Overcharge protection device and lithium ion battery

Abstract

The application discloses an overcharge protection device and a lithium ion battery. The overcharge protection device comprises a positive electrode protection electrode electrically connected with a positive electrode assembly, a negative electrode protection electrode electrically connected with a negative electrode assembly, a conductive structure arranged between the positive electrode protection electrode and the negative electrode protection electrode, and an insulating thermal melting layer covering the conductive structure. The conductive structure conducts the positive electrode protection electrode and the negative electrode protection electrode after the insulating thermal melting layer is melted by heat. The conductive structure comprises a plurality of thermal melting conductive particles clamped between the positive electrode protection electrode and the negative electrode protection electrode, and the outer layer of each thermal melting conductive particle is covered with the insulating thermal melting layer. The application is designed with the insulating thermal melting layer which melts when the lithium ion battery is overcharged and heated, thereby conducting the positive electrode protection electrode and the negative electrode protection electrode to discharge and bypassing the overcharge current between the positive electrode assembly and the negative electrode assembly. The structure is simple and has high reliability.

Description

Technical Field

[0001] This invention relates to the field of battery abuse safety protection technology, and in particular to overcharge protection devices and lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries use lithium metal, lithium alloys, or carbon materials as the negative electrode material and lithium compounds such as lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and lithium nickel cobalt manganese oxide as the positive electrode, employing a non-aqueous electrolyte solution. Overcharging a lithium-ion battery causes the electrolyte to heat up and decompose, producing gas. This gas creates pressure inside the sealed battery, causing the lithium-ion battery to expand, potentially leading to an explosion and fire.

[0003] Existing overcharge protection solutions typically involve designing a protection circuit or an external overcharge protection structure for the lithium-ion battery. For example, an invention patent titled "Lithium-ion Battery Charging Protection Circuit" describes a charging protection circuit that includes a primary overcharge protection circuit and a secondary process protection circuit. One end of the primary overcharge protection circuit is connected to the positive terminal of the power supply, and one end of the secondary overcharge protection circuit is connected to the other end of the primary overcharge protection circuit and the other end is connected to the positive terminal of the battery. The secondary overcharge protection circuit includes a control unit, a detection unit, and a trigger signal latching unit. This type of charging protection circuit design is complex, uses a large number of components, has significant potential for failure, and has low reliability.

[0004] For example, a utility model patent entitled "A Lithium-ion Battery with Overcharge Protection Structure" describes a lithium-ion battery body and an overcharge protection structure both mounted in a mounting bracket. The overcharge protection structure includes a clamping component, a driving component, and a power detection component. After the battery is fully charged, the overcharge protection structure separates the charger from the lithium-ion battery body. This overcharge protection structure significantly increases the size of the lithium-ion battery. The clamping component and the driving component have a difficult-to-fit relationship, resulting in low reliability. Furthermore, it imposes limitations on the shape and size of the charger, making it impractical.

[0005] Therefore, how to design safe and reliable overcharge protection devices and lithium-ion batteries is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0006] To address the shortcomings of existing overcharge protection schemes, such as complex structure and low reliability, this invention proposes an overcharge protection device and a lithium-ion battery, which have the advantages of simple structure, low cost, and high reliability.

[0007] The technical solution adopted in this invention is to design an overcharge protection device, including: a positive protection electrode electrically connected to the positive electrode component, a negative protection electrode electrically connected to the negative electrode component, a conductive structure disposed between the positive protection electrode and the negative protection electrode, and an insulating heat-melting layer covering the conductive structure; the conductive structure conducts electricity between the positive protection electrode and the negative protection electrode after the insulating heat-melting layer is heated and melted.

[0008] The positive protection electrode and / or negative protection electrode are provided with a resistive layer.

[0009] In some embodiments, the insulating heat-fusion layer is composed of one or more of PP, PE, PVC, PET, PBT, acrylic, and PS, and the insulating heat-fusion layer melts when the temperature reaches above 120°C to expose the conductive structure.

[0010] In some embodiments, the thermally conductive structure includes a plurality of hot-melt conductive particles sandwiched between a positive protection electrode and a negative protection electrode, each hot-melt conductive particle having a metal layer covered with an insulating hot-melt layer.

[0011] In some embodiments, the metal layer comprises one or more of Al, Cu, Ni, Ti, Fe, stainless steel, Au, Ag, graphite, and CNT, and adjacent hot-melt conductive particles are fixed by bonding.

[0012] In some embodiments, the hot-melt conductive particles further have a non-metallic layer, wherein the metallic layer covers the non-metallic layer, and the metallic layer comprises one or more of Al, Cu, Ni, Ti, Fe, stainless steel, Au, Ag, graphite, and CNT, and the non-metallic layer comprises one or more of CaO2, Al2O3, TiO2, SiO2, MgO, Fe2O3, MnO2, Mn3O4, and Fe3O4.

[0013] Preferably, the conductive structure is magnetic, and the positive and negative protective electrodes are attracted and connected through the conductive structure.

[0014] Preferably, the overcharge protection device further includes a heating device, which is installed on the surface of the positive protection electrode and / or the negative protection electrode, and provides heat to the insulating heat-melting layer when the heating device is working.

[0015] The present invention also provides a lithium-ion battery, comprising: a housing, a positive electrode assembly and a negative electrode assembly disposed inside the housing, and a separator disposed between the positive electrode assembly and the negative electrode assembly, wherein the positive electrode assembly and the negative electrode assembly are connected to the above-mentioned overcharge protection device; when the lithium-ion battery is overcharged, the overcharge protection device connects the positive electrode protection electrode and the negative electrode protection electrode to discharge, and bypasses the overcharge current between the positive electrode assembly and the negative electrode assembly.

[0016] Preferably, the overcharge protection device is located inside the housing, and a diaphragm is provided between the overcharge protection device and its adjacent positive or negative electrode assembly.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. It is designed with an insulating heat-melting layer, which melts when the lithium-ion battery is overcharged. It connects the positive and negative protection electrodes through a conductive structure to discharge, while bypassing the overcharge current between the positive and negative electrode components. The structure is simple and highly reliable.

[0019] 2. The overcharge protection device is located inside the casing. It utilizes the characteristics of increased internal temperature and pressure of the lithium-ion battery during overcharging to make the positive and negative protection electrodes conductive. The lithium-ion battery has a compact structure, small volume change, and high practicality. Attached Figure Description

[0020] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein:

[0021] Figure 1 This is a schematic diagram of the internal structure of the lithium-ion battery of the present invention;

[0022] Figure 2 This is a schematic cross-sectional view of the hot-melt conductive particles according to a partial embodiment of the present invention;

[0023] Figure 3 This is a schematic cross-sectional view of the hot-melt conductive particles according to another embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the resistor layer installation of the present invention;

[0025] Figure 5 This is a schematic diagram of the installation of the heating device of the present invention;

[0026] Figure 6 This is a front view of the heating device of the present invention;

[0027] Figure 7 This is a cross-sectional schematic diagram of the heating device of the present invention;

[0028] Figure label:

[0029] 1. Positive electrode assembly; 11. Positive electrode current collector; 12. Positive electrode material; 2. Negative electrode assembly; 21. Negative electrode current collector; 22. Negative electrode material; 3. Separator; 4. Overcharge protection device; 41. Positive electrode protection electrode; 42. Negative electrode protection electrode; 43. Insulating heat-melting layer; 44. Resistive layer; 45. Heat-melting conductive particles; 451. Metal layer; 452. Non-metallic layer; 46. Heating device; 461. Resistance wire; 462. Insulating film. Detailed Implementation

[0030] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] like Figure 1 As shown, the overcharge protection device 4 proposed in this invention is suitable for use in batteries, especially lithium-ion batteries. Taking a lithium-ion battery as an example, a lithium-ion battery has a casing, at least one positive electrode component 1, at least one negative electrode component 2, and a separator 3, etc. The casing is filled with an electrolyte. The positive electrode component 1 and the negative electrode component 2 are both installed in the casing. Adjacent positive electrode components 1 and negative electrode components 2 are arranged opposite to each other. The separator 3 separates the positive electrode component 1 and the negative electrode component 2. The positive electrode component 1 is composed of a positive current collector 11 and a positive electrode material 12 disposed on the positive current collector 11. The negative electrode component 2 is composed of a negative current collector 21 and a negative electrode material 22 disposed on the negative current collector 21. Taking a lithium iron phosphate battery as an example, the positive current collector 11 is aluminum foil, the positive electrode material 12 is lithium iron phosphate, etc., the negative current collector 21 is copper foil, and the negative electrode material 22 is graphite.

[0032] like Figures 1 to 3 As shown, the overcharge protection device 4 includes a positive protection electrode 41, a negative protection electrode 42, a conductive structure, and an insulating heat-fusion layer 43. The positive protection electrode 41 is connected in parallel with the positive electrode assembly 1, and the negative protection electrode 42 is connected in parallel with the negative electrode assembly 2. The conductive structure is disposed between the positive protection electrode 41 and the negative protection electrode 42. The insulating heat-fusion layer 43 covers the outside of the conductive structure. After the insulating heat-fusion layer 43 is heated and melted, the conductive structure conducts electricity between the positive protection electrode 41 and the negative protection electrode 42 for discharge, while simultaneously bypassing the overcharge current between the positive electrode assembly 1 and the negative electrode assembly 2, effectively providing overcharge protection. It should be noted that in some feasible embodiments, the negative protection electrode 41 is made of copper foil, and the negative protection electrode 42 is made of aluminum foil. Of course, the positive protection electrode 41 can also be made of a mixture of aluminum and / or titanium, and the negative protection electrode 42 can also be made of a mixture of copper and / or nickel, as long as the conductivity is met. The insulating heat-fusion layer 43 is an organic coating layer, which is composed of one or more of PP, PE, PVC, PET, PBT, acrylic, and ABS. This ensures that the insulating heat-fusion layer 43 melts at temperatures above 120℃ to expose the conductive structure. The resistivity of the insulating heat-fusion layer 43 is less than 10⁻⁶. 3 Ω·m is the insulation coefficient, and the resistivity of the conductive structure is in the range of 10. -6 Ω·m and above.

[0033] like Figure 4As shown, to improve safety, at least one of the positive protection electrode 41 and the negative protection electrode 42 is provided with a resistive layer 44. When the conductive structure is connected to the positive protection electrode 41 and the negative protection electrode 42 for discharge, the overcharge current between the positive electrode assembly 1 and the negative electrode assembly 2 is bypassed and shunted to the branch where the positive protection electrode 41 and the negative protection electrode 42 are located, thus achieving safe and reliable overcharge protection. It should be understood that the resistive layer 44 can be made of conventional materials, such as resin, conductive materials, and adhesives. The present invention does not impose any special restrictions on the specific composition of the resistive layer 44.

[0034] like Figure 2 As shown, in a portion of the embodiments provided by the present invention, the thermally conductive structure includes a plurality of hot-melt conductive particles 45 sandwiched between the positive protection electrode 41 and the negative protection electrode 42. Each hot-melt conductive particle 45 is composed of a metal layer 451 and an insulating hot-melt layer 43 arranged sequentially from the inside to the outside. The insulating hot-melt layer 43 covers the outer wall of the metal layer 451. Adjacent hot-melt conductive particles 45 are bonded together with adhesive, and the volume ratio between the adhesive and the hot-melt conductive particles 45 is 1:9. The metal layer 451 contains one or more of Al, Cu, Ni, Ti, Fe, stainless steel, Au, Ag, graphite, and CNT. When the shape of the hot-melt conductive particles 45 is selected as spheres, their diameter ranges from 100 to 10,000 nm, and the thickness of the insulating hot-melt layer 43 ranges from 10 to 5,000 nm.

[0035] like Figure 3 As shown, in another embodiment of the present invention, the thermally conductive structure includes a plurality of hot-melt conductive particles 45 sandwiched between the positive protection electrode 41 and the negative protection electrode 42. Each hot-melt conductive particle 45 is composed of a non-metallic layer 452, a metal layer 451 and an insulating hot-melt layer 43 arranged sequentially from the inside to the outside. The metal layer 451 covers the outer wall of the non-metallic layer 452, and the insulating hot-melt layer 43 covers the outer wall of the metal layer 451. The metal layer 451 includes one or more of Al, Cu, Ni, Ti, Fe, stainless steel, Au, Ag, graphite and CNT. The non-metallic layer 452 includes one or more of CaO2, Al2O3, TiO2, SiO2, MgO, Fe2O3, MnO2, Mn3O4 and Fe3O4. When the shape of the hot-melt conductive particle 45 is selected as a sphere, the thickness of the metal layer 451 ranges from 10 to 5000 nm, the thickness of the non-metal layer 452 ranges from 100 to 10,000 nm, and the thickness of the insulating hot-melt layer 43 ranges from 10 to 5000 nm.

[0036] In some preferred embodiments, the conductive structure is magnetic, and the positive protection electrode 41 and the negative protection electrode 42 are attracted and connected through the conductive structure. There are various ways to achieve the attraction connection. Taking one example, the non-metallic layer 452 is made of magnetic Fe3O4, and both the positive protection electrode 41 and the negative protection electrode 42 are made of nickel-based stainless steel or carbon steel. The magnetic properties of the non-metallic layer 452 attract the nickel-based stainless steel or carbon steel, and the overcharge protection device 4 has a self-binding function under the action of magnetic force.

[0037] like Figures 5 to 7 As shown, in some preferred embodiments, the overcharge protection device 4 is further designed with a heating device 46. The heating device 46 uses a resistance wire 461, which is wrapped with an insulating film 462. The insulating film 462 is installed and fixed on the surface of the positive protection electrode 41 and / or the negative protection electrode 42. When the heating device 46 is working, it provides heat to the insulating heat-melting layer 43. The opening or closing of the heating device 46 is controlled according to the operating status of the lithium-ion battery. In practical applications, the operating status can be reflected by detecting parameters such as the current, voltage, temperature, or pressure of the lithium-ion battery. When the lithium-ion battery is overcharged, the heating device is turned on so that the insulating heat-melting layer 43 on the outer layer of the conductive structure melts quickly, resulting in a faster response speed and higher reliability of the overcharge protection.

[0038] like Figure 1 As shown, in some feasible embodiments provided by the present invention, the overcharge protection device 4 is disposed on one side inside the housing. The positive electrode protection electrode 41, the negative electrode protection electrode 42, the positive electrode assembly 1 and the negative electrode assembly 2 are parallel to each other. A separator 3 is provided between the overcharge protection device 4 and its adjacent positive electrode assembly 1 or negative electrode assembly 2. The characteristics of the lithium-ion battery that the internal temperature rises and the pressure increases when overcharged make the positive electrode protection electrode 41 and the negative electrode protection electrode 42 conduct.

[0039] When the overcharge protection device 4 is located outside the outermost positive electrode assembly 1, the negative electrode protection electrode 42 is located between the positive electrode protection electrode 41 and the positive electrode assembly 1, and the negative electrode protection electrode 42 is positioned opposite to the positive electrode assembly 1. The heating device 46 is installed on the surface of the positive electrode protection electrode 41 facing away from the negative electrode protection electrode 42, and the resistive layer 44 is installed on the surface of the negative electrode protection electrode 42 facing away from the positive electrode protection electrode 41. When the overcharge protection device 4 is located outside the outermost negative electrode assembly 2, the positive electrode protection electrode 41 is located between the negative electrode protection electrode 42 and the negative electrode assembly 2, and the positive electrode protection electrode 41 is positioned opposite to the negative electrode assembly 2. The heating device 46 is installed on the outer surface of the negative electrode protection electrode 42 facing away from the positive electrode protection electrode 41, and the resistive layer 44 is installed on the surface of the positive electrode protection electrode 41 facing away from the negative electrode protection electrode 42. It should be understood that the above are only illustrative examples of some embodiments, and the heating device 46 and the resistive layer 44 can be selectively applied in the overcharge protection device 4 according to actual needs.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An overcharge protection device, characterized in that, include: A positive protection electrode electrically connected to the positive electrode assembly, a negative protection electrode electrically connected to the negative electrode assembly, a conductive structure disposed between the positive protection electrode and the negative protection electrode, and an insulating heat-fusion layer covering the conductive structure; the conductive structure conducts electricity between the positive protection electrode and the negative protection electrode after the insulating heat-fusion layer is heated and melted. The conductive structure includes a plurality of hot-melt conductive particles sandwiched between the positive protection electrode and the negative protection electrode. Each hot-melt conductive particle has a metal layer, which is covered by the insulating hot-melt layer. The conductive structure is magnetic, and the positive protection electrode and the negative protection electrode are attracted and connected through the conductive structure. The hot-melt conductive particles also have a non-metallic layer, which is covered by the metal layer. The metal layer contains one or more of Al, Cu, Ni, Ti, Fe, SS, Au, and Ag, and the non-metallic layer contains one or more of CaO2, Al2O3, TiO2, SiO2, MgO, Fe2O3, MnO, Mn3O4, and Fe3O4. The positive protection electrode is provided with a resistive layer, which is installed on the side surface of the positive protection electrode that is away from the negative protection electrode. And / or the negative electrode protection electrode is provided with a resistive layer, which is installed on the side surface of the negative electrode protection electrode opposite to the positive electrode protection electrode.

2. The overcharge protection device according to claim 1, characterized in that, The insulating heat-fusion layer is composed of one or more of PP, PE, PVC, PET, PBT, acrylic, and ABS. The insulating heat-fusion layer melts when the temperature reaches above 120°C to expose the conductive structure.

3. The overcharge protection device according to claim 1 or 2, characterized in that, Also includes: A heating device is installed on the surface of the positive protection electrode and / or the negative protection electrode, and the heating device provides heat to the insulating heat-melting layer when it is in operation.

4. Lithium-ion batteries, including: A housing, a positive electrode assembly and a negative electrode assembly disposed inside the housing, and a separator disposed between the positive electrode assembly and the negative electrode assembly, characterized in that the positive electrode assembly and the negative electrode assembly are connected to the overcharge protection device according to any one of claims 1 to 3; when the lithium-ion battery is overcharged, the overcharge protection device connects the positive electrode protection electrode and the negative electrode protection electrode to discharge, and bypasses the overcharge current between the positive electrode assembly and the negative electrode assembly.

5. The lithium-ion battery according to claim 4, characterized in that, The overcharge protection device is located inside the housing, and a diaphragm is provided between the overcharge protection device and its adjacent positive or negative electrode component.

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