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US-20260125510-A1 - COPOLYMER

US20260125510A1US 20260125510 A1US20260125510 A1US 20260125510A1US-20260125510-A1

Abstract

A copolymer that exhibits a positive temperature coefficient (PTC) effect and an oxidation potential which are controlled according to objectives. Such a conductive copolymer cannot affect or can rather improve, in a normal state, performance and operation of a secondary battery by exhibiting excellent electrical properties such as low resistance, and can form, in an abnormal state, a current collector for an electrode, an electrode, and a secondary battery including same. Also provided is a use of the copolymer.

Inventors

  • Hyun Ju Choi
  • Yu Mi Lee
  • Joon Koo Kang
  • Hee Myeong Yang
  • Ki Hwan Kim
  • Eun Kyoung Park
  • In Taek Song
  • JONG KWAN KOH
  • Woo Hyung Cho
  • Seok Kyeong Lee

Assignees

  • LG CHEM, LTD.
  • LG ENERGY SOLUTION, LTD.

Dates

Publication Date
20260507
Application Date
20231019
Priority Date
20221019

Claims (20)

  1. 1 . A copolymer, comprising: a thiophene unit; and a unit of Formula 3 below: wherein, R 5 , R 6 and R 7 are each independently hydrogen, a polar functional group, or a hydrocarbon functional group.
  2. 2 . The copolymer according to claim 1 , wherein: the polar functional group is a carboxyl group, a hydroxy group, an amino group, a cyano group, a nitro group, an ether group, or a functional group of Formula 4 below; and the hydrocarbon functional group is an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylcarbonyl group, or an alkylcarbonyloxy group: wherein, L 3 is a single bond, an alkylene group, or an alkylidene group, L 4 is an alkylene group or an alkylidene group, R 8 is hydrogen or an alkyl group, and n is a number in a range of 1 to 10.
  3. 3 . The copolymer according to claim 1 , having an oxidation potential of 4.00 V or less relative to lithium.
  4. 4 . The copolymer according to claim 1 , comprising, as the thiophene unit, a thiophene unit having a hydrocarbon functional group.
  5. 5 . The copolymer according to claim 1 , comprising, as the thiophene unit, a first thiophene unit having a hydrocarbon functional group with 10 or more carbon atoms and a second thiophene unit having a hydrocarbon functional group with 9 or less carbon atoms.
  6. 6 . The copolymer according to claim 5 , wherein the hydrocarbon functional group of the first or second thiophene unit is a linear or branched alkyl group, alkenyl group, or alkynyl group.
  7. 7 . The copolymer according to claim 5 , wherein a ratio of the total mole number of the first and second thiophene units is 30 mol % or more.
  8. 8 . The copolymer according to claim 5 , wherein a ratio M2/M1 of the mole number M2 of the second thiophene unit to the mole number M1 of the first thiophene unit is in a range of 0.01 to 100.
  9. 9 . The copolymer according to claim 4 , further comprising, as the thiophene unit, a thiophene unit having a polar functional group.
  10. 10 . The copolymer according to claim 9 , comprising the thiophene unit having a hydrocarbon functional group in an amount of 1 mole to 500 moles per mole of the thiophene unit having a polar functional group.
  11. 11 . The copolymer according to claim 1 , comprising the unit of Formula 3 in a ratio of 1 to 90 mol %.
  12. 12 . The copolymer according to claim 1 , having a DC resistance of 10,000 Ω·cm or less.
  13. 13 . The copolymer according to claim 1 , having an AC impedance resistance of 1,000Ω or less.
  14. 14 . The copolymer according to claim 1 , wherein ΔR1 of Equation 1 below is 100 Ω·cm/° C. or more, and a temperature R n at which the ΔR1 of 100 Ω·cm/° C. or more is confirmed is 80° C. or more: Δ ⁢ R ⁢ 1 = Max ⁢ { ( R n + 5 / R n ) / 5 } [ Equation ⁢ 1 ] wherein, R n is the DC resistance at any temperature n° C. within a temperature range of 25° C. to 135° C., and R n+5 is the DC resistance at a temperature ((n+5°) C) 5° C. higher than the temperature n° C., and Max{(R n+5 /R n )/5} is the maximum value among the (R n+5 /R n )/5 values confirmed within the temperature range of 25° C. to 135° C.
  15. 15 . The copolymer according to claim 1 , wherein ΔR2 of Equation 2 below is 10 Ω/° C. or more, and a temperature at which the ΔR2 of 10 Ω/° C. or more is confirmed is 80° C. or more: Δ ⁢ R ⁢ 2 = Max ⁢ { ( R z + 5 / R z ) / 5 } [ Equation ⁢ 2 ] wherein, R z is an AC impedance resistance at any temperature n° C. within a temperature range of 25° C. to 135° C., and R z+5 is an AC impedance resistance at a temperature ((n+5°) C) 5° C. higher than the temperature n° C., and Max{(R z+5 /R z )/5} is the maximum value among the (R z+5 /R z )/5 values confirmed within the temperature range of 25° C. to 135° C.
  16. 16 . A current collector for an electrode having: a current collector body; and a polymer layer formed on the current collector body and comprising the copolymer of claim 1 .
  17. 17 . An electrode, comprising: a current collector body; an active material layer formed on the current collector body and comprising an electrode active material; and a polymer layer formed between the current collector body and the active material layer and comprising the copolymer of claim 1 .
  18. 18 . The electrode according to claim 17 , wherein RV of Equation 3 below is more than 100: RV = 100 × _ Va / Vp [ Equation ⁢ 3 ] wherein, Va is the oxidation potential of the electrode active material, and Vp is the oxidation potential of the copolymer or the polymer layer.
  19. 19 . An electrode assembly, comprising the electrode of claim 17 .
  20. 20 . A secondary battery, comprising the electrode of claim 17 .

Description

CROSS-CITATION WITH RELATED APPLICATIONS This application is a National Stage Application of International Application No. PCT/KR2023/016284 filed on Oct. 19, 2023, which claims the benefit of and priority to Korean Patent Application No. 10-2022-0134842 dated Oct. 19, 2022, the disclosure of which is incorporated herein by reference in its entirety. TECHNICAL FIELD This specification discloses a copolymer and a use thereof. BACKGROUND An energy storage technology has expanded application areas to mobile phones, tablet and notebook PCs, or electric vehicles, and the like. As the data processing speed of mobile devices such as mobile phones or tablets increases and their usage hours also increase, the development of secondary batteries with high energy density and operating potential, long cycle life, and low self-discharge rate is in progress. In addition, as major developed countries suppress production of cars driven by internal combustion engines to alleviate global warming and air pollution, major automobile manufacturers also develop various electric vehicles, and thus the importance of secondary batteries having high energy density, high discharge voltage, and output stability increases as driving sources thereof. However, according to the above trend, the occurrence frequency of ignition or explosion accidents due to overcharging, high-temperature exposure or outer shocks, and the like in devices or automobiles using secondary batteries as an energy source also increases. As a main cause of such accidents, a short phenomenon, in which a positive electrode and a negative electrode inside an electrode assembly come into direct contact with each other mainly due to external stimuli, is known. When the secondary battery is overcharged or exposed to high temperatures or external stimuli, the short phenomenon can occur by the separator shrinkage due to the internal temperature increase of the secondary battery, or the internal structure destruction of the secondary battery due to outer shocks, and the like. When the short phenomenon occurs, migration of lithium ions and electrons is concentrated through the region where the positive electrode and the negative electrode are in direct contact with each other, so that internal heat generation can be promoted. Accordingly, it is known that as gas or the like is generated inside the battery, the volume expands, and the risk of ignition increases. DETAILED DESCRIPTION The present specification discloses a copolymer and a use thereof. The present specification is intended to disclose a conductive copolymer exhibiting a PTC (positive temperature coefficient) effect and an oxidation potential, which are controlled according to objectives. Such a conductive copolymer cannot affect or can rather improve, in a normal state, performance and operation of a secondary battery by exhibiting excellent electrical properties such as low resistance, and can form, in an abnormal state, a current collector for an electrode, an electrode, and a secondary battery comprising the same, which can ensure stability. The present specification also discloses a use of the copolymer. In this specification, the term “room temperature” means a natural temperature without heating or cooling, where the room temperature may be, for example, any one temperature in a range of 10° C. to 30° C., or a temperature of about 23° C., about 25° C., or about 27° C. or so. Among the physical properties mentioned in this specification, when the measurement temperature affects the physical property, the relevant physical property is a physical property measured at room temperature, unless otherwise specified. The unit of temperature in this specification is Celsius (° C.), unless otherwise specified. In this specification, the term “normal pressure” means a natural pressure without pressurization or depressurization, which may usually mean a pressure of about 730 mmHg to 790 mmHg or so. Among the physical properties mentioned in this specification, when the measurement pressure affects the physical property, the relevant physical property is a physical property measured at normal pressure, unless otherwise specified. Among the physical properties mentioned in this specification, when the measurement humidity affects the result, the relevant physical property is a physical property measured at humidity under standard conditions, unless otherwise specified. The humidity under standard conditions means any relative humidity in a range of 40% to 60% in relative humidity, which means, for example, relative humidity of 55%, or 60% or so. In this specification, the term “normal state” means a normal operating state of a secondary battery (e.g., a normal charging or discharging state of a secondary battery), or a storage state thereof. In this specification, the term “abnormal state” means a dangerous state in which abnormal charge flow, abnormal heating, or explosion, and the like occurs due to an external impact a