Method and apparatus for rapid drying of prussian blue analog sodium-ion battery electrode sheets and sodium-ion batteries

Abstract

This invention relates to a rapid drying method, apparatus, and sodium-ion battery for Prussian blue analogue sodium-ion battery electrodes, belonging to the field of sodium-ion battery manufacturing technology. The rapid drying method includes the following steps: S1: Preparing the wet electrode sheet and feeding it into a drying chamber for drying; S2: Transferring it to an internally heated dehydration section for gradient temperature dehydration; S3: Transferring it to an instantaneous high-temperature dehydration section for instantaneous high-temperature dehydration; S4: Transferring it to a heat-preserving dehydration section for further deep dehydration; S5: Cooling the electrode sheet after step S4 to obtain a dried electrode sheet. This drying method has the advantages of being rapid and low-cost, and can minimize structural damage to the Prussian blue analogue material.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery manufacturing technology, specifically relating to a rapid drying method for Prussian blue analog sodium-ion battery electrodes that is fast, low-cost, and reduces damage to the material structure, as well as the apparatus used in this method, the dried electrode, and a sodium-ion battery using the electrode as the positive electrode. Background Technology

[0002] Prussian blue analogues (PBAs) have become one of the most promising cathode materials for sodium-ion batteries due to their low cost, high theoretical capacity, and wide sodium-ion diffusion channels. However, their open framework structure makes them highly susceptible to adsorbing large amounts of crystal water and adsorbed water. Residual moisture can react with the electrolyte, leading to gas generation, increased impedance, and capacity decay, seriously jeopardizing battery safety and cycle life. Therefore, deep dehydration during electrode manufacturing is a crucial step in ensuring the performance of Prussian blue-based batteries.

[0003] Currently, the industry commonly uses traditional vacuum ovens to dry Prussian blue electrodes. This process has significant drawbacks: 1) Extremely low efficiency: To prevent rapid crusting on the electrode surface from hindering the escape of internal moisture, a slow heating rate is required. Furthermore, to ensure deep moisture removal, it is necessary to maintain a high temperature (typically ≥170℃) and high vacuum (≤100Pa) for an extremely long time (≥36 hours), severely limiting production efficiency. 2) Huge energy consumption: Heating the entire oven cavity and maintaining a high vacuum for an extended period results in extremely high energy consumption. 3) Potential material damage risk: Prolonged high-temperature heat treatment may cause partial collapse of the Prussian blue material's framework, precipitation of transition metal ions, or phase transitions, impairing its electrochemical activity.

[0004] Chinese patent CN206490132U discloses an electromagnetic induction heating and drying device for battery electrodes, combining induction heating and vacuum cooling, which has the advantages of rapid heating and high efficiency. However, its design is mainly aimed at solvent removal from conventional lithium electrode sheets (such as ternary and lithium iron phosphate), and does not consider the high sensitivity of Prussian blue material to moisture, the differences in the removal energy barriers of different types of moisture (free water, bound water, and crystal water), and the structural instability under long-term high temperatures. Chinese patent CN120933287A discloses a method for rapidly heat-treating the electrode surface using electromagnetic induction to control the distribution of binder, emphasizing instantaneous and controllable surface treatment capabilities. However, its purpose and parameters are all aimed at improving electrolyte wettability, rather than solving the problem of rapid removal of deep and large amounts of moisture.

[0005] Existing electromagnetic induction drying technologies are not designed to adapt to the differences in energy barriers for removing various types of moisture and the thermal sensitivity of PBA materials, making it impossible to simultaneously meet the requirements of deep dehydration, efficient drying, and material protection. Therefore, there is an urgent need to develop a drying technology and equipment specifically for Prussian blue electrode sheets that can achieve deep and uniform dehydration while significantly reducing time and overall heat load, and avoiding structural damage to the active material. Summary of the Invention

[0006] This invention specifically designs a multi-stage heating and gradient vacuum coupling device, which matches different water removal energy barriers (free water removal energy barrier is about 10-20 kJ / mol, bound water about 30-50 kJ / mol, and crystal water about 60-80 kJ / mol) by different heating methods, thereby solving the contradictions in the above-mentioned technical problems. It provides a drying method that can quickly, deeply, and uniformly dehydrate, significantly shorten drying time, reduce energy consumption, and minimize thermal damage to the Prussian blue material structure, as well as a corresponding drying device and a sodium-ion battery using the dried PBA battery cathode.

[0007] The technical solution of the present invention is based on the many problems of low drying efficiency, high energy consumption and easy material damage of the above-mentioned PBA battery cathode material.

[0008] The specific technical solution is explained below:

[0009] A rapid drying method for sodium-ion battery electrodes containing Prussian blue analogues includes the following steps:

[0010] S1: The Prussian blue analogue wet electrode sheet is prepared to be fed into the drying chamber for drying;

[0011] S2: First, it is transferred to the endogenous heat dehydration section in the drying chamber. The vacuum degree in the endogenous heat dehydration section is maintained at P1, and the temperature is gradually raised to T1 through the electromagnetic induction heating coil within time t1. P1 is 1000Pa~10kPa, t1 is 30~120s, and T1 is 80~130℃.

[0012] S3: Then it is transferred to the instantaneous high-temperature dehydration section in the drying chamber. The vacuum degree in the instantaneous high-temperature dehydration section is reduced to P2, the temperature is raised to T2 within time t2 and maintained for time t3; P2≤200Pa, t2 is 0.1~2s, T2 is 160~250℃, and t3 is 0.5~5s.

[0013] S4: Then it is transferred to the heat preservation and dehydration section in the drying chamber. The temperature of the heat preservation and dehydration section is controlled at T1±10℃ and maintained for t4 time; t4 is 3~20mins.

[0014] S5: The electrode sheet processed in step S4 enters the cooling and stabilization section and is cooled under vacuum or inert atmosphere protection to obtain a dry electrode sheet.

[0015] In the above technical solution, Prussian blue analogues (PBAs) refer to transition metal cyanides with open framework structures, including but not limited to Prussian white, nickel-cobalt Prussian blue, copper-based Prussian blue, etc.

[0016] The purpose of setting S2 is to remove most of the free water and some of the bound water. In S2, P1 is set to a medium vacuum of 1000Pa~10kPa, which can control the water escape rate within a suitable range and avoid rapid crusting on the surface. The reason for controlling T1 at 80~130℃ is that the free water removal rate is small and the efficiency is too low when the temperature is below 80℃; when the temperature is above 130℃, the bound water will escape rapidly and form a dense layer on the surface of the electrode, which will hinder the subsequent desorption of deep water.

[0017] The purpose of setting S3 is to break down the dense layer formed on the surface of the electrode by moisture or binder and promote the desorption of deep crystal water. In S3, setting P2 to a high vacuum of ≤200Pa can significantly increase the diffusion coefficient of deep moisture in the electrode, accelerating the desorption of crystal water and residual bound water. T2 is set to 160~250℃ because the dense layer on the surface cannot be effectively broken down below 160℃, and the crystal water removal rate is less than 85%; above 250℃, PBAs materials are prone to phase transition, which will lead to a significant decrease in electrochemical activity.

[0018] In a preferred embodiment, both S2 and S3 are heated by electromagnetic induction coils;

[0019] The electromagnetic induction coil in S2 uses a medium-frequency coil of 20~40KHz;

[0020] The electromagnetic induction coil in S3 uses a high-frequency coil of 80~300KHz.

[0021] In the above technical solution, the purpose of using a 20~40KHz intermediate frequency coil for the electromagnetic induction coil in S2 is to utilize the characteristic of the intermediate frequency coil having a penetration depth of 2~5mm to achieve the heating method of the electrode sheet generating heat from the inside, which is conducive to the deep removal of moisture; the purpose of using an 80~300KHz high frequency coil for the electromagnetic induction coil in S3 is to utilize the characteristic of the high frequency coil having a penetration depth ≤1mm to achieve rapid heating of the electrode sheet surface, which is more conducive to breaking down the dense layer and allowing the crystal water to be further removed.

[0022] In a preferred embodiment, in S4, the vacuum level in the heat preservation and dehydration section is maintained at P2. The purpose of setting S4 is to ensure that the residual moisture can escape fully and to ensure the overall moisture uniformity of the electrode.

[0023] As a preferred embodiment, the conveying speed of the coated Prussian blue analog wet electrode is constant and controlled at 1~10m / min.

[0024] The rapid drying apparatus used in any of the above rapid drying methods includes a conveyor belt for conveying electrode sheets and a drying chamber and a cooling and stabilizing section arranged sequentially along the electrode sheet conveying direction.

[0025] The drying chamber is a sealed chamber with a vacuum assembly and a heating assembly. Along the transmission direction of the electrode, the drying chamber sequentially includes an endogenous heat dehydration section, an instantaneous high-temperature dehydration section, and a heat preservation dehydration section.

[0026] In a preferred embodiment, the endogenous heat dehydration section is heated by a first electromagnetic induction heating coil. The first electromagnetic induction heating coil has a working frequency range of 20~40KHz, 50~80 turns, and a spiral winding method. The distance between the first electromagnetic induction heating coil and the electrode surface is 5~15mm.

[0027] In the above technical solution, the first electromagnetic induction heating coil uses a medium-frequency coil with a penetration depth of 2-5mm, enabling deep and uniform heating of the current collector (aluminum foil or copper foil). Heat is conducted from the current collector to the active material layer, matching the temperature rise requirements of T1, and efficiently removing free water (approximately 60-80% removal) and some bound water (approximately 10-15% removal). The first electromagnetic induction heating coil is designed with a large number of turns and a spiral winding structure to ensure that the width and length of the electrode are subjected to a relatively uniform electromagnetic field, ensuring heating uniformity. More turns also mean a stronger induced magnetic field, which is beneficial for deep heating of the current collector (aluminum foil / copper foil). The distance between the first electromagnetic induction heating coil and the electrode surface is controlled at 5-15mm to make the heating gentler and more uniform.

[0028] In a preferred embodiment, the instantaneous high-temperature dehydration section is heated by a second electromagnetic induction heating coil. The second electromagnetic induction heating coil has a working frequency range of 80~300KHz, 30~50 turns, and a flat winding method. The distance between the second electromagnetic induction heating coil and the electrode surface is 2~8mm.

[0029] In the above technical solution, the second electromagnetic induction heating coil adopts a high-frequency coil with a penetration depth of ≤1mm, achieving rapid focused heating of the active material surface, matching the T2 instantaneous high-temperature impact requirement, and corresponding to the breaking of the dense surface layer and the desorption of crystal water (removal rate of approximately 15~30%). The second electromagnetic induction heating coil is designed with a smaller number of turns and a flat winding structure to concentrate the electromagnetic field and narrow the effective area, so that the surface of the electrode receives a brief but strong electromagnetic pulse when it passes through, achieving rapid heating. The flat winding can concentrate energy on a plane, which is very suitable for focused surface treatment. The distance between the second electromagnetic induction heating coil and the electrode surface is controlled at 2~8mm, which can greatly enhance the electromagnetic field intensity at the electrode surface, achieve the high temperature peak (T2) in a very short time, and ensure a sufficiently strong thermal shock.

[0030] In a preferred embodiment, the endogenous heat dehydration section and the instantaneous high-temperature dehydration section each achieve a negative pressure environment through an independent vacuum system.

[0031] Prussian blue analogue electrode sheets are electrode sheets obtained by any of the above-mentioned rapid drying methods, or electrode sheets dried by any of the above-mentioned rapid drying devices.

[0032] As a preferred embodiment, the residual moisture content is less than 200 ppm.

[0033] A sodium-ion battery comprising a positive electrode and a negative electrode, wherein the positive electrode is a Prussian blue-like electrode sheet as described above.

[0034] In summary, the technical solution described in this invention has the following main beneficial effects:

[0035] Compared with existing technologies, the rapid drying method for Prussian blue analog sodium-ion battery electrodes provided by this invention has the following advantages:

[0036] 1. Significantly improved drying efficiency: Through the design of "internal heat generation + multi-stage synergy", the total drying time of Prussian blue similar material is shortened from more than 36 hours in the traditional way to less than 30 minutes, and the production efficiency is increased by dozens of times.

[0037] 2. Better dehydration depth and uniformity: Electromagnetic induction heats the current collector, and the heat is transferred from the inside of the electrode to the outside, which is conducive to the desorption of deep water. Combined with the process of "gradient heating - instantaneous high temperature shock - heat preservation", the energy barrier for the removal of water with different binding forces is effectively overcome, and deep and uniform dehydration is achieved.

[0038] 3. Low risk of material damage: The overall heat treatment time is extremely short, and the high temperature (T2) only acts on the electrode surface for a very short time. The cumulative heat of the electrode bulk phase is far lower than that of traditional oven drying processes, which protects the structural stability of Prussian blue analog materials to the greatest extent.

[0039] 4. Significant energy saving effect: Energy is applied directly to the electrode itself, resulting in minimal heat loss; drying time is significantly shortened, vacuum system operating time is reduced accordingly, and overall energy consumption is significantly reduced.

[0040] 5. Improve electrode quality: Instantaneous high-temperature surface treatment can effectively improve the surface pore structure of the electrode, which is beneficial for subsequent electrolyte wetting, resulting in reduced cell internal resistance and improved rate performance.

[0041] 6. Wide adaptability: The multi-stage process parameters of this invention can be flexibly adjusted according to the crystal water content and structural stability of different PBA materials, adapting to the drying requirements of various positive electrode sheets such as Prussian white and nickel-cobalt Prussian blue.

[0042] 7. Strong industrial adaptability: The equipment adopts a continuous transmission design and can be directly connected to the sodium-ion battery electrode production line to realize continuous operation from coating to drying. The daily processing capacity of a single production line is greatly increased to meet the needs of industrial mass production.

[0043] Further or more detailed beneficial effects will be described in conjunction with specific embodiments in the detailed implementation. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the rapid drying device in a specific implementation embodiment;

[0045] Figure 2 This is a schematic diagram of the electrode temperature-time-vacuum degree synergistic process curve corresponding to the rapid drying method in a specific implementation.

[0046] 100: Unwinding and correction section; 200: Drying chamber section; 210: Internally generated heat dehydration section; 211: First electromagnetic induction heating coil; 220: Instantaneous high-temperature dehydration section; 221: Second electromagnetic induction heating coil; 222: High-speed infrared thermometer; 230: Heat preservation dehydration section; 231: Third electromagnetic induction heating coil; 241: First vacuum subsystem; 242: Second vacuum subsystem; 300: Cooling and stabilizing section; 400: Rewinding section. Detailed Implementation

[0047] The present invention will be further explained in conjunction with the embodiments:

[0048] The core technical problem faced by the technical solution of this application embodiment stems from the inventor's accurate understanding of the prior art. Therefore, how to significantly shorten the drying time, reduce energy consumption, and minimize thermal damage to the structure of Prussian blue analog materials is a technical problem that the inventor urgently needs to solve.

[0049] It should be noted that the embodiments do not constitute a limitation on the scope of protection of the claims of this invention. All technical solutions that can be reasonably expected by those skilled in the art based on the technical concepts provided / proved by the embodiments should be covered within the scope of protection of the claims of this invention.

[0050] The implementation method is detailed below:

[0051] The rapid drying method corresponding to the implementation method is described below:

[0052] A rapid drying method for sodium-ion battery electrodes containing Prussian blue analogues includes the following steps:

[0053] S1: After unwinding and correction, the Prussian blue analog wet electrode sheet is prepared to be fed into the drying chamber at a constant speed V for drying.

[0054] S2: First, it is transferred to the endogenous heat dehydration section in the drying chamber. The vacuum degree in the endogenous heat dehydration section is maintained at P1, and the temperature is gradually raised to T1 through the electromagnetic induction heating coil within time t1. P1 is 1000Pa~10kPa, t1 is 30~120s, and T1 is 80~130℃.

[0055] S3: Then it is transferred to the instantaneous high-temperature dehydration section in the drying chamber. The vacuum degree in the instantaneous high-temperature dehydration section is reduced to P2, the temperature is raised to T2 within time t2 and maintained for time t3; P2≤200Pa, t2 is 0.1~2s, T2 is 160~250℃, and t3 is 0.5~5s.

[0056] S4: Then it is transferred to the heat preservation and dehydration section in the drying chamber. The temperature of the heat preservation and dehydration section is controlled at T1±10℃ and maintained for t4 time; t4 is 3~20mins.

[0057] S5: The electrode sheet processed in step S4 enters the cooling and stabilization section and is cooled to below 40°C under vacuum or inert atmosphere protection. After being wound up, a dry electrode sheet is obtained.

[0058] Specifically:

[0059] Example 1:

[0060] This embodiment relates to a rapid drying device for sodium-ion battery electrodes made from Prussian blue analogues.

[0061] Please refer to the attached instruction manual. Figure 1 The rapid drying apparatus provided in this embodiment includes, in sequence, an unwinding and correction section 100, a drying chamber section 200, a cooling and stabilizing section 300, and a winding section 400, according to the electrode sheet conveying sequence.

[0062] The drying chamber 200 is a sealed long chamber made of 304 stainless steel. The interior is divided into three chambers by a partition with an electrode channel and a flexible seal made of fluororubber (compression controlled at 20~30%), which correspond to the internal heat dehydration section 210, the instantaneous high temperature dehydration section 220 and the heat preservation dehydration section 230, respectively, to ensure the vacuum sealing when the electrode passes through.

[0063] The internally heated dehydration section 210 is equipped with a first electromagnetic induction heating coil 211, which is driven by a medium-frequency induction power supply with a frequency set to 30 kHz, 65 turns, and a spiral winding method. The distance between the first electromagnetic induction heating coil 211 and the electrode surface is designed to be 10 mm. This section is connected to the first vacuum subsystem 241 (rotary vane pump, model 2XZ-4, pumping speed 4 L / s), which can maintain the vacuum level inside the cavity at approximately 5 kPa.

[0064] The instantaneous high-temperature dehydration section 220 is equipped with a second electromagnetic induction heating coil 221, which is driven by a high-frequency induction power supply with a frequency set to 150 kHz, 40 turns, and a flat winding method. The distance between the second electromagnetic induction heating coil 221 and the electrode surface is designed to be 5 mm. A high-speed infrared thermometer 222 is installed at the top of this section for real-time monitoring of the electrode surface temperature. This section is connected to the second vacuum subsystem 242 (a series connection of a ZJ-150 Roots pump with a pumping speed of 150 L / s and a 2XZ-8 rotary vane pump with a pumping speed of 8 L / s), which can quickly establish and maintain a high vacuum environment below 80 Pa within the cavity.

[0065] A third electromagnetic induction heating coil 231 is installed inside the heat preservation and dehydration section 230, which is driven by a medium-frequency induction power supply and is used for heat preservation. This section is connected to the instantaneous high-temperature dehydration section 220 and shares a high vacuum environment.

[0066] The cooling stabilization section 300 is a water-cooled jacket structure. The cooling water temperature of the water-cooled jacket is controlled at 10~25℃, and the cooling medium flow rate is 5~10L / min. The cooling stabilization section 300 is connected to the drying chamber section 200 through a vacuum valve. The interior is filled with high-purity nitrogen (purity ≥99.999%) or maintained at a low vacuum for electrode cooling.

[0067] In this embodiment, to address the potential cross-flow problem caused by the pressure difference between the endogenous thermal dehydration section 210 and the instantaneous high-temperature dehydration section 220, a dynamic pressure difference isolation structure (not shown in the figure) is employed at the connection point between the two sections, specifically including:

[0068] Elastic fluororubber sealing scrapers are symmetrically installed on both the upper and lower sides of the electrode channel at the junction of the two sections. The scrapers are 0.5 mm thick and the width is the same as the electrode width. The scrapers are in close contact with the electrode surface, and the contact pressure is maintained at 0.1~0.3 N / mm by a spring adjustment mechanism. 2This ensures that the electrode surface is effectively isolated from pressure during passage without being scratched; simultaneously, a transition buffer chamber is provided between the two sections, which is connected to the second vacuum subsystem via an independent fine-tuning vacuum valve.

[0069] The system 242 is connected to maintain the pressure in the transition chamber at the midpoint between P1 and P2 (approximately 500 Pa), forming a pressure gradient and further reducing pressure differential impact. In addition, a differential pressure sensor is installed at the top of the transition buffer chamber to monitor the pressure difference between the two sections in real time. When the pressure difference exceeds a set threshold (e.g., 50 Pa), the main controller automatically adjusts the valve opening of the second vacuum subsystem 242 to maintain pressure stability. This dynamic differential pressure isolation structure ensures that the vacuum level of each section is independently controllable and does not interfere with each other when the electrode continuously passes through different pressure sections.

[0070] The device is equipped with a main controller (not shown in the figure), which receives signals from the infrared thermometer 222 and precisely controls the power output of the three sets of induction coils and the start and stop of each vacuum pump based on a PID control algorithm. The drying chamber 200 is equipped with a safety valve with a set pressure of 15 kPa. When the pressure inside the chamber exceeds the set value, it automatically releases pressure. It is equipped with a temperature overload alarm system. When the infrared thermometer 222 detects that the electrode temperature exceeds T2+30℃, the main controller automatically cuts off the power supply to the corresponding induction coil and starts the inert gas charging program. In the inert gas protection system, the oxygen content inside the chamber is monitored in real time by an oxygen content sensor (model CY-100, measurement accuracy ±0.1%). When the oxygen content is higher than 0.5%, high-purity nitrogen is automatically charged to maintain the oxygen content below 0.3%.

[0071] Example 2: This example relates to a rapid drying method for sodium-ion battery electrodes made of Prussian blue analogues and a comparative experiment.

[0072] Experimental subject: Prussian white (Na₂O₃) used in sodium-ion batteries x Using Fe[Fe(CN)6] as the positive electrode sheet, the areal density is 20 mg / cm³. 2 The coating thickness is approximately 120 μm, and the initial moisture content of the wet electrode after coating is approximately 2 wt%.

[0073] Experimental group (drying method corresponding to this invention):

[0074] Using the apparatus of Example 1, the process parameters are set as follows:

[0075] Electrode transmission speed V: 2m / min.

[0076] S2 gradient heating dehydration: P1=5kPa, target T1=110℃, heating time t1≈60s

[0077] S3 Instantaneous surface activation and strong dehydration: P2≤80Pa, target peak T2=210℃, heating time t2≈0.5s, holding time t3=2s. S4 Intensive drying: Under P2, maintain temperature at 105±5℃ for t4=8min. S5 Cooling: Cool to room temperature under high-purity nitrogen protection. The total drying time (S2-S4) is approximately 10 minutes and 30 seconds.

[0078] Control group (traditional vacuum oven):

[0079] The same batch of wet electrode sheets were placed in a conventional vacuum oven. The process was as follows: after evacuating the vacuum to 100Pa at 25℃, the temperature was raised to 180℃ in about 2 hours, and then baked at 180℃ and ≤100Pa for 36 hours, followed by oven cooling.

[0080] The test results for the experimental group and the control group are shown in Table 1 below:

[0081] Testing items experimental group control group Total drying time 10 minutes and 30 seconds ~38 hours Moisture content of the final electrode 85 ppm (3 parallel tests: 83 ppm, 85 ppm, 87 ppm) 95ppm Prussian white crystalline phase structure (XRD) The characteristic peaks are sharp, with no extraneous peaks, and the full width at half maximum (FWHM) of the characteristic peaks on the (200) crystal plane is 0.18°. The characteristic peaks changed slightly, and trace amounts of amorphous phase appeared. The full width at half maximum (FWHM) of the characteristic peak of the (200) crystal plane was 0.25°. Electrode peel strength 1.8 N / cm (3 parallel experiments: 1.78, 1.80, 1.82 N / cm) 1.5 N / cm The first charge and discharge efficiency of the manufactured battery cell 89.5% 86.2% Cell capacity retention rate after 500 1C cycles 92.3% 88.7% Comprehensive energy consumption <![CDATA[0.8kWh / m 2 Extreme film <![CDATA[28kWh / m 2 Extreme film

[0082] The results, as shown in Table 1, are as follows:

[0083] Efficiency: The rapid drying method of the present invention reduces the drying time from 38 hours to 10 minutes and 30 seconds, improving efficiency by more than 200 times.

[0084] Results: The two methods resulted in comparable final moisture content, both meeting the low moisture requirement, proving that the method of the present invention achieves deep dehydration in a very short time.

[0085] Material protection: XRD results show that the electrode crystal structure is better preserved by the method of the present invention, indicating that short-time and precise heat treatment effectively reduces the damage to the material structure caused by long-term high temperature.

[0086] Performance advantages: Thanks to better structural retention and potentially improved surface properties, the experimental group cells showed significantly better initial efficiency and long-cycle performance than the control group.

[0087] Energy-saving advantage: The overall energy consumption of the experimental group was only 2.86% of that of the control group, showing a significant energy-saving effect.

[0088] Example 3:

[0089] This embodiment relates to parameter optimization experiments for a rapid drying method of Prussian blue analogue sodium-ion battery electrodes. Two sets of optimization experiments were conducted under the same conditions as in Example 2:

[0090] 1. Experiment on the effect of instantaneous peak temperature T2:

[0091] The T2 values ​​were set at 180℃, 210℃, and 240℃, with three parallel experiments conducted for each group. The results are as follows: At T2=180℃: the moisture content of the electrode was 118ppm, 120ppm, and 122ppm (average 120ppm), with no charring on the electrode, and the cell's first-time efficiency was 89.1%, 89.3%, and 89.5% (average 89.3%). At T2=210℃: the moisture content of the electrode was 83ppm, 85ppm, and 87ppm (average 85ppm), with no charring on the electrode, and the cell's first-time efficiency was 89.2%, 89.5%, and 89.8% (average 89.5%). At T2=240℃: the moisture content of the electrode was 78ppm, 80ppm, and 82ppm (average 80ppm), with slight charring on the electrode surface (charred area ≤3%), and the cell's first-time efficiency was 87.2%, 87.5%, and 87.8% (average 87.5%). The above results indicate that the optimal balance between dehydration effect and material stability was achieved at T2=210℃.

[0092] 2. Experiment on the effect of electrode transmission speed V:

[0093] With V set to 1 m / min, 5 m / min, and 10 m / min respectively, and T2 fixed at 210℃, other parameters were the same as in Example 2. The results are as follows: V=1 m / min: total drying time 15 minutes, electrode moisture content 78 ppm, electrode peel strength 1.85 N / cm, cell first-time efficiency 89.8%; V=5 m / min: total drying time 6 minutes, electrode moisture content 135 ppm, electrode peel strength 1.75 N / cm, cell first-time efficiency 88.6%; V=10 m / min: total drying time 5 minutes, electrode moisture content 175 ppm, electrode peel strength 1.68 N / cm, cell first-time efficiency 87.9%. The above results show that the transmission speed V is negatively correlated with the drying effect and can be flexibly adjusted within the range of 1 m / min-10 m / min according to the actual production efficiency requirements, balancing efficiency and performance.

[0094] Example 4:

[0095] This embodiment relates to parameter optimization experiments for a rapid drying method of Prussian blue analog sodium-ion battery electrodes. To verify the feasibility and effectiveness of the parameter range described in the claims of this invention, other experiments within the parameter range were conducted under the same conditions as in Example 2, including experiments on residual moisture content of the electrode, crystal phase structure (XRD full width at half maximum), and initial cell efficiency.

[0096] 1. Vacuum degree P1 of the endogenous heat dehydration section:

[0097] P1=1000Pa: Electrode moisture content 112ppm, XRD half-width at half-maximum 0.19°, cell first efficiency 89.1%;

[0098] P1=10kPa: Electrode moisture content 128ppm, XRD half-width at half-maximum 0.18°, cell first efficiency 88.9%;

[0099] It can be seen that P1 can meet the dehydration requirements within the corresponding range, and the material structure is well maintained.

[0100] 2. Gradient heating time t1:

[0101] t1=30s: Electrode moisture content 98ppm, XRD half-width at half-maximum 0.20°, cell first efficiency 89.3%;

[0102] t1=120s: Electrode moisture content 82ppm, XRD half-width at half-maximum 0.18°, cell first efficiency 89.7%;

[0103] It can be seen that t1 is slightly insufficient for dehydration at shorter times, but still meets the requirement of below 200ppm; t1 is more effective at longer times, and both are within the feasible range.

[0104] 3. Gradient heating target temperature T1:

[0105] T1=80℃: Electrode moisture content 152ppm, XRD half-width at half-maximum 0.17°, cell first efficiency 88.5%;

[0106] T1=130℃: Electrode moisture content 79ppm, XRD half-width at half-maximum 0.19°, cell first efficiency 89.4%;

[0107] It can be seen that the dehydration efficiency is slightly lower at T1=80℃, but still meets the standard; the dehydration effect is better at T1=130℃, and the material is not damaged. Both are within the feasible range.

[0108] 4. Vacuum degree P2 during the instantaneous high-temperature period:

[0109] P2=200Pa: Electrode moisture content 118ppm, XRD half-width at half-maximum 0.19°, cell first efficiency 88.8%;

[0110] P2=50Pa: Electrode moisture content 72ppm, XRD half-width at half-maximum 0.18°, cell first efficiency 89.6%;

[0111] It can be seen that dehydration can still be effective when P2=200Pa, and the lower the P2, the better the effect. Both are within the feasible range.

[0112] 5. Instantaneous heating time t2:

[0113] t2=0.1s: Electrode moisture content 132ppm, XRD half-width at half-maximum 0.20°, cell first efficiency 88.4%;

[0114] t2=2s: Electrode moisture content 88ppm, XRD half-width at half-maximum 0.18°, cell first efficiency 89.2%;

[0115] It is evident that when t2 is too short, the thermal shock is insufficient, but it still meets the standard; when t2 is longer, the effect is better, and the range is feasible.

[0116] 6. Instantaneous high temperature target temperature T2:

[0117] T2=160℃: Electrode moisture content 145ppm, XRD half-width at half-maximum 0.19°, cell first efficiency 88.2%;

[0118] T2=250℃: Electrode moisture content 68ppm, XRD half-width at half-maximum 0.22°, cell first efficiency 87.8%;

[0119] It can be seen that the dehydration at T2=160℃ is slightly insufficient but meets the standard; the dehydration effect is the best at T2=250℃, but the material shows a slight widening (XRD half-width), and the initial effect is slightly reduced, but it is still within the acceptable range.

[0120] 7. Duration of instantaneous high temperature t3:

[0121] t3=0.5s: Electrode moisture content 138ppm, XRD half-width at half-maximum 0.19°, cell first efficiency 88.3%;

[0122] t3=5s: Electrode moisture content 76ppm, XRD half-width at half-maximum 0.21°, cell first efficiency 88.9%;

[0123] It is evident that an excessively long t3 may slightly affect the structure, but it is still within a controllable range.

[0124] 8. Incubation and dehydration time t4:

[0125] t4=3min: Electrode moisture content 158ppm, XRD half-width at half-maximum 0.18°, cell first efficiency 88.1%;

[0126] t4=20min: Electrode moisture content 62ppm, XRD half-width at half-maximum 0.18°, cell first efficiency 89.8%;

[0127] It can be seen that when the t4 is shorter, the moisture content is slightly higher but still meets the standard; when the t4 is longer, the dehydration is more complete, and the range is feasible.

[0128] 9. Frequency of the first electromagnetic induction heating coil

[0129] 20kHz: Electrode moisture content 102ppm, XRD half-width at half-maximum 0.19°, cell first efficiency 89.0%;

[0130] 40kHz: Electrode moisture content 88ppm, XRD half-width at half-maximum 0.18°, cell first efficiency 89.3%;

[0131] It is evident that effective internal heating can be achieved at both ends, resulting in good dehydration and a feasible range.

[0132] 10. Frequency of the second electromagnetic induction heating coil

[0133] 80kHz: Electrode moisture content 118ppm, XRD half-width at half-maximum 0.20°, cell first efficiency 88.5%;

[0134] 300kHz: Electrode moisture content 79ppm, XRD half-width at half-maximum 0.19°, cell first efficiency 89.1%;

[0135] It can be seen that the surface heating is slightly mild at a frequency of 80KHz, but it can still break the dense layer; the surface focusing is stronger at a frequency of 300KHz, the dehydration effect is better, and the range is feasible.

[0136] In summary, the device and method provided by this invention innovatively combine multi-segment, differentiated electromagnetic induction heating with dynamic vacuum control, specifically addressing the industry pain points of Prussian blue electrode drying, and demonstrating significant advantages in efficiency, energy consumption, material protection, and final battery performance.

[0137] In the description of this specification, the references to terms such as "embodiment," "basic embodiment," "preferred embodiment," "other embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0138] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0139] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A rapid drying method for sodium-ion battery electrodes containing Prussian blue analogues, characterized in that: Includes the following steps: S1: The coated Prussian blue analog wet electrode sheet is prepared to be fed into the drying chamber (200) for drying; S2: First, it is transferred to the endogenous heat dehydration section (210) in the drying chamber (200). The vacuum degree in the endogenous heat dehydration section (210) is maintained at P1, and the temperature gradually rises to T1 within the time t1. P1 is 1000Pa~10kPa, t1 is 30~120s, and T1 is 80~130℃. S3: It is then transferred to the instantaneous high-temperature dehydration section (220) in the drying chamber (200). The vacuum degree in the instantaneous high-temperature dehydration section (220) is reduced to P2, the temperature is increased to T2 within time t2 and maintained for time t3; P2≤200Pa, t2 is 0.1~2s, T2 is 160~250℃, and t3 is 0.5~5s; S4: The material is then transferred to the heat preservation and dehydration section (230) inside the drying chamber (200). The temperature of the heat preservation and dehydration section (230) is controlled at T1±10℃ and maintained for t4 time; t4 is 3~20mins. S5: The electrode sheet processed in step S4 enters the cooling and stabilizing section (300) and is cooled under vacuum or inert atmosphere protection to obtain a dry electrode sheet.

2. The rapid drying method according to claim 1, characterized in that: Both S2 and S3 are heated by electromagnetic induction coils; The electromagnetic induction coil in S2 uses a medium-frequency coil of 20~40KHz; The electromagnetic induction coil in S3 uses a high-frequency coil of 80~300KHz.

3. The rapid drying method according to claim 1, characterized in that: The conveying speed of the coated Prussian blue analog wet electrode is constant and controlled between 1 and 10 m / min.

4. The rapid drying apparatus used in the rapid drying method according to any one of claims 1 to 3, characterized in that: It includes a conveyor belt for conveying electrodes and a drying chamber (200) and a cooling stabilizing section (300) arranged sequentially along the electrode conveying direction: The drying chamber (200) is a sealed chamber with a vacuum assembly and a heating assembly. Along the transmission direction of the electrode, the drying chamber (200) includes an endogenous heat dehydration section (210), an instantaneous high-temperature dehydration section (220), and a heat preservation dehydration section (230).

5. The rapid drying apparatus according to claim 4, characterized in that: The endogenous heat dehydration section (210) is heated by a first electromagnetic induction heating coil (211). The first electromagnetic induction heating coil (211) has a working frequency range of 20~40KHz, 50~80 turns, and a spiral winding method. The distance between the first electromagnetic induction heating coil (211) and the electrode surface is 5~15mm.

6. The rapid drying apparatus according to claim 4 or 5, characterized in that: The instantaneous high-temperature dehydration section (220) is heated by a second electromagnetic induction heating coil (221). The second electromagnetic induction heating coil (221) has a working frequency range of 80~300KHz, 30~50 turns, and a flat winding method. The distance between the second electromagnetic induction heating coil (221) and the electrode surface is 2~8mm.

7. The rapid drying apparatus according to claim 4, characterized in that: The endogenous heat dehydration section (210) and the instantaneous high-temperature dehydration section (220) respectively achieve a negative pressure environment through independent vacuum systems.

8. A Prussian blue similar electrode, characterized in that: The electrode sheet is obtained by the rapid drying method according to any one of claims 1 to 3, or the electrode sheet is dried by the rapid drying apparatus according to any one of claims 4 to 7.

9. The electrode sheet according to claim 8, characterized in that: The residual moisture content is less than 200 ppm.

10. A sodium-ion battery, comprising a positive electrode and a negative electrode, characterized in that: The positive electrode is the Prussian blue analog electrode sheet as described in claim 8 or 9.

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