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EP-4530591-B1 - STRAIN SENSOR, MANUFACTURING METHOD OF STRAIN SENSOR, AND SECONDARY BATTERY EQUIPPED WITH STRAIN SENSOR

EP4530591B1EP 4530591 B1EP4530591 B1EP 4530591B1EP-4530591-B1

Inventors

  • HAN, JONG CHAN
  • KIM, GI YOUNG
  • YU, KI JUN
  • KIM, TAE MIN
  • KIM, KYU BEEN

Dates

Publication Date
20260513
Application Date
20240813

Claims (12)

  1. A strain sensor (1) comprising: a backing part (10) attachable to an exterior of a case of a secondary battery (200), a strain gauge (20) installed on the backing part (10) and formed of single-crystal silicon; a wiring part (30) stacked on the backing part (10), along with the strain gauge (20), and electrically connected to the strain gauge (20); and an encapsulation part (40) fixed to the backing part (10) and configured to surround the strain gauge (20) and the wiring part (30) excluding a portion of the wiring part (30), characterized in that the backing part (10) comprises: a first deformation layer (12) disposed so as to be in contact with an exterior of the secondary battery (200); a second deformation layer (16) located above the first deformation layer (12); and a boundary layer (14) located between the first deformation layer (12) and the second deformation layer (16); wherein the first deformation layer (12) is configured to undergo compressive strain and the second deformation layer (16) is configured to undergo tensile strain in response to a swelling phenomenon of the secondary battery (200).
  2. The strain sensor (1) as claimed in claim 1, wherein a thickness of the backing part (10) is 10 or more times a thickness of the encapsulation part.
  3. The strain sensor (1) as claimed in claim 1 or 2, wherein the backing part (10) comprises polyimide.
  4. The strain sensor (1) as claimed in claim 1, 2 or 3, wherein: a thickness of the strain gauge (20) is 100 to 300 nm; and a thickness of the backing part (10) is 10 to 50 µm.
  5. A manufacturing method of a strain sensor (1), comprising: preparing a silicon-on-insulator (SOI) wafer (100) configured such that a single-crystal silicon thin film layer (110), an insulating oxide film layer (120), and a base wafer layer (130) are sequentially stacked; forming holes by forming a hole pattern (150) in the single-crystal silicon thin film layer (110) using a photolithography process; removing an oxide film by removing the insulating oxide film layer (120) from the SOI wafer (100); moving the single-crystal silicon thin film layer (110) from the base wafer layer (130) to a backing part (10), wherein the backing part (10) comprises: a first deformation layer (12) disposed so as to be in contact with an exterior of the secondary battery (200); a second deformation layer (16) located above the first deformation layer (12); and a boundary layer (14) located between the first deformation layer (12) and the second deformation layer (16); removing a photoresist (170) remaining on the single-crystal silicon thin film layer (110); patterning the single-crystal silicon thin film layer (110) to form a strain gauge (20) using masking and etching processes; forming a wiring part (30) by depositing a metal film (180) configured to be the wiring part (30) on an exterior of the backing part (10) and by performing the photolithography process; and forming an encapsulation part (40) on the backing part (10) configured to surround the strain gauge (20) and the wiring part (30), wherein the first deformation layer (12) is configured to undergo compressive strain and the second deformation layer (16) is configured to undergo tensile strain in response to a swelling phenomenon of the secondary battery (200).
  6. The manufacturing method as claimed in claim 5, wherein, in preparing the SOI wafer (100), the single-crystal silicon thin film layer (110) is doped with p-type boron impurities by ion implantation at a concentration of 5e17 to 5e18 cm-3.
  7. The manufacturing method as claimed in claim 5 or 6, wherein forming the holes comprises: stacking the photoresist (170) on the single-crystal silicon thin film layer (110); forming the hole pattern (150) including microholes with a micrometer-scale diameter by using a light source; and dry-etching the single-crystal silicon thin film layer (110) exposed through the hole pattern (150) by using a reactive ion etching (RIE) process.
  8. The manufacturing method as claimed in claim 7, wherein a thickness of the photoresist (170) is 300 to 600 nm, and/or wherein the hole pattern (150) is configured such that the microholes have a diameter of 3 µm and are arranged at intervals of 50 µm.
  9. The manufacturing method as claimed in any one of claims 5 to 8, wherein, in removing the oxide film, the insulating oxide film layer (120) is removed by putting the SOI wafer (100) provided with the hole pattern (150) formed thereon into a hydrofluoric acid solution.
  10. The manufacturing method as claimed in any one of claims 5 to 9, wherein moving the single-crystal silicon thin film layer (110) comprises: separating the single-crystal silicon thin film layer (110) from the base wafer layer (130) using a polydimethylsiloxane (PDMS) stamp; spin-coating the backing part (40) formed of a polyimide film with liquid polyimide, and after the spin-coating, soft-baking the backing part (40); and transferring the single-crystal silicon thin film layer (110) separated by the PDMS stamp to the backing part (40) after the soft-baking, and optionally wherein removing the photoresist (170) comprises: removing the photoresist (170) using acetone; and hard-baking the backing part (40) provided with the single-crystal silicon thin film layer (110) transferred thereto after removing the photoresist (170), and optionally wherein: for the soft-baking, curing is performed at a temperature of 100 to 110 °C for 30 to 50 seconds; and for the hard-baking, curing is performed at a temperature of 195 to 205 °C for 2 hours.
  11. The manufacturing method as claimed in any one of claims 5 to 10, wherein patterning the single-crystal silicon thin film layer (110) comprises: applying the photolithography process to the single-crystal silicon thin film layer (110); and forming the strain gauge (20) by dry-etching the single-crystal silicon thin film layer (110) into a zigzag shape or a serpentine shape using a reactive ion etching (RIE) process, and/or wherein the metal film (180) comprises at least one of copper, aluminum, gold, or silver, and/or wherein forming the encapsulation part (40) comprises: stacking epoxy on the backing part (10) configured to surround the strain gauge (20) and the wiring part (30); and processing the epoxy stacked on the backing part (10) into a shape of the encapsulation part (40) through the photolithography process to expose a portion of the wiring part (30).
  12. A secondary battery (200) comprising: a case (210) configured to surround an exterior of an electrode assembly (220); and a strain sensor (1) attached to an exterior of the case (210), the strain sensor (1) configured to detect deformation of the case (210), wherein the strain sensor (1) is as claimed in any one of claims 1 to 4, and wherein the backing part (10) is attached to the exterior of the case (210).

Description

FIELD Embodiments relate to a strain sensor, a manufacturing method of the strain sensor, a secondary battery equipped with the strain sensor. BACKGROUND Secondary batteries are power storage systems which provide excellent energy density by converting electrical energy into chemical energy and storing the chemical energy. Compared to primary batteries which may not be recharged, secondary batteries may be recharged and may be widely used in information technology (IT) devices, such as smartphones, cellular phones, laptops, and tablet computers. Recently, to prevent environmental pollution, interest in electric vehicles has increased and, accordingly, high-capacity secondary batteries are being adopted for electric vehicles. It is desirable that these secondary batteries have characteristics such as high density, high output, and stability. The information disclosed in this section is provided only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art. Attention is also drawn to the disclosure of US2011/226069A and CN112913068A. SUMMARY The invention provides a strain sensor as defined in claim 1 and a manufacturing method as defined in claim 5. Embodiments provide a strain sensor capable of measuring deformation and/or swelling of a secondary battery, a manufacturing method of the strain sensor, a secondary battery equipped with the strain sensor. A strain sensor according to one aspect of the present invention is provided as claimed in claim 1. In some examples, a thickness of the backing part may be 10 or more times a thickness of the encapsulation part. In some examples, the backing part may include polyimide. In some examples, a thickness of the strain gauge may be 100 to 300 nm, and a thickness of the backing part may be 10 to 50 µm. A manufacturing method of a strain sensor according to another aspect of the present invention is provided as claimed in claim 5. In some examples, in preparing the SOI wafer, the single-crystal silicon thin film layer may be doped with p-type boron impurities by ion implantation at a concentration of 5e17 to 5e18 cm-3. In some examples, forming the holes may include stacking the photoresist on the single-crystal silicon thin film layer, forming the hole pattern including microholes with a micrometer-scale diameter by using a light source, and dry-etching the single-crystal silicon thin film layer exposed through the hole pattern by using a reactive ion etching (RIE) process. In some examples, a thickness of the photoresist may be 300 to 600 nm. In some examples, the hole pattern may be configured such that the microholes have a diameter of 3 µm and are arranged at intervals of 50 µm. In some examples, in removing the oxide film, the insulating oxide film layer may be removed by putting the SOI wafer provided with the hole pattern formed thereon into a hydrofluoric acid solution. In some examples, moving the single-crystal silicon thin film layer may include separating the single-crystal silicon thin film layer from the base wafer layer using a polydimethylsiloxane (PDMS) stamp, spin-coating the backing part formed of a polyimide film with liquid polyimide, and then (e.g., after the spin-coating) soft-baking the backing part, and transferring the single-crystal silicon thin film layer separated by the PDMS stamp to the backing part after soft-baking. In some examples, removing the photoresist may include removing the photoresist using acetone, and hard-baking the backing part provided with the single-crystal silicon thin film layer transferred thereto after removing the photoresist. In some examples, for soft-baking, curing may be performed at a temperature of 100 to 110 °C for 30 to 50 seconds. In some examples, for hard-baking, curing may be performed at a temperature of 195 to 205 °C for 2 hours. In some examples, patterning the single-crystal silicon thin film layer may include applying the photolithography process to the single-crystal silicon thin film layer, and forming the strain gauge by dry-etching the single-crystal silicon thin film layer into a zigzag shape or a serpentine shape using a reactive ion etching (RIE) process. In some examples, in forming the wiring part, the metal film may include at least one of copper, aluminum, gold, or silver. In some examples, forming the encapsulation part may include stacking epoxy on the backing part configured to surround the strain gauge 20 and the wiring part, and processing the epoxy stacked on the backing part into a shape of the encapsulation part through the photolithography process to expose a portion of the wiring part. A secondary battery according to yet another aspect of the present invention is provided as claimed in claim 12. At least some of the above and other features of the invention are set out in the claims. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in this specification, i