A processing technology for improving the wettability of cylindrical battery cells

Abstract

The application discloses a processing technology for improving the wettability of a cylindrical battery cell, which comprises the following steps: S1, placing a wound core after winding horizontally in a positioning jig with a positioning groove; S2, controlling the wound core to rotate around its axis at a first preset speed; S3, arranging one or more kneading rollers above the wound core, the axis of the kneading roller being parallel to the axis of the wound core, and controlling the kneading roller to rotate in the direction opposite to the rotating direction of the wound core at a second preset speed; S4, making the kneading roller contact the surface of the wound core and applying a predetermined pressure; and S5, continuously kneading the surface of the wound core for a preset time. Compared with the prior art, the application can effectively reduce the tightness of the wound core, increase the internal gap, and thus improve the wettability of the electrolyte.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary battery preparation, and particularly relates to a processing technology for improving the wettability of a cylindrical battery cell. BACKGROUND

[0002] Cylindrical battery cells are widely used in portable electronic devices, power tools, electric vehicles, and other fields due to their compact structure, high energy density, and mature manufacturing process. However, a key challenge in the manufacturing process of cylindrical battery cells is how to ensure that the electrolyte can fully infiltrate the electrode material while maintaining the stability of the cell structure.

[0003] Traditional cylindrical battery cell manufacturing processes usually use high-tension winding methods to ensure the tightness and mechanical strength of the wound cell structure. Although this method can improve the energy density and structural stability of the cell, it also leads to a serious problem: the wound cell is too tight, reducing the internal porosity and hindering the penetration and infiltration of the electrolyte.

[0004] The full infiltration of the electrolyte is crucial for the performance of the battery. It not only affects the capacity and rate performance of the battery, but also directly relates to the cycle life and safety of the battery. Insufficient infiltration can lead to a decrease in the utilization rate of electrode materials, increase the internal resistance of the battery, and even cause safety hazards.

[0005] Currently, the industry has tried various methods to improve the wettability of the electrolyte, such as extending the injection time, increasing the injection pressure, and using low-viscosity electrolyte. However, these methods either have limited effect or bring other adverse effects. For example, extending the injection time will reduce production efficiency, and using low-viscosity electrolyte may affect the long-term stability of the battery.

[0006] Therefore, there is an urgent need for a new processing technology that can effectively reduce the tightness of the wound cell and increase the internal voids without affecting the stability of the cell structure, thereby significantly improving the wettability of the electrolyte. This not only improves the overall performance of the battery, but also optimizes production efficiency and reduces manufacturing costs. SUMMARY

[0007] The purpose of the present application is to provide a processing technology for improving the wettability of a cylindrical battery cell, which can effectively reduce the tightness of the wound cell and increase the internal voids without affecting the stability of the cell structure, thereby improving the wettability of the electrolyte.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0009] A processing technology for improving the wettability of a cylindrical battery cell, comprising the following steps:

[0010] S1, placing the finished winding core horizontally in a positioning jig with a positioning slot;

[0011] S2, rotating the winding core around its axis at a first preset speed;

[0012] S3, arranging one or more kneading rollers above the winding core, the axis of the kneading rollers being parallel to the axis of the winding core, and rotating the kneading rollers in the direction opposite to the rotation direction of the winding core at a second preset speed;

[0013] S4, contacting the kneading rollers with the surface of the winding core and applying a predetermined pressure;

[0014] S5, continuously kneading the surface of the winding core for a preset time.

[0015] Preferably, the first preset speed is 40-80 rpm, and the second preset speed is 50-90 rpm.

[0016] Preferably, the predetermined pressure is 10-15 N / cm. 2 Preferably, the preset time is 1-10 s.

[0017] Preferably, the finished winding core is inserted into a winding needle coinciding with the axis of the winding core, and the winding core is rotated by driving the motor to control the rotation of the winding needle.

[0018] Preferably, the depth of the positioning slot is 1 / 4-1 / 2 of the diameter of the winding core.

[0019] Preferably, the kneading rollers are arranged in at least two, the at least two kneading rollers are arranged along the axis and the axis of each kneading roller coincides.

[0020] Preferably, the kneading rollers are smooth metal or plastic, the diameter of the kneading rollers is 30-40 mm, and the total length of the kneading rollers is equal to the length of the winding core.

[0021] Preferably, the method further comprises a step of pretreating the winding core in a vacuum drying box before the kneading treatment; the pretreatment temperature is 55-65℃, and the pretreatment time is 1-3 h.

[0022] Preferably, the method further comprises a cooling and setting step after the kneading treatment, wherein the winding core is placed in an environment with a temperature of 25℃ and a relative humidity of ≤30% for cooling for 10-30 min.

[0023] Preferably, the method further comprises applying ultrasonic vibration to the winding core during the kneading process, the frequency of the ultrasonic vibration is 20-40 kHz, and the power is 50-100 W.

[0024] Preferably, in step S5, the surface of the winding core is subjected to a multi-stage rubbing treatment, which includes three stages:

[0025] First stage: rubbing continuously for 1-3 s at a pressure of 5-8 N / cm 2 and a speed of 80-90 rpm;

[0026] Second stage: rubbing continuously for 2-6 s at a pressure of 10-13 N / cm 2 and a speed of 50-60 rpm;

[0027] Third stage: rubbing continuously for 1-3 s at a pressure of 15-18 N / cm 2 and a speed of 30-40 rpm.

[0028] Preferably, the process further comprises a step of subjecting the surface of the winding core to plasma treatment after the rubbing is completed, wherein the plasma treatment uses oxygen plasma and the treatment time is 20-60 s.

[0029] Compared with the prior art, the present application has at least the following beneficial effects:

[0030] 1) The present application achieves uniform rubbing treatment of the surface of the winding core by horizontally placing the winding core and controlling its rotation in combination with the rubbing roller rotating in the opposite direction; this method can effectively reduce the tightness of the winding core, increase the internal voids, and significantly improve the wettability of the electrolyte without affecting the stability of the structure of the winding core.

[0031] 2) The contact of the rubbing roller with the surface of the winding core and the predetermined pressure applied can accurately control the rubbing strength and avoid damage to the winding core; the continuous rubbing for a predetermined time ensures the consistency and controllability of the treatment, which is conducive to quality control in batch production. DETAILED DESCRIPTION

[0032] The technical solutions of the present application will be described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0033] The present application provides a processing technology for improving the wettability of a cylindrical battery core, which comprises the following steps:

[0034] S1. Winding core positioning: horizontally placing the completed winding core in a positioning jig with a positioning groove; the positioning jig is made of high-strength engineering plastic, and the depth of the positioning groove is 1 / 4-1 / 2 of the diameter of the winding core, so as to ensure that the winding core is stably placed and has sufficient surface exposed to the rubbing roller.

[0035] S2. Core rotation: control the core to rotate around its axis at a first preset speed; insert the core into the winding needle coinciding with its axis, and rotate the core by driving the winding needle to rotate through the motor, wherein the motor can be a precision stepper motor, and the rotation speed can be accurately adjusted to adapt to different specifications of the core;

[0036] S3. Rubbing roller setting: one or more rubbing rollers are arranged above the core; the axis of the rubbing roller is parallel to the axis of the core, and is driven by an independent servo motor to rotate at a second preset speed in the direction opposite to the rotation direction of the core;

[0037] S4. Pressure application: make the rubbing roller contact the surface of the core and apply a predetermined pressure; the pressure can be adjusted by a precision pneumatic control system, and can be adjusted in real time according to the specifications of the core and the rubbing requirements.

[0038] S5. Continuous rubbing: rub the surface of the core for a preset time; the rubbing time can be accurately controlled by the PLC control system to ensure consistency in processing.

[0039] In an embodiment according to the application, the first preset speed is 40-80 rpm, and the second preset speed is 50-90 rpm. The rubbing effect can be ensured while the impact on the structure of the core is minimized.

[0040] In an embodiment according to the application, the predetermined pressure is 10-15 N / cm 2 , and the preset time is 1-10 s. The processing parameters are highly adaptable to different specifications of the core, which can ensure the rubbing effect and avoid excessive processing.

[0041] In an embodiment according to the application, the rubbing roller is provided with at least two rubbing rollers, the at least two rubbing rollers are arranged along the axis and the axis of each rubbing roller coincides. The setting of multiple rubbing rollers can process different parts of the core at the same time, improving the processing efficiency and uniformity.

[0042] In an embodiment according to the application, the rubbing roller is smooth metal or plastic, the diameter of the rubbing roller is 30-40 mm, and the total length of the rubbing roller is equal to the length of the core. The optimization of the material and size specifications of the rubbing roller ensures the stability of the rubbing process and the integrity of the surface of the core.

[0043] In an embodiment according to the application, it further comprises the step of pretreating the core in a vacuum drying box before rubbing treatment; the temperature of the pretreatment is 55-65℃, and the time is 1-3 h. The vacuum drying pretreatment step can remove the residual moisture in the core to create ideal conditions for subsequent rubbing treatment.

[0044] In one embodiment of this application, a cooling and shaping step is further included after kneading, wherein the core is placed in an environment with a temperature of 25°C and a relative humidity of ≤30% for 10–30 minutes to cool. The cooling and shaping step helps stabilize the core structure and prevents the rebound effect after kneading.

[0045] In one embodiment according to this application, the process further includes applying ultrasonic vibration to the core during the kneading process. The frequency of the ultrasonic vibration is 20–40 kHz, and the power is 50–100 W. The introduction of ultrasonic vibration can further promote the relaxation of the internal structure of the core and enhance the kneading effect.

[0046] In one embodiment of this application, in step S5, the surface of the core is subjected to a multi-stage rubbing process, which includes three stages:

[0047] Phase 1: Applying a pressure of 5-8 N / cm 2 Knead continuously for 1-3 seconds at a speed of 80-90 rpm.

[0048] Second stage: Using a pressure of 10-13 N / cm 2 Knead continuously for 2-6 seconds at a speed of 50-60 rpm.

[0049] Third stage: Using a pressure of 15-18 N / cm 2 Knead continuously for 1-3 seconds at a speed of 30-40 rpm.

[0050] Among them, the multi-stage kneading process gradually increases pressure and decreases speed, achieving progressive relaxation from the surface to the deep layers, which is more conducive to maintaining the overall structure of the core.

[0051] In one embodiment of this application, the process further includes a step of plasma treatment of the core surface after kneading. The plasma treatment uses oxygen plasma and lasts for 20-60 seconds. Plasma treatment can improve the affinity of the core surface and further enhance the wetting effect of the electrolyte.

[0052] In summary, this invention, through a meticulously designed kneading process combined with multiple optimization measures, effectively reduces the core compactness and increases internal porosity without affecting the core structure's stability. This method not only improves the wettability of the electrolyte but also offers advantages such as ease of operation, strong adaptability, and high controllability.

[0053] The implementation and advantages of this application will be further explained below with reference to specific embodiments.

[0054] Example 1

[0055] The embodiment provides a processing technology for improving the wettability of a cylindrical battery cell, and comprises the following steps.

[0056] S1. The wound core after winding is horizontally placed in a positioning jig with a positioning groove; the positioning jig is made of polytetrafluoroethylene, the depth of the positioning groove is 1 / 4 of the diameter of the wound core, so that the wound core is stably placed and has sufficient surface exposed to the kneading roller;

[0057] S2. The wound core is controlled to rotate at a speed of 60 rpm around its axis; the wound core is inserted into a winding needle coinciding with the axis of the wound core, and the wound core is rotated by driving the winding needle to rotate through a stepping motor;

[0058] S3. Three kneading rollers are arranged above the wound core, are arranged along the axis and have their axes coinciding with each other, the axes of the kneading rollers are parallel to the axis of the wound core, and the kneading rollers are driven by independent servo motors to rotate at a speed of 70 rpm in the direction opposite to the rotation direction of the wound core; wherein the kneading rollers are made of smooth stainless steel and have a diameter of 30 mm and a total length equal to the length of the wound core;

[0059] S4. The kneading rollers are brought into contact with the surface of the wound core and a pressure of 12 N / cm 2 is applied; the pressure is adjusted by a precise air pressure control system, so that the kneading effect is ensured and excessive extrusion deformation is avoided;

[0060] S5. The surface of the wound core is continuously kneaded for a preset time of 5 s; the kneading time is accurately controlled by a PLC control system, so that the consistency of the processing is ensured.

[0061] The wound core is formed by sequentially stacking and winding the positive plate, the diaphragm and the negative plate, and the wound core is fixed by using a tape after winding is completed; the positive plate comprises an aluminum foil and a positive active material layer arranged on the aluminum foil, the positive active material layer comprises 95wt% of a positive active material (NCM523), 2wt% of a conductive agent (ketjen black) and 3wt% of a binder (PVDF); the negative plate comprises a copper foil and a negative active material layer arranged on the copper foil, the negative active material layer comprises 95wt% of a negative active material (graphite), 2wt% of a conductive agent (conductive carbon black) and 3wt% of a binder (SBR); and the diaphragm is a polyolefin diaphragm with a thickness of 16 μm.

[0062] The wound core after processing is placed in an aluminum plastic film, packaged by using a heat sealing machine, and injected with a predetermined amount of electrolyte (1MLiPF6 EC / DMC / EMC = 1:1:1), so that a soft package cylindrical battery is obtained.

[0063] Embodiment 2

[0064] Different from example 1, in this embodiment, the core is put into a vacuum drying oven for pretreatment before the kneading treatment, the pretreatment temperature is 60℃, and the time is 2h. After the pretreatment, the core is taken out, and then the steps of example 1 are followed to perform the kneading treatment.

[0065] Example 3

[0066] Different from example 2, in this embodiment, the core is put into a vacuum drying oven for pretreatment before the kneading treatment, the pretreatment temperature is 60℃, and the time is 2h. After the pretreatment, the core is taken out, and then the steps of example 1 are followed to perform the kneading treatment.

[0067] Other than example 2, which will not be repeated here.

[0068] Example 4

[0069] Different from example 3, in this embodiment, the core is put into a vacuum drying oven for pretreatment before the kneading treatment, the pretreatment temperature is 60℃, and the time is 2h. After the pretreatment, the core is taken out, and then the steps of example 1 are followed to perform the kneading treatment.

[0070] Other than example 3, which will not be repeated here.

[0071] Example 5

[0072] Different from example 4, in this embodiment, in step S5, the surface of the core is subjected to multi-stage kneading treatment, which includes three stages:

[0073] First stage: continuous kneading for 2s at a pressure of 6N / cm 2 and a speed of 85rpm;

[0074] Second stage: continuous kneading for 4s at a pressure of 12N / cm 2 and a speed of 55rpm;

[0075] Third stage: continuous kneading for 2s at a pressure of 16N / cm 2 and a speed of 35rpm.

[0076] In the method, a large speed and a small pressure are used in the initial stage of the rubbing to quickly remove the protrusions on the surface of the winding core; a moderate speed and pressure are used in the middle stage of the rubbing to effectively reduce the overall tightness of the winding core; and a small speed and a large pressure are used in the later stage of the rubbing to finally flatten and shape the surface of the winding core, so that the best rubbing effect is obtained.

[0077] Other than the embodiment 4, the same as the embodiment 4 will not be repeated here.

[0078] Embodiment 6

[0079] Different from the embodiment 5, the embodiment 6 further comprises a step of performing plasma treatment on the surface of the winding core after the rubbing, and the plasma treatment uses oxygen plasma and the treatment time is 40s. The plasma treatment can improve the wettability of the surface of the winding core and further improve the infiltration effect of the electrolyte.

[0080] Other than the embodiment 5, the same as the embodiment 5 will not be repeated here.

[0081] Comparative example 1

[0082] The winding core is prepared by using a conventional winding process, and the winding core after winding is not subjected to rubbing treatment.

[0083] The cylindrical batteries prepared in the embodiments and the comparative example are subjected to the following electrochemical performance tests, and the test results are shown in Table 1.

[0084] 1. Electrolyte infiltration rate test:

[0085] 1) The treated winding core is injected with a predetermined amount of electrolyte in a vacuum environment;

[0086] 2) After standing for 24 hours, the winding core is taken out, and the actual absorbed electrolyte mass is measured by using a precision balance;

[0087] 3) Electrolyte infiltration rate = (actual absorbed electrolyte mass / theoretical maximum absorption) x 100%.

[0088] 2. First charge-discharge efficiency test:

[0089] 1) The treated winding core is assembled into a battery;

[0090] 2) A battery test system is used to perform the first charge-discharge at a rate of 0.1C;

[0091] 3) First charge-discharge efficiency = (first discharge capacity / first charge capacity) x 100%.

[0092] 3. Capacity retention rate test after 100 cycles:

[0093] 1) 100 charge-discharge cycles at 1C rate using battery test system;

[0094] 2) Record discharge capacity at 1st and 100th cycle;

[0095] 3) Capacity retention after 100 cycles = (discharge capacity at 100th cycle / discharge capacity at 1st cycle) x 100%.

[0096] 4) Rate capability (3C / 0.5C capacity ratio) test:

[0097] 1) First complete charge-discharge at 0.5C rate, record discharge capacity;

[0098] 2) Then complete charge-discharge at 3C rate, record discharge capacity;

[0099] 3) 3C / 0.5C capacity ratio = (discharge capacity at 3C rate / discharge capacity at 0.5C rate) x 100%.

[0100] The test results are shown in Table 1 below.

[0101] Table 1

[0102]

[0103] The test results of Table 1 are analyzed as follows:

[0104] 1. Comparative analysis of examples and comparative examples:

[0105] 1) Electrolyte impregnation rate: the electrolyte impregnation rate of Examples 1-6 ranges from 88% to 97%, while that of Comparative Example 1 is 76%; the impregnation rate of all examples is significantly higher than that of the comparative example.

[0106] 2) First charge-discharge efficiency: the first charge-discharge efficiency of Examples 1-6 ranges from 89% to 94%, while that of Comparative Example 1 is 82%; the first charge-discharge efficiency of all examples is higher than that of the comparative example.

[0107] 3) Capacity retention after 100 cycles: the capacity retention of Examples 1-6 ranges from 86% to 93%, while that of Comparative Example 1 is 79%; the capacity retention of all examples is higher than that of the comparative example.

[0108] 4) Rate capability: the 3C / 0.5C capacity ratio of Examples 1-6 is 80%-89%, while that of Comparative Example 1 is 71%; the rate capability of all examples is significantly better than that of the comparative example.

[0109] In summary, the battery prepared by the processing technology of the present application is obviously superior to the battery prepared by the conventional method without kneading treatment in various performance indexes, especially in the improvement of electrolyte impregnation rate and rate capability.

[0110] 2. Comparison analysis between each embodiment

[0111] 1) Electrolyte impregnation rate: from Example 1 to Example 6, the impregnation rate gradually increases, which is 88%, 91%, 93%, 95%, 96% and 97% respectively. With each optimization step, the impregnation rate is increased by about 2 percentage points on average.

[0112] 2) First charge-discharge efficiency: from Example 1 to Example 6, the first charge-discharge efficiency gradually increases, which is 89%, 90%, 91%, 92%, 93% and 94% respectively. With each optimization step, the efficiency is increased by about 1 percentage point on average.

[0113] 3) Capacity retention rate after 100 cycles: from Example 1 to Example 6, the capacity retention rate gradually increases, which is 86%, 88%, 90%, 91%, 92% and 93% respectively. With each optimization step, the capacity retention rate is increased by about 1.5 percentage points on average.

[0114] 4) Rate capability: from Example 1 to Example 6, the 3C / 0.5C capacity ratio gradually increases, which is 80%, 82%, 84%, 86%, 87% and 89% respectively. With each optimization step, the rate capability is increased by about 2 percentage points on average.

[0115] In summary, there is an obvious synergistic effect between each optimization step. With the increase of optimization steps, each performance index shows a steady upward trend. Among them, the improvement of electrolyte impregnation rate and rate capability is the most significant, indicating that the processing technology of the present application is particularly effective in improving electrolyte distribution and increasing electrode material utilization.

[0116] It should be noted that the contents not described in detail in the present specification belong to the prior art known to those skilled in the art, which will not be described here.

[0117] Based on the disclosure and teaching of the above description, those skilled in the art of the present application can also make changes and modifications to the above embodiments. Therefore, the present application is not limited to the above specific embodiments, and any obvious improvements, replacements or modifications made by those skilled in the art based on the present application all belong to the protection scope of the present application. In addition, although some specific terms are used in the present specification, these terms are only for convenience of description and do not constitute any limitation on the present application.

Claims

1. A processing technology for improving the wettability of cylindrical battery cells, characterized in that, Includes the following steps: S1. Place the wound core horizontally in a positioning fixture with a positioning groove; S2. Control the winding core to rotate around its axis at a first preset speed, wherein the first preset speed is 40~80 rpm; S3. One or more kneading rollers are arranged above the core, the axis of the kneading rollers is parallel to the axis of the core, and the kneading rollers are controlled to rotate at a second preset speed in the opposite direction to the rotation direction of the core, the second preset speed being 50~90 rpm; S4. Make the kneading rollers contact the surface of the core and apply a predetermined pressure, the predetermined pressure being 10~15 N / cm²; S5. Perform a multi-stage kneading process on the surface of the core, the multi-stage kneading process including three stages: First stage: Use a pressure of 5-8 N / cm² and a speed of 80-90 rpm to knead continuously for 1-3 seconds; Second stage: Use a pressure of 10-13 N / cm² and a speed of 50-60 rpm to knead continuously for 2-6 seconds; Third stage: Use a pressure of 15-18 N / cm² and a speed of 30-40 rpm to knead continuously for 1-3 seconds.

2. The processing technology for improving the wettability of cylindrical battery cells according to claim 1, characterized in that: The kneading rollers are provided in at least two, and the at least two kneading rollers are arranged at intervals along the axis, and the axes of each kneading roller coincide.

3. The processing technology for improving the wettability of cylindrical battery cells according to claim 1, characterized in that: The kneading roller is made of smooth metal or plastic, with a diameter of 30-40 mm, and the total length of the kneading roller is equal to the length of the core.

4. The processing technology for improving the wettability of cylindrical battery cells according to claim 1, characterized in that: It also includes a step of pre-treating the core in a vacuum drying oven before the kneading process; the pre-treatment temperature is 55~65℃ and the time is 1~3h.

5. The processing technology for improving the wettability of cylindrical battery cells according to claim 1, characterized in that: It also includes a cooling and shaping step after kneading, in which the core is placed in an environment with a temperature of 25°C and a relative humidity of ≤30% for 10~30 minutes to cool.

6. The processing technology for improving the wettability of cylindrical battery cells according to claim 1, characterized in that: It also includes applying ultrasonic vibration to the core during the kneading process, wherein the frequency of the ultrasonic vibration is 20~40 kHz and the power is 50~100 W.

7. The processing technology for improving the wettability of cylindrical battery cells according to claim 1, characterized in that: It also includes a step of plasma treatment on the surface of the core after kneading, wherein the plasma treatment uses oxygen plasma and the treatment time is 20-60 seconds.

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