KR-20260066343-A - ELECTROLYTE FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME

KR20260066343AKR 20260066343 AKR20260066343 AKR 20260066343AKR-20260066343-A

Abstract

The present invention relates to an electrolyte for a lithium secondary battery having excellent low-temperature and high-rate performance and a lithium secondary battery including the same. Specifically, it relates to an electrolyte for a lithium secondary battery capable of resolving the problem of irreversible performance degradation when the battery is operated at low temperatures and charged at high speeds through a solvent combination, and a lithium secondary battery including the same capable of excellent negative electrode reversibility and capacity development.

Inventors

최장욱
이지민
김민관
코스쿤, 알리

Assignees

서울대학교산학협력단
유니버시티 오프 프리보그

Dates

Publication Date: 20260512
Application Date: 20241104

Claims (9)

lithium salts; and In an electrolyte for a lithium secondary battery comprising a mixed solvent, The above mixed solvent is, A first solvent comprising an ether-based solvent; A second solvent comprising an ether-based solvent substituted with an electron-withdrawing group or a steric hindrance substituent within the solvent molecule; and A third solvent comprising a sulfonamide-based solvent in which an electron-withdrawing group is substituted within the solvent molecule; Electrolyte for lithium secondary batteries.
In paragraph 1, Based on the total moles of the mixed solvent, the first solvent is included in an amount of 20 mol% to 40 mol%, and the second solvent and the third solvent are each independently included in an amount of 10 mol% to 70 mol%. Electrolyte for lithium secondary batteries.
In paragraph 1, The first solvent mentioned above is a high-coordination solvent, and The above second solvent and third solvent are low-coordinate solvents, and The high-coordination solvent and the low-coordination solvent are included in a molar ratio of 1:2 to 1:4, Electrolyte for lithium secondary batteries.
In paragraph 3, The electron withdrawer substituted in the molecule of the above low-coordinate solvent compound is a halogen group, Electrolyte for lithium secondary batteries.
In paragraph 3, The electron withdrawer substituted on the molecule of the above low-coordination solvent compound is one or more selected from the group consisting of a monofluoroalkyl group, a difluoroalkyl group, a trifluoroalkyl group, a monochloroalkyl group, a dichloroalkyl group, a trichloroalkyl group, a monofluoroalkyl sulfonyl group, a difluoroalkyl sulfonyl group, a trifluoroalkyl sulfonyl group, a monochloroalkyl sulfonyl group, a dichloroalkyl sulfonyl group, a dichloroalkyl sulfonyl group, and a trichloroalkyl sulfonyl group. Electrolyte for lithium secondary batteries.
In paragraph 1, The above electrolyte for a lithium secondary battery further comprises a carbonate-based solvent, Electrolyte for lithium secondary batteries.
In paragraph 1, The first to third solvents included in the above mixed solvent each comprise a compound represented by the following chemical formulas 1 to 3, Electrolyte for lithium-ion batteries: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3]
In paragraph 1, The first solvent comprises a compound having a binding energy for lithium ions of 2.5 eV to 3.2 eV, and The second solvent and the third solvent comprise a compound having a lower bond energy than the first solvent, Electrolyte for lithium secondary batteries.
anode; A cathode; a separator interposed between the anode and the cathode; and A lithium secondary battery comprising an electrolyte for a lithium secondary battery according to any one of claims 1 to 8.

Description

Electrolyte for lithium secondary battery and lithium secondary battery including the same The present invention relates to an electrolyte for a lithium secondary battery having excellent low-temperature and high-rate performance and a lithium secondary battery including the same. Specifically, the invention relates to an electrolyte for a lithium secondary battery capable of improving the low-temperature characteristics and rate characteristics of the battery by combining a solvent used in the electrolyte to increase the reversibility of lithium ions. The applications of lithium-ion batteries are rapidly expanding, not only as portable power sources for mobile phones, laptop computers, digital cameras, and camcorders, but also as medium-to-large power sources for power tools, electric bicycles, hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). With this expansion of application fields, the demand for batteries capable of high-speed charging at room temperature and use in low-temperature environments below 0°C is also increasing. Lithium-ion batteries generally use organic electrolytes, but these electrolytes exhibit reduced ion transportability and lithium-ion charge storage reversibility during room-temperature fast charging or in low-temperature environments. Consequently, lithium-ion batteries using organic electrolytes face the problem of insufficient capacity and performance degradation under room-temperature fast charging and low-temperature conditions. Therefore, research is needed on electrolytes for lithium secondary batteries that can enhance ion transportability and lithium ion charge storage reversibility so that the battery can operate stably even under room temperature fast charging conditions and low temperature conditions. Figure 1 is a graph comparing the molecular orbital energy levels of each solvent used in the mixed solvent. Figure 2 shows the morphology of lithium electrodeposited on the surface of a copper electrode in the 6th cycle after fabricating a Li||Cu half-cell using the electrolyte of Preparation Example 1 and performing lithium electrodeposition/deposition. Figures 3 to 5 show the morphology of lithium electrodeposited on the surface of a copper electrode in the 6th cycle after performing lithium electrodeposition/deposition and fabricating a Li||Cu half-cell using Comparative Manufacturing Examples 1 to 3. Figure 6 is a graph showing the results of the Step chronoamperometry test (oxidation stability test) of the electrolytes according to Examples 1-3, Comparative Examples 1-3, 2-3, and 3-3. Figure 7 is a graph comparing the solvation structures of electrolytes according to Preparation Example 1 and Comparative Preparation Examples 1 to 3. FIG. 8 is a graph comparing the Coulomb efficiency of the batteries in Example 1-1, Comparative Example 1-1, and Comparative Example 6-1 under room temperature fast charging and discharging conditions. FIG. 9 is a graph comparing the lifespan performance of the batteries in Example 1-2, Comparative Example 1-2, and Comparative Example 4 under room temperature fast charging and discharging conditions. Figure 10 is a graph comparing the lifespan performance of the batteries of Examples 2 to 4 under room temperature fast charging and discharging conditions. Figure 11 is a graph comparing the lifespan performance of Comparative Example 2 and Comparative Example 3 batteries under room temperature fast charging and discharging conditions. Figure 12 is a graph comparing the lifespan performance of Comparative Example 5 and Comparative Example 6 batteries under room temperature fast charging and discharging conditions. FIG. 13 is a graph comparing the Coulomb efficiency of the batteries in Example 1-1, Comparative Example 3-1, and Comparative Example 5-1 under low temperature and low speed charge/discharge conditions. FIG. 14 is a graph comparing the lifespan performance of the batteries in Examples 1-2, Comparative Example 3, and Comparative Example 5 under low temperature and low speed charge/discharge conditions. The principles of a preferred embodiment of the present invention will be explained in detail below with reference to the attached drawings and description. However, the drawings and descriptions below relate to preferred embodiments among various methods for effectively explaining the features of the present invention, and the present invention is not limited to the drawings and descriptions below. Meanwhile, terms such as "first" or "second" may be used to describe various components, but these terms should be interpreted solely for the purpose of distinguishing one component from another. For example, a first component may be named a second component, and similarly, a second component may be named a first component. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to specify