A thermal cut-off device

Abstract

The utility model discloses a thermal fuse cutter, including a shell, a heating plate, two main circuit electrode plates, an upper heat-conducting electrode plate, a fusible alloy and a fuse-aiding agent; the upper heat-conducting electrode plate is arranged between the two main circuit electrode plates, and is arranged relative to the two main circuit electrode plates; the heating plate is arranged below the two main circuit electrode plates and the upper heat-conducting electrode plate, one electrode of the heating element is connected to the two main circuit electrode plates through the upper heat-conducting electrode plate, the fusible alloy and the two main circuit electrode plates, and the other electrode is connected to the controlled electrode, so that the heating plate is connected to the control circuit. Through the design of the upper heat-conducting electrode plate, the heat of the heating plate is transferred to the fusible alloy through the heat-conducting electrode plate and the main circuit electrode plate, reducing the heat transfer loss and achieving rapid fusing; at the same time, the relative positions of the main circuit electrode plate, the heating plate and the fusible alloy are adjusted, so that the current carrying capacity is enhanced, and the length and width of the product can be made more compact under the condition of ensuring the thermal insulation performance of the product.

Description

Technical Field

[0001] The utility model relates to the field of thermal fuse cutters, in particular to a thermal fuse cutter with an upper heat-conducting electrode sheet. Background Art

[0002] The thermal cutoff consists of a housing, two main circuit electrodes, a controlled electrode, a heating plate, a fusible alloy, a fuse, etc. Inside the thermal cutoff, the two main circuit electrodes are connected by a fusible alloy, and the heating plate includes a heating element and two electrodes, one electrode is connected to the two main circuit electrodes by a fusible alloy, and the other electrode is connected to the controlled electrode. When in use, the two main circuit electrodes of the thermal cutoff are connected in series in the main circuit, and the controlled electrode is connected to an external control circuit to control the heating circuit of the heating plate; when the main circuit has an overcurrent or short circuit, the internal fusible alloy heats up and melts itself, thereby cutting off the power supply; when the main circuit has an abnormal overcharge, the control circuit connects the heating circuit of the heating plate, and the heating plate heats up to melt the fusible alloy, thereby cutting off the main circuit.

[0003] It is usually used as secondary protection for lithium-ion battery packs, so that they can act in time when they are exposed to overcurrent and overcharging risks, effectively reducing the fire and explosion caused by lithium-ion battery failures such as overcharging, overdischarging and short circuit, so that the damage to circuits and devices is controlled in the smallest possible area. The existing controlled fuse has a melting time of 20-30s, which cannot meet the melting time requirement of 10s for existing cars. Utility Model Content

[0004] In view of the above-mentioned defects of the prior art, the utility model provides a new type of thermal cutoff, which can improve the current carrying capacity of the product, achieve rapid fusing, and meet the fusing time requirements in automotive applications. The technical solution is as follows:

[0005] A thermal cut-off device comprises a housing, a heating plate, two main circuit electrode plates, a controlled electrode, an upper heat-conducting electrode plate, a fusible alloy and a flux;

[0006] A cavity is formed inside the shell;

[0007] The inner end portions of the two main circuit electrode sheets located in the cavity are spaced apart in the cavity;

[0008] The upper heat-conducting electrode sheet is arranged between the two main circuit electrode sheets and is spaced apart from the two main circuit electrode sheets;

[0009] The heating plate is arranged below the two main circuit electrode plates and the upper heat-conducting electrode plate;

[0010] The heating plate includes a ceramic substrate, and a first electrode and a second electrode electrically connected to a heating element inside the ceramic substrate; the first electrode is a pad-type electrode, which is welded to the upper heat-conducting electrode sheet, and the second electrode is electrically connected to the controlled electrode, or forms the controlled electrode;

[0011] The fusible alloy is attached to the inner end portions of the two main circuit electrode sheets and the upper surface of the upper heat-conducting electrode sheet, and contacts the inner end portions of the two main circuit electrode sheets and the upper heat-conducting electrode sheet to form a heat-conducting and electrical-conducting connection;

[0012] The flux is coated on the surface of the fusible alloy.

[0013] Through the design of the upper thermally conductive electrode sheet, the heat of the heating sheet is transferred to the fusible alloy through the thermally conductive electrode sheet and the main circuit electrode sheet, reducing heat transfer losses and achieving rapid fusing. At the same time, the relative positions of the main circuit electrode sheet, the heating sheet and the fusible alloy are adjusted to enhance the current carrying capacity, and the length and width of the product can be made more compact while ensuring the thermal insulation performance of the product.

[0014] Furthermore, the length and width of the upper heat-conducting electrode sheet are equal to those of the first electrode, and the thickness of the upper heat-conducting electrode sheet is equal to that of the main circuit electrode sheet, so as to ensure that the fusible alloy can be evenly attached to the main circuit electrode sheet and the upper heat-conducting electrode sheet.

[0015] Furthermore, the upper heat-conducting electrode sheet is provided with capillaries to provide a shrinkage space for the molten alloy. The molten alloy will be rapidly adsorbed onto the upper heat-conducting electrode due to the capillary phenomenon, thereby improving the fusing effect of the fusible alloy and increasing the shrinkage space of the molten alloy.

[0016] Furthermore, the inner end portions of the two main circuit electrode sheets located in the cavity are arranged relatively spaced apart in the cavity.

[0017] Furthermore, the first electrode is arranged in the middle of the upper surface of the ceramic substrate, and the second electrode is led out from the back side of the ceramic substrate in a lead manner; the heating plate also includes a third electrode, and the third electrode is arranged on both sides of the first electrode and has no electrical connection with the heating element; the two third electrodes are respectively welded to the two main circuit electrode sheets.

[0018] Furthermore, the inner end of the main circuit electrode sheet is provided with a tooth-shaped structure, and the tooth-shaped structure faces the upper heat-conducting electrode sheet. The tooth-shaped structure provides a shrinkage space for the fusible alloy after melting, thereby improving the pressure resistance of the fusible alloy after melting.

[0019] Furthermore, the fusible alloy includes multiple fusible alloy sheets, each of which is placed in parallel to form a parallel circuit. The fusible alloy is assembled into multiple sheets, which increases the current carrying capacity while reducing the cross-sectional area of ​​the fusible alloy, thereby accelerating the melting speed of the fusible alloy.

[0020] Furthermore, the thermal fuse cutoff device further comprises a lower heat-conducting electrode sheet, and the lower heat-conducting electrode sheet is arranged under the heating sheet in a close manner, so that the heat distribution is more uniform and the unit heating efficiency of the heating sheet is improved.

[0021] In some embodiments, the housing includes a housing body, an upper cover plate and a lower cover plate; the housing body and the two main circuit electrode sheets are integrally injection molded. The main circuit electrode sheet and the housing are integrally injection molded to improve the stability of the electrode sheet and ensure the stability of the product's electrical performance.

[0022] In a certain embodiment, the shell includes a shell body, an upper cover plate and a lower cover plate, and the lower cover plate is the bottom of the shell; the shell body and the lower cover plate are integrally injection molded, the lead-out end of the main circuit electrode sheet is a pin type, led out from the bottom of the shell, and the controlled electrode is a pin type, led out from the bottom of the shell.

[0023] In one embodiment, the lead-out end of the main circuit electrode sheet is a flat plate with holes, which is led out from both sides of the shell; the controlled electrode is a lead type, and the second electrode is led out from the side of the shell in a lead manner to form the controlled electrode.

[0024] In one embodiment, the lead-out end of the main circuit electrode sheet is a step-type, and is led out from both sides of the shell; the controlled electrode is a pad-type, and is arranged on the bottom surface of the shell.

[0025] In one embodiment, the lead-out end of the main circuit electrode sheet is stepped and led out from both sides of the shell; the controlled electrode is lead-wire type, and the second electrode is led out from the side of the shell in a lead-wire manner to form the controlled electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a three-dimensional exploded view of the first embodiment of the utility model;

[0027] Figure 2 It is a cross-sectional view of the first embodiment of the utility model;

[0028] Figure 3 It is a three-dimensional view of the first embodiment of the utility model;

[0029] Figure 4 This is a schematic diagram of the structure of the heating plate of the utility model;

[0030] Figure 5This is a schematic diagram of the structure of the main circuit electrode sheet of the utility model;

[0031] Figure 6 It is a three-dimensional exploded view of the second embodiment of the utility model;

[0032] Figure 7 It is a cross-sectional view of the second embodiment of the utility model;

[0033] Figure 8 It is a three-dimensional view of the second embodiment of the utility model;

[0034] Fig. 9 It is a three-dimensional exploded view of the third embodiment of the utility model;

[0035] Fig.10 It is a cross-sectional view of the third embodiment of the utility model;

[0036] Fig.11 It is a three-dimensional view of the third embodiment of the utility model;

[0037] Fig.12 It is a three-dimensional diagram of the fourth embodiment of the utility model;

[0038] Fig.13 It is a cross-sectional view of the fourth embodiment of the present utility model.

[0039] in:

[0040] 1-Heating plate;

[0041] 2-upper thermal conductive electrode;

[0042] 3, 4 - main circuit electrode sheet;

[0043] 5-lower thermal conductive electrode;

[0044] 6 - Fusible alloys;

[0045] 7-Fusing agent;

[0046] 8 - housing;

[0047] 9 - controlled electrode;

[0048] 11-Ceramic substrate;

[0049] 12 - pad electrode;

[0050] 13 - lead electrode;

[0051] 14, 15 - auxiliary electrodes;

[0052] 21 - pores;

[0053] 31, 41 - end of the cavity;

[0054] 32, 42 - lead-out end;

[0055] 81 - housing body;

[0056] 82 - upper cover;

[0057] 83 - lower cover;

[0058] 311, 411 - Toothed structure. DETAILED DESCRIPTION

[0059] To further illustrate the various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, a person of ordinary skill in the art should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0060] The utility model is now further described in conjunction with the accompanying drawings and specific implementation methods.

[0061] Example 1

[0062] Figures 1 to 5 A novel embodiment of a thermal cutoff with an upper heat-conducting electrode sheet is provided.

[0063] In this embodiment, the thermal fuse cutter is composed of a heating plate 1, a lower heat-conducting electrode plate 5, an upper heat-conducting electrode plate 2, main circuit electrode plates 3, 4, a fusible alloy 6, a flux 7, a housing 8, a controlled electrode 9, etc.

[0064] A cavity is formed in the housing 8 .

[0065] like Figure 4 As shown, the heating plate 1 includes a ceramic substrate 11, a pad electrode 12, a lead electrode 13 and auxiliary electrodes 14 and 15. The pad electrode 12 is arranged on the front of the ceramic substrate 11, located in the middle of the front of the heating plate 1; the lead electrode 13 is led out from the back of the ceramic substrate 11. The pad electrode 12 and the lead electrode 13 are two lead-out electrodes of the heating element in the ceramic substrate 11. The auxiliary electrodes 14 and 15 are not connected to the heating element, and are respectively arranged on both sides of the pad electrode 12, and are used to be welded and connected with the two main circuit electrode sheets 3 and 4 to strengthen the structural connection strength of the heating plate 1 and the main circuit electrode sheets 3 and 4.

[0066] The upper thermally conductive electrode sheet 2 is a highly conductive and thermally conductive metal sheet such as a copper sheet. Its length and width are comparable to those of the pad electrode 12, and its thickness is comparable to that of the main circuit electrode sheets 3 and 4. The upper thermally conductive electrode sheet 2 and the pad electrode 12 are bonded to better transfer the heat of the heating sheet 1, draw the heat out from above the heating sheet 1, and at the same time serve as an electrical connection.

[0067] In this embodiment, the intracavity ends 31, 41 of the two main circuit electrode sheets 3, 4 are arranged above the heating sheet 1, and are respectively welded to the auxiliary electrodes 14 on both sides of the heating sheet 1, thereby fixing the heating sheet 1 and the two main circuit electrode sheets 3, 4 together to provide a reliable structural connection.

[0068] In this embodiment, the two main circuit electrode sheets 3 and 4 are led out from both sides of the bottom of the housing 8 , and the cavity ends 31 and 41 of the two main circuit electrode sheets 3 and 4 are arranged relatively spaced apart in the cavity.

[0069] It should be emphasized that in specific applications, the inner end portions 31 and 41 of the two main circuit electrode sheets 3 and 4 are not limited to being arranged relative to each other in the cavity, but can also be arranged in parallel, that is, the two main circuit electrode sheets 3 and 4 can be led out from the same side of the shell 8.

[0070] The fusible alloy 6 is attached to the ends of the two main circuit electrode sheets 3 and 4 in the cavity and to the upper heat conductive electrode sheet 2. The fusible alloy 6 is electrically connected to the two main circuit electrode sheets 3 and 4 and the upper heat conductive electrode sheet 2 by low temperature welding.

[0071] Solder paste is printed on the upper heat-conducting electrode sheet 2 and the main circuit electrode sheets 3 and 4, and a fusible alloy 6 is assembled and soldered together by reflow soldering to achieve a heat-conducting connection, and an electrical connection is established between the two main circuit electrode sheets 3 and 4 and the heating sheet 1; at the same time, the lead-out electrode 13 of the heating sheet 1 is connected to the controlled electrode 9, and the heating sheet is connected to the control circuit through the controlled electrode 9.

[0072] Preferably, the length and width of the fusible alloy 6 are comparable to the upper surface of the heating plate 1 , so as to provide a reliable electrical connection between the pad electrode 12 and the main circuit electrode plates 3 , 4 .

[0073] In this embodiment, the upper heat-conducting electrode sheet 2 is designed to adjust the relative positions of the main circuit electrode sheets 3, 4, the heating sheet 1 and the fusible alloy 6, so that the length and width of the product can be made more compact while ensuring the thermal insulation performance of the product.

[0074] In this embodiment, the substrate 11 of the heating plate 1 is made of ceramic material, which can be used as the insulating material of the two electrode plates of the main circuit to improve the electrical strength.

[0075] It should be noted that the fusible alloy 6 can be assembled in a single piece or multiple pieces. Multiple pieces of fusible alloy are placed in parallel to form a parallel circuit, and each piece of fusible metal can work independently and melt when heated. The fusible alloy is assembled in multiple pieces, which increases the current carrying capacity while reducing the cross-sectional area of ​​the fusible alloy flowing through, and can accelerate the melting speed of the fusible alloy.

[0076] Usually, a flux 7 is coated on the upper surface of the fusible alloy 6. The flux 7 can ensure reliable fusing of the fusible alloy 6 when the fusible alloy 6 is fusing.

[0077] In this embodiment, the lower heat-conducting electrode sheet 5 and the bottom of the heating sheet 1 are attached to each other, so that the lower surface of the heating sheet 1 heats more evenly, and the heat is dissipated into the cavity through the lower heat-conducting electrode sheet 5; thermal grease is applied between the two to enhance the heat conduction effect. In specific implementation, thermal grease is applied to the back of the heating sheet 1 to make the heat transfer distribution more even.

[0078] In order to further improve the fusing effect of the fusible alloy 6, the present embodiment also adopts the following design:

[0079] like Figure 5 As shown, preferably, the end faces of the in-cavity ends 31, 41 of the main circuit electrode sheets 3, 4 are tooth-like structures 311, 411, and the in-cavity ends 31, 41 of the tooth-like structures can provide space for adsorbing the fusible alloy 6 in a molten state.

[0080] The upper heat-conducting electrode sheet 2 itself has a certain adsorption effect on the fusible alloy 6 in a molten state.

[0081] like Figure 1 As shown, preferably, capillary pores 21 are further provided on the upper heat-conducting electrode sheet 2 to enhance the adsorption effect on the fusible alloy 6 in a molten state.

[0082] In this embodiment, for easy assembly, the housing 8 is composed of a housing body 81, an upper cover plate 82 and a lower cover plate 83. Since the lead-out ends of the main circuit electrode sheets 3 and 4 are pin-type pins, preferably, the lower cover plate 83 and the housing body 81 are injection molded together.

[0083] During the product assembly process, after welding is completed, the upper cover plate 82 and the shell body 81 need to be assembled together, and then the opening on the shell 8 is sealed with a sealing material such as epoxy resin.

[0084] Preferably, the upper cover plate 82 and the shell body 81 are assembled in a manner including ultrasonic welding, gluing and bayonet assembly, etc. The shell body 81 is provided with a notch for leading out the lead electrode 13, and the notch is sealed with a sealing material such as epoxy resin after the shell assembly is completed.

[0085] In this embodiment, the structure type of the thermal fuse cutout is a pin type, specifically:

[0086] The lead ends 32 and 42 of the two main circuit electrode sheets 3 and 4 are pin-shaped, and the controlled electrode 9 is pin-shaped. The lead electrode 13 of the heating sheet 1 is connected to the controlled electrode 9, and the controlled electrode 9 is led out from the housing by pins to form a pin-shaped controlled electrode. This structure is suitable for installation methods such as wave soldering and reflow soldering.

[0087] Preferably, the lead-out ends of the two main circuit electrode sheets 3 and 4 may also be in a stepped shape, a flat plate with holes, or other shapes.

[0088] Preferably, the lead electrode 13 can be connected to the pad on the bottom plate to form a pad-type controlled electrode; it can be led out from the reserved hole of the electrode sheet on the shell body or from the lower cover plate, so as to be in the same plane as the main circuit electrode sheet or perpendicular to the main circuit electrode sheet to meet the installation requirements at various angles.

[0089] Example 2

[0090] like Figure 6-Figure 8 As shown, the difference between this embodiment and embodiment 1 is that:

[0091] The lead-out ends 32, 42 of the two main circuit electrode sheets 3, 4 are of a flat plate with holes.

[0092] The housing 8 is composed of a housing body 81, an upper cover plate 82 and a lower cover plate 83. Preferably, the upper cover plate 82, the lower cover plate 83 and the housing body 81 are assembled by ultrasonic welding, glue bonding and bayonet assembly.

[0093] Preferably, the two main circuit electrode sheets 3 and 4 and the shell body 81 are integrally injection-molded to form an electrode sheet assembly, which can ensure the stability of the protector product structure and facilitate the assembly of the protector product.

[0094] The lead electrode 13 is led out from the side of the shell body 81 to form a lead-type controlled electrode 9.

[0095] Example 3

[0096] like Figures 9 to 11 As shown, the difference between this embodiment and embodiment 1 is that:

[0097] The lead-out ends 32 and 42 of the two main circuit electrode sheets 3 and 4 are of a stepped type.

[0098] The housing 8 is composed of a housing body 81, an upper cover plate 82 and a lower cover plate 83. Preferably, the upper cover plate 82, the lower cover plate 83 and the housing body 81 are assembled by ultrasonic welding, glue bonding and bayonet assembly.

[0099] Preferably, the two main circuit electrode sheets 3 and 4 and the shell body 81 are integrally injection-molded to form an electrode sheet assembly, which can ensure the stability of the protector product structure and facilitate the assembly of the protector product.

[0100] The controlled electrode 9 is disposed in a pad-type manner on the lower surface of the lower cover plate 83, so as to be on the same level as the two main circuit electrode sheets. The controlled electrode 9 is welded to the lead electrode 13 led out from the lower cover plate 83 to form a pad-type controlled electrode.

[0101] This structure is suitable for installation methods such as reflow soldering.

[0102] Example 4

[0103] like Figure 12 to Figure 13 As shown, the difference between this embodiment and embodiment 1 is that:

[0104] The lead-out ends 32 and 42 of the two main circuit electrode sheets 3 and 4 are of a stepped type.

[0105] The housing 8 is composed of a housing body 81, an upper cover plate 82 and a lower cover plate 83. Preferably, the upper cover plate 82, the lower cover plate 83 and the housing body 81 are assembled by ultrasonic welding, glue bonding and bayonet assembly.

[0106] Preferably, the two main circuit electrode sheets 3, 4 and the shell body 81 are integrally injection molded to form an electrode sheet assembly, which can ensure the stability of the structure of the protector product and facilitate the assembly of the protector product. Of course, in other embodiments, the two main circuit electrode sheets 3, 4 and the shell body 81 can be manufactured separately and then assembled.

[0107] The lead electrode 13 is led out from the side of the housing body 81 to form a lead-type controlled electrode 9 .

[0108] This structure is suitable for installation methods such as manual soldering and reflow soldering.

[0109] Embodiments 1 to 4 are preferred product structures of the thermal cutoff.

[0110] Although the present invention has been specifically demonstrated and described in conjunction with the preferred embodiments, those skilled in the art should understand that various changes may be made to the present invention in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A thermal cutoff device, characterized in that: It includes a shell, a heating plate, two main circuit electrode plates, a controlled electrode, an upper heat-conducting electrode plate, a fusible alloy and a flux; A cavity is formed inside the shell; The inner end portions of the two main circuit electrode sheets located in the cavity are spaced apart in the cavity; The upper heat-conducting electrode sheet is arranged between the two main circuit electrode sheets and is spaced apart from the two main circuit electrode sheets; The heating plate is arranged below the two main circuit electrode plates and the upper heat-conducting electrode plate; The heating plate includes a ceramic substrate, and a first electrode and a second electrode electrically connected to a heating element inside the ceramic substrate; the first electrode is a pad-type electrode, which is welded to the upper heat-conducting electrode sheet, and the second electrode is electrically connected to the controlled electrode, or forms the controlled electrode; The fusible alloy is arranged at the inner end of the two main circuit electrode sheets and above the upper heat-conducting electrode sheet, and is welded to the inner end of the two main circuit electrode sheets and the upper heat-conducting electrode sheet to form a heat-conducting and electrical-conducting connection; The flux is coated on the surface of the fusible alloy.

2. The thermal cutoff device according to claim 1, characterized in that: The length and width of the upper heat-conducting electrode sheet are equal to those of the first electrode; the thickness of the upper heat-conducting electrode sheet is equal to that of the main circuit electrode sheet.

3. The thermal cutoff device according to claim 1, wherein: The upper heat-conducting electrode sheet is provided with capillaries.

4. The thermal cutoff device according to claim 1, wherein: The cavity ends of the two main circuit electrode sheets are located in the cavity and are arranged relatively spaced apart in the cavity.

5. The thermal cutoff device according to claim 1, wherein: The first electrode is arranged in the middle of the upper surface of the ceramic substrate, and the second electrode is led out from the back side of the ceramic substrate in a lead manner; the heating plate also includes a third electrode, which is arranged on both sides of the first electrode and has no electrical connection with the heating element; the two third electrodes are respectively welded to the two main circuit electrode sheets.

6. The thermal cutoff device according to claim 1, characterized in that: The inner end of the main circuit electrode sheet is configured as a tooth-shaped structure, and the tooth-shaped structure faces the upper heat-conducting electrode sheet.

7. The thermal cutoff device according to claim 1, wherein: The fusible alloy comprises a plurality of fusible alloy sheets, each of which is placed in parallel to form a parallel circuit.

8. The thermal cutoff device according to claim 1, wherein: It also includes a lower heat-conducting electrode sheet, which is arranged under the heating sheet in a close fit.

9. The thermal cutoff device according to claim 1, wherein: The shell comprises a shell body, an upper cover plate and a lower cover plate; the shell body and two main circuit electrode sheets are integrally injection molded.

10. The thermal cutoff according to any one of claims 1 to 8, characterized in that: The shell includes a shell body, an upper cover plate and a lower cover plate, and the lower cover plate is the bottom of the shell; the shell body and the lower cover plate are integrally injection molded, the lead-out end of the main circuit electrode sheet is a pin type, and is led out from the bottom of the shell, and the controlled electrode is a pin type, and is led out from the bottom of the shell.

11. The thermal cutoff according to any one of claims 1 to 9, characterized in that: The lead-out end of the main circuit electrode sheet is a flat plate with holes, and is led out from both sides of the shell; the controlled electrode is a lead-wire type, and the second electrode is led out from the side of the shell in a lead-wire manner to form the controlled electrode.

12. The thermal cutoff according to any one of claims 1 to 9, characterized in that: The lead-out end of the main circuit electrode sheet is a step-type and is led out from both sides of the shell; the controlled electrode is a pad-type and is arranged on the bottom surface of the shell.

13. The thermal cutoff according to any one of claims 1 to 9, characterized in that: The lead-out end of the main circuit electrode sheet is step-shaped and is led out from both sides of the shell; the controlled electrode is lead-wire-shaped, and the second electrode is led out from the side of the shell in a lead-wire manner to form the controlled electrode.

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