A periodic microstructure pole piece based on microwave drying and a preparation method and application thereof

Abstract

This invention relates to the field of lithium-ion battery technology, and more particularly to a periodic microstructured electrode based on microwave drying, its preparation method, and its application. By introducing standing wave vibration and selective microwave heating during the electrode slurry drying process, a controllable, periodic peak-valley microstructure is constructed on the electrode surface. Precise control of the microstructure is achieved by controlling the vibration frequency, power, and slurry coating thickness. The periodic peak-valley structure constructs short-range, directional, and highly interconnected ion transport channels within the electrode, improving the ion transport efficiency and electrochemical reaction uniformity of thick electrodes, reducing interfacial impedance, and achieving a synergistic breakthrough in high load and high rate performance, thus driving the development of high-energy-density batteries towards high-power-density.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a periodic microstructure electrode based on microwave drying, its preparation method, and its application. Background Technology

[0002] With the rapid development of electric vehicles, energy storage systems, and portable electronic devices, the demand for high-energy-density and high-power-density lithium-ion batteries is becoming increasingly urgent. In battery design, increasing electrode thickness is one of the effective ways to improve energy density. Thick electrodes (usually referring to single-sided thicknesses exceeding 100 μm, or even 200 μm or more) can significantly increase the active material loading per unit area, thereby increasing the areal capacity of the battery without increasing its volume, which has significant engineering application value.

[0003] However, as electrode thickness increases, its performance under high-rate charge-discharge conditions significantly degrades, exhibiting problems such as increased polarization, poor rate capability, limited lithium-ion transport, and stress concentration within the electrode. Currently, strategies for improving the rate performance of thick electrodes mainly include: optimizing electrode structure design, such as gradient electrodes and porous structures; introducing functional conductive additives, such as carbon nanotubes and graphene; regulating the binder system; and developing novel electrolytes to improve ionic conductivity. However, existing technologies still have the following shortcomings: most structural designs struggle to balance high load capacity and high rate performance, often sacrificing rate response while increasing areal capacity; and the construction of conductive networks often relies on high amounts of conductive agents, leading to an increase in the proportion of inactive components in the electrode, which in turn reduces energy density.

[0004] Therefore, there is an urgent need to develop a thick electrode rate performance enhancement technology to achieve a synergistic breakthrough in high load and high rate performance, providing key technical support for the development of next-generation high energy density and high power density lithium-ion batteries. Summary of the Invention

[0005] In view of this, the present invention proposes a periodic microstructured electrode based on microwave drying, its preparation method, and its application. By introducing standing wave vibration and microwave selective heating during the electrode slurry drying process, a controllable, periodic peak-valley microstructure is constructed on the electrode surface. Utilizing the rapid heating of the microwave body and the directional effect of the standing wave disturbance, the structural shaping of the slurry in the semi-drying stage is completed in a very short time, avoiding common problems in traditional drying such as cracking, unevenness, and sedimentation. The periodic peak-valley structure constructs short-range, directional, and highly interconnected ion transport channels inside the electrode, fundamentally solving the bottleneck problems of limited ion diffusion and poor electrolyte wetting in thick electrodes.

[0006] The technical solution of this invention is implemented as follows: In a first aspect, the present invention provides a method for preparing periodic microstructured electrodes based on microwave drying, comprising the following steps: S1, the slurry is uniformly coated on one side of the current collector to obtain the electrode sheet; S2, the electrode is fixed in a microwave drying device, which is equipped with a piezoelectric vibration exciter; S3, start the piezoelectric vibration exciter to form a standing wave on the electrode surface, and induce the slurry to form a periodic peak-valley structure; S4. Turn on the microwave drying equipment to heat the peak area. When the slurry is half dry, turn off the standing wave generator. After the electrode is dry, turn off the microwave drying equipment and cool it to obtain a periodic microstructure electrode.

[0007] Based on the above technical solutions, preferably, in step S1, the coating thickness is 100~500μm.

[0008] Based on the above technical solutions, preferably, the slurry includes a positive electrode slurry or a negative electrode slurry.

[0009] Based on the above technical solutions, preferably, the slurry comprises active substances, conductive agents, and binders.

[0010] The active material is LiFePO4, the conductive agent is conductive carbon black (SP), the binder is polyvinylidene fluoride (PVDF), and the mass ratio of the active material: conductive agent: binder is 90:5:5.

[0011] Based on the above technical solutions, preferably, the viscosity of the slurry is 2000~6000 mPa·s; more preferably, the viscosity of the slurry is 4500 mPa·s.

[0012] Based on the above technical solutions, preferably, in step S3, the frequency of the piezoelectric vibration exciter is 100~1000 kHz and the output power is 1~200 W.

[0013] Based on the above technical solutions, it is further preferred that the frequency of the piezoelectric vibration exciter is 120~600 kHz and the output power is 10~200 W; even more preferably, the frequency of the piezoelectric vibration exciter is 200 kHz and the output power is 100 W.

[0014] In this invention, the frequency of the piezoelectric vibration exciter is controlled to regulate the wavelength of the standing wave, thereby controlling the period of the formed microstructure; the output power of the piezoelectric vibration exciter is controlled to regulate the amplitude, thereby controlling the height of the microstructure peak, thus achieving precise, controllable and repeatable patterned design of the electrode microstructure, breaking through the limitations of traditional uniform coating.

[0015] Based on the above technical solutions, preferably, by changing the position of the standing wave generator and adjusting the direction of the standing wave, the standing wave is at a 90-degree angle to the coating direction.

[0016] Based on the above technical solutions, preferably, the wavelength of the standing wave is set to 1 to 10 times the coating thickness, that is, the corresponding microstructure period is 0.5 to 5 times the coating thickness; the amplitude of the standing wave is 0.1 to 0.45 times the coating thickness.

[0017] Based on the above technical solutions, a further preferred option is that the wavelength of the standing wave is set to 6 times the coating thickness, and the amplitude of the standing wave is 0.3 times the coating thickness.

[0018] Based on the above technical solutions, preferably, in step S3, the period of the periodic peak-trough structure is 0.5 to 5 times the coating thickness, and the peak height is 0.1 to 0.45 times the coating thickness.

[0019] Based on the above technical solutions, a further preferred embodiment is that the period of the periodic peak-trough structure is 3 times the coating thickness and the peak height is 0.3 times the coating thickness.

[0020] The final microstructure period and peaks correspond to the coating thickness, and the microstructure can be precisely controlled by adjusting the process parameters, resulting in excellent overall performance.

[0021] Based on the above technical solutions, preferably, in step S4, the viscosity of the slurry when it is semi-dry is 30000~50000 mPa·s.

[0022] After the standing wave stabilizes, microwave heating is activated to simultaneously solidify the slurry during morphology formation, achieving simultaneous vibration and solidification. When the slurry reaches a semi-dry state, the standing wave is turned off to prevent excessive disturbance to the initially solidified structure, while also avoiding the formation of dry zones and cracks, thereby improving the integrity of the structure.

[0023] In this step, microwave heating can adaptively heat the generated crest-valley microstructures. Based on the difference in dielectric loss between the crest and valley regions, microwaves selectively heat the crest region. The slurry concentration in the crest region can reach 1.2 to 1.8 times that of the original coating slurry, while the valley region may be as low as 50 to 60 wt% of the original slurry. This concentration difference originates from the hydrodynamic compression effect caused by standing waves, leading to slurry enrichment at the crest, resulting in a higher dielectric loss in the crest region than in the valley region. Microwave selective heating of the crest region utilizes local temperature rise differences to accelerate solvent evaporation, increase local viscosity, and suppress collapse. The slurry concentration in the valley region is low, resulting in low dielectric loss. Slow heating maintains a moderate degree of softness, preventing excessive drying that could lead to structural collapse. Microwave heating is intelligently coupled with the standing wave morphology, accelerating solvent evaporation in the crest region and slowly drying in the valley region, suppressing collapse and fusion, and achieving self-stabilizing curing of the periodic structure. The aforementioned slurry concentration refers to the total solid mass percentage of active materials, conductive agents, and binders per unit volume of slurry.

[0024] Based on the above technical solutions, a further preferred embodiment is that the viscosity of the slurry when semi-dry is 40000 mPa·s.

[0025] Based on the above technical solutions, preferably, in step S4, the heating temperature of the microwave drying equipment is 80~100℃; more preferably, the heating temperature of the microwave drying equipment is 90℃.

[0026] Secondly, a periodic microstructure electrode is provided, which is prepared by the microwave drying-based method for preparing periodic microstructure electrodes as described above.

[0027] Thirdly, the application of the periodic microstructure electrode as described above in the preparation of lithium-ion batteries is provided.

[0028] Based on the above technical solutions, preferably, the periodic microstructure electrode sheet is subjected to a rolling process before being used to prepare a lithium-ion battery. The rolling process is carried out under the conditions of 10~30MPa pressure and 0.5~2 m / min speed for 2~3 rolling passes.

[0029] Based on the above technical solutions, a further optimized method is to perform two-stage rolling at a low pressure of 20MPa and a low speed of 1 m / min.

[0030] Unlike conventional rolling processes, multiple rolling processes are performed under low pressure and low speed to avoid damaging the already formed peak-valley microstructure.

[0031] The method for preparing periodic microstructured electrodes based on microwave drying of the present invention has the following advantages over the prior art: 1. By introducing a standing wave generator (such as a piezoelectric element or a tuning fork) during the microwave drying process, a periodic peak-valley structure is formed on the surface of the slurry using the standing wave, thereby achieving precise, controllable, and repeatable microstructure design of the electrode microstructure and breaking through the limitations of traditional uniform coating.

[0032] 2. By utilizing the difference in dielectric loss between the peak and trough regions of the microstructure, local selective heating can be achieved. Microwave heating is intelligently coupled with the standing wave morphology to achieve adaptive heating.

[0033] 3. After the standing wave stabilizes, microwave heating is activated to allow the slurry to solidify simultaneously during morphology formation, achieving simultaneous vibration and solidification. When the slurry reaches a semi-dry state, the standing wave is turned off to avoid disturbing the already formed framework and improve the stability of the structure.

[0034] 4. The peak-valley microstructure constructs short-range, directional ion transport channels inside the electrode, effectively shortening the diffusion distance of lithium ions in the solid phase. Especially under high-rate charge and discharge conditions, it significantly reduces diffusion resistance and improves ion transport efficiency. The microstructure increases the pore connectivity and tortuosity control capability inside the electrode, making it easier for the electrolyte to penetrate into the deep layers of the electrode and achieve uniform wetting, thereby reducing interfacial impedance and improving the uniformity of electrochemical reactions.

[0035] 5. Suitable for high-performance fabrication of thick electrodes: It is particularly suitable for the fabrication of high-load thick electrodes (single-sided thickness of 100~250μm or more), effectively solving key bottleneck problems such as limited ion / electron transport, stress concentration, and poor structural stability in thick electrodes, and promoting the development of high-energy-density batteries towards high-power-density. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the periodic microstructure of the present invention. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] All materials used in this invention are commercially available products.

[0040] Example 1 1. Prepare the slurry.

[0041] Weigh 0.5g of PVDF powder and add it to 7.2 mL of NMP solvent. Stir at 600 rpm for 45 minutes to completely dissolve the PVDF and obtain a homogeneous solution. Then add 0.5g of conductive carbon black and continue stirring for 30 minutes to initially disperse the conductive agent. Then add 9g of LiFePO4 in batches, stirring for 10 minutes after each batch to ensure that the active powder is fully wetted, and obtain a mixed slurry. Then ball mill and shear mix the mixed slurry for later use. At this time, the viscosity of the slurry is about 4500 mPa·s.

[0042] 2. The above slurry is uniformly coated on one side of an aluminum foil to a thickness of 150 μm. The two ends of the electrode are fixed to a piezoelectric vibration device. The frequency of the piezoelectric vibration device is set to 200 kHz, the output power to 100 W, and the phase difference to 90°. The period of the resulting microstructure is preset to be 3 times the coating thickness (i.e., 450 μm), and the amplitude is controlled to be 0.3 times the coating thickness (i.e., 45 μm). Stabilization is performed for 5 minutes. Periodic peaks (high concentration areas) and troughs (low concentration areas) form a microstructure on the slurry surface. A schematic diagram of the microstructure is shown below. Figure 1 As shown.

[0043] 3. Selective microwave heating: With the standing wave stable, turn on the microwave drying equipment. The microwave frequency is 2.45 GHz, the output power is 300 W, the microwave heating temperature is 90℃, and the heating time is 1.5 minutes. At this time, the slurry reaches a semi-dry state (viscosity of about 40,000 mPa·s), and a microporous structure is initially formed at the peak of the wave.

[0044] 4. Turn off the piezoelectric vibration exciter (standing wave generator) to stop the standing wave disturbance. Continue heating with the microwave drying equipment for 1 minute to completely dry the electrode. Remove the electrode and cool it to room temperature to obtain a positive electrode with a periodic microstructure.

[0045] The surface profile of the prepared positive electrode was scanned using a white-light interferometric profilometer. In the obtained cross-sectional profile curves, the horizontal distance between adjacent peaks and the vertical height difference between peaks and troughs were directly measured. The results showed that the electrode surface exhibited a periodic alternating peak and trough structure with a period of approximately 450 μm and a peak height of approximately 50 μm.

[0046] Example 2 1. Prepare the slurry.

[0047] Weigh 0.5g of PVDF powder and add it to 8.5 mL of NMP solvent. Stir at 600 rpm for 45 minutes to completely dissolve the PVDF and obtain a homogeneous solution. Then add 0.5g of conductive carbon black and continue stirring for 30 minutes to initially disperse the conductive agent. Then add 9g of LiFePO4 in batches, stirring for 10 minutes after each batch to ensure that the active powder is fully wetted, and obtain a mixed slurry. Then ball mill and shear mix the mixed slurry for later use. At this time, the viscosity of the slurry is about 2000 mPa·s.

[0048] 2. Coat the above slurry evenly on one side of the aluminum foil with a coating thickness of 100μm; fix both ends of the electrode to the piezoelectric vibration device, set the frequency of the piezoelectric vibration device to 300kHz, the output power to 10W, and the phase difference to 90°, so that the period of the formed microstructure is preset to 3 times the coating thickness (i.e., 300μm), the amplitude is controlled to 0.3 times the coating thickness (i.e., 30μm), and stabilize for 5 minutes.

[0049] 3. Selective microwave heating: With the standing wave stable, turn on the microwave drying equipment. The microwave frequency is 2.45 GHz, the output power is 300 W, the microwave heating temperature is 80℃, and the heating time is 1.5 minutes. At this time, the slurry reaches a semi-dry state (viscosity of about 30,000 mPa·s), and a microporous structure is initially formed at the peak of the wave.

[0050] 4. Turn off the piezoelectric vibration exciter (standing wave generator) to stop the standing wave disturbance. Continue heating with the microwave drying equipment for 1 minute to completely dry the electrode. Remove the electrode and cool it to room temperature to obtain a positive electrode with a periodic microstructure.

[0051] The surface profile of the prepared positive electrode was scanned using a white-light interferometric profilometer. The results showed that the electrode surface exhibited a periodic alternating structure of peaks and troughs, with a period of approximately 300 μm and a peak height of approximately 30 μm.

[0052] Example 3 1. Prepare the slurry.

[0053] Weigh 0.5g of PVDF powder and add it to 6.2 mL of NMP solvent. Stir at 600 rpm for 45 minutes to completely dissolve the PVDF and obtain a homogeneous solution. Then add 0.5g of conductive carbon black and continue stirring for 30 minutes to initially disperse the conductive agent. Then add 9g of LiFePO4 in batches, stirring for 10 minutes after each batch to ensure that the active powder is fully wetted, and obtain a mixed slurry. Then ball mill and shear mix the mixed slurry for later use. At this time, the viscosity of the slurry is about 6000 mPa·s.

[0054] 2. Coat the above slurry evenly on one side of the aluminum foil to a thickness of 500 μm; fix both ends of the electrode to the piezoelectric vibration device, set the frequency of the piezoelectric vibration device to 60 kHz, the output power to 200 W, and the phase difference to 90°, so that the period of the formed microstructure is preset to 3 times the coating thickness (i.e., 1500 μm), the amplitude is controlled to 0.3 times the coating thickness (i.e., 150 μm), and stabilize for 5 minutes.

[0055] 3. Selective microwave heating: With the standing wave stable, turn on the microwave drying equipment. The microwave frequency is 2.45 GHz, the output power is 300 W, the microwave heating temperature is 100℃, and the heating time is 2.5 minutes. At this time, the slurry reaches a semi-dry state (viscosity of about 50,000 mPa·s), and a microporous structure is initially formed at the peak of the wave.

[0056] 4. Turn off the piezoelectric vibration exciter (standing wave generator) to stop the standing wave disturbance. Continue heating with the microwave drying equipment for 1 minute to completely dry the electrode. Remove the electrode and cool it to room temperature to obtain a positive electrode with a periodic microstructure.

[0057] The surface profile of the prepared positive electrode was scanned using a white-light interferometric profilometer. The results showed that the electrode surface exhibited a periodic alternating structure of peaks and troughs, with a period of approximately 1500 μm and a peak height of approximately 150 μm.

[0058] Example 4 The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2, the frequency of the piezoelectric vibration device is set to 120 kHz. The results show that the electrode surface exhibits a periodic alternating structure of peaks and troughs, with a period of approximately 750 μm (5 times the coating thickness) and a peak height of approximately 50 μm.

[0059] Example 5 The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2, the frequency of the piezoelectric vibration device is set to 600 kHz. The results show that the electrode surface exhibits a periodic alternating structure of peaks and troughs, with a period of about 150 μm (1 time the coating thickness) and a peak height of about 50 μm.

[0060] Comparative Example 1 The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2, the frequency of the piezoelectric vibration device is set to 100 kHz. The results show that the electrode surface exhibits a periodic alternating structure of peaks and troughs, with a period of about 900 μm (6 times the coating thickness) and a peak height of about 50 μm.

[0061] Comparative Example 2 The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2, the frequency of the piezoelectric vibration device is set to 1000 kHz. The results show that the electrode surface exhibits a periodic alternating structure of peaks and troughs, with a period of about 90 μm (0.5 times the coating thickness) and a peak height of about 50 μm.

[0062] Example 6 The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2, the coating thickness is 100 μm. The results show that the electrode surface exhibits a periodic alternating structure of peaks and troughs, with a period of approximately 450 μm and a peak height of approximately 48 μm. At this point, the amplitude to coating thickness ratio is 0.45.

[0063] Example 7 The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2, the coating thickness is 300 μm. The results show that the electrode surface exhibits a periodic alternating structure of peaks and troughs, with a period of approximately 450 μm and a peak height of approximately 44 μm. At this point, the amplitude to coating thickness ratio is 0.15.

[0064] Example 8 The preparation method in this embodiment is basically the same as that in Example 1, except that in step 2, the coating thickness is 400 μm. The results show that the electrode surface exhibits a periodic alternating structure of peaks and troughs, with a period of approximately 450 μm and a peak height of approximately 41 μm. At this point, the amplitude to coating thickness ratio is 0.11.

[0065] Comparative Example 3 The preparation method of this comparative example is basically the same as that of Example 1, except that the coating thickness is 50 μm in step 2. The results show that although the electrode surface has a periodic structure, the peak height collapses significantly due to the large amplitude / thickness ratio (0.9), resulting in poor stability. The measured peak height is about 32 μm, and the period is still about 450 μm.

[0066] Comparative Example 4 The preparation method of this comparative example is basically the same as that of Example 1, except that in step 2, the coating thickness is 500 μm. The results show that although there is a periodic structure on the electrode surface, the peak height is significantly insufficient due to the small amplitude / thickness ratio (0.09). The measured peak height is about 30 μm, and the period is still about 450 μm.

[0067] Example 9 This embodiment is basically the same as Embodiment 1, except that the power of the piezoelectric vibration device is adjusted to 11W, that is, the amplitude is controlled at 0.1 times the coating thickness (i.e., 15μm). As a result, the microstructure has lower peaks and shallower troughs, but the structure is regular and without cracks.

[0068] Example 10 This embodiment is basically the same as Embodiment 1, except that the power of the piezoelectric vibration device is adjusted to 200W, that is, the amplitude is controlled at 0.45 times the coating thickness (i.e., 67.5μm). As a result, the peaks of the microstructure are higher, the top is slightly rough, and the troughs are deeper.

[0069] Comparative Example 5 This comparative example is basically the same as Example 1, except that the power of the piezoelectric vibration device was adjusted to 8W, that is, the amplitude was controlled at 0.08 times the coating thickness (i.e., 12μm). As a result, the peaks of the microstructure were not very obvious, and the troughs were almost indistinguishable.

[0070] Comparative Example 6 This comparative example is basically the same as Example 1, except that the power of the piezoelectric vibration device was adjusted to 220W, that is, the amplitude was controlled at 0.5 times the coating thickness (i.e., 75μm). As a result, the peaks were too high, obvious microcracks appeared, and some of the bottoms of the troughs peeled off.

[0071] Comparative Example 7 The preparation method of this comparative example is basically the same as that of Example 1, except that microwave heating was not used. Instead, after the peak-valley microstructure was induced by standing wave, the conventional hot air drying method was used for heating.

[0072] Application example: 1. The periodic microstructured electrode sheets prepared in the above examples and comparative examples were transferred to a rolling mill and rolled 2-3 times at a low pressure of 20 MPa and a low speed of 1 m / min. During the rolling process, flexible roller surfaces were used to avoid rigid contact. At the same time, the periodic microstructured electrode sheet prepared in Example 1 was rolled using a conventional rolling process at a pressure of 200 MPa, as Comparative Example 8.

[0073] 2. The positive electrode sheets from Examples 1-10 and Comparative Examples 1-8, after being rolled, were used as positive electrodes and assembled with negative electrode sheets, a separator, and an electrolyte to form a coin cell (CR2032). The negative electrode sheet was graphite, the electrolyte was a 1 mol / L LiPF6 solution, the solvent was a 1:1 volume ratio EC and DMC mixture, and the separator was Celgard 2500. After assembling the coin cells using conventional methods, performance testing was performed using the following methods: Rate performance: Charge and discharge tests were conducted at rates of 0.1C, 0.2C, 0.5C, 1C, 2C and 5C within the voltage range of 2.5~4.2V, and the discharge specific capacity of the last cycle at each rate was recorded.

[0074] Cycle performance: The battery was subjected to 500 charge-discharge cycles at 1C rate, and the capacity retention rate after the 500th cycle was recorded (based on the discharge capacity of the first cycle).

[0075] Electrochemical impedance spectroscopy (EIS): With the battery fully charged, EIS tests were performed using an electrochemical workstation at a frequency range of 0.01 Hz - 100 kHz and a perturbation voltage of 5 mV. The results are shown in Table 1.

[0076] Table 1 Performance data of lithium-ion batteries prepared with different electrodes

[0077] According to Table 1: 1.1C discharge specific capacity.

[0078] Examples 1-10: all were 150–158 mAh / g, close to about 90% of the theoretical value (170 mAh / g), indicating that the structure did not damage the utilization rate of active materials; Examples 1, 7, 8, and 10 were slightly higher because the microstructure improved ion / electron transport and enhanced the uniformity of electrochemical reactions; Comparative Examples 3, 4, 5, and 6: due to structural instability (collapse, cracks, improper amplitude), the utilization rate of active materials decreased, resulting in lower capacity; Comparative Example 7: without microwave heating, the structural stability was poor, but it still had good performance (similar to Example 1), indicating that the standing wave formation structure was effective; Comparative Example 8: conventional high-pressure rolling (200 MPa) damaged the microstructure, leading to a decrease in performance, verifying the necessity of the "low-pressure, low-speed rolling" of this invention.

[0079] 2. 2C / 0.1C Capacity Retention Rate (Rate Performance).

[0080] Rate performance is a key indicator reflecting the lithium-ion transport capability at high rates. Examples 1, 7, and 10 all have rate performance >80%, indicating that the microstructure significantly reduces diffusion resistance, facilitating high-rate charge and discharge. Examples 2, 4, 5, 6, and 8 have rate performance between 70% and 80%, with slightly off-center structural periods or amplitudes, resulting in moderate performance. Comparative Examples 1, 2, 3, 4, 5, 6, and 7 have rate performance <70%, especially Comparative Example 2 (too small a period) and Comparative Example 6 (too large an amplitude), showing significantly worse performance. Comparative Example 8 has a rate performance of only 60%, due to the destruction of the microstructure, resulting in a significant decrease in rate performance. It is evident that the more regular the periodic microstructure, the higher the peaks and the deeper the troughs, and the more stable the structure, the better the rate performance.

[0081] 3. Capacity retention rate after 500 cycles of 1C.

[0082] Examples 1, 7, and 10: Capacity retention >92%, indicating structural stability, uniform stress distribution, and resistance to cracking during cycling; Example 3: Despite its large thickness (500 μm), the structure remains intact, with a retention rate of 88%, superior to conventional thick electrodes; Comparative Examples 3, 4, 5, and 6: Numerous structural defects lead to easy collapse during cycling and rapid capacity decay; Comparative Example 8: Due to microstructure damage, cycling performance significantly decreased (82%). It is evident that microstructures can effectively alleviate stress concentration within thick electrodes and improve cycling stability.

[0083] 4. Charge transfer impedance Rct (EIS).

[0084] The smaller the Rct, the faster the charge transfer and the more efficient the interfacial reaction. Examples 1 and 10 have optimal Rct values ​​of 25–26 Ω due to strong conductive networks in the peak region and good electrolyte wetting. Examples 7 and 8 have Rct values ​​of 27–29 Ω, indicating good structure, but slightly weaker than the optimal value. Comparative Examples 1, 2, 3, 4, 5, 6, and 7 have Rct values ​​>35 Ω, especially Comparative Example 6 (microcracked) and Comparative Example 5 (weak structure), where Rct >60 Ω. Comparative Example 8 has an Rct value of 40 Ω, due to the disruption of the microstructure and increased interfacial impedance. Conclusion: Periodic microstructures reduce interfacial impedance and enhance reaction kinetics through short-range ion channels and uniform wetting.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing periodic microstructured electrodes based on microwave drying, characterized in that, Includes the following steps: S1, the slurry is uniformly coated on one side of the current collector to obtain the electrode sheet; S2, the electrode is fixed in a microwave drying device, which is equipped with a piezoelectric vibration exciter; S3, start the piezoelectric vibration exciter to form a standing wave on the electrode surface, and induce the slurry to form a periodic peak-valley structure; S4. Turn on the microwave drying equipment to heat the slurry until it is half dry, then turn off the standing wave generator. After the electrode is dry, turn off the microwave drying equipment and cool it to obtain a periodic microstructure electrode.

2. The method for preparing periodic microstructured electrodes based on microwave drying as described in claim 1, characterized in that: In step S1, the coating thickness is 100~500μm.

3. The method for preparing periodic microstructured electrodes based on microwave drying as described in claim 2, characterized in that: The slurry comprises active substances, conductive agents, and binders.

4. The method for preparing periodic microstructured electrodes based on microwave drying as described in claim 1, characterized in that: In step S3, the frequency of the piezoelectric vibration exciter is 100~1000 kHz and the output power is 1~200 W.

5. The method for preparing periodic microstructured electrodes based on microwave drying as described in claim 1, characterized in that: In step S3, the period of the periodic peak-trough structure is 0.5 to 5 times the coating thickness, and the peak height is 0.1 to 0.45 times the coating thickness.

6. The method for preparing periodic microstructured electrodes based on microwave drying as described in claim 1, characterized in that: In step S4, the viscosity of the slurry when it is semi-dry is 30,000~50,000 mPa·s.

7. The method for preparing periodic microstructured electrodes based on microwave drying as described in claim 1, characterized in that: In step S4, the heating temperature of the microwave drying equipment is 80~100℃.

8. A periodic microstructure electrode, characterized in that: It is prepared by the method for preparing periodic microstructured electrodes based on microwave drying as described in any one of claims 1 to 7.

9. The application of the periodic microstructure electrode as described in claim 8 in the preparation of lithium-ion batteries.

10. The application as described in claim 9, characterized in that: Before being used to prepare lithium-ion batteries, the periodic microstructured electrode is first subjected to a rolling process, which is carried out under the conditions of 10~30MPa pressure and 0.5~2 m / min speed for 2~3 rolling passes.

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