Manufacturing method for inhibiting wrinkles of pole piece and pole piece
Through the collaborative design of gradient temperature field and dynamic viscosity control, combined with pulse drying and real-time feedback correction, the wrinkle problem of lithium-ion battery electrode coating was solved, battery performance and production efficiency were improved, and additional costs were avoided.
Patent Information
- Application Number
- CN202510574629.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-06
- Publication Date
- 2025-09-19
AI Technical Summary
In the existing technology of lithium-ion battery electrode manufacturing, wrinkle defects are prone to appear on the coating surface, resulting in increased contact impedance and decreased battery performance, and existing improvement methods affect production efficiency or increase costs.
The method of gradient temperature field, dynamic viscosity matching control, pulsed curing locking and defect feedback correction is adopted. Through non-uniform temperature field, real-time viscosity monitoring and surface tension control, combined with pulse hot air and infrared radiation drying, uniform curing and stability of the coating are achieved.
It effectively suppresses coating wrinkle defects, improves the surface quality and production consistency of the electrode, maintains production efficiency and avoids additional costs, and significantly improves the electrochemical performance of the battery.
Smart Images
Figure CN120662518A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of battery pole piece preparation, and in particular relates to a production method and a pole piece for suppressing wrinkles on the pole piece. Background Art
[0002] Lithium-ion batteries are core energy storage devices in the new energy sector. The quality of their electrode manufacturing is directly related to the electrochemical performance and safety of the battery. In the electrode coating process, wrinkle defects on the coating surface are a long-standing technical problem in this field. Specifically, the surface of the active material coating after drying appears to have irregular wrinkles similar to orange peel (such as Figure 1 This phenomenon not only affects the apparent quality of the electrode, but also increases the contact impedance between the electrode material and the current collector, leading to serious problems such as battery cycle capacity attenuation and decreased thermal stability.
[0003] Traditional theoretical research suggests that wrinkle defects primarily arise from two factors: First, during the drying process of the wet film after coating, solvent evaporation creates a temperature gradient between the surface and bottom layers of the slurry. This Marangoni effect triggers internal convection within the slurry, leading to turbulent streaks on the coating surface. Second, excessively rapid drying rates can cause the slurry to solidify prematurely before it has fully leveled, forming a solidification front characterized by surface tension imbalance. Industry statistics show that in current production processes, the defective rate of electrodes due to wrinkles generally remains at 8-15%, severely restricting the mass production efficiency of high-quality power batteries.
[0004] In the existing technology, the industry generally adopts two improvement solutions: the first is to control the drying process parameters, such as lowering the oven temperature and slowing down the transmission speed, so that the wet film maintains a longer leveling time. However, this method extends the drying time by more than 30%, resulting in a significant decrease in equipment production capacity, and it is difficult to adapt to new slurry systems with high solid content and high viscosity. The second improvement approach is to add high-boiling point solvents and fluorine-based surfactants to the slurry to suppress the convection effect by reducing the surface tension gradient. However, this method has obvious defects: residual additives will affect the interfacial stability of the electrode material and reduce the cycle life of the battery; at the same time, the introduction of special solvents increases the cost of the slurry and makes waste liquid treatment more difficult.
[0005] Therefore, there is an urgent need to develop a new process that can achieve precise suppression of wrinkle defects without affecting production efficiency or increasing material costs. Summary of the Invention
[0006] The purpose of the present invention is to provide a method for preventing wrinkles on a pole piece in order to address the deficiencies of the prior art and to effectively prevent wrinkles on the pole piece coating.
[0007] To achieve the above object, the present invention provides the following technical solutions:
[0008] A method for preventing wrinkles on a pole piece comprises the following steps:
[0009] S1. Gradient Temperature Field Construction: A non-uniform temperature field is established in the coating oven along the electrode transmission direction, so that the temperature gradient decreases with transmission distance; S2. Dynamic Viscosity Matching Control: The slurry viscosity μ is monitored in real time through an online viscosity sensor, and the temperature and wind speed of each section of the oven are dynamically adjusted according to the μ value; S3. Pulsed Curing Lock: When the coating surface tension γ drops to a preset threshold, a combined drying method of pulsed hot air and infrared radiation is initiated; S4. Defect Feedback Correction: Surface roughness Ra is detected online using a laser confocal microscope, and the gradient attenuation coefficient k is automatically adjusted based on the Ra value.
[0010] Furthermore, the temperature gradient distribution in step S1 satisfies the following relationship: ΔT(x) = T0- k·ln(x / x0+1) where: ΔT(x) represents the temperature value at a distance of x meters from the oven inlet, in °C; T0 is the initial temperature at the oven inlet, with a value range of 40°C≤T0≤50°C; k is the gradient attenuation coefficient, with a value range of 3°C≤k≤5°C; x is the coordinate of the electrode transmission direction, with a value of 0≤x≤L, and L is the total length of the oven, in m;
[0011] x0 is 1m.
[0012] Furthermore, the lateral wind speed distribution in step S1 satisfies: V(y) = Vmax [1 - (y / W)²] wherein: V(y) represents the wind speed at a distance of y meters from the center line of the nozzle, in units of m / s; Vmax is the maximum wind speed at the center of the nozzle, with a value range of 0.3m / s≤Vmax≤0.5m / s; W is the nozzle width, with a value of 1.1-1.2 times the width of the coating die head; y is the lateral coordinate, satisfying |y|≤W / 2.
[0013] Furthermore, the viscosity control in step S2 must satisfy the following equation: μ·τ = C, where μ is the real-time monitored slurry viscosity in mPa·s; τ is the leveling time in the range of 30s≤τ≤60s; and C is the material constant in the range of 1.5*10 5 mPa·s·s≤C≤3*10 5 mPa·s·s.
[0014] Furthermore, in step S3: the preset threshold is surface tension γ=20-25mN / m; the pulse hot air parameters include: temperature Tp=80-100℃, pulse frequency f=5-10Hz, pulse width Δt=0.5-2s; the infrared radiation parameters include: wavelength λ=3-5μm, power density Pd=1-3kW / m².
[0015] Furthermore, the adjustment strategy for the surface roughness Ra in step S4 is: when Ra>0.8μm, the gradient attenuation coefficient is corrected in real time according to k'=k[1+α(Ra / R0-0.8)]; where: k is the original gradient attenuation coefficient, k' is the corrected coefficient, α is the adjustment coefficient and 0.2≤α≤0.5,
[0016] R0 is 1μm.
[0017] Furthermore, the pulse hot air adopts an alternating mode: the first pulse stage: temperature T p1 =90-100℃ and wind speed V p1 =0.1-0.3m / s, duration t1; second pulse stage: temperature T p2 =70-80℃ and wind speed V p2 =1.5-2m / s, duration t2; the time ratio t1:t2=1:2~1:3.
[0018] Furthermore, step S2 also includes applying a directional magnetic field: the magnetic field strength B=0.1T-0.3T; the direction of the magnetic field is parallel to the transmission direction of the pole piece, so that the conductive particles are arranged along the leveling direction.
[0019] Furthermore, in step S4, the following model is used to predict the wrinkle defect probability P: P = 1 / [1 + e^{-(aμ+bk+cγ+d)}], where μ is the real-time viscosity value, bk is the gradient attenuation term, and cγ is the surface tension term; the coefficients satisfy: a = (0.05-0.1) / mPa·s, b = (0.3-0.5) / °C, c = (0.2-0.4) / mN / m, and d = -5 to -3;
[0020] Parameter adjustment is triggered when P ≥ 0.01.
[0021] Furthermore, the gradient temperature field is established by using a multi-section independent temperature control module, with the spacing between each temperature zone being 200-300mm and the temperature control accuracy being ±0.5°C.
[0022] Furthermore, the method further includes a pre-drying stage: the slurry is pre-dried at a vacuum degree of ≤100 Pa and a temperature of 55° C. for 3 hours before coating.
[0023] In addition, the present invention also provides a pole piece, which is manufactured by the above-mentioned manufacturing method for suppressing wrinkles on the pole piece.
[0024] Compared with the prior art, the present invention has at least the following beneficial effects:
[0025] 1) This invention utilizes a coordinated design of temperature and flow fields, mitigating differences in solvent evaporation rates through a non-uniform temperature field. Combined with dynamic viscosity matching control, this synchronizes slurry leveling and drying processes, avoiding convection effects caused by surface tension gradients. 2) This invention utilizes pulsed curing lock, initiating pulse drying at the critical value of the coating surface tension. This achieves a balance between efficient curing and structural stability through segmented control.
[0026] 3) The present invention adopts real-time feedback correction and a closed-loop control system based on laser confocal detection to correct process deviations in a timely manner, ensuring production consistency and improving yield.
[0027] 4) The invention effectively solves the wrinkle defect problem caused by uneven solvent volatilization in traditional processes through the synergistic effect of gradient temperature field control and dynamic adjustment mechanism, and significantly improves the surface quality of the coating without reducing production efficiency or introducing additives. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 Schematic diagram of the structure with wrinkle defects on the surface of the electrode. DETAILED DESCRIPTION
[0029] The following will clearly and completely describe the technical solutions of the present invention in conjunction with specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0030] According to a first aspect of the present application, the present application provides a method for preventing wrinkles from occurring on a pole piece, comprising the following steps:
[0031] S1. Gradient Temperature Field Construction: A non-uniform temperature field is established in the coating oven along the electrode transmission direction, so that the temperature gradient decreases with transmission distance; S2. Dynamic Viscosity Matching Control: The slurry viscosity μ is monitored in real time through an online viscosity sensor, and the temperature and wind speed of each section of the oven are dynamically adjusted according to the μ value; S3. Pulsed Curing Lock: When the coating surface tension γ drops to a preset threshold, a combined drying method of pulsed hot air and infrared radiation is initiated; S4. Defect Feedback Correction: Surface roughness Ra is detected online using a laser confocal microscope, and the gradient attenuation coefficient k is automatically adjusted based on the Ra value.
[0032] In one embodiment of the present application, the temperature gradient distribution of step S1 satisfies the following relationship: ΔT(x) = T0 - k·ln(x / x0+1) wherein: ΔT(x) represents the temperature value at a distance of x meters from the oven inlet, in °C; T0 is the initial temperature of the oven inlet, with a value range of 40°C ≤ T0 ≤ 50°C; k is the gradient attenuation coefficient, with a value range of 3°C ≤ k ≤ 5°C; x is the coordinate of the pole piece transmission direction, with a value of 0 ≤ x ≤ L, and L is the total length of the oven, in m;
[0033] x0 is the reference distance, which is set to 1m, so that ln(x / x0+1) is a dimensionless value.
[0034] Among them, the high temperature at the inlet promotes initial leveling, and the low temperature at the outlet delays the final curing, so that the solvent evaporation rate gradually transitions smoothly along the transmission direction, avoiding sudden changes in surface tension caused by local rapid volatilization; the logarithmic temperature gradient can better adapt to the volatilization characteristics of different slurries compared to the linear gradient (for example, high-solid content slurry requires a more gradual temperature drop rate); the natural temperature drop trend reduces the demand for forced cooling and reduces equipment energy consumption.
[0035] In one embodiment of the present application, the lateral wind speed distribution in step S1 satisfies: V(y) = Vmax·[1 -(y / W)²] wherein: V(y) represents the wind speed at a distance of y meters from the center line of the nozzle, in m / s; Vmax is the maximum wind speed at the center of the nozzle, with a value range of 0.3m / s≤Vmax≤0.5m / s; W is the nozzle width, with a value of 1.1-1.2 times the width of the coating die head, in m; y is the lateral coordinate, in m, satisfying |y|≤W / 2.
[0036] Among them, the parabolic wind speed distribution ensures the uniformity of the lateral wind exposure of the coating, eliminates the problem of local over-drying in the edge area caused by excessive wind speed, and reduces the lateral thickness deviation to 1 / 3 of the traditional process.
[0037] In one embodiment of the present application, the viscosity control in step S2 must satisfy the following: μ·τ = C, where μ is the real-time monitored slurry viscosity in mPa·s; τ is the leveling time, with a value range of 30s≤τ≤60s; C is the material constant, with a value range of 1.5*10 5 mPa·s·s≤C≤3*10 5 mPa·s·s.
[0038] Among them, when the slurry viscosity increases, the leveling time is automatically shortened, overcoming the inefficiency of the traditional process of fixed leveling time and adapting to the high-viscosity slurry system; the temperature / wind speed is adjusted in real time through viscosity feedback to eliminate the fluctuation of wrinkle defects caused by batch differences; and the use of surfactants is avoided to eliminate the side effect of increased interfacial impedance.
[0039] Among them, the slurry composition of the present application can be a positive electrode slurry or a negative electrode slurry, for example: the positive electrode slurry composition can be: NCM811 (mass ratio 95%), conductive carbon black (mass ratio 2%), PVDF (mass ratio 3%), the solvent is NMP, and the solid content is 45%; the negative electrode slurry composition can be: graphite (mass ratio 95%), CMC (mass ratio 2%), SBR (mass ratio 3%), the solvent is deionized water, and the solid content is 50%.
[0040] In one embodiment of the present application, in step S3: the preset threshold is surface tension γ=20-25mN / m; the pulse hot air parameters include: temperature Tp=80-100°C, pulse frequency f=5-10Hz, pulse width Δt=0.5-2s; the infrared radiation parameters include: wavelength λ=3-5μm, power density Pd=1-3kW / m².
[0041] Among them, the surface tension threshold triggers the combined drying of pulsed hot air and infrared radiation; the pulsed hot air is started when the surface tension drops to the critical value to avoid leveling interruption caused by premature curing; high-temperature infrared radiation promotes the volatilization of the underlying solvent, and the high-speed pulse airflow carries away the residual solvent on the surface to achieve uniform curing of the entire coating; pulsed energy supply reduces hot air consumption by more than 30% compared with continuous drying.
[0042] In one embodiment of the present application, the adjustment strategy for the surface roughness Ra in step S4 is: when Ra>0.8μm, the gradient attenuation coefficient is corrected in real time according to k'=k[1+α(Ra / R0-0.8)]; where: k is the original gradient attenuation coefficient, k' is the corrected coefficient, α is the adjustment coefficient and 0.2≤α≤0.5,
[0043] R0 is 1μm.
[0044] Among them, through online monitoring of surface roughness Ra, process parameters can be corrected in a timely manner to avoid defect accumulation; automatic adjustment of the gradient coefficient k expands the process window and can accommodate slurry viscosity fluctuations of ±20%; it reduces the need for manual intervention and improves production continuity and consistency.
[0045] In one embodiment of the present application, the pulse hot air adopts an alternating mode: the first pulse stage: the temperature T p1 =90-100℃ and wind speed V p1 =0.1-0.3m / s, duration t1; second pulse stage: temperature T p2 =70-80℃ and wind speed V p2 =1.5-2m / s, duration t2; the time ratio t1:t2=1:2~1:3.
[0046] Among them, the slow deep drying in the first stage is combined with the rapid surface curing in the second stage, which not only ensures the full volatilization of the solvent inside the coating, but also prevents the surface from cracking, significantly improving the mechanical integrity of the electrode.
[0047] In one embodiment of the present application, step S2 further includes applying a directional magnetic field: magnetic field strength B=0.1T-0.3T; the direction of the magnetic field is parallel to the transmission direction of the pole piece, so that the conductive particles are arranged along the leveling direction.
[0048] Among them, the magnetic field drives the conductive agent (such as carbon black) to arrange along the leveling direction, forming a continuous conductive path, reducing the in-plane impedance of the electrode; the directional arrangement structure inhibits the tendency of the coating to crack during the cyclic charge and discharge process.
[0049] In one embodiment of the present application, the following model is used in step S4 to predict the wrinkle defect probability P: P = 1 / [1 + e^{-(aμ+bk+cγ+d)}], where: μ is the real-time viscosity value (mPa·s), k is the gradient attenuation coefficient (°C), and γ is the surface tension value (mN / m);
[0050] a is the viscosity influence coefficient, which characterizes the contribution of viscosity to defect formation and has a value range of (0.05-0.1) / mPa·s;
[0051] b is the temperature gradient influence coefficient, which characterizes the contribution of temperature gradient to defect suppression, and its value range is (0.3-0.5) / ℃;
[0052] c is the surface tension influence coefficient, which characterizes the contribution of surface tension to defect formation, and its value range is (0.2-0.4) / mN / m;
[0053] d is a bias term used to adjust the probability distribution, with a value range of -5 to -3;
[0054] Parameter adjustment is triggered when P ≥ 0.01.
[0055] Among them, through the coordinated prediction of multiple parameters (μ, k, γ), the risk of wrinkle defects can be predicted in advance; compared with the traditional single threshold alarm, the adjustment instruction can be triggered 5-10 seconds in advance to achieve preventive control.
[0056] In one embodiment of the present application, the gradient temperature field is established using a multi-zone independent temperature control module, with each zone spaced 200-300mm apart and a temperature control accuracy of ±0.5°C. The modular temperature zone design allows for local temperature fine-tuning, flexibly adapting to different electrode sizes and avoiding end-of-line defects caused by temperature drift in long electrodes.
[0057] In one embodiment of the present application, the method further includes a pre-drying stage: the slurry is pre-dried at a vacuum level of ≤100 Pa and a temperature of 55°C for 3 hours before coating. Vacuum pre-drying removes bubbles from the slurry, reduces the formation of micropores during the drying process, reduces the porosity of the coating, and improves the electrode compaction density.
[0058] According to the second aspect of the present application, the present application further provides a pole piece, which is manufactured by the above-mentioned manufacturing method for suppressing wrinkles on the pole piece.
[0059] The implementation and advantages of this application will be further explained below with reference to specific embodiments.
[0060] Example 1
[0061] This embodiment provides a method for preventing wrinkles on a pole piece, comprising the following steps:
[0062] Step S1: Gradient temperature field construction
[0063] 1) Equipment configuration: Use a zoned independent temperature-controlled oven (e.g., length L = 20m, divided into 20 temperature zones, each zone 1m), and each temperature zone is equipped with a PID temperature control module (accuracy ±0.5°C).
[0064] 2) Temperature setting: Set the temperature of each zone according to the formula ΔT(x)=T0−k·ln(x / x0+1):
[0065] The inlet temperature T0 = 45°C and the gradient attenuation coefficient k = 4°C.
[0066] Example temperature distribution: ;
[0067] 3) Transverse wind speed control: Nozzle width W = 0.46m (coating die width 0.4m × 1.15), center wind speed Vmax = 0.4m / s. The transverse wind speed distribution V(y) = 0.4 × [1 − (y / 0.46)^2] (when W = 0.46m, y∈[-0.23m, 0.23m]) is adjusted by the variable frequency fan.
[0068] Step S2: Dynamic viscosity matching control
[0069] 1) Viscosity Monitoring: An online rotational viscometer (Brookfield DV2T) was installed at the coating die outlet to collect real-time slurry viscosity μ (range 3000-8000 mPa·s). The slurry composition was: NCM811 (95% by mass), conductive carbon black (2% by mass), PVDF (3% by mass), the solvent was NMP, and the solids content was 45%.
[0070] 2) Leveling time control: Dynamically adjust the transmission speed v=L / τ through the PLC controller to ensure μ·τ=2*10 5 mPa·s·s:
[0071] When μ=5000mPa·s, τ=2*10 5 / 5000=40s→Transmission speed v=20m / 40s=0.5m / s;
[0072] When μ=4000mPa·s, τ=2*10 5 / 4000=50s→v=20m / 50s=0.4m / s.
[0073] 3) Magnetic field assistance: A NdFeB permanent magnet array is installed above the coating area with a magnetic field strength of B = 0.2T and the direction of the magnetic field is parallel to the transmission direction of the pole piece.
[0074] Step S3: Pulse curing and locking
[0075] 1) Surface tension monitoring: A pendant drop surface tensiometer (Krüss DSA100) was used, and pulse drying was triggered when γ dropped to 22 mN / m.
[0076] 2) Pulse parameters:
[0077] The first stage (t1): temperature T p1 =95℃, wind speed V p1 =0.2m / s, duration t1=2s;
[0078] The second stage (t2): temperature T p2 =75℃, wind speed V p2 =1.8m / s, duration t2=4s (t1:t2=1:2);
[0079] 3) Infrared radiation: medium-wave infrared heater (wavelength 4μm) with a power density of 2kW / m² and a phase difference of 1 / 3 cycle with the hot air pulse.
[0080] Step S4: Defect feedback and correction
[0081] 1) Online detection: A Keyence VK-X300 laser confocal microscope with a sampling frequency of 10 Hz was used to detect the surface roughness Ra.
[0082] 2) Parameter adjustment: When Ra>0.8μm:
[0083] Gradient decay coefficient update: k'=k×[1+0.35(Ra / R0−0.8)].
[0084] 3) Defect probability prediction: The model P=1 / [1+e^{-(0.08μ+0.4k+0.3γ-4)}] is used to calculate the defect risk in real time. When P≥0.01, parameter adjustment is automatically triggered.
[0085] Examples 2-3
[0086] The difference from Example 1 is that the parameters are adjusted differently, see Table 1 below for details.
[0087] Table 1 ;
[0088] The rest is the same as in Example 1 and will not be described again here.
[0089] Comparative Examples 1-3
[0090] Among them, comparative example 1 adopts conventional process, and specific parameters are shown in Table 2;
[0091] Among them, Comparative Example 2 adopts a pulse-free step, and the specific parameters are shown in Table 2;
[0092] Among them, Comparative Example 3 adopts a step without a magnetic field, and the specific parameters are shown in Table 2.
[0093] Table 2 ;
[0094] The rest is the same as in Example 1 and will not be described again here.
[0095] The following performance tests were performed on the pole pieces prepared in the above embodiment and comparative example, respectively. The test results are shown in Tables 3 to 5.
[0096] 1. Wrinkle defect rate test:
[0097] 1) Test equipment:
[0098] Keyence VK-X300 laser confocal microscope;
[0099] Sample cutting machine (precision cutting accuracy ±0.1mm);
[0100] Image analysis software (Image-Pro Plus 6.0);
[0101] 2) Operation steps:
[0102] Sampling: At the 10th, 30th and 50th minutes of continuous electrode production, 1m long electrode samples were cut respectively;
[0103] Cutting: Cut each electrode into 10 pieces (10cm×10cm) evenly along the horizontal direction, for a total of 30 test samples;
[0104] Scan detection:
[0105] Laser wavelength: 408nm, objective lens magnification 50×;
[0106] Scanning step: 0.5μm, Z-axis resolution 0.01μm;
[0107] For each sample, five test areas were selected (center and four corners, area 1×1 cm²);
[0108] Data processing:
[0109] Set Ra>1μm as defect area;
[0110] Calculate the defect area ratio: Defect rate (%) = (number of defective pixels / total number of pixels) × 100;
[0111] The average of 30 samples is taken as the final result.
[0112] 2. Production efficiency test
[0113] 1) Test equipment:
[0114] Production line PLC data acquisition system;
[0115] Electronic timer (accuracy 0.01s);
[0116] Encoder tachometer;
[0117] 2) Operation steps:
[0118] Speed calibration:
[0119] Use an encoder to measure the transfer roller speed n (rpm);
[0120] Calculate the linear velocity v=πDn / 1000, where D is the roller diameter (preset D=200mm);
[0121] Run the test continuously:
[0122] The production line runs continuously for 8 hours, and the effective production time is recorded (excluding the time for reel change and downtime due to failure);
[0123] Calculate the total length of qualified pole pieces L (m);
[0124] Efficiency calculation:
[0125] Production speed = L / (8×60) (unit: m / min);
[0126] Output efficiency = production speed × pass rate × 60;
[0127] Pass rate = number of qualified sampling tests / total number of samples × 100% (sampling once every 30 minutes).
[0128] 3. Electrochemical performance test
[0129] 1) Test equipment:
[0130] BluePower CT3001A battery test system;
[0131] Glove box (water oxygen value ≤ 0.1ppm);
[0132] Button battery mold (CR2032);
[0133] 2) Battery assembly
[0134] Electrode processing: Punch the test electrode into Φ14mm discs (active material loading 12mg / cm²);
[0135] Counter electrode: Use metal lithium sheet (Φ16mm, thickness 0.5mm);
[0136] Electrolyte: 1M LiPF6 in EC:DMC:EMC=1:1:1 (volume ratio) + 2% VC additive;
[0137] Diaphragm: Celgard 2325;
[0138] 3) Test procedures
[0139] Chemical cycle:
[0140] 0.1C constant current charging to 4.3V, then switch to constant voltage charging until the current is ≤ 0.05C;
[0141] After standing for 5 minutes, discharge at 0.1C to 2.8V;
[0142] Cycle test:
[0143] 1C constant current charge and discharge, voltage window 2.8-4.3V;
[0144] Cycle 500 times and record the discharge capacity each time;
[0145] Capacity retention rate calculation:
[0146] Retention rate (%) = (500th capacity / 3rd capacity) × 100.
[0147] Table 3 Wrinkle defect rate test Group Defect rate (%) Ra average value (μm) Example 1 0.7 0.52 Example 2 0.4 0.48 Example 3 0.6 0.54 Comparative Example 1 12.3 1.85 Comparative Example 2 2.1 0.91 Comparative Example 3 1.8 0.89
[0148] Table 4 Production efficiency test ;
[0149] Table 5 Electrochemical performance test ;
[0150] The above test results are analyzed as follows:
[0151] 1. Comparative analysis between the embodiment and the comparative example:
[0152] 1) Wrinkle defect rate (Table 3):
[0153] The defect rate of the embodiment group is significantly lower than that of all the comparative examples, indicating that the gradient temperature field + dynamic regulation is the core of defect suppression.
[0154] The defect rate of comparative example 1 (constant temperature process) is as high as 12.3%, proving that the traditional process cannot solve the problem of uneven volatilization.
[0155] The defect rate of comparative example 2 (no pulse) is 2.1%, indicating that pulse locking is crucial to the quality of surface curing.
[0156] 2) Production efficiency (Table 4):
[0157] The output efficiency of Example 2 is as high as 4200 m / h, which is significantly higher than that of Comparative Example 1, reflecting the high efficiency of dynamic viscosity matching.
[0158] Although Comparative Example 2 adopts dynamic control, the qualified rate drops to 97.9% due to the lack of pulse curing.
[0159] 3) Cycling performance (Table 5):
[0160] The capacity retention rate of Example 2 is 94.1%, which is significantly improved compared with Comparative Example 1.
[0161] The retention rate of comparative example 3 (no magnetic field) was 89.2%, proving that the magnetic field assisted in optimizing the electrode conductive network.
[0162] 2. Comparative Analysis between Examples
[0163] 1) Gradient attenuation coefficient k:
[0164] Example 2 (k = 4) has the lowest defect rate (0.4%), which is better than k = 3 and k = 5, indicating that k = 4 ° C is the best balance point.
[0165] 2) Pulse time ratio:
[0166] Example 2 (1:2.5) has a higher output efficiency than Example 1 (1:2) (4200 vs. 3900 m / h), indicating that appropriately extending the low-temperature stage can improve drying uniformity.
[0167] 3) Magnetic field strength:
[0168] The cycle retention rate of Example 3 (0.3 T) is slightly lower than that of Example 2 (0.2 T), suggesting that an excessively strong magnetic field may cause agglomeration of the conductive particles.
[0169] It should be noted that the contents not described in detail in this specification belong to the existing technology well known to professional and technical personnel in this field and will not be repeated here.
[0170] Based on the disclosure and teachings of the above description, those skilled in the art will be able to make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the above specific embodiments. Any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention fall within the scope of protection of the present invention. In addition, although certain specific terms are used in this description, these terms are only for convenience of description and do not constitute any limitation to the present invention.
Claims
1. A method for suppressing wrinkles on a pole piece, characterized in that: The following steps are involved: S1. Gradient Temperature Field Construction: A non-uniform temperature field is established in the coating oven along the electrode transport direction, causing the temperature to decrease gradually with transport distance. S2. Dynamic Viscosity Matching Control: The slurry viscosity μ is monitored in real time using an online viscosity sensor, and the temperature and air speed of each oven section are dynamically adjusted based on the μ value. S3. Pulse Curing Lock: When the coating surface tension γ drops to a preset threshold, pulsed hot air and infrared radiation combined drying is initiated. S4. Defect feedback correction: Use a laser confocal microscope to measure the surface roughness Ra online and automatically adjust the gradient attenuation coefficient k based on the Ra value.
2. The method for suppressing wrinkles on an electrode according to claim 1, characterized in that: The temperature gradient distribution in step S1 satisfies the following relationship: ΔT(x) = T0- k·ln(x / x0+1) Where: ΔT(x) represents the temperature value at a distance of x meters from the oven inlet, in °C; T0 is the initial temperature at the oven inlet, ranging from 40°C ≤ T0 ≤ 50°C; k is the gradient attenuation coefficient, ranging from 3°C ≤ k ≤ 5°C; x is the coordinate of the electrode transmission direction, ranging from 0 ≤ x ≤ L, L is the total length of the oven, in meters; x0 is 1m.
3. The manufacturing method for suppressing wrinkles on an electrode according to claim 1, characterized in that: The lateral wind speed distribution in step S1 satisfies: V(y) = Vmax [1 - (y / W)²], wherein: V(y) represents the wind speed at a distance of y meters from the center line of the nozzle, in m / s; Vmax is the maximum wind speed at the center of the nozzle, with a value range of 0.3m / s≤Vmax≤0.5m / s; W is the nozzle width, which is 1.1-1.2 times the width of the coating die head; y is the lateral coordinate, satisfying |y|≤W / 2.
4. The manufacturing method for suppressing wrinkles on an electrode according to claim 1, characterized in that: In step S2, the viscosity control must satisfy the following: μ·τ = C, where μ is the real-time monitored slurry viscosity in mPa·s; τ is the leveling time, with a range of 30s≤τ≤60s; and C is the material constant, with a range of 1.5*10 5 mPa·s·s≤C≤3*10 5 mPa·s·s.
5. The manufacturing method for suppressing wrinkles on an electrode according to claim 1, characterized in that: In step S3: the preset threshold is surface tension γ=20-25 mN / m; Pulse hot air parameters include: temperature Tp = 80-100 ° C, pulse frequency f = 5-10 Hz, pulse width Δt = 0.5-2s; infrared radiation parameters include: wavelength λ = 3-5 μm, power density Pd = 1-3 kW / m².
6. The manufacturing method for suppressing wrinkles on an electrode according to claim 1, characterized in that: The adjustment strategy for the surface roughness Ra in step S4 is: when Ra>0.8μm, the gradient attenuation coefficient is corrected in real time according to k'=k[1+α(Ra / R0-0.8)]; where: k is the original gradient attenuation coefficient, k' is the corrected coefficient, α is the adjustment coefficient and 0.2≤α≤0.5, and R0 is 1μm.
7. The manufacturing method for suppressing wrinkles on an electrode according to claim 1, characterized in that: The gradient temperature field is established by using a multi-section independent temperature control module, with the spacing between each temperature zone being 200-300mm and the temperature control accuracy being ±0.5°C.
8. The manufacturing method for suppressing wrinkles on an electrode according to claim 1, characterized in that: The pulse hot air adopts an alternating mode: the first pulse stage: temperature T p1 =90-100℃ and wind speed V p1 =0.1-0.3m / s, duration t1; second pulse stage: temperature T p2 =70-80℃ and wind speed V p2 =1.5-2m / s, duration t2; the time ratio t1:t2=1:2~1:
3.
9. The manufacturing method for suppressing wrinkles on an electrode according to claim 1, characterized in that: Step S2 also includes applying a directional magnetic field: the magnetic field strength is B = 0.1T~0.3T; the direction of the magnetic field is parallel to the transmission direction of the pole piece, so that the conductive particles are arranged along the leveling direction.
10. A pole piece, characterized in that: The electrode is manufactured by the method for suppressing wrinkles on the electrode according to any one of claims 1 to 9.