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EP-4742350-A1 - ELECTROLYTE FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME

EP4742350A1EP 4742350 A1EP4742350 A1EP 4742350A1EP-4742350-A1

Abstract

An embodiment of the present disclosure provides an electrolyte for a lithium secondary battery and a lithium secondary battery including the same. According to some embodiments, the electrolyte for a lithium secondary battery may include an additive including a compound having a specific structure, an organic solvent and a lithium salt. Accordingly, a lithium secondary battery including the electrolyte for a lithium secondary battery may exhibit improved cycle life characteristics and high-temperature storage characteristics.

Inventors

  • LEE, MIN HEE
  • PARK, KI SUNG
  • KIM, JONG CHAN
  • CHO, IN HAENG

Assignees

  • SK On Co., Ltd.
  • SK Innovation Co., Ltd.

Dates

Publication Date
20260513
Application Date
20251016

Claims (15)

  1. An electrolyte for a lithium secondary battery comprising: an additive comprising a compound having a structure represented by Formula 1 below; an organic solvent; and a lithium salt: (in Formula 1, R 1 and R 2 form a carbonyl group together with the carbon atom to which they are bonded, or R 1 and R 2 are linked to the carbon atom to which they are bonded to form a 4- to 7-membered heterocycloalkyl group including at least one oxygen atom, the heterocycloalkyl group is unsubstituted or substituted with at least one hydrogen atom replaced by an alkyl group having 1 to 4 carbon atoms, L 1 and L 2 are each independently an alkylene group having 1 to 5 carbon atoms, and X is an oxygen atom or an alkoxylene group having 1 to 3 carbon atoms).
  2. The electrolyte for a lithium secondary battery according to claim 1, wherein R 1 and R 2 form a carbonyl group together with the carbon atom to which they are bonded, or R 1 and R 2 are linked to the carbon atom to which they are bonded to form a 5- or 6-membered heterocycloalkyl group including at least one oxygen atom, the heterocycloalkyl group is unsubstituted or substituted with at least one hydrogen atom replaced by an alkyl group having 1 to 3 carbon atoms, L 1 and L 2 are each independently an alkylene group having 1 to 4 carbon atoms, and X is an oxygen atom, a methoxylene group, or an ethoxylene group.
  3. The electrolyte for a lithium secondary battery according to claim 1 or claim 2, wherein R 1 and R 2 form a carbonyl group together with the carbon atom to which they are bonded, or R 1 and R 2 are linked to the carbon atom to which they are bonded to form 1,3-dioxolane, the 1,3-dioxolane is unsubstituted or substituted with at least one hydrogen atom replaced by a methyl group or an ethyl group, L 1 and L 2 are each independently an alkylene group having 1 to 4 carbon atoms, and X is an oxygen atom.
  4. The electrolyte for a lithium secondary battery according to any one of claims 1 to 3, wherein the compound having the structure represented by Formula 1 comprises a compound having a structure represented by any one of Formula 2-1 to Formula 2-5 below:
  5. The electrolyte for a lithium secondary battery according to any one of claims 1 to 4, wherein the organic solvent comprises at least one selected from the group consisting of a carbonate organic solvent, an ester organic solvent, an ether organic solvent, a ketone organic solvent, and an aprotic organic solvent.
  6. The electrolyte for a lithium secondary battery according to any one of claims 1 to 5, wherein the organic solvent comprises a cyclic carbonate solvent and a linear carbonate solvent.
  7. The electrolyte for a lithium secondary battery according to claim 6, wherein the ratio of the volume of the cyclic carbonate solvent to the volume of the linear carbonate solvent in the organic solvent is 1/9 to 1.
  8. The electrolyte for a lithium secondary battery according to any one of claims 1 to 7, wherein the content of the additive is 0.1% by weight to 10% by weight based on the total weight of the electrolyte.
  9. The electrolyte for a lithium secondary battery according to any one of claims 1 to 8, wherein the content of the additive is 0.1% by weight to 3% by weight based on the total weight of the electrolyte.
  10. The electrolyte for a lithium secondary battery according to any one of claims 1 to 9, wherein the lithium salt comprises at least one selected from the group consisting of LiPF 6 , LiClO 4 , LiBF 4 , LiFSI, LiTFSI, LiBOB, LiFOB, LiDFOB, LiDFBP, LiTFOP, LiPO 2 F 2 , 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, LiSCN, and LiC(CF 3 SO 2 ) 3 .
  11. The electrolyte for a lithium secondary battery according to any one of claims 1 to 10, wherein the electrolyte further comprises at least one auxiliary additive selected from the group consisting of a fluorine-containing carbonate compound, a lithium phosphate compound, a sultone compound, and a sulfate compound.
  12. The electrolyte for a lithium secondary battery according to claim 11, wherein the auxiliary additive comprises fluoroethylene carbonate (FEC), lithium difluorophosphate (LiDFP), 1,3-propane sultone (PS), and 1,2-ethylene sulfate (ESA).
  13. The electrolyte for a lithium secondary battery according to claim 11 or claim 12, wherein the content of the auxiliary additive is 0.01% by weight to 10% by weight based on the total weight of the electrolyte.
  14. The electrolyte for a lithium secondary battery according to any one of claims 11 to 13, wherein the weight ratio of the content of the auxiliary additive to the content of the additive in the electrolyte is 0.1 to 15.
  15. A lithium secondary battery comprising: an electrode assembly comprising a cathode and an anode that are repeatedly stacked; and the electrolyte for a lithium secondary battery according to any one of claims 1 to 14, which impregnates the electrode assembly.

Description

BACKGROUND 1. Field of the Invention The present disclosure relates to an electrolyte for a lithium secondary battery and a lithium secondary battery including the same. More specifically, the present disclosure relates to an electrolyte for a lithium secondary battery including a solvent and an electrolyte salt, and a lithium secondary battery including the electrolyte. 2. Description of the Related Art Secondary batteries are batteries that can be repeatedly charged and discharged, and have been widely applied as power sources for portable electronic devices, such as mobile phones and laptop PCs. Among secondary batteries, a lithium secondary battery has a high operating voltage and a high energy density per unit weight, making it advantageous in terms of charging speed and weight reduction. In this regard, the lithium secondary battery has been actively developed and applied in various industrial fields. A lithium secondary battery may include, for example, an electrode assembly including a cathode, an anode and a separation membrane interposed between the cathode and the anode, and an electrolyte in which the electrode assembly is impregnated. The lithium secondary battery may further include, for example, an outer case in the form of a pouch for accommodating the electrode assembly and the electrolyte. The cathode of a lithium secondary battery may be fabricated by, for example, applying a cathode slurry including a cathode active material, a binder, and, optionally, a conductive material, to a cathode current collector, followed by drying and roll-pressing. The cathode active material may be a material capable of reversible intercalation and deintercalation of lithium ions. For example, the cathode active material may be a lithium metal oxide including a metal element such as nickel (Ni), cobalt (Co) or manganese (Mn). When a lithium secondary battery is repeatedly charged and discharged, side reactions between the lithium metal oxide and the electrolyte may occur, thereby degrading the stability and cycle life characteristics of the lithium secondary battery. Meanwhile, as the application range of lithium secondary batteries continues to expand, superior cycle life characteristics, high capacity, and operational stability are increasingly required. Accordingly, there is a need to develop a lithium secondary battery that provides consistent output and capacity even during repeated charge and discharge cycles. SUMMARY An object of the present disclosure is to provide an electrolyte for a lithium secondary battery having improved chemical stability. Another object of the present disclosure is to provide a lithium secondary battery having improved cycle life characteristics and high-temperature storage characteristics. An electrolyte for a lithium secondary battery according to exemplary embodiments may include: an additive including a compound having a structure represented by Formula 1 below; an organic solvent; and a lithium salt. In Formula 1, R1 and R2 may form a carbonyl group together with the carbon atom to which they are bonded, or R1 and R2 may be linked to the carbon atom to which they are bonded to form a 4- to 7-membered heterocycloalkyl group including at least one oxygen atom, the heterocycloalkyl group may be unsubstituted or substituted with at least one hydrogen atom replaced by an alkyl group having 1 to 4 carbon atoms, L1 and L2 may each independently be an alkylene group having 1 to 5 carbon atoms, and X may be an oxygen atom or an alkoxylene group having 1 to 3 carbon atoms. In some embodiments, R1 and R2 may form a carbonyl group together with the carbon atom to which they are bonded, or R1 and R2 may be linked to the carbon atom to which they are bonded to form a 5- or 6-membered heterocycloalkyl group including at least one oxygen atom, the heterocycloalkyl group may be unsubstituted or substituted with at least one hydrogen atom replaced by an alkyl group having 1 to 3 carbon atoms, L1 and L2 may each independently be an alkylene group having 1 to 4 carbon atoms, and X may be an oxygen atom, a methoxylene group, or an ethoxylene group. In some embodiments, R1 and R2 may form a carbonyl group together with the carbon atom to which they are bonded, or R1 and R2 may be linked to the carbon atom to which they are bonded to form 1,3-dioxolane, the 1,3-dioxolane may be unsubstituted or substituted with at least one hydrogen atom replaced by a methyl group or an ethyl group, L1 and L2 may each independently be an alkylene group having 1 to 4 carbon atoms, and X may be an oxygen atom. In some embodiments, the compound having the structure represented by Formula 1 may include a compound having a structure represented by any one of Formula 2-1 to Formula 2-5 below. In some embodiments, the organic solvent may include at least one selected from the group consisting of a carbonate organic solvent, an ester organic solvent, an ether organic solvent, a ketone organic solvent, and an aprotic o