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EP-4742416-A1 - SEPARATOR AND ELECTROCHEMICAL DEVICE INCLUDING THE SAME

EP4742416A1EP 4742416 A1EP4742416 A1EP 4742416A1EP-4742416-A1

Abstract

Provided is a separator including: a substrate; an inorganic particle layer formed on at least any one surface of the substrate; and an adhesive layer formed on the at least one inorganic particle layer, wherein when adhesive strength between a probe and a surface of the separator, which is measured at a stage temperature of x°C using the probe having a spring constant of 40 N/m, an average radius of 8 nm, and a scanning speed of 0.5 Hz, is Fx, F40 is 1 nN to 30 nN, and the separator satisfies the following Equation 1 : F 75 / F 40 ≥ 5 .

Inventors

  • KIM, DONG JAE
  • YUN, CHEOL MIN
  • Jang, Dong II
  • LEE, SOON BO

Assignees

  • SK Innovation Co., Ltd.
  • SK IE Technology Co., Ltd.

Dates

Publication Date
20260513
Application Date
20251022

Claims (15)

  1. A separator comprising: a substrate; an inorganic particle layer formed on at least any one surface of the substrate; and an adhesive layer formed on the at least one inorganic particle layer, wherein when adhesive strength between a probe and a surface of the separator measured at a stage temperature of x°C using the probe of an atomic force microscope (AFM) is Fx, F40 is 1 nN to 30 nN, and the separator satisfies the following Equation 1: F 75 / F 40 ≥ 5 , wherein Fx is measured at a spring constant of 40 N/m, an average radius of 8 nm, and a scanning speed of 0.5 Hz.
  2. The separator of claim 1, wherein the adhesive layer includes an acryl-based polymer binder.
  3. The separator of claim 1 or 2, wherein the adhesive layer includes a particulate polymer binder, preferably wherein the particulate polymer binder is a particulate acryl-based polymer binder including a repeating unit derived from a compound represented by Chemical Formula 1: wherein R 1 is hydrogen or a C 1-10 alkyl group; and R 2 is hydrogen or a C 1-20 hydrocarbon group.
  4. The separator of any one of the preceding claims, wherein the adhesive layer comprises a particulate polymer binder having a core-shell structure.
  5. The separator of claim 4, wherein a glass transition temperature of the particulate polymer binder having the core-shell structure satisfies at least one of the followings: i) a glass transition temperature of the core in the particulate polymer binder is 30°C to 70°C, ii) a glass transition temperature of the shell of the particulate polymer binder is 70°C to 110°C, and/or iii) a glass transition temperature (Tg,c) of the core and the glass transition temperature (Tg,s) of the shell satisfy the following Equation 2: 50 ° C ≤ Tg , c + Tg , s / 2 ≤ 90 ° C .
  6. The separator of any one of the preceding claims, wherein the adhesive layer includes a copolymer composed of a repeating unit derived from an acryl-based monomer; and a copolymer composed of a repeating unit derived from an acryl-based monomer and styrene.
  7. The separator of any one of the preceding claims, wherein the adhesive layer includes a particulate acryl-based polymer binder having an average particle diameter (D50) of 400 nm to 800 nm.
  8. The separator of any one of the preceding claims, wherein the F75 is 40 nN to 300 nN, and/or wherein Equation 1 satisfies F75/F40 ≥ 10.
  9. The separator of any one of the preceding claims, wherein the inorganic particle layer includes inorganic particles and a polymer binder, optionally wherein a weight ratio between the inorganic particles and the polymer binder is 90:10 to 99:1.
  10. The separator of any one of the preceding claims, wherein the inorganic particle layer includes inorganic particles having an average particle diameter (D50) of 100 nm to 1500 nm.
  11. The separator of any one of the preceding claims, wherein the inorganic particle layer includes first and second types of inorganic particles respectively exhibiting different particle size distributions, the first inorganic particles having an average particle diameter (D50) of 100 nm to 500 nm, and the second inorganic particles having an average particle diameter (D50) of 500 nm to 1500 nm.
  12. The separator of any one of the preceding claims, wherein the inorganic particle layer has a thickness of 0.5 µm to 3.0 um, and/or wherein the adhesive layer has a thickness of 0.05 µm to 2.0 µm.
  13. An electrochemical device comprising a separator according to any one of the preceding claims, optionally wherein the separator is faced with an anode electrode and a cathode electrode.
  14. An electrochemical device of claim 13, wherein the electrochemical device is a secondary battery, preferably a lithium secondary battery.
  15. Use of a separator for suppressing increase of the internal resistance in an electrochemical device as the number of charge/discharge cycles N increases, wherein the number of cycles N is 300 or more, when an internal resistance value of the electrochemical device is increased by 30% as compared with initial resistance before starting a charge/discharge cycle, wherein one charge/discharge cycle is set by charging from 2.5 V to 4.2 V at 0.5 C, and by discharging at 0.5 C to 2.5 V after discharging the electrochemical device to 2.5 V, and wherein C denotes the C-rate or charging speed, 1 C being defined as one hour to fully charge the electrochemical device.

Description

TECHNICAL FIELD The following disclosure relates to a separator and an electrochemical device including the same, and use of the separator. BACKGROUND In recent years, there has been a rapidly growing interest in electrochemical devices used in mobile phones, laptops, electric vehicles, and other devices having electrochemical devices, and their energy storage technology. In particular, research on a separator, which is one of the main constituent elements determining the characteristics of a secondary battery which is the electrochemical device, is being actively performed. Since the separator is impregnated with an electrolyte and functions as an ion channel, it has a great influence on the physical properties in the performance of the secondary battery. In this regard, a method of improving thermal resistance of a separator by mixing inorganic particles having high thermal resistance with a binder and coating a porous substrate with the mixture is known, and technology development research for sufficiently improving internal resistance while simultaneously securing adhesive strength between a separator and an electrode is in progress. SUMMARY An embodiment of the present disclosure is directed to providing a separator in which adhesive strength of a surface of the separator measured using a probe of an atomic force microscope (AFM) capable of temperature adjustment is implemented in a specific range. Another embodiment of the present disclosure is directed to providing an electrochemical device including the separator. In one general aspect, a separator includes: a substrate; an inorganic particle layer formed on at least any one surface of the substrate; and an adhesive layer formed on the at least one inorganic particle layer, wherein when adhesive strength between a probe and a surface of the separator measured at a stage temperature of x°C using the probe of an atomic force microscope is Fx,F40 is 1 nN to 30 nN, andthe separator satisfies the following Equation 1: F75/F40≥5.wherein Fx is measured at a spring constant of 40 N/m, an average radius of 8 nm, and a scanning speed of 0.5 Hz,In an exemplary embodiment, the adhesive layer may include an acryl-based polymer binder. In an exemplary embodiment, the adhesive layer may include a particulate polymer binder. In an exemplary embodiment, the particulate polymer binder may be a particulate acryl-based polymer binder including a repeating unit derived from a compound represented by Chemical Formula 1: wherein R1 is hydrogen or a C1-10 alkyl group; andR2 is hydrogen or a C1-20 hydrocarbon group. In an exemplary embodiment, the adhesive layer may comprise a particulate polymer binder having a core-shell structure. In an exemplary embodiment, a glass transition temperature of the particulate polymer binder having the core-shell structure may satisfy at least one of the followings: i) a glass transition temperature of the core may be 30°C to 70°C,ii) a glass transition temperature of the shell of the particulate polymer binder may be 70°C to 110°C, and/oriii) the glass transition temperature (Tg,c) of the core and the glass transition temperature (Tg,s) of the shell may satisfy the following Equation 2: 50°C≤Tg,c+Tg,s/2≤90°C. In an exemplary embodiment, the adhesive layer may include a copolymer composed of a repeating unit derived from an acryl-based monomer; and a copolymer composed of a repeating unit derived from an acryl-based monomer and styrene. In an exemplary embodiment, the adhesive layer may include a particulate polymer binder or a particulate acryl-based polymer binder having an average particle diameter (D50) of 400 nm to 800 nm. In an exemplary embodiment, the F75 may be 40 nN to 300 nN. In an exemplary embodiment, Equation 1 may satisfy F75/F40 ≥ 10. In an exemplary embodiment, the inorganic particle layer may include inorganic particles and the polymer binder. In an exemplary embodiment, a weight ratio between the inorganic particles and the polymer binder is 90:10 to 99:1. In an exemplary embodiment, the inorganic particle layer may include inorganic particles having an average particle diameter (D50) of 100 nm to 1500 nm. In an exemplary embodiment, the inorganic particle layer may include first and second types of inorganic particles respectively exhibiting different particle size distributions, the first inorganic particles having an average particle diameter (D50) of 100 nm to 500 nm, and the second inorganic particles having an average particle diameter of 500 nm to 1500 nm. In an exemplary embodiment, the inorganic particle layer may have a thickness of 0.5 µm to 3.0 µm. In an exemplary embodiment, the adhesive layer may have a thickness of 0.05 µm to 2.0 µm. In another general aspect, an electrochemical device includes a separator of the present disclosure, optionally the separator is faced with an anode electrode and a cathode electrode. In another general aspect, the electrochemical device is a secondary battery, preferably a