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KR-20260064608-A - POLYMER ELECTROLYTE MEMBRANE FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME

KR20260064608AKR 20260064608 AKR20260064608 AKR 20260064608AKR-20260064608-A

Abstract

A polymer electrolyte membrane for a lithium secondary battery according to the present disclosure comprises a copolymer. The copolymer comprises a main chain comprising a first repeating unit represented by the following chemical formula 1 and a second repeating unit represented by the following chemical formula 2, a fluoroalkyl group bonded as a side chain to the main chain, and a nitrogen-based cationic functional group bonded as a side chain to the main chain through a linker. A lithium secondary battery according to the present disclosure comprises the polymer electrolyte membrane for a lithium secondary battery.

Inventors

  • 이한솔
  • 박명수
  • 김기현
  • 황순식
  • 정유경
  • 김유은

Assignees

  • 에스케이온 주식회사
  • 경상국립대학교산학협력단

Dates

Publication Date
20260507
Application Date
20251029
Priority Date
20241030

Claims (15)

  1. A main chain comprising a first repeating unit represented by the following chemical formula 1 and a second repeating unit represented by the following chemical formula 2; Fluoroalkyl groups bonded as side chains to the main chain; and Polymer electrolyte membrane for a lithium secondary battery comprising a copolymer having a nitrogen-based cationic functional group that is bonded as a side chain to the main chain through a linker: [Chemical Formula 1] [Chemical Formula 2] (In the above chemical formulas 1 to 2, R1 to R2 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms, and R3 to R6 are each independently an alkyl group having 1 to 60 carbon atoms, an alkenyl group having 2 to 60 carbon atoms, an alkynyl group having 2 to 60 carbon atoms, or an arylthioxy group having 6 to 60 carbon atoms, and n, m, p, and q are each independently integers of 0 or 1 to 4, and * is a joint point).
  2. In claim 1, the polymer electrolyte membrane for a lithium secondary battery is represented by the following chemical formula 1-1: [Chemical Formula 1-1] .
  3. In claim 1, the polymer electrolyte membrane for a lithium secondary battery, wherein the above chemical formula 2 is represented by the following chemical formula 2-1: [Chemical Formula 2-1] .
  4. A polymer electrolyte membrane for a lithium secondary battery according to claim 1, wherein the ratio of the number of the first repeating unit to the number of the second repeating unit is 0.1 to 10.
  5. A polymer electrolyte membrane for a lithium secondary battery according to claim 1, wherein the fluoroalkyl group has a structure in which at least one of the hydrogens of an alkyl group having 1 to 10 carbon atoms is substituted with fluorine.
  6. A polymer electrolyte membrane for a lithium secondary battery according to claim 1, wherein the fluoroalkyl group comprises at least one selected from the group consisting of a trifluoromethyl group, a pentafluoroethyl group, a trifluoroethyl group, and a heptafluoropropyl group.
  7. A polymer electrolyte membrane for a lithium secondary battery according to claim 1, wherein the fluoroalkyl group is directly bonded to the main chain.
  8. A polymer electrolyte membrane for a lithium secondary battery according to claim 1, wherein the nitrogen-based cationic functional group comprises at least one selected from the group consisting of quaternary ammonium, imidazolium, and pyridinium.
  9. A polymer electrolyte membrane for a lithium secondary battery, wherein the linker comprises an alkylene group having 1 to 20 carbon atoms.
  10. A polymer electrolyte membrane for a lithium secondary battery according to claim 1, wherein the main chain comprises a third repeating unit represented by the following chemical formula 3: [Chemical Formula 3] (In the above chemical formula 3, R f is a fluoroalkyl group having 1 to 10 carbon atoms, and L is a linker that is directly bonded or an alkylene group having 1 to 10 carbon atoms, and R 7 to R 9 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms, and X - 는 NO 3 - , N(CN) 2 - , BF 4 - , ClO 4 - , PF 6 - , (CF 3 ) 2 PF 4 - , (CF 3 ) 3 PF 3 - , (CF 3 ) 4 PF 2 - , (CF 3 ) 5 PF - , (CF 3 ) 6 P - , CF 3 SO 3 - , CF 3 CF 2 SO 3 - , (CF 3 SO 2 ) 2 N - , (FSO 2 ) 2 N - , CF 3 CF 2 (CF 3 ) 2 CO - , (CF 3 SO 2 ) 2 CH - , (SF 5 ) 3 C - , (CF 3 SO 2 ) 3 C - , CF 3 (CF 2 ) 7 SO 3 - , CF 3 CO₂- , CH₃CO₂- , SCN- , or ( CF₃CF₂SO₂ ) ₂N- , and * is a joint point).
  11. A polymer electrolyte membrane for a lithium secondary battery according to claim 1, wherein the weight-average molecular weight of the copolymer is 10 kg/mol to 400 kg/mol.
  12. A polymer electrolyte film for a lithium secondary battery having a thickness of 20 μm to 100 μm in claim 1.
  13. A polymer electrolyte membrane for a lithium secondary battery having an ionic conductivity of 1 * 10⁻⁵ S/cm to 70 * 10⁻⁵ S/cm in claim 1.
  14. In claim 1, the polymer electrolyte membrane comprises a lithium salt, and A polymer electrolyte membrane for a lithium secondary battery, wherein the content of the lithium salt is 50% to 90% by weight of the total weight of the polymer electrolyte membrane.
  15. anode; A cathode facing the anode; and A lithium secondary battery comprising a polymer electrolyte membrane for a lithium secondary battery of claim 1 disposed between the anode and the cathode.

Description

Polymer Electrolyte Membrane for Lithium Secondary Battery and Lithium Secondary Battery Including the Same The present disclosure provides a polymer electrolyte membrane for a lithium secondary battery and a lithium secondary battery including the same. Rechargeable batteries are batteries capable of repeated charging and discharging, and with the advancement of the information and communication and display industries, they are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptop PCs. Furthermore, recently, battery packs containing rechargeable batteries are being developed and applied as power sources for eco-friendly vehicles, such as electric cars. Among secondary batteries, active research and development is being conducted on lithium-ion batteries due to their high operating voltage and energy density per unit weight, as well as their advantages in charging speed and weight reduction. Recently, lithium-ion batteries with high energy density and rapid charging characteristics are being researched and developed. In this case, heat accumulates inside the battery during repeated charging and discharging cycles, which can cause a fire. Fire safety of batteries can be improved by using solid or semi-solid electrolytes. Solid or semi-solid electrolytes may have lower fluidity and less deformation due to heat compared to liquid electrolytes, and thus battery stability can be improved. However, to increase the capacity and size of batteries, structural modifications, processing, and physical property improvements of the electrolyte layer may be necessary to improve the lifespan characteristics and stability of lithium batteries. Figure 1 is a graph of the 1H -NMR results of the copolymers of Synthesis Examples 1 and 2. Figure 2 shows the FT-IR analysis results of the copolymers of Synthesis Examples 1 to 3. Figure 3 shows the DSC analysis results of the copolymers of Synthesis Examples 1 to 3. Figure 4 is the strain-stress curve of the copolymers of Synthesis Examples 1 and 2. Figure 5 shows the EIS results of the polymer electrolyte membranes of Examples 1 to 4. The present disclosure provides a polymer electrolyte membrane for a lithium secondary battery comprising a copolymer having nitrogen-based cationic functional groups bonded as side chains to a main chain. Additionally, the present disclosure provides a lithium secondary battery comprising said polymer electrolyte membrane for a lithium secondary battery. The present disclosure will be described in detail below. However, this is merely illustrative and the present disclosure is not limited to the specific embodiments described illustratively. A polymer electrolyte membrane for a lithium secondary battery according to exemplary embodiments (hereinafter abbreviated as polymer electrolyte membrane) comprises a copolymer having a main chain comprising a first repeating unit and a second repeating unit. The above first repeating unit is represented by the following chemical formula 1. [Chemical Formula 1] In the above formula 1, R1 and R2 are each independently hydrogen or an alkyl group having 1 to 10 carbon atoms. In some embodiments, R1 and R2 may each independently hydrogen or an alkyl group having 1 to 3 carbon atoms. For example, R1 and R2 may each be a methyl group. The first repeating unit may include a fluorenyl moiety. Accordingly, the free volume between copolymer chains may be increased, and the rate at which the crystallinity of the copolymer increases may be reduced. Accordingly, a copolymer with a high molecular weight may be realized, and the durability of the polymer electrolyte membrane may be improved. In the above formula 1, R3 to R4 may each independently be an alkyl group having 1 to 60 carbon atoms, an alkenyl group having 2 to 60 carbon atoms, an alkynyl group having 2 to 60 carbon atoms, or an arylthioxy group having 6 to 60 carbon atoms. For example, R3 and R4 may be hydrogen or an alkyl group having 1 to 5 carbon atoms. In the above chemical formula 1, n and m are each independently 0 or integers from 1 to 4. For example, n and m can each independently be 0 or 1. In the above chemical formula 1, * is a bonding point. A repeating unit such as the chemical formula 2 or chemical formula 3 described later may be bonded to the above bonding point. According to exemplary embodiments, the above chemical formula 1 can be represented by the following chemical formula 1-1. [Chemical Formula 1-1] The above second repeating unit is represented by the following chemical formula 2. [Chemical Formula 2] In the above chemical formula 2, R5 to R6 are each independently an alkyl group having 1 to 60 carbon atoms, an alkenyl group having 2 to 60 carbon atoms, an alkynyl group having 2 to 60 carbon atoms, or an arylthioxy group having 6 to 60 carbon atoms. For example, R5 and R6 may each independently be hydrogen or an alkyl group having 1 to 5 carbon atoms. In the above chemical fo