KR102277754B1 - Electrolyte Solution for Secondary Battery and Secondary Battery Comprising the Same - Google Patents

Abstract

The present invention relates to a non-aqueous electrolyte for a secondary battery and a secondary battery comprising the same, wherein 1,3-propanediol cyclic sulfate, a negative electrode film-forming additive, and a positive electrode action additive are added to the non-aqueous electrolyte for a secondary battery according to the present invention. It has the effect of improving storage, lifespan characteristics and high rate characteristics.

Description

Electrolyte solution for secondary battery and secondary battery including same {Electrolyte Solution for Secondary Battery and Secondary Battery Comprising the Same}

The present invention relates to an electrolyte solution for a secondary battery and a secondary battery comprising the same, and more particularly, by adding 1,3-propanediol cyclic sulfate, a negative electrode film forming additive, and a positive electrode action additive to an electrolyte for a secondary battery, high temperature storage characteristics, high temperature It relates to a non-aqueous electrolyte for a secondary battery having the effect of improving lifespan characteristics and high rate characteristics, and a secondary battery including the same.

Recently, as portable electronic devices become thinner, smaller and lighter, secondary batteries used as power sources are also small and lightweight, can be charged and discharged for a long time, and efforts to improve high-rate characteristics are being concentrated.

Secondary batteries include lead-acid batteries, nickel-cadmium (Ni-Cd) batteries, nickel-hydrogen (Ni-MH) batteries, lithium batteries, etc., depending on the material of the anode or cathode, and the unique characteristics of electrode materials. The potential and energy density are determined by Among them, lithium secondary batteries have high energy density due to the low oxidation/reduction potential and molecular weight of lithium, and thus are widely used as driving power sources for portable electronic devices such as notebook computers, camcorders, or mobile phones.

A lithium secondary battery using a non-aqueous electrolyte is used as a positive electrode coated with a lithium metal mixed oxide capable of desorption and insertion of lithium ions as a positive electrode active material on a metal as a positive electrode, and carbon material or metallic lithium as a negative electrode active material on a metal as a negative electrode It is used by coating, and an electrolyte solution in which lithium salt is appropriately dissolved in an organic solvent is placed with the positive and negative electrodes interposed therebetween. The organic solvent of the electrolyte may be decomposed on the electrode surface during charging and discharging of the battery or co-intercalated between the carbon material anode layers to collapse the anode structure, thereby impairing the stability of the battery.

However, it is known that a solid electrolyte interface (SEI) film formed on the surface of the anode by reduction of the electrolyte solvent during initial charging of the battery can solve these problems.

Nevertheless, the SEI film collapses due to repeated charging and discharging, and the lifespan and performance of the secondary battery, especially under high temperature, are deteriorated due to the low thermal stability of the SEI film.

Therefore, as a prior art for solving the above problems, Korean Patent Registration No. 10-1492686 discloses lithium oxalyl difluoroborate (LiODFB), a vinylidene carbonate-based compound, a sulfate-based compound, and an electrolyte containing a sultone-based compound. Although the additive and the non-aqueous electrolyte containing the same are disclosed, the capacity recovery and retention rate during high-temperature storage are not described, and there is a limit in improving the discharge efficiency at high C-rate with the mentioned composition.

In addition, Korean Patent No. 10-1538485 discloses a non-aqueous electrolyte for secondary batteries containing alkylene sulfate, ammonium compound, and vinylene carbonate of a specific chemical formula, but due to the absence of a positive electrode additive, the stability of the positive electrode at a high rate is reduced. It is difficult to realize the capacity, and there is a problem in that the long-term life efficiency is lowered because the stable anode film formation and the transition metal elution cannot be prevented.

에서의 수명 특성을 향상시키는 효과에 대해서는 개시된 바가 전혀 없다. 아울러, 본 출원인도 리튬 디플루오로포스페이트 및 고리형 설페이트 화합물을 함유하는 전해액의 상온 및 고온에서의 수명특성 및 고온보존특성이 향상되는 것을 확인하였으나, 고온 저장 중 저항이 증가되는 문제를 해결하지 못하였다. 따라서, 고온 저장 중 저항이 증가되는 것을 억제하면서 개선된 용량 유지율 및 수명 유지율을 동시에 만족할 수 있는 최적의 첨가제 조성을 함유하는 전해액에 대한 연구가 필요한 실정이다.U.S. Patent Application Laid-Open No. 2017/0301952 A1 discloses a non-aqueous electrolyte for secondary batteries comprising a cyclic sultonate, cyclic sulfate, silane phosphate and/or silane borate compound and a fluorophosphate salt, and Korean Patent Laid-Open No. 2016-0144123 is an electrolyte containing vinylene carbonate and a cyclic sulfate compound and is known for its effects on high-temperature stability, low-temperature discharge capacity, and room-temperature lifespan characteristics. However, by adding lithium difluorophosphate, the increase in resistance during high-temperature storage is suppressed or , high temperature (70

There is no disclosure about the effect of improving the lifespan characteristics in In addition, the present applicant also confirmed that the lifespan characteristics and high temperature storage characteristics at room temperature and high temperature of an electrolyte containing lithium difluorophosphate and a cyclic sulfate compound are improved, but the problem of increased resistance during high temperature storage cannot be solved. did. Therefore, there is a need for research on an electrolyte solution containing an optimal additive composition capable of simultaneously satisfying an improved capacity retention ratio and a life retention ratio while suppressing an increase in resistance during high-temperature storage.

Therefore, there is still a demand for the development of additives capable of improving the lifespan characteristics and stability of secondary batteries at high temperatures.

Accordingly, the present inventors have made diligent efforts to solve the above problems. As a result, by adding lithium difluorophosphate, vinylene carbonate and cyclic sulfate compounds to the electrolyte for secondary batteries, the resistance increase during high-temperature storage is suppressed, and high-temperature storage characteristics , it was confirmed that the high temperature life characteristics and high rate characteristics were improved, and the present invention was completed.

An object of the present invention is to provide a non-aqueous electrolyte for a secondary battery having improved lifespan characteristics and high temperature storage characteristics at high temperatures.

Another object of the present invention is to provide a secondary battery having excellent lifespan characteristics and high temperature storage characteristics at high temperatures.

In order to achieve the above object, (A) a lithium salt; (B) a non-aqueous organic solvent; (C) 1,3-propanediol cyclic sulfate; (D) at least one selected from the group consisting of vinylene carbonate, fluorinated ethylene carbonate and vinylene ethylene carbonate cathodic film-forming additives; and (E) adiponitrile, succinonitrile, 1.3,6-hexanetricarbonitrile, 2,4,8,10-tetraoxa-3,9- Dithiaspiro[5,5]undecane-3,3,9,9-tetraoxide (2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,3,9,9- tetraoxide), lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, lithium bis(oxalato)borate, and lithium bis(fluorosulfonyl)imide. Provided is an electrolyte for a secondary battery comprising a working additive.

The present invention also provides a secondary battery comprising a positive electrode, a negative electrode, and the electrolyte solution.

The non-aqueous electrolyte according to the present invention has an effect of improving high-temperature storage characteristics, high-temperature lifespan characteristics, and high-rate characteristics by using 1,3-propanediol cyclic sulfate, a specific anode film forming additive, and a specific anode action additive.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is those well known and commonly used in the art.

In the present invention, 1,3-propanediol cyclic sulfate, vinylene carbonate, and fluorinated ethylene carbonate are added to the non-aqueous electrolyte of the secondary battery. carbonate) and at least one selected from the group consisting of vinylene ethylene carbonate Cathode film forming additive and adiponitrile, succinonitrile, 1.3,6-hexanetricarbonitrile, 2,4,8,10-tetraoxa-3,9 -dithiaspiro[5,5]undecane-3,3,9,9-tetraoxide (2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,3,9,9 -tetraoxide), lithium difluorophosphate, lithium difluoro bis (oxalato) phosphate, lithium bis (oxalato) borate, and at least one selected from the group consisting of lithium bis (fluorosulfonyl) imide It was confirmed that the addition of the positive electrode additive significantly improved the lifespan characteristics, storage characteristics, and high rate characteristics of the secondary battery at high temperature.

Accordingly, the present invention in one aspect, (A) a lithium salt; (B) a non-aqueous organic solvent; (C) 1,3-propanediol cyclic sulfate; (D) at least one selected from the group consisting of vinylene carbonate, fluorinated ethylene carbonate and vinylene ethylene carbonate cathodic film-forming additives; and (E) adiponitrile, succinonitrile, 1.3,6-hexanetricarbonitrile, 2,4,8,10-tetraoxa-3,9- Dithiaspiro[5,5]undecane-3,3,9,9-tetraoxide (2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,3,9,9- tetraoxide), lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, lithium bis(oxalato)borate, and lithium bis(fluorosulfonyl)imide. It relates to an electrolyte for a secondary battery comprising a working additive.

In another aspect, the present invention relates to a secondary battery including a positive electrode, a negative electrode, and the non-aqueous electrolyte.

Hereinafter, the present invention will be described in detail.

The non-aqueous electrolyte for a secondary battery according to the present invention includes (A) a lithium salt; (B) a non-aqueous organic solvent; (C) 1,3-propanediol cyclic sulfate; (D) at least one negative electrode film-forming additive selected from the group consisting of vinylene carbonate, fluorinated ethylene carbonate, and vinylene ethylene carbonate; and (E) adiponitrile, succinonitrile, 1.3,6-hexanetricarbonitrile, 2,4,8,10-tetraoxa-3,9- Dithiaspiro[5,5]undecane-3,3,9,9-tetraoxide (2,4,8,10-tetraoxa-3,9-dithiaspiro[5.5]undecane-3,3,9,9- tetraoxide), lithium difluorophosphate, lithium difluorobis(oxalato)phosphate, lithium bis(oxalato)borate, and lithium bis(fluorosulfonyl)imide. It may contain functional additives.

In the present invention, each component contained in the electrolyte solution for a secondary battery will be described in detail.

(A) lithium salt

The electrolyte for a secondary battery according to the present invention contains a lithium salt as a solute of the electrolyte. The lithium salt is not limited, but LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , CF ₃ SO ₃ Li, LiC(CF ₃ SO ₂ ) _{3 ,} LiCl, LiI, LiSCN, LiB(C ₂ O ₄ ) _{2 ,} LiF ₂ BC ₂ O ₄ , LiPF ₄ (C ₂ O ₄ ), LiPF ₂ (C ₂ O ₄ ) ₂ , It may be one or a mixture of two or more selected from the group consisting of LiP(C ₂ O ₄ ) ₃ and LiPO ₂ F _{2 , preferably lithium hexafluorophosphate (LiPF 6} ). The concentration of the lithium salt is preferably used within the range of 0.1M to 2.0M, more preferably from 0.7M to 1.6M, and when it is less than 0.1M, the conductivity of the electrolyte is lowered so that it is fast between the positive and negative electrodes of the secondary battery. The performance of the electrolyte for transferring ions at a rate is poor, and when it exceeds 2.0M, the viscosity of the electrolyte increases and the mobility of lithium ions decreases. These lithium salts act as a source of lithium ions in the battery to enable the operation of a basic lithium secondary battery.

(B) non-aqueous organic solvent

The electrolyte for a secondary battery according to the present invention includes a non-aqueous organic solvent. The non-aqueous organic solvent may be at least one selected from the group consisting of a cyclic carbonate, a chain carbonate, and a propionate. Wherein the cyclic carbonate is ethylene carbonate (ethyl carbonate, EC), propylene carbonate (PC), butylene carbonate (butylene carbonate, BC), vinylene carbonate (vinylene carbonate, VC), γ- butyrolactone (γ -butyrolactone) and one or more carbonates selected from the group consisting of mixtures thereof, wherein the chain carbonate is dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate , DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (ethylmethyl carbonate, EMC), and mixtures thereof It may be one or more carbonates selected from the group consisting of. In the electrolyte solution according to an embodiment of the present invention, when the non-aqueous organic solvent is a mixed solvent of a cyclic carbonate-based solvent and a chain-type carbonate-based solvent, the mixing volume ratio of the chain-type carbonate-based solvent: the cyclic carbonate-based solvent is 1: It may be 1 to 9:1, and preferably, it may be used by mixing in a volume ratio of 1.5:1 to 4:1.

In addition, the propionate is methyl propionate (methyl propionate), ethyl propionate (ethyl propionate), propyl propionate (propyl propionate), butyl propionate (butyl propionate) and mixtures thereof from the group consisting of It may be one or more propion esters selected.

(C) 1,3-propanediol cyclic sulfate

The electrolyte for a secondary battery according to the present invention includes 1,3-propanediol cyclic sulfate. The 1,3-propanediol cyclic sulfate is represented by the formula (1).

[Formula 1]

The 1,3-propanediol cyclic sulfate acts as a film repair additive to improve the high temperature exposure environment by reducing gas.

In the present invention, the content of 1,3-propanediol cyclic sulfate may be added in an amount of 0.05 to 10% by weight, preferably 0.2 to 5% by weight, and more preferably 0.5 to 3% by weight based on the electrolyte. , when it is less than 0.05% by weight, it is not sufficient to form a stable film in a high-temperature environment, so there is a problem in that the effect of suppressing the side reaction of the electrode interface during high-temperature cycle and high-temperature storage is insufficient, and when it exceeds 10% by weight, Rather, there is a problem in that the cell resistance is increased due to the increase in the film resistance, and thus the lifespan is reduced.

(D) Cathode film forming additive

The electrolyte for a secondary battery according to the present invention is at least one negative electrode film selected from the group consisting of vinylene carbonate (VC), fluorinated ethylene carbonate (FEC) and vinylene ethylene carbonate (VEC). forming additives. The vinylene carbonate, fluorinated ethylene carbonate, and vinylene ethylene carbonate are representative nonionic additives and have structures of Chemical Formulas 2 to 4, respectively.

[Formula 2]

[Formula 3]

[Formula 4]

By adding at least one negative electrode film forming additive selected from the group consisting of vinylene carbonate, fluorinated ethylene carbonate) and vinylene ethylene carbonate, long-term storage stability and long life at room temperature/high temperature can be improved.

In the present invention, the content of the negative electrode film-forming additive may be added in an amount of 0.05 to 20% by weight, preferably 0.2 to 10% by weight, more preferably 0.2 to 5% by weight based on the electrolyte, and less than 0.05% by weight. In this case, the effect of forming a stable film (SEI) on the negative electrode is insignificant, and when it exceeds 20% by weight, the secondary battery characteristics such as an increase in irreversible capacity or a decrease in lifespan due to an increase in resistance within the battery are rather deteriorated. have.

(E) anodizing additive

The electrolyte for a secondary battery according to the present invention is adiponitrile (AN), succinonitrile (SN), 1.3,6-hexanetricarbonitrile (1.3,6-hexanetricarbonitrile, HTCN), 2,4,8 , 10-tetraoxa-3,9-dithiaspiro [5,5] undecane-3,3,9,9-tetraoxide (2,4,8,10-tetraoxa-3,9-dithiaspiro [5.5] undecane-3,3,9,9-tetraoxide, BSA), pentaerythritol disulfate, lithium difluorophosphate (LFP), lithium difluorobis(oxalato)phosphate bis(oxalate) phosphate, LiDFBOP), lithium bis(oxalato) borate (LiBOB), lithium difluoro(oxalate) borate (LiFOB), and lithium bis(LiFOB) It may be at least one selected from the group consisting of fluorosulfonyl)imide (lithium bis(fluorosulfonyl)imide, LiFSI). The adiponitrile, succinonitrile, 1.3,6-hexanetricarbonitrile, 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9 ,9-tetraoxide and lithium difluorophosphate are representative nonionic additives and have structures of Chemical Formulas 5 to 9, respectively.

[Formula 5]

[Formula 6]

[Formula 7]

[Formula 8]

[Formula 9]

In addition, in the present invention, the lithium difluoro bis (oxalato) phosphate (lithium difluoro bis (oxalate) phosphate, LiDFBOP), lithium bis (oxalato) borate (lithium bis (oxalato) borate, LiBOB), lithium di Fluoro (oxalato) borate (lithium difluoro (oxalate) borate, LiFOB) and lithium bis (fluorosulfonyl) imide (lithium bis (fluorosulfonyl) imide (LiFSI)) are representative ionic additives, and each of Chemical Formulas 10 to 13 has the structure of

[Formula 10]

[Formula 11]

[Formula 12]

[Formula 13]

In the present invention, the content of the anode action additive may be added in an amount of 0.05 to 10% by weight, preferably 0.05 to 5% by weight, more preferably 0.2 to 3% by weight, based on the electrolyte, and when it is less than 0.05% by weight is insufficient to form a stable low-resistance interfacial layer at the positive electrode or the transition metal ion stabilization function of the positive electrode is poor. There is a problem in that the characteristics of the secondary battery are rather deteriorated.

The electrolyte of the lithium ion secondary battery of the present invention usually maintains stable characteristics in a temperature range of -20 to 50 °C. The electrolyte solution of the present invention may be applied to a lithium ion secondary battery, a lithium ion polymer battery, and the like.

In the present invention, as the cathode material of the lithium secondary battery, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , or LiNi _1-xy Co _x M _y O ₂ (0≤x≤1, 0≤y≤1, 0 ≤x+y≤1, M uses a lithium metal oxide such as Al, Sr, Mg, La, etc.), and crystalline or amorphous carbon, carbon composite, lithium metal, or lithium alloy is used as the anode material. do. The active material is applied to the current collector of a thin plate with an appropriate thickness and length, or the active material itself is applied in the form of a film and wound or laminated together with a separator, which is an insulator, to make an electrode group, and then placed in a can or similar container, followed by trialkyl A lithium ion secondary battery is prepared by injecting a non-aqueous electrolyte containing silyl sulfate and a phosphite-based stabilizer. As the separator, a resin such as polyethylene or polypropylene may be used.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not limited by these examples.

[Example]

Example 1

_{LiCoO 2} as a positive electrode active material, polyvinylidene fluoride (PVdF) as a binder, and carbon black as a conductive material were mixed in a weight ratio of 92:4:4, and then dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode slurry. prepared. The slurry was coated on an aluminum foil having a thickness of 20 μm, dried and rolled to prepare a positive electrode.

A negative active material slurry by mixing crystalline artificial graphite as an anode active material, acetylene black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder in a weight ratio of 92:1:7 and dispersing in N-methyl-2-pyrrolidone was prepared. This slurry was coated on a copper foil having a thickness of 15 μm, dried and rolled to prepare a negative electrode.

A thickness of 20 μm between the prepared electrodes Film made of polyethylene (PE) The separator was stacked, wound and compressed to construct a cell using a pouch having a thickness of 6 mm x 35 mm x 60 mm, and the following non-aqueous electrolyte was injected to prepare a lithium secondary battery.

_{1.0M LiPF 6} was added to a non-aqueous organic solvent in which ethylene carbonate (EC) and ethylmethyl carbonate (EMC) were mixed at 3:7 (v/v), 1 wt% of vinylene carbonate, 1,3-propane An electrolyte for a secondary battery was prepared by adding 2 wt% of diol cyclic sulfate (1,3-PDS) and 2 wt% of succinonitrile (SN).

Example 2

A secondary battery was manufactured in the same manner as in Example 1, except that 2% by weight of 1.3,6-hexanetricarbonitrile (HTCN) was added instead of 2% by weight of succinonitrile (SN) in the electrolyte for secondary battery of Example 1.

Example 3

A secondary battery was manufactured in the same manner as in Example 1, except that 1% by weight of 1.3,6-hexanetricarbonitrile (HTCN) was additionally added to the electrolyte solution for a secondary battery.

Example 4

1.3-propanediol cyclic sulfate (1, instead of 2 wt% of 1,3-propanediol cyclic sulfate (1,3-PDS) and 2 wt% of succinonitrile (SN)) in the electrolyte solution for secondary batteries of Example 1 (1, 3-PDS) 1% by weight and 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (BSA) 1% by weight A secondary battery was prepared in the same manner except for adding .

Example 5

Adding 2 wt% of 1.3-propanediol cyclic sulfate (1,3-PDS) instead of 1 wt% of 1,3-propanediol cyclic sulfate (1,3-PDS) in the electrolyte solution for secondary batteries of Example 4 A secondary battery was manufactured in the same manner except for this.

Example 6

1 wt% of 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (BSA) in the electrolyte solution for secondary batteries of Example 4 A secondary battery was prepared in the same manner except for adding 1 wt% of lithium difluorophosphate (LFP) instead.

Example 7

Adding 2 wt% of 1.3-propanediol cyclic sulfate (1,3-PDS) to the electrolyte solution for secondary batteries of Example 6 instead of 1 wt% of 1,3-propanediol cyclic sulfate (1,3-PDS) A secondary battery was manufactured in the same manner except for this.

Example 8

1 wt% of 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (BSA) in the electrolyte solution for secondary batteries of Example 4 A secondary battery was manufactured in the same manner except for adding 1 wt% of lithium bis(oxalato)borate (LiBOB) instead.

Example 9

1 wt% of 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (BSA) in the electrolyte solution for secondary batteries of Example 4 A secondary battery was prepared in the same manner except for adding 1 wt% of lithium difluoro(oxalato)borate (LiFOB) instead.

Example 10

1 wt% of 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (BSA) in the electrolyte solution for secondary batteries of Example 4 A secondary battery was prepared in the same manner except for adding 1 wt% of lithium bis(fluorosulfonyl)imide (LiFSI) instead.

Example 11

1 wt% of 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (BSA) in the electrolyte solution for secondary batteries of Example 4 A secondary battery was prepared in the same manner except for adding 1 wt% of lithium difluorobis(oxalato)phosphate (LiDFOP) instead.

Comparative Example 1

In the same manner as in Example 1, except that vinylene carbonate (VC), 1,3-propanediol cyclic sulfate (1,3-PDS) and succinonitrile (SN) were not added to the electrolyte solution for secondary batteries of Example 1 A secondary battery was manufactured.

Comparative Example 2

A secondary battery was prepared in the same manner as in Comparative Example 1, except that 1% by weight of 1,3-propanediol cyclic sulfate (1,3-PDS) was added to the electrolyte solution for secondary batteries.

Comparative Example 3

A secondary battery was prepared in the same manner as in Comparative Example 1, except that 2% by weight of 1,3-propanediol cyclic sulfate (1,3-PDS) was added to the electrolyte for secondary battery.

Comparative Example 4

A secondary battery was manufactured in the same manner as in Comparative Example 1, except that 3 wt% of 1,3-propanediol cyclic sulfate (1,3-PDS) was added and added to the electrolyte solution for a secondary battery.

Comparative Example 5

A secondary battery was manufactured in the same manner as in Comparative Example 1, except that 1 wt% of vinylene carbonate (VC) was added to the electrolyte solution for a secondary battery.

Comparative Example 6

A secondary battery was manufactured in the same manner as in Comparative Example 3, except that 1 wt% of vinylene carbonate (VC) was added to the electrolyte solution for a secondary battery.

Comparative Example 7

A secondary battery was manufactured in the same manner as in Comparative Example 3, except that 2% by weight of succinonitrile (SN) was added to the electrolyte for secondary battery.

Comparative Example 8

A secondary battery was manufactured in the same manner as in Comparative Example 3, except that 2% by weight of 1.3,6-hexanetricarbonitrile (HTCN) was added to the electrolyte solution for a secondary battery.

Comparative Example 9

1 wt% of 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (BSA) in the electrolyte for secondary battery of Comparative Example 3 A secondary battery was manufactured in the same manner except for adding and adding .

Comparative Example 10

A secondary battery was manufactured in the same manner as in Comparative Example 3, except that 1 wt% of lithium difluorophosphate (LFP) was added to the electrolyte solution for a secondary battery.

Comparative Example 11

A secondary battery was manufactured in the same manner as in Comparative Example 3, except that 1 wt% of lithium bis(oxalato)borate (LiBOB) was added and added to the secondary battery electrolyte.

Comparative Example 12

A secondary battery was prepared in the same manner as in Comparative Example 3, except that 1% by weight of lithium difluoro (oxalato) borate (LiFOB) was added to the electrolyte solution for a secondary battery.

Comparative Example 13

A secondary battery was manufactured in the same manner as in Comparative Example 3, except that 1% by weight of lithium bis(fluorosulfonyl)imide (LiFSI) was added to the electrolyte solution for secondary battery.

Comparative Example 14

A secondary battery was manufactured in the same manner as in Comparative Example 3, except that 1% by weight of lithium dioxalidifluorophosphate (LiDFOP) was added to the electrolyte solution for a secondary battery.

Comparative Example 15

A secondary battery was manufactured in the same manner as in Comparative Example 4, except that 2% by weight of succinonitrile (SN) was added to the electrolyte for secondary battery.

Comparative Example 16

A secondary battery was manufactured in the same manner as in Comparative Example 4, except that 2% by weight of 1.3,6-hexanetricarbonitrile (HTCN) was added to the electrolyte for a secondary battery.

Comparative Example 17

1 wt% of 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (BSA) in the electrolyte for secondary battery of Comparative Example 4 A secondary battery was manufactured in the same manner except for adding and adding .

Comparative Example 18

A secondary battery was manufactured in the same manner as in Comparative Example 4, except that 1 wt% of lithium difluorophosphate (LFP) was added to the electrolyte solution for a secondary battery.

Comparative Example 19

A secondary battery was manufactured in the same manner as in Comparative Example 4, except that 1 wt% of lithium bis(oxalato)borate (LiBOB) was added and added in the electrolyte solution for a secondary battery.

Comparative Example 20

A secondary battery was prepared in the same manner as in Comparative Example 4, except that 1% by weight of lithium difluoro(oxalato)borate (LiFOB) was added to the electrolyte solution for a secondary battery.

Comparative Example 21

A secondary battery was manufactured in the same manner as in Comparative Example 4, except that 1 wt% of lithium bis(fluorosulfonyl)imide (LiFSI) was added to the electrolyte solution for a secondary battery of Comparative Example 4.

Comparative Example 22

A secondary battery was manufactured in the same manner as in Comparative Example 4, except that 1% by weight of lithium dioxalidifluorophosphate (LiDFOP) was added to the electrolyte for a secondary battery.

The electrolyte compositions of Examples 1 to 11 and Comparative Examples 1 to 22 are shown in Table 1.

Comparative Example/Example Electrolyte composition (100wt%) Comparative Example 1 Ref. ^One) Comparative Example 2 Ref.+ 1,3-PDS ²⁾ 1wt% Comparative Example 3 Ref.+ 1,3-PDS ²⁾ 2wt% Comparative Example 4 Ref.+ 1,3-PDS ²⁾ 3wt% Comparative Example 5 Ref.+ VC ³⁾ 1wt% Comparative Example 6 Ref.+ 1,3-PDS 2wt% + VC 1wt% Comparative Example 7 Ref.+ 1,3-PDS 2wt% + SN ⁴⁾ 2wt% Comparative Example 8 Ref.+ 1,3-PDS 2wt% + HTCN ⁵⁾ 2wt% Comparative Example 9 Ref.+ 1,3-PDS 2wt% + BSA ⁶⁾ 1wt% Comparative Example 10 Ref.+ 1,3-PDS 2wt% + LFP ⁷⁾ 1wt% Comparative Example 11 Ref.+ 1,3-PDS 2wt% + LiBOB ⁸⁾ 1wt% Comparative Example 12 Ref.+ 1,3-PDS 2wt% + LiFOB ⁹⁾ 1wt% Comparative Example 13 Ref.+ 1,3-PDS 2wt% + LiFSI ¹⁰⁾ 1wt% Comparative Example 14 Ref.+ 1,3-PDS 2wt% + LiDFOP ¹¹⁾ 1wt% Comparative Example 15 Ref.+ VC 1wt% + SN 2wt% Comparative Example 16 Ref.+ VC 1wt% + HTCN 2wt% Comparative Example 17 Ref.+ VC 1wt% + BSA 1wt% Comparative Example 18 Ref.+ VC 1wt% + LFP 1wt% Comparative Example 19 Ref.+ VC 1wt% + LiBOB 1wt% Comparative Example 20 Ref.+ VC 1wt% + LiFOB 1wt% Comparative Example 21 Ref.+ VC 1wt% + LiFSI 1wt% Comparative Example 22 Ref.+ VC 1wt% + LiDFOP 1wt% Example 1 Ref.+ VC 1wt% + 1,3-PDS 2wt% + SN 2wt% Example 2 Ref.+ VC 1wt% + 1,3-PDS 2wt% + HTCN 2wt% Example 3 Ref.+ VC 1wt% + 1,3-PDS 2wt% + SN 1wt% + HTCN 1wt% Example 4 Ref.+ VC 1wt% + 1,3-PDS 1wt% + BSA 1wt% Example 5 Ref.+ VC 1wt% + 1,3-PDS 2wt% + BSA 1wt% Example 6 Ref.+ VC 1wt% + 1,3-PDS 1wt% + LFP 1wt% Example 7 Ref.+ VC 1wt% + 1,3-PDS 2wt% + LFP 1wt% Example 8 Ref.+ VC 1wt% + 1,3-PDS 2wt% + LiBOB 1wt% Example 9 Ref.+ VC 1wt% + 1,3-PDS 2wt% + LiFOB 1wt% Example 10 Ref.+ VC 1wt% + 1,3-PDS 2wt% + LiFSI 1wt% Example 11 Ref.+ VC 1wt% + 1,3-PDS 2wt% + LiDFOP 1wt%

* Note 1) Ref.: 1.0M LiPF ₆ , EC/EMC=3/7 (v/v)

2) 1,3-PDS: 1,3-propanediol cyclic sulfate

3) VC: vinyl carbonate

4) SN: succinonitrile

5) HTCN: 1.3,6-hexanetricarbonitrile (1.3,6-hexanetricarbonitrile)

6) BSA: 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (2,4,8,10-tetraoxa -3,9-dithiaspiro[5.5]undecane-3,3,9,9-tetraoxide)

7) LFP: lithium difluorophosphate

8) LiBOB: lithium bis(oxalato) borate

9) LiFOB: lithium difluoro (oxalate) borate

10) LiFSI: lithium bis(fluorosulfonyl)imide

11) LiDFOP: lithium difluoro bis(oxalate)phosphate

[Evaluation of physical properties]

1. Battery high temperature storage evaluation

After the formation of the secondary battery into which the electrolyte prepared in Examples and Comparative Examples was put, 1C was discharged and charged, the 1C capacity was checked, and the cell thickness and impedance were measured.

The measured cell (cell) was stored at 70° C. and after one week had elapsed, the cell thickness was measured to confirm the degree of swelling. In addition, the holding capacity (Rc) was obtained by directly discharging at 1C, and then the recovery capacity (Rt) was measured by discharging at 1C after charging again. Impedance was also measured under the same conditions as in the initial stage to calculate the rate of change compared to the initial stage.

70℃ high temperature storage evaluation conditions

1) Check the 1C capacity by measuring the secondary battery in a fully formed state under the following conditions.

Discharge: CC 1C, 2.75V cut-off (rest time=10min) => 1C initial capacity

Charge: CC/CV 4.2V/1C, 0.05C cut-off

2) Measure the initial cell thickness and impedance.

AC 10mV

Impedance: 90000Hz to 0.05Hz

3) 1 week storage at 70℃

4) Check the degree of swelling by measuring the cell thickness

5) Measure retention/recovery capacity under the following conditions.

Discharge: CC 1C/2.75V cut-off (rest time=10min) => Rt

Charge: CC/CV 4.2V/1C, 0.05C cut-off (rest time=10min)

Discharge: CC 1C/2.75V cut-off => Rc

6) Measure the impedance under the same conditions as the initial one.

2. Battery life evaluation

After completing the formation of the secondary battery prepared in Examples and Comparative Examples, the secondary battery was charged at 1C to 4.2V, and then discharged at 2C to 3V. This process was repeated 500 times to measure life characteristics (cycle performance).

Cycle performance was evaluated at room temperature (25°C) and high temperature (45°C), and the discharge capacity at 500 cycles was measured as a percentage of the initial capacity.

3. 2V Cycle Condition

Charge: CC/CV 4.2V/1C, 0.1C cut-off (rest time=10min

Discharge: CC 2C/3V cut-off (rest time=10min)

4. Discharge conditions by C-rate

Charge: CC/CV 4.2V/0.5C, 0.05C or 3hr cut-off

Discharge: CC 3C or 5C/3V cut-off

Table 2 shows the thickness increase rate, output decrease rate, impedance increase rate, capacity retention rate, capacity recovery rate, room temperature cycle, high temperature cycle performance evaluation and discharge efficiency for each rate measured in Examples and Comparative Examples.

70℃ after 1 week 500 cycle completion standard Discharge efficiency by rate Example/
comparative example thickness
Increase (%) Print
Decrease rate (%) Impedance
Increase (%) Capacity retention rate
(%) capacity recovery rate
(%) room temperature cycle
(%) High temperature 45℃ Cycle
(%) 3C discharge
efficiency
(%) 5C discharge
efficiency
(%) Comparative Example 1 38% 65% 197% 44% 50% 40% 16% 89 70 Comparative Example 2 19% 65% 141% 56% 66% 65% 21% 89 78 Comparative Example 3 17% 50% 138% 58% 68% 62% 20% 89 80 Comparative Example 4 15% 45% 130% 60% 70% 60% 17% 90 83 Comparative Example 5 21% 36% 81% 86% 90% 86% 80% 90 85 Comparative Example 6 8% 32% 74% 86% 90% 82% 70% 91 85 Comparative Example 7 20% 45% 120% 72% 82% 75% 42% 88 73 Comparative Example 8 18% 42% 100% 70% 79% 73% 40% 88 74 Comparative Example 9 20% 40% 195% 78% 83% 82% 38% 89 70 Comparative Example 10 29% 59% 238% 75% 79% 75% 12% 88 71 Comparative Example 11 70% 62% 240% 58% 61% 72% 22% 75% 67% Comparative Example 12 95% 68% 235% 61% 65% 67% 19% 78% 68% Comparative Example 13 42% 65% 220% 63% 67% 67% 32% 76% 67% Comparative Example 14 10% 60% 135% 85% 88% 82% 10% 80% 77% Comparative Example 15 24% 50% 216% 79% 87% 82% 80% 91 72 Comparative Example 16 25% 48% 172% 76% 85% 75% 70% 90 72 Comparative Example 17 22% 40% 162% 83% 88% 84% 78% 92 85 Comparative Example 18 19% 37% 154% 85% 90% 85% 80% 93 87 Comparative Example 19 50% 39% 163% 66% 69% 89% 80% 82% 67% Comparative Example 20 70% 53% 157% 70% 73% 86% 79% 87% 70% Comparative Example 21 30% 34% 155% 74% 77% 88% 83% 84% 69% Comparative Example 22 20% 36% 165% 82% 86% 85% 80% 92% 86% Example 1 4% 28% 52% 93% 94% 88% 82% 95 87 Example 2 3% 26% 40% 90% 92% 87% 78% 95 87 Example 3 3% 24% 48% 92% 97% 93% 89% 96 88 Example 4 2% 18% 72% 91% 95% 97% 93% 99 94 Example 5 One% 15% 62% 95% 98% 96% 92% 99 95 Example 6 4% 14% 50% 92% 96% 98% 94% 99 94 Example 7 3% 10% 45% 93% 97% 96% 92% 99 95 Example 8 5% 20% 53% 88% 90% 97% 92% 93% 79% Example 9 8% 28% 45% 90% 92% 95% 89% 97% 82% Example 10 5% 21% 43% 91% 94% 96% 90% 93% 80% Example 11 2% 26% 50% 93% 98% 92% 88% 98% 92%

As shown in Table 2, it was confirmed that the electrolyte solution of Examples of the present invention has improved high-temperature life even after storage at high temperature (70° C.) compared to Comparative Examples, and the EIS is reduced, so that high-temperature storage characteristics are remarkably improved.

In particular, compared to Comparative Example 6, Example 5 reduced the thickness after high temperature storage by 7%, output 17%, capacity retention rate 9%, recovery rate 8% improvement, room temperature life 14%, high temperature life 22% improvement, EIS 12% reduction, 3C discharge Efficiency was improved by 8% and 5C discharge efficiency by 10%.

Compared to Comparative Example 9, Example 5 reduced thickness after high temperature storage by 19%, output 25%, capacity retention rate 17%, recovery rate 15% improvement, room temperature life 14%, high temperature life 54% improvement, EIS 133% reduction, 3C discharge efficiency 10 %, 5C discharge efficiency was improved by 25%.

Compared to Comparative Example 17, Example 5 reduced thickness by 21% after high temperature storage, output 25%, capacity retention rate 12%, recovery rate 10% improvement, room temperature life 12%, high temperature life 14% improvement, EIS 100% reduction, 3C discharge efficiency 7 %, 5C discharge efficiency was improved by 10%.

Compared to Comparative Example 6, Example 7 reduced thickness after high temperature storage by 5%, output 22%, capacity retention rate 7%, recovery rate 7% improvement, room temperature life 14%, high temperature life 22% improvement, EIS 29% reduction, 3C discharge efficiency 8 %, 5C discharge efficiency was improved by 10%.

Compared to Comparative Example 10, Example 7 reduced thickness after high temperature storage by 26%, output 49%, capacity retention rate 18%, recovery rate 18% improvement, room temperature life 21%, high temperature life 80% improvement, EIS 193% reduction, 3C discharge efficiency 11 %, 5C discharge efficiency was improved by 24%.

Compared to Comparative Example 18, Example 7 reduced the thickness after high temperature storage by 16%, output 27%, capacity retention rate 8%, recovery rate 7% improvement, room temperature life 11%, high temperature life 12% improvement, EIS 109% reduction, 3C discharge efficiency 6 %, 5C discharge efficiency was improved by 8%.

The embodiment of the present invention has an effect of improving high temperature storage characteristics, high temperature lifespan characteristics, and high rate characteristics.

As the specific parts of the present invention have been described in detail above, it will be apparent to those of ordinary skill in the art that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. will be. Accordingly, it is intended that the substantial scope of the invention be defined by the claims and their equivalents.

Claims (9)

Electrolyte for secondary batteries, including:
(A) lithium salts;
(B) a non-aqueous organic solvent;
(C) 0.05-10 wt% of 1,3-propanediol cyclic sulfate;
(D) 0.05-20 wt% of at least one negative electrode film-forming additive selected from the group consisting of vinylene carbonate and vinylene ethylene carbonate; and
(E) 2,4,8,10-tetraoxa-3,9-dithispiro[5,5]undecane-3,3,9,9-tetraoxide (2,4,8,10-tetraoxa- 3,9-dithiaspiro[5.5]undecane-3,3,9,9-tetraoxide) and lithium difluorophosphate, lithium difluoro bis(oxalate)phosphate , lithium bis(oxalato) borate, lithium difluoro(oxalate) borate, and lithium bis(fluorosulfonyl)imide ) of one or more anodizing additives selected from the group consisting of imide) in an amount of 0.05 to 10% by weight.
According to claim 1, wherein the lithium salt is LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , CF ₃ SO ₃ Li And LiC(CF ₃ SO ₂ ) ₃ Electrolyte for a secondary battery, characterized in that at least one selected from the group consisting of.
The electrolyte solution for a secondary battery according to claim 1, wherein the non-aqueous organic solvent is at least one selected from the group consisting of cyclic carbonate, chain carbonate, and propionate.
The method according to claim 3, wherein the cyclic carbonate is at least one carbonate selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone, and mixtures thereof, and the chain carbonate is dimethyl An electrolyte for a secondary battery, characterized in that at least one carbonate selected from the group consisting of carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylmethyl carbonate, and mixtures thereof.
According to claim 3, wherein the propionate is methyl propionate (methyl propionate), ethyl propionate (ethyl propionate), propyl propionate (propyl propionate), butyl propionate (butyl propionate) and mixtures thereof Electrolyte for secondary batteries, characterized in that at least one propion ester selected from the group consisting of
delete delete delete A secondary battery comprising a positive electrode, a negative electrode, and the electrolyte of any one of claims 1 to 5.