Lithium battery cell with internal short circuit self-open circuit protection

Abstract

The invention relates to the technical field of lithium batteries, and discloses a lithium battery cell with internal short circuit self-open circuit protection. Comprising a shell, an electrode assembly arranged in the shell, electrolyte, a positive pole and a negative pole, the positive pole and the negative pole are electrically connected with a positive electrode and a negative electrode of the electrode assembly respectively, and the electrode assembly comprises a positive plate, a negative plate and a diaphragm spaced between the positive plate and the negative plate; the battery is characterized in that a temperature or current sensitive fusible or high-resistance variable structure is integrated on the current collector of the positive plate and / or the negative plate, and the structure can automatically form a physical open circuit or a high-impedance area on a current path where a fault point is located when local temperature rise or sudden current increase exceeds a preset threshold value due to internal short circuit of the battery cell; therefore, short-circuit current is rapidly inhibited and thermal runaway spreading is prevented. By constructing a fuse or current gate type intrinsic safety structure in the current collector, the problems that when an existing lithium battery is subjected to internal short circuit (such as diaphragm failure, metal dendritic crystal puncture, impurity mixing and the like), a short circuit loop cannot be automatically cut off, so that current is intensively released, the temperature is sharply increased, and the service life of the lithium battery is influenced are solved. And the major safety problems of thermal runaway, fire and even explosion are further caused.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically to a lithium battery cell with intrinsic safety features, particularly a lithium battery cell structure that can automatically cut off the fault current path when an internal short circuit occurs. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, electric vehicles, and energy storage systems due to their high energy density and long cycle life. However, safety remains a major challenge, with internal short circuits being one of the most dangerous causes of thermal runaway, fire, and even explosion. Internal short circuits can be caused by various factors, such as lithium dendrites piercing the separator, metal impurities introduced during manufacturing, or electrode material expansion and peeling after long-term cycling.

[0003] Currently, safety protection measures for lithium battery short circuits mainly focus on the external level, such as: 1. Use high-strength diaphragms: such as ceramic-coated diaphragms, to delay dendrite penetration, but cannot completely prevent it and may still fail when subjected to internal pressure impact.

[0004] 2. Adding electrolyte flame retardants: affects the electrochemical performance of the battery.

[0005] 3. External protection circuits: such as the overcurrent protection function in the battery management system. Their response speed is limited by the signal acquisition, processing and relay action time, usually in the millisecond range. For sudden and severe internal short circuits, there is often a lag, and the current cannot be cut off in time before thermal runaway occurs.

[0006] 4. Installing a fuse outside the battery cell: This also results in a response delay and makes it impossible to accurately locate and isolate the specific short circuit point inside the battery cell.

[0007] Existing technologies lack a fundamental solution for rapidly and autonomously disconnecting current from its source within the battery cell. Therefore, there is an urgent need for an internal short-circuit self-protection structure that is integrated within the battery cell, responds quickly, and does not affect normal electrical performance. Summary of the Invention

[0008] The technical problem to be solved by this invention is to provide a lithium battery cell with internal short-circuit self-breaking protection, addressing the aforementioned deficiencies of the prior art. This cell integrates a current-temperature sensitive element at a critical location in its current collector, enabling it to automatically and rapidly form a high-resistance or physical break in the current path at the fault point in the early stages of an internal short circuit. This confines the short-circuit fault to a localized area, preventing it from evolving into global thermal runaway.

[0009] The technical solution adopted by the present invention to solve its technical problem is: to provide a lithium battery cell with internal short circuit self-breaking protection, including a shell, an electrode assembly, an electrolyte and a terminal post, wherein the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator spaced therebetween, the positive electrode sheet includes a positive current collector and a positive active material layer, and the negative electrode sheet includes a negative current collector and a negative active material layer.

[0010] The core improvement of this invention is that a current-temperature sensitive element is integrated on the positive current collector and / or the negative current collector; when a short circuit occurs inside the cell and causes the current flowing through the sensitive element or the temperature of the area where the sensitive element is located to exceed a preset safety threshold, the resistance of the sensitive element increases abruptly or is physically disconnected, thereby cutting off or significantly suppressing the current loop at the short circuit point.

[0011] Preferably, the current-temperature sensitive element is a weak structure with a predetermined cross-sectional area formed on the current collector by etching, stamping, or deposition. The shape of this weak structure can be hourglass-shaped, narrow-necked, sawtooth-shaped, or wavy. When a large short-circuit current flows through this point, according to Joule's law, the weak part will heat up rapidly due to its relatively high resistance, and the temperature will quickly rise to the melting point or softening point of the current collector material, causing the part to melt and break, thus achieving a physical circuit break.

[0012] Preferably, the current-temperature sensitive element is a fusible segment made of a low-melting-point metal, alloy, or conductive composite material doped with a low-melting-point filler. This fusible segment can be connected to the current collector by welding, riveting, or integral molding with it. Its melting point is designed to be lower than that of the current collector body material but higher than the upper limit of the cell's normal operating temperature. In the event of a short-circuit temperature rise, this fusible segment will preferentially melt and disconnect.

[0013] Preferably, the current-temperature sensitive element is a positive temperature coefficient material layer coated or laminated onto a localized area of ​​the current collector. The PTC material conducts electricity at normal temperatures, but its resistance increases dramatically by several orders of magnitude when the temperature exceeds its Curie point, effectively blocking the current. The heat generated by a short circuit can rapidly transform the PTC material layer into a high-resistivity state.

[0014] Preferably, the current-temperature sensing elements are arranged in an array or grid on the current collector, with each sensing element corresponding to and protecting an independent electrode area, thereby achieving "zonal isolation" and minimizing the scope of fault impact.

[0015] Preferably, the current-temperature sensitive element is located at the root of the connection between the current collector and the tab, or at the junction of the active material coating area and the empty foil area in the middle section of the current collector. These locations are key channels through which current gathers or flows, and placing a protective structure at these locations yields the highest efficiency.

[0016] The beneficial effects of this invention are: 1. Extremely fast response speed: The protection mechanism is based on physical principles and has a response time in the microsecond range, which is much faster than external electronic protection circuits. It can act in time before the thermal runaway chain reaction starts.

[0017] 2. High intrinsic safety: The protection structure is directly integrated into the current path, blocking the energy release at its source and achieving fundamental protection.

[0018] 3. High reliability: Simple structure, does not rely on complex sensors and control systems, and has a clear failure mode.

[0019] 4. Minimal impact on normal performance: Under normal operating conditions, the resistance increase of a properly designed sensitive element is negligible, having almost no impact on the battery's energy density, internal resistance, and cycle life.

[0020] 5. Wide applicability: This principle can be applied to different packaging forms such as cylindrical, square, and soft-pack, as well as different structures such as wound and stacked cells.

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0022] Figure 1 This is a planar unfolded schematic diagram of the lithium battery cell electrode assembly provided in Embodiment 1 of the present invention, which focuses on showing the weak structure integrated in the current collector hollow foil region; Figure 2 yes Figure 1 The enlarged schematic diagram of the weak structure (hourglass shape) shown in the diagram illustrates its weakest pre-fuse section. Figure 3 This is a comparative schematic diagram of the working principle of the cell-internal short-circuit self-breaking circuit protection of the present invention. The left and right comparisons intuitively show the whole process from the normal conduction state to the short-circuit trigger and the protection structure breaking the circuit. Figure 4 This is a schematic diagram of another embodiment provided in Embodiment 2 of the present invention, showing the structural layout of setting a positive temperature coefficient material layer on the current collector; Figure 5 This is a schematic diagram of another embodiment provided in Embodiment 3 of the present invention, showing a layout scheme in which the sensitive elements are distributed in an array or grid on the current collector.

[0024] Explanation of key component symbols in the attached diagram:

[0025] 11: Positive current collector 111: Weak structures (such as hourglass-shaped fuselage) 111a: Weak structure that has melted 12: Positive electrode active material layer 13: Diaphragm 14: Negative electrode active material layer 15: Negative current collector 16: Electrode (optional, if in) Figure 1 (Chinese annotation) 20: Cell casing 21: Negative electrode current collector (Example 2) 211: PTC material layer 24: Negative electrode active material layer (Example 2) 112: Sensitive Element Array A: Point of internal short circuit occurrence B: Possible short circuit point (local) I_normal: Normal operating current I_short: Short-circuit current.

Claims

1. A lithium battery cell with internal short-circuit self-breaking protection, comprising a casing, an electrode assembly, an electrolyte, and terminals, wherein the electrode assembly comprises a positive electrode, a negative electrode, and a separator spaced therebetween, the positive electrode comprising a positive current collector and a positive active material layer, and the negative electrode comprising a negative current collector and a negative active material layer, characterized in that: The positive current collector and / or negative current collector are integrated with current-temperature sensitive elements; when a short circuit occurs inside the cell and causes the current flowing through the sensitive element or the temperature of the area where the sensitive element is located to exceed a preset safety threshold, the resistance of the sensitive element increases abruptly or is physically disconnected, thereby cutting off or significantly suppressing the current loop at the short circuit point.

2. The lithium battery cell with internal short-circuit self-breaking protection according to claim 1, characterized in that, The current-temperature sensitive element is a weak structure with a predetermined cross-sectional area formed on the current collector by etching, stamping or deposition.

3. The lithium battery cell with internal short-circuit self-breaking protection according to claim 2, characterized in that, The shape of the weak structure is one of hourglass, narrow neck, sawtooth, or wavy.

4. The lithium battery cell with internal short-circuit self-breaking protection according to claim 1, characterized in that, The current-temperature sensitive element is a fusible segment made of a low-melting-point metal, alloy, or conductive composite material doped with a low-melting-point filler.

5. The lithium battery cell with internal short-circuit self-breaking protection according to claim 4, characterized in that, The fused section is connected to the current collector body by welding, riveting, or integral molding.

6. The lithium battery cell with internal short-circuit self-breaking protection according to claim 1, characterized in that, The current-temperature sensitive element is a layer of positive temperature coefficient material coated or laminated on a local area of ​​the current collector.

7. The lithium battery cell with internal short-circuit self-breaking protection according to any one of claims 1 to 6, characterized in that, The current-temperature sensing elements are arranged in an array or grid pattern on the current collector, with each sensing element corresponding to and protecting an independent local area.

8. The lithium battery cell with internal short-circuit self-breaking protection according to any one of claims 1 to 6, characterized in that, The current-temperature sensitive element is located at the root of the connection between the current collector and the tab, or at the junction of the active material coating area and the empty foil area in the middle section of the current collector.

9. The lithium battery cell with internal short-circuit self-breaking protection according to claim 1, characterized in that, The electrode has a wound structure or a stacked structure.

10. A battery module, characterized in that, It includes a plurality of lithium battery cells as described in any one of claims 1 to 9.

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