A multifunctional current collector and method for lithium battery formation process

Abstract

This invention relates to the field of lithium battery production equipment and testing technology, specifically a multifunctional current collector and method for lithium battery formation processes; it includes an insulating base, a lifting cylinder, a stacked guide plate, a coaxial probe, and a controller; the stacked guide plate is composed of a copper negative electrode array, an insulating film, and a voltage sampling plate stacked sequentially; the outer tube current needle and the inner core voltage needle of the coaxial probe are respectively connected to the corresponding plate layers; this invention also provides a control method that calculates the initial contact resistance by injecting a test current, and converts the dynamic contact resistance according to the continuous formation current and the temperature rise slope; when the dynamic contact resistance exceeds the limit, the cylinder is preferentially controlled to increase the downward stroke for mechanical pressure compensation; if it does not recover, the formation is derated; this invention eliminates the need for a separate wiring harness, greatly improving the convenience of disassembly and maintenance, and realizing early detection and rapid dynamic adjustment of contact deterioration trends.

Description

Technical Field

[0001] This invention relates to the field of lithium battery production equipment and testing technology, specifically to a multifunctional current collector and method for lithium battery formation processes. Background Technology

[0002] In the manufacturing and production of lithium batteries, the formation process is a crucial step in activating the battery's active materials. This process typically requires the use of probes in the current collector to mechanically press against the terminals of the battery to be formed, enabling high-current input and real-time acquisition of the terminal surface voltage. To accomplish the aforementioned conduction and measurement tasks, existing solutions generally employ a traditional negative electrode probe architecture with power leads and voltage sampling lines arranged separately. Although this solution possesses basic charge-discharge testing capabilities under conventional formation scenarios, its high dependence on complex wiring harness arrangements and numerous wire solder joints results in poor assembly consistency and makes independent disassembly and maintenance of the probes extremely difficult. Furthermore, the heat conduction path between the traditional probe head and the sampling position is not fixed, and localized heating caused by poor contact between the probe and the terminal is difficult to reliably identify using existing temperature data. The system often relies on preset absolute temperature thresholds for empirical judgment or post-event alarms, resulting in high response delays and a large unobservable range for state estimation, making it difficult to support early detection and rapid compensation adjustment of dynamic contact deterioration trends during the formation process.

[0003] Therefore, optimizing the mechanical pressing and guiding structure of the current collection device and improving the accuracy and timeliness of the dynamic sensing of the probe contact state have become urgent technical problems to be solved. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a multifunctional current collector and method for lithium battery formation processes. Specifically, the technical solution of this invention is as follows:

[0005] A multifunctional current collector for lithium battery formation process includes:

[0006] An insulating base has a stepped positioning hole on its bottom surface that extends to its top surface;

[0007] The lifting cylinder has its piston rod end connected to the top of the insulating base, and the cylinder body connected to the external assembly frame.

[0008] The stacked flow guide plate, connected to the bottom surface of the insulating base, includes a copper negative electrode array, a polyimide insulating film, and a glass fiber voltage sampling plate arranged in sequence;

[0009] The stacked flow guide plate has a plug-in through hole corresponding to the stepped positioning hole. The plug-in through hole has a first conductive ring and a second conductive ring respectively on the hole wall of the layer where the copper negative electrode and the glass fiber voltage sampling plate are located. A thermistor is provided on the top surface of the copper negative electrode.

[0010] Coaxial probes are inserted into the insertion through-hole, including an outer tube current probe and an inner core voltage probe;

[0011] The tail of the external tube current needle is provided with an elastic sleeve that is interference-fitted with the first conductive ring;

[0012] The inner core voltage needle passes through the inner cavity of the outer tube current needle, and its tail extends out of the outer tube current needle and is provided with a contact spring that is interference-fitted with the second conductive ring.

[0013] The controller controls the lifting cylinder and acquires temperature data from the thermistor.

[0014] Furthermore, the piston rod stroke of the lifting cylinder is 100mm, and the end of the piston rod of the lifting cylinder is fixedly connected to the top center of the insulating base by flange bolts.

[0015] Furthermore, the insulating base is a cuboid epoxy resin board, and the stacked guide plate is fixedly connected to the bottom surface of the insulating base by insulating bolts.

[0016] Furthermore, the thickness of the copper negative electrode array is 5mm, the thickness of the glass fiber voltage sampling plate is 2mm, and the copper negative electrode array, the polyimide insulating film, and the glass fiber voltage sampling plate are bonded together as a rigid whole through a hot pressing process.

[0017] Furthermore, the outer tube current needle is a beryllium copper alloy hollow tube, the elastic sleeve has a circumferentially distributed outward convex multi-lobed structure, and the interference fit between the elastic sleeve and the first conductive ring is 0.2 mm.

[0018] Furthermore, the inner core voltage needle is coaxially inserted into the inner cavity of the outer tube current needle through a polytetrafluoroethylene insulating sleeve. The contact spring has a circumferentially distributed multi-lobed elastic structure. Both the head of the outer tube current needle and the head of the inner core voltage needle are machined with annular array toothed contact surfaces.

[0019] Furthermore, a copper busbar is crimped to the side of the copper negative electrode busbar, and the copper busbar is connected to an external formation power supply. A gold finger slot is printed on the side of the glass fiber voltage sampling board, and the gold finger slot is connected to an external formation voltage detection circuit. The thermistor is located 10mm away from the edge of the insertion hole.

[0020] A multifunctional current collection control method for lithium battery formation process includes:

[0021] The lifting cylinder is controlled to extend and drive the insulating base to descend, so that the head of the coaxial probe is pressed against the surface of the electrode post of the battery to be formed.

[0022] A step test current is injected into the outer tube current needle through the copper negative electrode, and the voltage drop on the electrode surface fed back by the inner core voltage needle is obtained simultaneously.

[0023] The initial contact resistance is calculated based on the voltage drop across the electrode surface and the step test current.

[0024] A continuous forming current is output to the external tube current needle, a set time interval is obtained, and the temperature data recorded by the thermistor is obtained according to the set time interval, thereby calculating the temperature rise slope.

[0025] The dynamic contact resistance is obtained by converting the formation current and the temperature rise slope.

[0026] Further, the step of calculating the dynamic contact resistance based on the formation current and the temperature rise slope includes:

[0027] Obtain the pre-calibrated thermal capacity coefficient of the copper negative electrode array and the body resistance of the coaxial probe;

[0028] The total heat power is calculated by multiplying the temperature rise slope by the heat capacity coefficient of the copper negative electrode array.

[0029] The heating power of the body is calculated by multiplying the square of the current into the resistance of the coaxial probe.

[0030] The contact surface heating power is calculated by subtracting the body heating power from the total heat power, and the dynamic contact resistance is calculated by dividing the contact surface heating power by the square of the formation current.

[0031] Further, after the step of calculating the dynamic contact resistance based on the formation current and the temperature rise slope, the following steps are included:

[0032] The dynamic contact resistance is compared with the initial contact resistance;

[0033] If the dynamic contact resistance is less than or equal to the initial contact resistance If so, the current formation current will be maintained and operation will continue;

[0034] If the dynamic contact resistance is greater than the initial contact resistance Then control the lifting cylinder to increase The downward stroke increases the mechanical contact pressure;

[0035] The temperature data recorded by the thermistor is acquired in real time, and the dynamic contact resistance is recalculated.

[0036] If the recalculated dynamic contact resistance is less than or equal to the initial contact resistance. If so, the current formation current will be maintained and operation will continue;

[0037] If the recalculated dynamic contact resistance is greater than the initial contact resistance... Then control the reduction of the formation current to the original set value. Perform a devaluation and record the exception code.

[0038] The present invention has the following beneficial effects:

[0039] 1. This invention uses a stacked current guide plate and coaxial probes to sequentially stack a copper negative electrode busbar, a polyimide insulating film, and a glass fiber voltage sampling plate. Conductivity is achieved by using the elastic sleeve at the tail of the outer tube current needle to interfere with the first conductive ring, and the contact spring at the tail of the inner core voltage needle to interfere with the second conductive ring. This structure replaces the traditional separate and complicated wire harness arrangement, which not only significantly improves assembly consistency but also allows the coaxial probe to be directly plugged in and replaced, greatly improving the convenience of independent disassembly and maintenance of the equipment.

[0040] 2. This invention utilizes a thermistor installed on the top surface of the copper negative electrode array to acquire temperature data. The controller calculates the dynamic contact resistance based on the continuous formation current and the calculated temperature rise slope. This method overcomes the limitations of relying solely on absolute temperature values ​​for judgment due to lag. By comparing the dynamic contact resistance with the initial contact resistance, the controller prioritizes controlling the lifting cylinder to increase the downward stroke to increase the mechanical contact pressure when the limit is exceeded. If the condition does not improve, the formation current is reduced for derating formation, thereby achieving early detection and rapid dynamic adjustment of the contact deterioration trend. Attached Figure Description

[0041] The following drawings, which illustrate embodiments of this application, are incorporated herein by reference and are used to understand this application. The drawings show embodiments of this application and their descriptions, serving to explain the principles of this application. In the drawings:

[0042] Figure 1 This is a schematic diagram of the overall structure of the device;

[0043] Figure 2 This is a schematic diagram of the stepped positioning hole structure of the device;

[0044] Figure 3 This is a schematic diagram of the coaxial probe structure of the device;

[0045] Figure 4 This is a schematic diagram of the stacked guide vane structure of the device;

[0046] Figure 5 This is a flowchart of the method of the present invention.

[0047] In the diagram: 1. Insulating base; 2. Stepped positioning hole; 3. Lifting cylinder; 4. Piston rod; 5. Cylinder body; 6. Formation frame; 7. Stacked guide plate; 8. Copper negative electrode busbar; 9. Polyimide insulating film; 10. Fiberglass voltage sampling plate; 11. Insertion through hole; 12. First conductive ring; 13. Second conductive ring; 14. Thermistor; 15. Coaxial probe; 16. Outer tube current needle; 17. Inner core voltage needle; 18. Elastic sleeve; 19. Contact spring; 20. Flange bolt; 21. Insulating bolt; 22. PTFE insulating sleeve; 23. Annular array toothed contact surface; 24. Lead-out copper busbar; 25. Gold finger slot; 26. Battery to be formed; 27. Terminal post. Detailed Implementation

[0048] In the following description, numerous specific details are set forth to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that embodiments of this application may be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with embodiments of this application.

[0049] Example 1:

[0050] Combination Figures 1 to 4 As shown, a multifunctional current collector for lithium battery formation process includes:

[0051] An insulating base 1 has a stepped positioning hole 2 extending from its bottom surface to its top surface;

[0052] The lifting cylinder 3 has its piston rod 4 end connected to the top of the insulating base 1, and the cylinder body 5 connected to the external assembly frame 6.

[0053] The stacked flow guide plate 7 is attached to the bottom surface of the insulating base 1 and includes a copper negative electrode row 8, a polyimide insulating film 9 and a glass fiber voltage sampling plate 10 arranged sequentially.

[0054] The stacked flow guide plate 7 has a plug-in through hole 11 corresponding to the stepped positioning hole 2. The plug-in through hole 11 has a first conductive ring 12 and a second conductive ring 13 respectively on the hole wall of the layer where the copper negative electrode 8 and the glass fiber voltage sampling plate 10 are located. The copper negative electrode 8 has a thermistor 14 on its top surface.

[0055] The coaxial probe 15 is inserted into the insertion through hole 11 and includes an outer tube current needle 16 and an inner core voltage needle 17.

[0056] The tail of the outer tube current needle 16 is provided with an elastic sleeve 18 that is interference-fitted with the first conductive ring 12;

[0057] The inner core voltage needle 17 passes through the inner cavity of the outer tube current needle 16, and its tail extends out of the outer tube current needle 16 and is provided with a contact spring 19 that is interference-fitted with the second conductive ring 13.

[0058] The controller controls the lifting cylinder 3 and acquires the temperature data of the thermistor 14;

[0059] In the lithium battery formation process of this embodiment, the traditional negative electrode probe usually uses a method of separating the power wire and the voltage sampling line to achieve conductivity and measurement. This method has limitations in terms of the number of wire solder joints, the consistency of wire bundle arrangement, and independent maintenance of probes. In addition, the heat conduction path between the probe head and the sampling position is not fixed, making it difficult to stably identify local heating caused by poor contact through temperature data.

[0060] To solve the above problems, this embodiment includes an insulating base 1, a lifting cylinder 3, a stacked guide plate 7, a coaxial probe 15, and a controller. The insulating base 1 is used to support the stacked guide plate 7 and the coaxial probe 15, and provides axial guidance and installation reference for the coaxial probe 15 through the stepped positioning hole 2. The stepped positioning hole 2 is used not only for geometric positioning in this invention, but also to limit the relative coaxiality between the coaxial probe 15 and the stacked guide plate 7, so as to reduce the contact resistance fluctuation caused by the insertion misalignment.

[0061] The cylinder body 5 of the lifting cylinder 3 is fixed to the formation frame 6, and the end of the piston rod 4 is connected to the top of the insulating base 1, thereby driving the insulating base 1 and the stacked guide plate 7 to rise and fall as a whole, so that the head of the coaxial probe 15 forms a controlled pressure connection with the terminal post 27 of the battery to be formed.

[0062] The stacked current guide plate 7 is composed of a copper negative electrode 8, a polyimide insulating film 9, and a glass fiber voltage sampling plate 10 stacked in sequence. The copper negative electrode 8 is responsible for the conduction of large current and heat conduction. The polyimide insulating film 9 is used to achieve dielectric isolation between the power circuit and the voltage sampling circuit. The glass fiber voltage sampling plate 10 is used to provide a stable voltage sampling connection path.

[0063] The insertion through hole 11 penetrates the stacked flow guide plate 7, and a first conductive ring 12 is set on the copper negative electrode row 8, and a second conductive ring 13 is set on the glass fiber voltage sampling plate 10, so as to correspond to the insertion and conduction of the outer tube current needle 16 and the inner core voltage needle 17 respectively.

[0064] The thermistor 14 is attached to the top surface of the copper negative electrode 8 to continuously collect temperature data in the area near the insertion hole 11. Since the copper negative electrode 8 is a rigid heat conductor and the coaxial probe 15 forms a fixed heat transfer path from the probe head to the copper negative electrode 8 after insertion, the temperature rise detected by the thermistor 14 can reflect the heating state of the probe contact surface.

[0065] The coaxial probe 15 adopts a coaxial arrangement of current channel and voltage channel. The outer tube current needle 16 forms a stable high current contact with the first conductive ring 12 through the elastic sleeve 18. The inner core voltage needle 17 passes through the inner cavity of the outer tube current needle 16 and forms a low current sampling contact with the second conductive ring 13 through the contact spring 19.

[0066] This structure ensures that the current injection path and voltage measurement path are spatially aligned with a consistent pressing reference, thereby reducing measurement errors caused by independent probe offset. The controller is electrically connected to the lifting cylinder 3, the thermistor 14, the formation power supply, and the voltage detection circuit. On the one hand, the controller outputs action commands to control the downward pressing and return of the lifting cylinder 3. On the other hand, it receives temperature data output by the thermistor 14 to combine current and voltage data to determine the contact state.

[0067] Through the above structural combination, the device can simultaneously achieve mechanical crimping, negative maximum current conduction, voltage sampling, temperature sensing and contact state control. Furthermore, a single coaxial probe 15 can be directly pulled out from the insertion hole 11 for replacement without disassembling the entire bundle of wires, making it suitable for repeated maintenance in chemical formation production lines.

[0068] The piston rod 4 of the lifting cylinder 3 has a stroke of 100mm, and the end of the piston rod 4 of the lifting cylinder 3 is fixedly connected to the top center of the insulating base 1 by flange bolts 20.

[0069] The lifting cylinder 3 is used to provide the pressing displacement between the coaxial probe 15 and the battery terminal 27. Its stroke setting is directly related to the equipment's adaptability to different tooling heights, tolerance accumulation, and abnormal compensation displacement. In this embodiment, the piston rod 4 of the lifting cylinder 3 has a stroke of 100mm. This value is used to cover the installation error of the formation fixture, the assembly height difference of the insulating base 1, the height fluctuation of the battery terminal 27, and the additional pressing displacement required for subsequent contact compensation.

[0070] In the initial state of the equipment, the piston rod 4 retracts, keeping the coaxial probe 15 at a distance from the battery terminal 27, which facilitates loading and unloading. Before the formation begins, the controller drives the piston rod 4 to extend to the predetermined pressing position, so that the head of the coaxial probe 15 contacts the terminal 27. During the formation process, if the dynamic contact resistance obtained by the controller based on the temperature data increases, the pressing stroke can be increased further based on the original pressing position.

[0071] Since the total stroke is 100mm, the controller can perform secondary clamping within a safe range without affecting the return stroke and resetting of the mechanism; the end of the piston rod 4 is fixedly connected to the top center of the insulating base 1 by flange bolts 20. The purpose of this connection is to transmit the thrust of the piston rod 4 along the central axis of the insulating base 1, and reduce the tilting caused by uneven force on the stacked guide plate 7 on the bottom surface of the insulating base 1; the flange bolts 20 connection can adopt a four-point evenly distributed locking form. After the bolts are tightened, the end face of the piston rod 4 is in contact with the top of the insulating base 1, so that the lifting direction is basically consistent with the axis of the stepped positioning hole 2;

[0072] The arrangement of the top center connection of the insulating base 1 also allows multiple coaxial probes 15 to obtain a more uniform overall downward pressure when working on the same plate, reducing the wear of the insertion through hole 11 caused by unilateral force; the above stroke and connection method are used in combination so that the lifting cylinder 3 not only undertakes simple lifting action, but also undertakes the function of contact pressure compensation actuator, providing a mechanism basis for adding downward stroke in subsequent control methods;

[0073] The insulating base 1 is a rectangular epoxy resin board, and the laminated flow guide plate 7 is fixedly connected to the bottom surface of the insulating base 1 by insulating bolts 21.

[0074] In this device, the insulating base 1 serves a dual function as an installation support structure and electrical insulation. The insulating base 1 is set as a cuboid epoxy resin plate, which facilitates the planar reference fit with the formation frame 6, the flange of the lifting cylinder 3, and the stacked guide plate 7. On the other hand, the epoxy resin plate has stable mechanical strength and high volume resistivity, which can avoid the formation of parasitic conductive paths between the guide plate and the frame. The cuboid structure also facilitates the arrangement of multiple stepped positioning holes 2 and insulating bolt holes 21 in a rectangular array on its bottom surface, thereby adapting to the modular installation of parallel stations in the formation equipment.

[0075] The stacked flow guide plate 7 is fixedly connected to the bottom surface of the insulating base 1 by insulating bolts 21. The insulating bolts 21 not only provide mechanical locking, but also cut off the conductive and thermal bypass that may be formed by the metal fasteners.

[0076] If ordinary metal bolts are used, some of the heat in the copper negative electrode 8 may diffuse to the frame along the metal bolts, causing the temperature rise response collected by the thermistor 14 to be affected by additional heat dissipation; after using the insulating bolts 21, the heat is mainly transferred between the coaxial probe 15 and the copper negative electrode 8 along the designed rigid heat conduction path, thereby maintaining the correspondence between the temperature rise and the heating of the contact surface.

[0077] The stacked guide plate 7 is tightly fixed to the bottom surface of the insulating base 1, so that the insertion through hole 11 and the stepped positioning hole 2 remain corresponding after assembly, ensuring stable guiding accuracy when the coaxial probe 15 is inserted from top to bottom; the epoxy resin plate can also be cut into different lengths and widths according to the equipment size to adapt to different numbers of formation modules, while the fixing method of the insulating bolt 21 allows for quick disassembly and assembly during probe maintenance or guide plate replacement; thus, the combination of the cuboid epoxy resin plate and the insulating bolt 21 takes into account mechanical rigidity, electrical insulation and thermal path determinism, supporting the implementation conditions for subsequent temperature inversion calculations;

[0078] The thickness of the copper negative electrode 8 is 5mm, the thickness of the glass fiber voltage sampling plate 10 is 2mm, and the copper negative electrode 8, the polyimide insulating film 9 and the glass fiber voltage sampling plate 10 are bonded together as a rigid whole by hot pressing process.

[0079] The thickness of each layer and the interlayer bonding method in the stacked flow guide plate 7 determine the conductivity, sampling stability and thermal conductivity characteristics. In this embodiment, the thickness of the copper negative electrode 8 is 5 mm. This thickness is used to balance low resistance and high current transmission and stable heat capacity. Copper material has high conductivity. The 5 mm thickness can disperse the formation current in the plate body, reduce the voltage drop along the length of the plate, and at the same time make the area adjacent to the insertion hole 11 have measurable heat capacity so that the thermistor 14 can detect the temperature rise change from the probe contact surface.

[0080] The fiberglass voltage sampling board 10 is 2mm thick. This thickness is used to provide sufficient board rigidity to support the second conductive ring 13 and the gold finger slot 25, and to ensure the crimping stability of the inner core voltage pin 17 after the contact spring 19 is inserted.

[0081] The polyimide insulating film 9 is located between the copper negative electrode 8 and the glass fiber voltage sampling plate 10. It utilizes its temperature resistance and insulation properties to isolate the high current circuit and the voltage sampling circuit from each other. The three are bonded together as a rigid whole by hot pressing. The role of hot pressing in this invention is not only to laminate, but also to eliminate the relative displacement and local air gaps between the layers.

[0082] Specifically, in one application example of this embodiment, the parameters of the hot pressing process are set as follows: temperature 185°C, pressure 2.5MPa, and holding time 30min, to ensure that the polyimide insulating film 9 and the metal / glass fiber layers on both sides are fully impregnated and air bubbles are eliminated, forming a seamless heat conduction whole.

[0083] If there are gaps or slippery structures between layers, the heat will be affected by the fluctuation of interface thermal resistance when it propagates within the layer, and the relationship between the temperature rise slope and the actual heat generation power at the contact surface will be less stable.

[0084] After being formed into a rigid whole by hot pressing, the stacked guide plate 7 maintains geometric stability under mechanical pressure, pin vibration and temperature cycling conditions, thus fixing the relative positional relationship between the first conductive ring 12, the second conductive ring 13 and the thermistor 14. 8. Copper negative electrode, 9. Polyimide insulating film and The glass fiber voltage sampling board 10 is formed by hot pressing to create an integral structure, which enables the stacked flow guide plate 7 to simultaneously perform the functions of flow guiding, insulation, sampling and heat transfer reference, providing a stable physical basis for the conversion of dynamic contact resistance.

[0085] The outer tube current needle 16 is a beryllium copper alloy hollow tube, and the elastic sleeve 18 has a circumferentially distributed outward convex multi-lobed structure. The interference fit between the elastic sleeve 18 and the first conductive ring 12 is 0.2mm. When the formation interface heats up abnormally due to poor contact, the beryllium copper alloy outer tube current needle 16 expands radially due to heat. Under the strict constraint of the specific initial interference fit of 0.2mm, the radial thermal expansion deformation of the multi-lobed structure will be quickly converted into additional radial positive pressure on the hole wall of the first conductive ring 12. The lateral static friction force increment generated by this additional positive pressure can offset the axial micro-displacement caused by the softening of the outer tube current needle 16 due to heat. Thus, during the system communication and physical response delay period when the thermistor 14 senses the temperature rise signal and the controller finally triggers the lifting cylinder 3 to perform additional downward action, the pure mechanical passive locking of the large current channel and the self-maintenance of the contact pressure are achieved in advance, avoiding the avalanche-like surge of contact resistance during the response delay period.

[0086] The outer tube current needle 16 undertakes the main function of forming current conduction. Its material, structural form and the amount of fit between it and the first conductive ring 12 directly affect the conduction resistance, assembly and disassembly life and thermal conduction stability. In this embodiment, the outer tube current needle 16 is a beryllium copper alloy hollow tube.

[0087] The beryllium copper alloy has both conductivity and elastic recovery capability, and can maintain a relatively stable contact pressure under repeated insertion and removal conditions; the hollow tube structure provides coaxial space for the inner core voltage needle 17, so that the current circuit and voltage sampling circuit can be integrated on the same probe axis.

[0088] The elastic sleeve 18 at the tail of the outer tube current needle 16 has a circumferentially distributed convex multi-lobed structure. The so-called circumferentially distributed convex multi-lobed structure means that several elastic lobes are opened along the axial direction on its outer periphery, so that the tail end will radially contract during the insertion of the first conductive ring 12. After entering the installation position, it will rely on the material rebound to form a circumferential pressing contact with the hole wall. Compared with the traditional straight tube type, the circumferentially distributed convex multi-lobed elastic sleeve 18 can form multiple distributed contact areas in a limited installation space, reducing contact instability caused by local wear.

[0089] The interference fit between the elastic sleeve 18 and the first conductive ring 12 is 0.2 mm. This interference fit is a set value that balances insertability and contact retention force. If the interference fit is too small, the compression between the sleeve and the first conductive ring 12 will be insufficient, resulting in increased contact resistance and affecting the consistency of the thermal path. If the interference fit is too large, it may increase the assembly force and accelerate the wear of the conductive ring hole wall.

[0090] When the thickness is set to 0.2mm, the elastic sleeve 18 forms a stable elastic contact pressure after insertion, so that the outer tube current needle 16 and the copper negative electrode 8 can obtain a low-resistance, repeatable electrical connection. At the same time, this connection is also one of the important pathways for the probe to transfer heat to the copper negative electrode 8.

[0091] Since this plug-in connection replaces the flexible wire bonding connection, the probe can be replaced independently by axial pull-out after wear, without having to re-weld the main circuit of the formation power supply, thus simplifying the operation steps and maintaining the consistency of the thermal path after replacement.

[0092] The inner core voltage needle 17 is coaxially inserted into the inner cavity of the outer tube current needle 16 through the polytetrafluoroethylene insulating sleeve 22. The contact spring 19 has a multi-lobed elastic structure with circumferentially evenly distributed. Both the head of the outer tube current needle 16 and the head of the inner core voltage needle 17 are machined with annular array toothed contact surfaces 23.

[0093] The inner core voltage needle 17 is used to obtain the surface potential of the battery terminal 27. Its key requirements are stable sampling position, insulation and isolation from the high current channel, and small change in contact resistance. In this embodiment, the inner core voltage needle 17 is coaxially inserted into the inner cavity of the outer tube current needle 16 through the polytetrafluoroethylene insulating sleeve 22.

[0094] The polytetrafluoroethylene insulating sleeve 22 is used to form electrical isolation between the outer tube current needle 16 and the inner core voltage needle 17, and to limit the radial position of the inner core voltage needle 17 in the hollow tube, so as to prevent conductive contact with the inner wall of the outer tube current needle 16 during vibration or repeated crimping.

[0095] Since the voltage needle and current needle are coaxially arranged, they correspond to the same pressing center area when pressing against the pole 27, which can reduce the additional measurement error caused by sampling point deviation. The contact spring 19 at the tail of the inner core voltage needle 17 has a circumferentially distributed multi-lobed elastic structure. The circumferentially distributed multi-lobed elastic structure means that the contact spring 19 is composed of multiple elastic lobes evenly distributed along the circumference. When the second conductive ring 13 is inserted, each elastic lobe generates a radial pressing force, thereby forming multi-point contact with a small insertion force. This configuration is suitable for low-current, high-stability voltage sampling connection and allows the voltage needle to be independently installed and removed.

[0096] Both the head of the outer tube current needle 16 and the head of the inner core voltage needle 17 are machined with annular array toothed contact surfaces 23. In this invention, the annular array toothed contact surfaces 23 are used to improve the actual contact capability with the surface of the pole post 27.

[0097] Since there may be slight oxide film, surface roughness differences or residual contamination layer on the surface of the battery terminal 27 to be formed, local poor connection is easily formed when the flat end contacts; when the toothed contact surface is pressed, it can form a high local pressure at multiple tiny contact points, allowing the contact points to penetrate the surface film and establish a conductive channel.

[0098] The toothed contact surface at the head of the outer tube current needle 16 is responsible for forming a large current transmission contact, while the toothed contact surface at the head of the inner core voltage needle 17 is responsible for obtaining voltage data that is closer to the true potential of the surface layer of the pole post 27 in the same area.

[0099] By combining the polytetrafluoroethylene insulating sleeve 22, the circumferentially distributed multi-lobed elastic structure contact spring 19, and the toothed contact surface of the double needle head, stable conductivity and stable sampling can be achieved simultaneously in a single probe unit, supporting the accurate measurement of the initial contact resistance.

[0100] The side of the copper negative electrode 8 is crimped with a lead-out copper busbar 24, which is connected to an external formation power supply. The side of the fiberglass voltage sampling board 10 is printed with a gold finger slot 25, which is connected to an external formation voltage detection circuit. The position of the thermistor 14 is 10mm away from the edge of the insertion through hole 11.

[0101] In order to form a standardized interface between the stacked flow guide plate 7 and the external formation equipment, in this embodiment, a copper busbar 24 is crimped to the side of the copper negative electrode busbar 8, and a gold finger slot 25 is provided on the side of the fiberglass voltage sampling board 10.

[0102] The copper busbar 24 is used to connect the negative output terminal of the power supply to the copper negative busbar 8. The crimping method can be a bolt face-press connection, so that the copper busbar with a larger cross-sectional area and the copper negative busbar 8 form a low contact resistance conductive interface, reducing the additional heat generation at the high current input terminal. Since the copper negative busbar 8 carries the main circuit current, the copper busbar 24 is located on the side to avoid occupying the space above the plug-in hole 11, which facilitates the disassembly and assembly of the coaxial probe 15.

[0103] The fiberglass voltage sampling board 10 has a gold finger slot 25 printed on its side. The gold finger slot 25 is connected to the conductive traces inside the board and is connected to an external voltage detection circuit. This design integrates multiple voltage sampling interfaces into a board-side plug-in structure, which is beneficial for quick tooling assembly and replacement. The thermistor 14 is positioned 10mm away from the edge of the plug-in hole 11. This distance is set based on two considerations:

[0104] First, the thermistor 14 needs to be close enough to the insertion hole 11 so that the Joule heat generated by the probe contact surface can be transferred to the copper negative electrode array 8 through the outer tube current needle 16 and the first conductive ring 12 and can be detected in a short time.

[0105] Secondly, the thermistor 14 should not be too close to the edge of the insertion hole 11 to avoid the impact of pin installation and removal, local high stress on the hole wall, and heat dissipation at the metal edge on the temperature sampling stability.

[0106] When set to 10mm, the thermistor 14 is located in the near-end region of the main conduction path of contact heating, resulting in a faster temperature rise response and sufficient installation space. Through the relative position design of the copper busbar 24, gold finger slot 25 and the thermistor 14, the main circuit power supply, sampling signal output and thermal status monitoring are integrated on the same stacked guide plate 7, reducing the interface inconsistency problem caused by the traditional scattered wiring harness layout, and enabling the controller to synchronously acquire current, voltage and temperature related data.

[0107] Example 2:

[0108] Combination Figure 5 A multifunctional current collection control method for lithium battery formation process, comprising:

[0109] The lifting cylinder 3 extends and drives the insulating base 1 downward, so that the head of the coaxial probe 15 presses against the surface of the terminal post 27 of the battery to be formed.

[0110] A step test current is injected into the outer tube current needle 16 through the copper negative electrode 8, and the voltage drop on the surface of the pole 27 fed back by the inner core voltage needle 17 is obtained simultaneously.

[0111] The initial contact resistance was calculated based on the surface voltage drop of pole 27 and the step test current.

[0112] A continuous forming current is output to the external tube current needle 16, a set time interval is obtained, and the temperature data recorded by the thermistor 14 is obtained according to the set time interval, so as to calculate the temperature rise slope.

[0113] The dynamic contact resistance is obtained by converting the formation current and the temperature rise slope.

[0114] The control method is used to identify the change in the contact state between the probe and the battery terminal 27 during the formation process. After receiving the formation start command, the controller outputs an extension control signal to the lifting cylinder 3, so that the piston rod 4 of the lifting cylinder 3 pushes the insulating base 1 downward until the head of the coaxial probe 15 forms a pressure contact with the surface of the battery terminal 27 to be formed.

[0115] The compression state here is a prerequisite for subsequent resistance measurement and temperature inversion, because only under controlled contact pressure can the outer tube current needle 16 and the inner core voltage needle 17 establish stable conductive circuits and sampling circuits respectively; after the compression is completed, the power supply injects a step test current into the outer tube current needle 16 through the lead-out copper busbar 24 and the copper negative electrode busbar 8.

[0116] The step test current refers to the test current that rises from zero to a preset value and remains stable for a short time in a short period of time. Its purpose is to obtain the instantaneous voltage response after current injection without overheating the contact surface.

[0117] Simultaneously, the formation voltage detection circuit acquires the voltage drop data on the surface of the electrode 27 through the gold finger slot 25, the glass fiber voltage sampling board 10, the second conductive ring 13 and the inner core voltage needle 17; the controller divides the measured voltage drop by the step test current to obtain the initial contact resistance; this initial contact resistance is used to characterize the initial conduction state when the probe crimping is completed. If the value is too high, it indicates that the film layer on the surface of the electrode 27 is too thick or the mechanical crimping is insufficient.

[0118] After initial calibration, the controller switches the formation power supply to a continuous formation current output mode. When the continuous formation current flows through the contact surface between the outer tube current needle 16 and the electrode post 27, the Joule heat caused by the contact resistance will be transferred along the probe and the copper negative electrode array 8. The controller reads the temperature data recorded by the thermistor 14 at set time intervals. The set time interval can be set according to the thermal response speed. In this embodiment, 100ms can be used to balance sampling resolution and data processing burden.

[0119] The controller calculates the temperature rise slope based on the temperature difference and time difference between adjacent sampling points. Since the rigid structure of the device makes the thermal path basically fixed, the temperature rise slope can be used as a characterization of the degree of heating of the contact surface. The controller then calculates the dynamic contact resistance based on the formation current and the temperature rise slope, which is used to reflect the real-time contact status during the formation process. Compared with the method of judging anomalies based on a single temperature threshold, this method combines voltage testing with temperature response, which can identify the upward trend of contact resistance before poor contact causes significant macroscopic overheating.

[0120] The process of synchronously acquiring the voltage drop on the surface of the pole 27 requires the controller to perform no less than ten continuous samplings and take the average value within the last 20% of the time after the step test current reaches a steady state, so as to filter out the electrical spark interference or inductive voltage drop at the moment of contact; the selection of the time interval setting must meet the time constant requirement of the thermistor 14, preferably an integer multiple of the controller control cycle, so as to ensure strict alignment of the temperature rise slope calculation on the time axis;

[0121] The process of converting dynamic contact resistance based on formation current and temperature rise slope aims to transform the change in contact surface resistance, which cannot be directly measured online, into a state quantity calculated by current, voltage, and temperature. The controller uses the initial contact resistance as the electrical reference for establishing the crimp, the temperature sequence as the thermal response data, and the continuous formation current as the heating excitation data. It sequentially performs reference establishment, continuous sampling, and thermal response conversion operations to obtain the dynamic contact resistance.

[0122] During this process, if poor contact occurs between the probe and the electrode 27, the Joule heating of the contact surface will increase under the same formation current. Since the heat transfer path between the coaxial probe 15, the first conductive ring 12, the copper negative electrode array 8 and the thermistor 14 is fixed, the enhanced heating of the contact surface will directly manifest as an accelerated temperature rise near the thermistor 14. The controller identifies the contact state by monitoring the changes in the above temperature rise slope.

[0123] To ensure a more stable correlation between the temperature rise slope and the heating of the contact surface, the controller prioritizes valid data determination before entering dynamic calculation: only when the continuous formation current has reached the set value and remained stable, and the thermistor 14 has not experienced over-range jumps for several consecutive sampling cycles, will the corresponding temperature sequence be sent to subsequent calculations; the specific calculation and determination logic is as follows: the target value of the formation current is set to... , No. The next real-time current sampling value is When the following conditions are met:

[0124]

[0125] Furthermore, when maintaining ten consecutive sampling cycles, the current is determined to remain stable; the threshold for determining temperature jumps between adjacent cycles is set as follows. And the real-time temperature sampling sequence satisfies:

[0126]

[0127] At that time, it was determined that no over-range jump occurred; among them, The temperature at the current sampling time. The temperature at the previous sampling moment is used. If the current acquisition is in the instant of switching, the lifting cylinder 3 is performing an action, or there is a significant transient spike interference in the temperature sampling, the data of this period is only used for caching and does not participate in the dynamic contact resistance update, so as to reduce the impact of mechanical disturbance and current switching disturbance on the conversion result.

[0128] The step test current is preferably 5% to 15% of the continuous formation current, and the energizing duration is preferably 20ms to 100ms. The selection principle is to obtain a distinguishable voltage drop during the test, while avoiding significant temperature rise caused by the test current itself. When the specifications of the formation station are different, resulting in differences in the size or material of the electrode 27, the test amplitude that meets the voltage detection resolution requirements and does not cause significant temperature rise of the thermistor 14 can be pre-selected through no-load tooling test.

[0129] The physical meaning of setting the time interval is the time step of the controller to discretely sample the temperature data of the thermistor 14. This time step determines both the calculation resolution of the temperature rise slope and the response speed of the subsequent dynamic contact resistance update.

[0130] If the time interval is too short, the proportion of temperature measurement noise in adjacent sampling points will increase, which will easily lead to slope fluctuations. If the time interval is too long, the identification of contact deterioration will be delayed. Therefore, this embodiment takes 100ms as the preferred value and allows the adjustment within the range of 50ms to 500ms according to the response time of the thermistor 14 and the processing capability of the controller.

[0131] The temperature rise slope is calculated by dividing the difference between two adjacent effective temperature sampling values ​​by the corresponding time interval. The effective temperature sampling value is the temperature value after filtering. The filtering can be done by selecting the median of three consecutive samples. That is, the controller takes the median of three consecutive temperature sampling results near the current time as the current effective temperature value to reduce the impact of electromagnetic interference or instantaneous contact jitter on the calculation of the temperature rise slope.

[0132] Specifically, after acquiring the step test current value, the surface voltage drop of the pole 27, the continuous conversion current value, and the temperature sequence of the thermistor 14, the controller sequentially performs the operations of establishing a pressure connection, measuring the initial contact resistance, acquiring the temperature sequence, calculating the temperature rise slope, and converting the dynamic contact resistance, thereby generating dynamic contact resistance data for subsequent voltage compensation judgment and derating control.

[0133] The steps for calculating dynamic contact resistance based on formation current and temperature rise slope include:

[0134] Obtain the pre-calibrated thermal capacity coefficient of the copper negative electrode 8 and the body resistance of the coaxial probe 15;

[0135] The total heat power is calculated by multiplying the temperature rise slope by the heat capacity coefficient of copper negative electrode 8.

[0136] The heating power of the body is calculated by multiplying the square of the converted current by the body resistance of the coaxial probe 15.

[0137] The controller synchronously extracts the pneumatic back pressure fluctuation value of the lifting cylinder 3 in the current pressing state and the micro-force displacement of the piston rod 4 in real time. Combined with the structural stiffness of the annular array toothed contact surface 23, it calculates the instantaneous normal stress of the head of the outer tube current needle 16 and the surface of the pole post 27. Then, using a preset stress-resistance nonlinear mapping model, it performs high-frequency dynamic correction on the body resistance of the coaxial probe 15 to completely eliminate the reference drift interference caused by the back thrust generated by the local thermal micro-expansion of the pole post 27 during the formation process on the body heating power calculation.

[0138] The contact surface heating power is obtained by subtracting the body heating power from the total heat power, and the dynamic contact resistance is obtained by dividing the contact surface heating power by the square of the converted current.

[0139] The conversion of dynamic contact resistance is based on the thermal power balance relationship. The purpose is to convert the temperature change collected by the thermistor 14 into the contact surface resistance change. In this embodiment, the controller reads the current temperature value and the previous temperature value of the thermistor 14 in each sampling cycle, and divides the difference between the two by the corresponding time interval to obtain the current temperature rise slope. The copper negative electrode array 8 serves as the direct carrier for temperature sampling. Its thermal capacity coefficient can be predetermined by the structural size, material density and specific heat capacity, and stored in the controller parameter area.

[0140] The controller multiplies the temperature rise slope by the thermal capacity coefficient of the copper negative electrode assembly 8 to obtain the total heat power corresponding to the current sampling period. This total heat power represents the equivalent heat input power that can cause a localized temperature rise in the copper negative electrode assembly 8, originating from the resistance heating of the coaxial probe 15 and the heating of the probe tip contact surface. Since the sampling time interval is extremely short and it is in the initial stage of the temperature rise, the heat loss from this localized area to the external environment is negligible, or this loss has been equivalently factored into the thermal capacity coefficient. middle;

[0141] To separate the heating power of the contact surface, the controller further multiplies the square of the converted current by the resistance of the coaxial probe 15 body to obtain the heating power of the body; the resistance of the coaxial probe 15 body can be obtained through offline calibration, that is, the steady-state resistance of the probe structure itself is measured under standard conductor crimping conditions and written into the controller as a known constant.

[0142] The controller subtracts the body's heating power from the total heat power to obtain the contact surface heating power. Since the Joule heating of the contact surface satisfies the correspondence between electrical power, the square of the current, and the contact resistance, the controller then divides the contact surface heating power by the square of the converted current to obtain the dynamic contact resistance. This calculation process transforms the temperature rise signal detected by the thermistor 14 from merely a high-temperature alarm signal into a resistance directly related to the quality of electrical contact. The mathematical model for the dynamic contact resistance is expressed as follows:

[0143]

[0144] in, For dynamic contact resistance, The heat capacity coefficient of the copper negative electrode assembly (8). The temperature at the current sampling time. The temperature at the previous sampling time, where the subscript is... Indicates the sampling sequence number. To set the time interval, For continuous formation current, The body resistance of the coaxial probe 15;

[0145] To further clarify the above calculation process, an example is given: assuming it is continuously converted into current. The pre-calibrated coaxial probe 15 has a resistance of 60A. The heat capacity coefficient of the copper negative electrode assembly is 1.0 mΩ. The calibrated value is 40 J / ℃; if the controller detects a temperature rise within a 100 ms interval... If the temperature rise is 0.015℃, then the temperature rise slope is 0.15℃ / s;

[0146] Substituting into the formula, the total heat power is: The heating power of the main body is Therefore, the heating power at the contact surface is calculated as follows: The final calculated dynamic contact resistance for ;

[0147] Through this quantitative deduction, the controller can output specific resistance values ​​in real time; the formula establishes a linear mapping between the macroscopic temperature rise rate and the microscopic contact loss through the law of conservation of energy, enabling the controller to eliminate the interference of the probe's own heating and accurately extract the resistance change of the contact interface.

[0148] Since this method deducts the heating effect of the body resistance of the coaxial probe 15 in the calculation, the obtained dynamic contact resistance mainly reflects the change in the microscopic contact state between the probe head and the electrode 27, and is more suitable for identifying contact deterioration caused by thermal expansion, surface oxidation and local separation. For those skilled in the art, the thermal capacity coefficient of the copper negative electrode 8 and the body resistance of the coaxial probe 15 can be measured and calibrated according to the specific size of the device. As long as the above power separation and resistance conversion relationship is followed, this step can be achieved.

[0149] When the controller performs the above conversion: it calculates the result reflecting the local temperature rise rate based on the filtered temperature sequence and sampling time interval; it deducts the heat generated by the probe itself that is not related to contact deterioration by combining the continuous conversion current and the pre-calibrated body resistance of the coaxial probe 15; and it calculates the dynamic contact resistance of the current cycle based on the remaining contact surface heating power.

[0150] The total heat power is obtained by multiplying the temperature rise slope by the heat capacity coefficient of the copper negative electrode array 8. It is preferably understood as a local equivalent conversion within a short time window. The physical premise is that when the thermistor 14 is close to the insertion hole 11, the sampling time interval is short, and the temperature rise is in the early stage of change, the additional heat generated by the contact surface has not yet had time to diffuse to the whole structure. Therefore, the local area of ​​the copper negative electrode array 8 near the thermistor 14 can be regarded as the main heat absorber. Under this condition, the greater the local temperature rise rate, the greater the equivalent heat input received by the local area.

[0151] Therefore, the total thermal power in this embodiment is not an accurate expression of the total heat dissipation power of the whole machine, but a local equivalent thermal power used to compare the trend of contact heating changes in different sampling periods online; the controller preferably performs the above conversion in the initial stage of temperature rise or in a stable discrete interval where the temperature difference between adjacent sampling periods is small.

[0152] If thermistor 14 detects that the temperature has entered a clear plateau period, the external cooling state has changed abruptly, or the temperature fluctuates repeatedly and significantly in adjacent cycles, the controller will determine that the interval is a non-optimal conversion interval. It can continue to sample but reduce the update weight of the conversion result of the current cycle or use the result output of the previous effective cycle.

[0153] The heat capacity coefficient of copper negative electrode 8 The calibration method is as follows: at a known ambient temperature, apply a constant calibration power to the coaxial probe 15. Record the temperature rise slope of the thermistor 14 during the linear segment before it reaches steady state. Among them, the temperature rise slope of the linear segment The automatic identification calculation model is as follows:

[0154] The controller collects the temperature sequence before reaching steady state and uses a sliding window method to extract continuous values. For each temperature data point, the least squares method is used to analyze it. Perform linear fitting on each data point and calculate the goodness of fit. When the calculation is obtained When the data within the time window is determined to be in a linear segment, the slope of the fitted line is used as... ;according to:

[0155]

[0156] The calculation is obtained and stored in the controller; where, For the applied constant calibration power, The fractional line represents the temperature rise slope of the thermistor in the linear segment before it reaches steady state, and represents a division operation. Through this calibration step, the controller can establish a thermo-electric conversion reference under a specific mechanical structure, thereby supporting the accurate conversion of subsequent dynamic contact resistance. The body resistance calibration steps of the coaxial probe 15 can be performed in the following order:

[0157] Step 1: Install the coaxial probe 15 to be calibrated onto the stacked flow guide plate 7 and press it against the standard copper block;

[0158] Step two: Inject a known constant current into the probe;

[0159] Step 3: Collect the steady-state voltage drop across the conductive path of the probe;

[0160] Step 4: Divide the steady-state voltage drop by the constant current to obtain the bulk resistance;

[0161] Step 5: Write this value into the controller parameter area as a deduction item for subsequent dynamic conversion; through the above definition, it is possible to avoid mistakenly writing abnormal contact resistance into the body parameters and ensure that the conversion object of dynamic contact resistance is clear.

[0162] The specific calculation process is as follows: First, calculate the total heat input based on the temperature change, then deduct the inherent heat generation of the probe, convert the heat power caused by the contact surface into dynamic contact resistance, and then pass the dynamic contact resistance to the subsequent comparison and execution control steps.

[0163] In actual control, if the calculated contact surface heating power is negative, the controller records the dynamic contact resistance of the current cycle as zero and maintains the result of the previous cycle as a smooth output, so as to indicate that the current temperature rise is mainly caused by the measurement disturbance rather than the actual contact deterioration.

[0164] After the step of calculating the dynamic contact resistance based on the conversion current and temperature rise slope, the following steps are included:

[0165] Compare the dynamic contact resistance with the initial contact resistance;

[0166] If the dynamic contact resistance is less than or equal to the initial contact resistance If so, the current formation current will be maintained and operation will continue;

[0167] If the dynamic contact resistance is greater than the initial contact resistance Then control the lifting cylinder 3 to increase The downward stroke increases the mechanical contact pressure;

[0168] The temperature data recorded by the thermistor 14 is acquired in real time, and the dynamic contact resistance is recalculated.

[0169] If the recalculated dynamic contact resistance is less than or equal to the initial contact resistance If so, the current formation current will be maintained and operation will continue;

[0170] If the recalculated dynamic contact resistance is greater than the initial contact resistance Then the formation current is reduced to the original set value. Perform a rate reduction conversion and log the exception code;

[0171] After completing the dynamic contact resistance conversion, the controller compares the dynamic contact resistance with the initial contact resistance to determine whether the contact condition has deteriorated beyond the allowable range.

[0172] The initial contact resistance represents the reference contact state when the crimping is established, while the dynamic contact resistance represents the real-time contact state during the formation process. The change in the ratio of the two can reflect the stability of the contact interface. When the dynamic contact resistance is less than or equal to 120% of the initial contact resistance, the controller determines that the current contact state is still within the allowable range and continues to operate with the existing pressing stroke and current formation current.

[0173] When the dynamic contact resistance is greater than 120% of the initial contact resistance, the controller determines that there is a significant deterioration trend in the contact interface; this deterioration trend may be due to local warping of the pole 27 after thermal expansion, slight springback of the probe contact tooth surface, or growth of the surface film layer.

[0174] To verify whether it can be restored by increasing mechanical pressure, the controller sends a compensation command to the lifting cylinder 3, causing the piston rod 4 to increase its downward stroke by 5mm based on the current displacement, so as to increase the clamping force of the coaxial probe 15 head on the pole post 27.

[0175] The purpose of adding 5mm is to provide additional displacement sufficient to change the number of micro-contact points and the crimping depth, while avoiding damage to the pole 27 or mechanical interference due to excessive pressing; after compensation, the controller continues to acquire the temperature data recorded by the thermistor 14 in real time and recalculates the dynamic contact resistance according to the steps.

[0176] After the lifting cylinder 3 increases its downward stroke by 5mm, the controller performs a mechanical stabilization delay of 3s, during which the calculation of the temperature rise slope is stopped; after the delay ends and the vibration of the mechanism decays, the controller clears the previous temperature buffer sequence and starts a new sampling window to reacquire temperature data.

[0177] This delay logic ensures that the recalculated dynamic contact resistance reflects the steady-state contact effect after pressure compensation, rather than the instantaneous data fluctuations caused by frictional heat generation or sudden changes in contact stress during the pressure compensation process. If the recalculated dynamic contact resistance is less than or equal to 120% of the initial contact resistance, it means that the additional pressure has enabled the contact surface to re-establish a lower contact resistance, and the controller maintains the current conversion current to continue operation.

[0178] If the recalculated dynamic contact resistance is still greater than 120% of the initial contact resistance, it indicates that the contact deterioration is not simply due to insufficient clamping, but may be caused by irreversible oxidation ablation or surface damage. In this case, continuing to maintain the original set current will increase the risk of local overheating.

[0179] The controller reduces the formation current to 50% of the original set value for derating formation and records the abnormal code. The abnormal code is associated with the corresponding work station or battery position, which facilitates subsequent manual inspection and quality traceability. Through the above comparison, pressure compensation, recalculation and derating processing steps, the control method combines mechanical execution with thermoelectric state determination, so that the device can make corresponding adjustments according to the changes in contact state during the formation process, reducing the burning and shutdown caused by poor contact between the probe and the electrode 27.

[0180] The above processing flow includes: determining whether to intervene based on the comparison between the current dynamic contact resistance and the initial contact resistance; if intervention is triggered, pressurization is performed and temperature data is re-acquired in an attempt to restore the normal crimping state through mechanical pressurization; if the situation is still not restored after pressurization, derating is performed and an error code is recorded; this process avoids unnecessary shutdowns or current reductions caused by local anomalies by prioritizing mechanical displacement compensation.

[0181] When the dynamic contact resistance is less than or equal to 120% of the initial contact resistance, the operation continues. The causal relationship is that the increase in dynamic contact resistance within this range is considered to be an allowable deviation caused by normal assembly fluctuations, material thermal drift, and acceptable contact changes, so no additional mechanical intervention is required.

[0182] When the dynamic contact resistance is greater than 120% of the initial contact resistance, pressure compensation is performed first. The causal relationship is that the excessive increase in contact resistance indicates that the number of actual contact points or the contact pressure may decrease. Increasing the mechanical pressing stroke can preferentially increase the number of micro contact points and improve the contact pressure. Therefore, pressure compensation is used as the first recovery method.

[0183] When the dynamic contact resistance after pressure replenishment is still greater than 120% of the initial contact resistance, derating is performed. The causal relationship is that this indicates that the contact deterioration has not been effectively restored by mechanical pressure. If the original current is maintained, the Joule heat of the contact surface will still be too high. Therefore, the formation current is reduced to suppress the risk of subsequent heating according to the square relationship of the current.

[0184] In this embodiment, 120% of the initial contact resistance represents the first-level intervention threshold, which is when the real-time contact resistance increases by more than 20% compared to the baseline state, exceeding the allowable range of normal assembly fluctuations and thermal drift.

[0185] The initial contact resistance of 120% represents the recovery judgment threshold during the pressure compensation and recalculation stage. It means that the contact state after pressure compensation should basically return to the range close to the initial crimping quality, allowing for a residual deviation of no more than 10%. The above two thresholds form a dual threshold logic of first relaxing the identification and then tightening the verification, so as to avoid frequent false triggering of pressure compensation due to a single threshold being too strict, and also to avoid missing the continuously deteriorating contact state due to a threshold being too lenient.

[0186] The above threshold can be determined by the following process: Under normal operating conditions, the initial contact resistance fluctuation range when the same type of battery terminal 27 and coaxial probe 15 are matched is statistically analyzed; the temperature rise and contact resistance changes are recorded in multiple formation cycles to determine the upper limit of natural drift in the thermal stability stage; the boundary value that can stably distinguish between the three states of normal, recoverable abnormal and unrecoverable abnormal is written into the controller parameter area.

[0187] The specific statistical calculation logic for the boundary value is as follows: extract the initial contact resistance sample data during the thermal stability phase of multiple transformation cycles, and calculate the sample mean. with standard deviation Based on the confidence interval distribution model of mathematical statistics, the first-level intervention threshold for recoverable anomalies that can cover the upper limit of natural drift is set as follows: And proportionally convert it to the initial contact resistance. ;

[0188] The threshold for determining the recovery of the contact surface after pressure replenishment is set to [value]. And proportionally convert it to the initial contact resistance. This statistical calculation model transforms qualitative fluctuation ranges into quantitative boundary values ​​that can be automatically generated by the algorithm.

[0189] The prerequisite for implementing this proportionalization is that the controller uses the baseline mean obtained from a large sample statistical analysis. The standard initial reference base is considered as the ideal crimping condition; the algorithm calculates the relative degradation ratio. To extract the inherent fluctuation range of the system, in the control parameters of this embodiment, the upper limit of this ratio coefficient is specifically set as the initial contact resistance. ;

[0190] Similarly, the pressure compensation verification ratio will be used. Adjusted to This conversion method allows the threshold judgment to be derived from actual working condition statistics and can also adaptively convert the initial contact resistance in the channel into a reasonable discrete deviation. Entry conditions corresponding to recoverable anomalies. The exit condition for successful recovery after pressure replenishment; the execution logic for increasing the downward pressure stroke by 5mm is as follows:

[0191] After the controller determines that the dynamic contact resistance exceeds the first-level intervention threshold, it does not immediately change the conversion current. Instead, it first sends a pressure compensation command to the lifting cylinder 3, so that the coaxial probe 15 adds displacement based on the current pressing position.

[0192] The 5mm displacement is not an arbitrary value, but a compensation step size set in conjunction with the 100mm total stroke. Its purpose is to ensure that the pressure compensation action has sufficient executable displacement, while reserving enough margin for the mechanism to return and reset again.

[0193] If the equipment model is different, the compensation step size can be written into the corresponding model parameters through pre-debugging without changing the above control logic. The logic of reducing the derating to 50% of the original set value is to suppress the risk of continued burning of the contact surface by significantly reducing the Joule heat according to the square relationship of the current when the contact state cannot be restored by pressure compensation, and to keep the current station under controlled operation rather than instantaneous power failure and shutdown.

[0194] This 50% can be determined through equipment verification tests. The selection principle is as follows: on the one hand, the contact surface heating should decrease significantly after derating, and on the other hand, the ability to perform basic formation on the battery cell should still be maintained. The abnormal code should at least include the workstation number, trigger time, pressure compensation execution status, and the recalculated dynamic contact resistance result, so as to trace whether the abnormality is caused by insufficient mechanical crimping or contact surface damage.

[0195] Therefore, the processing flow can be further clarified as follows: First, compare the dynamic contact resistance with the first-level intervention threshold. If it does not exceed the limit, continue the operation. If it exceeds the limit, perform a pressure replenishment. After pressure replenishment, compare it with the recovery judgment threshold. If it recovers, continue the operation. If it does not recover, enter the derating process and record the abnormal code.

[0196] This application has been described through the above embodiments; however, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit this application to the described embodiments. Those skilled in the art will understand that many more variations and modifications can be made based on the teachings of this application, and all such variations and modifications fall within the scope of protection claimed in this application.

Claims

1. A multifunctional current collector for lithium battery formation process, characterized in that, include: An insulating base (1) has a stepped positioning hole (2) extending from its bottom surface to its top surface. The lifting cylinder (3) has its piston rod (4) end connected to the top of the insulating base (1), and the cylinder body (5) connected to the external assembly frame (6). The stacked flow guide plate (7) is attached to the bottom surface of the insulating base (1) and includes a copper negative electrode row (8), a polyimide insulating film (9) and a glass fiber voltage sampling plate (10) arranged in sequence. The stacked flow guide plate (7) has a plug-in through hole (11) corresponding to the stepped positioning hole (2). The plug-in through hole (11) has a first conductive ring (12) and a second conductive ring (13) respectively on the hole wall of the layer where the copper negative electrode (8) and the glass fiber voltage sampling plate (10) are located. The copper negative electrode (8) has a thermistor (14) on its top surface. The coaxial probe (15) is inserted into the insertion through hole (11) and includes an outer tube current needle (16) and an inner core voltage needle (17). The tail of the outer tube current needle (16) is provided with an elastic sleeve (18) that is interference-fitted with the first conductive ring (12). The inner core voltage needle (17) passes through the inner cavity of the outer tube current needle (16), and its tail extends out of the outer tube current needle (16) and is provided with a contact spring (19) that is interference fit with the second conductive ring (13). The controller controls the lifting cylinder (3) and acquires the temperature data of the thermistor (14).

2. The multifunctional current collector for lithium battery formation process according to claim 1, characterized in that, The piston rod (4) of the lifting cylinder (3) has a stroke of 100mm, and the end of the piston rod (4) of the lifting cylinder (3) is fixedly connected to the top center of the insulating base (1) by flange bolts (20).

3. The multifunctional current collector for lithium battery formation process according to claim 1, characterized in that, The insulating base (1) is a rectangular epoxy resin board, and the stacked flow guide plate (7) is fixedly connected to the bottom surface of the insulating base (1) by insulating bolts (21).

4. The multifunctional current collector for lithium battery formation process according to claim 1, characterized in that, The thickness of the copper negative electrode (8) is 5mm, the thickness of the glass fiber voltage sampling plate (10) is 2mm, and the copper negative electrode (8), the polyimide insulating film (9) and the glass fiber voltage sampling plate (10) are bonded together as a rigid whole by hot pressing process.

5. The multifunctional current collector for lithium battery formation process according to claim 1, characterized in that, The outer tube current needle (16) is a beryllium copper alloy hollow tube, the elastic sleeve (18) has a circumferentially distributed outward convex multi-lobed structure, and the interference fit between the elastic sleeve (18) and the first conductive ring (12) is 0.2 mm.

6. The multifunctional current collector for lithium battery formation process according to claim 1, characterized in that, The inner core voltage needle (17) is coaxially inserted into the inner cavity of the outer tube current needle (16) through a polytetrafluoroethylene insulating sleeve (22). The contact spring (19) has a circumferentially distributed multi-lobed elastic structure. The head of the outer tube current needle (16) and the head of the inner core voltage needle (17) are both machined with annular array toothed contact surfaces (23).

7. The multifunctional current collector for lithium battery formation process according to claim 1, characterized in that, A copper negative electrode busbar (8) is crimped with a lead-out copper busbar (24), which is connected to an external formation power supply. A gold finger slot (25) is printed on the side of the glass fiber voltage sampling board (10), which is connected to an external formation voltage detection circuit. The thermistor (14) is located 10mm away from the edge of the insertion hole (11).

8. A control method, applied to the multifunctional current collector for the lithium battery formation process as described in claim 1, characterized in that, include: Control the lifting cylinder (3) to extend and drive the insulating base (1) to descend, so that the head of the coaxial probe (15) is pressed against the surface of the terminal post (27) of the battery to be formed (26); A step test current is injected into the outer tube current needle (16) through the copper negative electrode array (8), and the voltage drop on the surface of the pole (27) fed back by the inner core voltage needle (17) is obtained simultaneously. The initial contact resistance is calculated based on the voltage drop across the electrode (27) and the step test current. A continuous forming current is output to the outer tube current needle (16), a set time interval is obtained, and the temperature data recorded by the thermistor (14) is obtained according to the set time interval, thereby calculating the temperature rise slope. The dynamic contact resistance is obtained by converting the formation current and the temperature rise slope.

9. The control method according to claim 8, characterized in that, The steps for calculating the dynamic contact resistance based on the formation current and the temperature rise slope include: Obtain the pre-calibrated thermal capacity coefficient of the copper negative electrode array (8) and the body resistance of the coaxial probe (15); The total heat power is calculated by multiplying the temperature rise slope by the heat capacity coefficient of the copper negative electrode array (8); The heating power of the body is calculated by multiplying the square of the current into the resistance of the coaxial probe (15). The contact surface heating power is calculated by subtracting the body heating power from the total heat power, and the dynamic contact resistance is calculated by dividing the contact surface heating power by the square of the formation current.

10. The control method according to claim 8, characterized in that, After the step of calculating the dynamic contact resistance based on the formation current and the temperature rise slope, the following steps are included: The dynamic contact resistance is compared with the initial contact resistance; If the dynamic contact resistance is less than or equal to the initial contact resistance If so, the current formation current will be maintained and operation will continue; If the dynamic contact resistance is greater than the initial contact resistance Then control the lifting cylinder (3) to increase The downward stroke increases the mechanical contact pressure; The temperature data recorded by the thermistor (14) is acquired in real time, and the dynamic contact resistance is recalculated. If the recalculated dynamic contact resistance is less than or equal to the initial contact resistance. If so, the current formation current will be maintained and operation will continue; If the recalculated dynamic contact resistance is greater than the initial contact resistance... Then control the reduction of the formation current to the original set value. Perform a devaluation and record the exception code.

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