doping lithium, a silicon-based material having a high capacity has been in the spotlight as an alternative.

Meanwhile, the positive electrode includes a current collector and a positive electrode active material layer formed on the current collector. As the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) may be used, and in general, LiCoO ₂ , LiMn ₂ O ₄ , LiNi _1-x Co _x O ₂ (0 < x < 1), which has a structure that allows intercalation of lithium ions, such as lithium and transition metal oxides are mainly used.

Recently, by using a layered oxide containing an excess of lithium (ie, lithium-rich) as a cathode active material, a technique for improving the charge driving voltage of a battery has been studied. In this case, since a silicon-based material rather than a carbon-based material can be used as the negative electrode active material, the capacity of the battery can be further improved.

On the other hand, in a general lithium secondary battery, lithium salt dissolved in an organic solvent is used as an electrolyte. The over-lithium positive active material creates a high voltage environment while generating oxygen gas during the first charge, and the silicon-based negative active material is used for repeated charging and discharging. Accordingly, serious volume expansion occurs and cracks are formed on the surface thereof, and eventually, a decomposition reaction of the electrolyte solution is commonly induced on the surface of the electrode to which each of the active materials is applied.

As a result, the electrolyte is gradually depleted, and the electrochemical performance of the battery is rapidly deteriorated, and as a thick film acting as a resistance is formed on the surface of each electrode, the electrochemical reaction rate of the battery is reduced. In addition, there is a problem in that the electrochemical stability of the battery cannot be guaranteed because an acidic material (eg, HF, etc.) generated as a result of the decomposition of the electrolyte melts each electrode film or damages the positive electrode active material. An electrolyte solution with additives has been developed.

The functional additive includes a reductive decomposition additive, an oxidative decomposition additive, and a reactive additive, and the oxidative decomposition additive is a material that is oxidatively decomposed to form a protective film on the surface of the anode. can prevent this from happening.

When the oxidative decomposition type additive is added to the electrolyte solution, an overlithium positive electrode active material is applied to realize a high voltage lithium secondary battery, and the structure of the active materials is stably maintained while the battery is driven, so that the electrochemical performance and reaction rate of the battery and to improve stability.

<Oxidative decomposition type additive>

However, the existing developed oxidative decomposition additives do not sufficiently satisfy the capacity retention rate and lifespan maintenance rate.

Accordingly, the present inventors have tried to develop an oxidative decomposition type additive that prevents the decomposition of the electrolyte solution and prevents damage to the active material by adding it to the electrolyte solution. In this case, it was confirmed that the electrochemical performance, reaction rate, and stability of the lithium secondary battery can be improved, and the capacity retention ratio and life retention ratio can be sufficiently improved, and the present invention was completed.

[Formula 1]

In Formula 1, W is O, S, SO, SO2, NR, NCOR, NSO2R, Z is halogen, alkoxy, alkyl substituted B, P, or SO, SO2, CO, R is C1-C4 It is a hydrocarbon or C6~C12 aryl.

Preferably, the present invention provides a secondary battery electrolyte additive, wherein the cyclic ether diol derivative of Formula 1 is at least one compound selected from the following compound group A.

<Compound group A>

The compound represented by Formula 1 used as the oxidative decomposition additive of the present invention may be purchased or prepared.

<Electrolyte>

The present invention is an electrolyte; solvent; at least one oxidative decomposition type additive selected from the group consisting of cyclic ether diol derivative compounds represented by the following formula (1); And it provides a secondary battery electrolyte comprising a reductive decomposition additive.

The electrolyte of the present invention may contain 0.1 to 10% by weight, preferably 0.5 to 5% by weight, more preferably 1 to 3% by weight of the oxidative decomposition type additive relative to the total weight of the electrolyte. When the oxidative decomposition type additive is included in the above content, it is possible to prevent the decomposition of the electrolyte and prevent damage to the positive electrode active material, and as a result, it is possible to improve the capacity retention rate and lifespan maintenance ratio of the battery.

The present invention may further include a conventional oxidative decomposition type additive used in the art in addition to the oxidative decomposition type additive of the present invention.

The following LiFOB, LiBOB, WCA1, WCA2, WCA3, etc. are mentioned as said normal oxidative-decomposition type additive.

The present invention is one of fluoroethylene carbonate (FEC) and vinylene carbonate (VC), propanesultone (PS), propanylsultone (PRS) as a reductive decomposition additive, or these may contain a mixture of

The reductive decomposition additive may include 0.1 to 10% by weight, preferably 0.5 to 5% by weight, more preferably 1 to 3% by weight, based on the total weight of the electrolyte. When the reductive decomposition type additive is included in the above content, it is possible to prevent the decomposition of the electrolyte and prevent damage to the negative active material.

The electrolyte of the present invention may further include a reactive additive, and the reactive additive may be a compound containing a silyl group. Specifically, tris (trimethylsilyl) phosphite (TMSP), tris (trimethylsilyl) phosphate ( TMSPA) and the like. The reactive additive may include 0.1 to 10% by weight, preferably 0.5 to 5% by weight, more preferably 1 to 3% by weight, based on the total weight of the electrolyte.

The electrolyte of the present invention contains a lithium salt as an electrolyte, preferably LiPF ₆ , LiBF ₄ , LiClO ₄ , LiCl, LiBr, LiI, LiB ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN(SO ₂ C ₂ F ₅ ) ₂ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiB(C ₆ H ₅ ) ₄ , Li(SO ₂ F) ₂ N(LiFSI) and (CF ₃ SO ₂ ) ₂ NLi may be at least one selected from the group consisting of.

The concentration of the lithium salt in the electrolyte of the present invention may be 0.1 to 2 M.

The solvent included in the electrolyte solution of the present invention may be an organic solvent that is carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, aprotic solvent, or a combination thereof. The solvent is preferably ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), or a combination thereof. there is.

The lithium secondary battery electrolyte of the present invention is generally stable in a temperature range of -20 ℃ and can maintain electrochemically stable characteristics even at a voltage of 4.5V, so it can be applied to all lithium secondary batteries such as lithium ion batteries and lithium polymer batteries. there is.

<Secondary battery>

In another embodiment of the present invention, the present invention provides a positive electrode; cathode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte having ion conductivity by being impregnated in the positive electrode, the negative electrode, and the separator including an electrolyte, a solvent and an additive, wherein the additive is one selected from the group consisting of ionic compounds represented by Chemical Formulas 1 and 2 It provides a lithium secondary battery comprising an oxidative decomposition type additive and a reductive decomposition type additive comprising the above.

In another embodiment of the present invention, the electrolyte provides a lithium secondary battery that further includes a reactive additive including a silyl group.

The description of the electrolyte included in the secondary battery of the present invention is the same as that of the previous electrolyte.

The lithium secondary battery of the present invention includes a current collector as a positive electrode and a positive electrode active material layer formed on the current collector, and the positive electrode active material layer includes a positive electrode active material.

In the present invention, any positive electrode active material available in the art can be used as the positive electrode active material. For example, as a positive electrode active material, a lithium-containing transition metal oxide, that is, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium copper oxide, a lithium nickel-based oxide, a lithium manganese composite oxide, and a lithium-nickel-manganese-cobalt-based oxide At least one selected from the group consisting of may be preferably used, for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li(Ni _a Co _b Mn _c )O ₂ (0<a<1, 0 <b<1, 0<c<1, a+b+c=1), LiNi _1-y Co _y O ₂ (O<y<1), LiCo _1-y Mn _y O ₂ (O<y<1) ), LiNi _1-y Mn _y O ₂ (O≤y<1), Li(Ni _a Co _b Mn _c )O ₄ (0<a<2, 0<b<2, 0<c<2, a+ b+c=2), LiMn _2-z Ni _z O ₄ (0<z<2), LiMn _2-z Co _z O ₄ (0<z<2), LiCoPO ₄ and LiFePO ₄ selected from the group consisting of Any one or a mixture of two or more thereof may be used.

In addition, according to one embodiment, the lithium secondary battery of the present invention may include a lithium-rich positive electrode active material, and the positive electrode active material may include a compound represented by the following formula (7).

[Formula 7]

Li _x Ni _y Mn _z Co _w O ₂

In Formula 7, 1<x≤2, 0<y≤1, 0<z≤1, and 0<w≤1.

The positive active material layer also includes a binder and/or a conductive material.

The binder serves to adhere the positive active material particles well to each other and also to the positive active material to the current collector, and representative examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl. Chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyethylene, polypropylene , styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. may be used, but the present invention is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and in the battery configured, any electronic conductive material can be used as long as it does not cause chemical change, for example, natural graphite, artificial graphite, carbon black, acetylene black, ketjen Black, carbon fiber, copper, nickel, aluminum, metal powder, such as silver, metal fiber, etc. can be used, and also conductive material, such as polyphenylene derivative, can be used 1 type or in mixture of 1 type or more.

The lithium secondary battery includes a current collector as a negative electrode and a negative active material layer formed on the current collector, and the negative active material layer includes an anode active material. The present invention includes a carbon-based material, lithium metal, an alloy of lithium metal, silicon-based or transition metal oxide as a material capable of reversibly intercalating/deintercalating lithium ions as the anode active material.

The carbon-based material includes crystalline carbon and amorphous carbon. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon). or hard carbon, mesophase pitch carbide, and calcined coke.

The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn from the group consisting of Alloys of metals of choice may be used.

As the silicon-based material, a combination of graphite and silicon, a material in which silicon is coated on the surface of graphite particles, or a material in which silicon and carbon are simultaneously coated on the surface of graphite particles may be SiO _x , Si may be carbon-based.

Examples of the transition metal oxide include vanadium oxide and lithium vanadium oxide.

The negative active material layer may further include a binder and/or a conductive material.

The binder well adheres the negative active material particles to each other, and also serves to adhere the negative active material to the current collector, representative examples of which include polyvinyl alcohol, carboxylmethyl cellulose, carboxymethyl cellulose ( A mixture of carboxylmethyl cellulose / polyacrylic acid, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride fluoride), a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene (polyethylene), polypropylene (polypropylene), styrene-butadiene rubber, acrylated styrene-butadiene rubber, styrene-butadiene rubber/carboxymethylcellulose (carboxymethyl cellulose) mixture, epoxy resin (epoxy resin), or at least one of nylon (nylon) may be used, but is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and any electronically conductive material can be used as long as it does not cause a chemical change in the battery configured, and examples include natural graphite, artificial graphite, carbon-based materials such as carbon black, acetylene black, ketjen black, and carbon fiber; metal-based substances such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; conductive polymers such as polyphenylene derivatives; Alternatively, a conductive material including a mixture thereof may be used.

The average charging voltage of the lithium secondary battery may be 4.5 V or more. This is a high-range voltage that can be expressed when the positive electrode containing the overlithium positive electrode active material and the negative electrode containing the silicon-based negative electrode active material are applied, and can be stably maintained by the functional additive included in the electrolyte of the present invention. there is.

Hereinafter, examples will be given to describe the present invention in detail. However, the embodiment according to the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiment described in detail below. The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art.

Claims (8)

A secondary battery electrolyte additive comprising at least one selected from the group consisting of a cyclic ether diol derivative compound represented by the following formula (1).
[Formula 1]

In Formula 1, W is O, S, SO, SO2, NR, NCOR, NSO2R, Z is halogen, alkoxy, alkyl substituted B, P, or SO, SO2, CO, R is C1-C4 It is a hydrocarbon or C6~C12 aryl.
The secondary battery electrolyte solution additive according to claim 1, wherein the cyclic ether diol derivative compound is at least one compound selected from the group consisting of the following compound group A.
<Compound group A>

electrolyte; solvent; at least one oxidative decomposition type additive selected from the group consisting of compounds represented by Formula 1; and a secondary battery electrolyte comprising a reductive decomposition additive
The secondary battery electrolyte according to claim 3, comprising 0.1 to 10% by weight of an oxidative decomposition additive.
The secondary battery electrolyte according to claim 3, further comprising a reactive additive
anode; cathode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte having ion conductivity by being impregnated in the positive electrode, negative electrode and separator including an electrolyte, a solvent and an additive, wherein the additive includes the additive of claim 1 and the reductive decomposition type additive.
The lithium secondary battery according to claim 6, wherein the positive electrode includes a lithium-rich positive electrode active material.
The lithium secondary battery according to claim 6, wherein the negative electrode comprises a silicon-based material.