Magnetic responsive capsule, and preparation method and application thereof

Abstract

The present disclosure relates to the technical field of secondary batteries, and particularly relates to a magnetic response capsule and a preparation method and application thereof. The magnetic response capsule comprises an elastic shell layer, a magnetic film layer and a core material, the elastic shell layer has an accommodating space inside, and the core material is located in the accommodating space; the magnetic film layer is coated on the outer surface of the elastic shell layer; a tapered through hole is arranged on the elastic shell layer, and the tapered through hole has a tip end which is directed to the inner surface of the elastic shell layer; and the core material comprises sodium salt, and the particle size of the sodium salt is greater than the tip end aperture of the tapered through hole. By adding the magnetic response capsule into a sodium ion battery, the present disclosure reduces or even solves the capacity attenuation degradation and safety problems caused by the loss of active sodium ions, realizes the recovery or regulation of capacity in a timed, quantitative and on-demand manner, effectively promotes the recovery of battery capacity and the prolongation of cycle life, and is simple in process, easy to operate, and conducive to large-scale production.

Description

Technical Field

[0001] This disclosure relates to the field of secondary battery technology, and in particular to a magnetically responsive capsule, its preparation method, and its application. Background Technology

[0002] Currently, lithium-ion batteries dominate the field of large-scale energy storage due to their advantages such as high energy efficiency, long cycle life, and relatively mature technology. However, global lithium resources are limited and unevenly distributed. With the rapid development of large-scale energy storage technologies and electric vehicles, the contradiction of lithium resource shortage has gradually become apparent, leading to persistently high and continuously rising costs for lithium-ion batteries. Therefore, researchers have begun to focus on developing new, low-cost energy storage battery systems. Sodium-ion batteries, which operate on a similar principle to lithium-ion batteries, have emerged as a promising option, attracting significant interest from researchers.

[0003] From a thermodynamic and kinetic perspective, the chemical stability of the SEI film in sodium-ion batteries is generally worse than that in lithium-ion batteries, and its degradation is faster. This not only reduces the battery's lifespan and increases replacement costs, but also leads to a sharp increase in the number of discarded batteries as society further shifts towards electrification. Therefore, slowing down battery degradation or restoring battery capacity can effectively extend the battery's lifespan and, to some extent, save energy, time, and costs.

[0004] Generally, the capacity degradation of sodium-ion batteries during long-term use mainly occurs through two mechanisms: damage to active materials (such as irreversible phase transitions, particle cracking, and electrical contact loss) and loss of active ions (such as the consumption of the SEI film and electrolyte decomposition). In practical applications, batteries typically operate in systems with controlled temperature and humidity, where the loss of active ions is often the primary mode of capacity degradation. Therefore, mitigating the loss of active ions or increasing their quantity is crucial for extending battery life and promoting the widespread application of sodium-ion batteries.

[0005] Currently, methods to address or suppress the loss of active ions generally involve optimizing electrode material structure, improving electrolyte formulation and additives, and constructing a stable SEI film. Most strategies focus on suppressing the loss at the initial source and are concentrated on stabilizing the SEI film. However, there is very little discussion on how to restore the capacity decay that has already occurred during subsequent battery operation in a timely, quantitative, and on-demand manner, which has become an urgent problem to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this disclosure provides a magnetically responsive capsule, its preparation method, and its application.

[0007] In a first aspect, this disclosure provides a magnetically responsive capsule, the magnetically responsive capsule comprising an elastic shell, a magnetic film layer and a core material, wherein the elastic shell has an internal accommodating space and the core material is located in the accommodating space; the magnetic film layer covers the outer surface of the elastic shell. The elastic shell is provided with a tapered through hole, and the tip of the tapered through hole faces the inner surface of the elastic shell. The core material includes sodium salt; The particle size of the core material is larger than the aperture of the tip of the tapered through hole.

[0008] This disclosure presents a magnetic response capsule design. By adding the magnetic response capsule to a sodium-ion battery, the capacity decay and safety issues caused by the loss of active sodium ions are reduced or even resolved. The capacity can be restored or controlled in a timely, quantitative, and on-demand manner, effectively promoting the recovery of battery capacity and the extension of cycle life. The process is simple and easy to operate, which is conducive to achieving large-scale production.

[0009] Specifically, the elastic shell, through a tapered through-hole and a magnetic film layer, allows for controlled expansion of the tapered through-hole in the magnetic response capsule under an applied magnetic field, enabling timely release of the core material (capacity recovery agent). Upon removal of the applied magnetic field, the tapered through-hole returns to its original state. Compared to a straight-cylinder channel, the tapered through-hole is more advantageous for achieving rapid expansion. Specifically, under the influence of an applied magnetic field, the magnetic film layer converts magnetic force into mechanical force, which is transmitted to the elastic shell. The difference in diameter between the coarse and fine ends of the tapered through-hole provides effective space for mechanical deformation, thereby achieving rapid expansion.

[0010] The released core material undergoes a decomposition reaction during normal battery charging and discharging. Its decomposition potential is low, allowing for complete conversion within the typical battery voltage window. During decomposition, sodium ions are released and organic ligands are gasified, preventing further gas generation during subsequent cycles. Introducing capacity recovery agents into existing cycle-degraded batteries restores capacity without accelerating the degradation process. Furthermore, the battery's internal resistance remains stable, and its rate performance is unaffected. This non-invasive and rapid process maintains battery integrity and eliminates the need for disassembly.

[0011] This disclosure does not impose any special restrictions on the size and shape of the magnetic response capsule, as long as it can exist in the electrolyte and does not affect the battery structure.

[0012] The magnetic response capsule in a sodium-ion battery can be placed anywhere, for example, dispersed in the electrolyte; or it can be fixed at any position on the inner surface of the battery casing.

[0013] The following are preferred technical solutions of this disclosure, but are not intended to limit the technical solutions provided by this disclosure. The technical objectives and beneficial effects of this disclosure can be better achieved through the following technical solutions.

[0014] As a preferred technical solution of this disclosure, the particle size of the core material is 500nm-8μm, such as 500nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm or 8μm, but is not limited to the listed values. Other unlisted values ​​mentioned above are also applicable, preferably 1-3μm.

[0015] Furthermore, under a magnetic field strength of ≥0.12T, the aperture of the tip of the tapered through hole is larger than the particle size of the core material.

[0016] In this disclosure, controlling the particle size of the core material helps ensure its smooth release. If the particle size is too large, even if the tip of the conical through-hole in the elastic shell expands under the intervention of a magnetic field, the core material may become blocked at the tip and fail to release. If the particle size is too small, the size of the conical through-hole in the elastic shell changes accordingly, and the required size of the tip also needs to be reduced. This not only increases the difficulty of preparation but also requires an increase in magnetic field strength, which is not conducive to industrial applications.

[0017] Preferably, the aperture of the tip of the tapered through-hole is 100-300nm, such as 100nm, 150nm, 200nm, 250nm or 300nm; the aperture of the coarse end is 10-15μm, such as 10μm, 11μm, 12μm, 13μm, 14μm or 15μm, but is not limited to the listed values, and other values ​​not listed above are also applicable.

[0018] In this disclosure, the size of the tapered through-hole is influenced by multiple factors. A suitable tapered through-hole size, combined with a suitable magnetic film layer and an applied magnetic field strength, helps ensure that the core material achieves a minute-level response and smooth release.

[0019] As a preferred technical solution of this disclosure, the thickness of the elastic shell is 10-200μm, such as 10μm, 20μm, 50μm, 80μm, 100μm, 120μm, 150μm, 180μm or 200μm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0020] Preferably, the diameter of the elastic shell is 1mm-1cm, such as 1mm, 2mm, 3mm, 5mm, 8mm, 9mm or 1cm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0021] Preferably, the thickness of the magnetic film is 4-50 μm, such as 4 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0022] In this disclosure, the combination of an elastic shell and a suitable magnetic film layer helps ensure the smooth release of the core material and the restoration of the tapered through-hole. If the elastic shell is too thin, the channel may not be able to return to its original state after the magnetic field is removed; if the elastic shell is too thick, the applied magnetic field strength needs to be increased accordingly, increasing unnecessary costs and losses. If the magnetic film layer is too thin, the force on the through-hole will be smaller, resulting in poor magnetic response and a longer response time; if the magnetic film layer is too thick, the force will be greater, leading to wasted costs.

[0023] As a preferred technical solution of this disclosure, the core material includes one or more of sodium oxalate, sodium squartzate, sodium citrate or sodium trifluoromethanesulfonate, preferably sodium trifluoromethanesulfonate.

[0024] Compared to sodium oxalate, sodium squartzate, and sodium citrate, sodium trifluoromethanesulfinate has relatively superior electrochemical activity, high electrolyte solubility, good air stability, and is easy to store and handle. At the same time, it has a lower decomposition potential, can achieve complete conversion in a single charge within the normal voltage window, and leaves no residue in the battery after decomposition without damaging the internal battery components.

[0025] Preferably, the material of the elastic shell includes one or more of polyethylene terephthalate, polyethylene-methyl methacrylate ionomer, polycaprolactone, polylactic acid, polyvinyl alcohol, polyacrylic acid, polyisoprene, or polyurethane.

[0026] Preferably, the magnetic film layer comprises magnetic particles and a dispersant, wherein the mass of the magnetic particles accounts for 60%-90% of the total mass of the magnetic particles and the dispersant, for example, 60%, 70%, 80% or 90%, but is not limited to the listed values, and other values ​​not listed above are also applicable.

[0027] In this disclosure, controlling the appropriate proportion of magnetic particles in the mixture not only ensures uniform force on the conical through-hole when an external magnetic field is applied, but also helps to achieve minute-level magnetic response changes. If there are too few magnetic particles, the magnetic response effect is poor, the response time is long, and the hole-expanding effect is limited. If there are too many magnetic particles, significant aggregation will occur, leading to force dispersion and thus affecting the hole-expanding effect.

[0028] Preferably, the magnetic particles comprise micron-sized carbonyl iron powder and / or micron-sized iron(III) oxide.

[0029] Preferably, the dispersant comprises polydimethylsiloxane.

[0030] As a preferred technical solution of this disclosure, the magnetic response capsule further includes a protective film layer, which covers the outer surface of the magnetic film layer. The protective film layer has pores, and the diameter of the pores is larger than the particle size of the core material.

[0031] Preferably, the pore diameter of the protective film layer is 5-10 μm, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0032] Preferably, the thickness of the protective film layer is 1-5 μm, such as 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0033] In this disclosure, an appropriate protective film thickness serves both a protective function and ensures the smooth release of the core material. If the protective film is too thick, the channel becomes longer, increasing the difficulty of releasing the core material.

[0034] Preferably, the protective film layer is made of polypropylene film or polyethylene film.

[0035] In a second aspect, this disclosure provides a method for preparing a magnetically responsive capsule as described in the first aspect, the method comprising the following steps: (1) An elastic shell containing a core material is prepared by using any one or a combination of at least two of 3D printing technology, ion trajectory etching technology, mask technology, in-situ polymerization method or nano-micro jet method, wherein the elastic shell has a tapered through hole; (2) The magnetic film layer components are sprayed onto the outer surface of the elastic shell by dot spraying, and a magnetic film layer is formed after curing; optionally, a protective film layer is coated on the surface of the magnetic film layer to obtain a magnetic response capsule.

[0036] The preparation method described in this disclosure is simple and easy to operate, which is conducive to large-scale production. The dot-spraying process ensures that the conical channels are not blocked during the preparation of the magnetic film.

[0037] In this disclosure, there are no specific restrictions on the source of the core material; it can be purchased commercially or prepared in-house.

[0038] For example, the core material is sodium trifluoromethanesulfonate, and the preparation method of the core material includes: mixing trifluoromethanesulfonyl chloride, sodium bicarbonate, sodium sulfite and water, and then sequentially performing a first concentration, impurity removal, drying, a second concentration and recrystallization to obtain sodium trifluoromethanesulfonate.

[0039] Preferably, the molar ratio of trifluoromethanesulfonyl chloride, sodium bicarbonate, and sodium sulfite in step (1) is 1:(2-2.5):(2-2.5), such as 1:2:2, 1:2.2:2.2, or 1:2.5:2.5, but is not limited to the listed values. Other unlisted values ​​mentioned above are also applicable.

[0040] Preferably, the first concentration includes heating concentration, wherein the heating concentration temperature is 80-95℃, such as 80℃, 85℃, 90℃ or 95℃, etc.; and the time is 4-6h, such as 4h, 5h or 6h, etc., but is not limited to the listed values, and other values ​​not listed above are also applicable.

[0041] Preferably, the impurity removal includes dissolving the product after the first concentration in anhydrous ethanol, and then removing solid impurities through solid-liquid separation to obtain a filtrate.

[0042] Preferably, the drying process includes drying the filtrate with a desiccant, wherein the desiccant includes magnesium sulfate.

[0043] Preferably, the second concentration includes evaporation concentration using a rotary evaporator.

[0044] Preferably, the recrystallization includes recrystallization using ethanol.

[0045] Furthermore, the obtained sodium trifluoromethane sulfinate can be pulverized to the required particle size range as needed.

[0046] As a preferred technical solution of this disclosure, in step (1), the step of preparing the elastic shell layer containing the core material using the 3D printing technology, the nozzle temperature is 230-250℃, for example, 230℃, 240℃ or 250℃; the heated bed temperature is 80-90℃, for example, 80℃, 85℃ or 90℃; the fan speed percentage is 10%-25%, for example, 10%, 15%, 20% or 25%; the retraction distance is 1-2mm, for example, 1mm, 1.5mm or 2mm; the retraction speed is 20-30mm / s, for example, 20mm / s, 25mm / s or 30mm / s, but is not limited to the listed values, and other unlisted values ​​are also applicable.

[0047] As a preferred technical solution of this disclosure, the curing temperature in step (2) is 80-100℃, such as 80℃, 85℃, 90℃, 95℃ or 100℃, and the time is 1-2h, such as 1h, 1.2h, 1.4h, 1.6h, 1.8h or 2h, but is not limited to the listed values. Other unlisted values ​​mentioned above are also applicable.

[0048] Preferably, the method for coating the protective film layer in step (2) includes any one of thermal lamination, thermal spraying, or 3D printing.

[0049] Preferably, in the step of coating the protective film layer using the thermal bonding method, the thermal bonding temperature is 80-110℃ and the thermal bonding pressure is 0.5-4MPa.

[0050] A suitable thermal bonding temperature range ensures proper coating while preventing shrinkage or melting of the protective film. The thermal bonding pressure must be evenly distributed to ensure a tight interface without mechanical damage.

[0051] Preferably, in the step of coating the protective film layer using 3D printing, the nozzle temperature is 210-250℃, for example, 210℃, 220℃, 230℃, 240℃, or 250℃; the heated bed temperature is 60-90℃, for example, 60℃, 70℃, 80℃, or 90℃; the fan speed percentage is 10%-20%, for example, 10%, 15%, or 20%; the retraction distance is 1-2mm, for example, 1mm, 1.5mm, or 2mm; and the retraction speed is 20-30mm / s, for example, 20mm / s, 25mm / s, or 30mm / s, but is not limited to the listed values, and other unlisted values ​​mentioned above are also applicable.

[0052] Thirdly, this disclosure provides a sodium-ion battery, including an electrode assembly, an electrolyte, a magnetic response capsule, and a battery casing. The electrode assembly includes a positive electrode, a separator, and a negative electrode, with the separator located between the positive and negative electrode. The magnetic response capsule is accommodated in the space formed by the battery casing and the electrode assembly. The magnetic response capsule is the magnetic response capsule as described in the first aspect or the magnetic response capsule prepared by the preparation method described in the second aspect.

[0053] In this disclosure, the electrolyte of the battery is in a rich state, with a surplus (the percentage exceeding the minimum theoretical electrolyte volume) of 8-12 wt%, preferably 10 wt%.

[0054] Preferably, the total mass of the core material in the magnetic response capsule is 1%-3.1% of the mass of the electrolyte, such as 1%, 2% or 3.1%, but is not limited to the listed values. Other unlisted values ​​mentioned above are also applicable.

[0055] In this disclosure, a reasonable amount of core material added helps to improve capacity recovery and increase cycle performance. If the amount added is too small, the effect will be weak and the cycle performance will not be effectively increased; if the amount added is too large, it will exceed the solubility of the core material in the electrolyte, and the capacity will not be further improved.

[0056] Fourthly, this disclosure provides a method for applying the sodium-ion battery described in the third aspect: The application method includes: A magnetic field with an intensity of 0.12-0.23T is applied to the outside of the sodium-ion battery for 50-300s, causing the conical through-hole in the magnetic response capsule to undergo elastic deformation and release the core material; then, after standing, the battery is charged at 40-50℃ to restore the capacity of the sodium-ion battery.

[0057] The time can be selected as 50s, 60s, 90s, 120s, 150s, 180s, 210s, 240s, 270s or 300s, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0058] This disclosure allows for the release of the core material at any time by applying an external magnetic field, typically when the capacity of the sodium-ion battery has decayed to below 93%.

[0059] For the magnetically responsive capsule described in this disclosure, response changes on the order of minutes can be achieved by controlling an appropriate magnetic field strength. If the magnetic field strength is too low, the opening size of the conical through-hole is limited and time-consuming; if the magnetic field strength is too high, it may exceed the tolerance limit of the elastic shell, causing the capsule to twist and affecting the release effect of the core material.

[0060] In this disclosure, those skilled in the art can adjust the release amount of the core material by controlling the time. It can be released all at once or used in multiple stages. For example, multiple uses refer to releasing a portion of the core material initially, allowing it to stand, and then charging normally; when the capacity begins to decrease, a second release can be performed at an appropriate time, followed by a stand before normal charging and discharging again.

[0061] The technical solution provided in this disclosure has the following advantages compared with the prior art: (1) The present invention designs a magnetic response capsule. By adding the magnetic response capsule to the sodium-ion battery, the capacity decay and safety problems caused by the loss of active sodium ions can be reduced or even solved. The capacity of the sodium-ion battery can be restored or regulated in a timely and quantitative manner as needed, which can effectively promote the recovery of battery capacity and the extension of cycle life.

[0062] (2) The magnetic response capsule described in this disclosure controls the release of the core material according to the strength of the magnetic field, so that the operation of the battery cell is not affected by the temperature under all weather conditions. At the same time, the position of the magnetic response capsule can be adjusted according to the actual situation. The core material in the magnetic response capsule can be completely converted within the conventional battery voltage window without any extra steps, which can maintain the integrity of the battery well and does not require disassembly. Overall, it has obvious practicality.

[0063] (3) The preparation method described in this disclosure is simple and easy to operate, which is conducive to large-scale production and provides a new idea for subsequent sodium supplementation operations. Attached Figure Description

[0064] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0065] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0066] Figure 1 This is a schematic diagram illustrating the working principle of the magnetic response capsule described in a specific embodiment of this disclosure; The components are: 1. Protective film layer; 2. Elastic shell layer; 2-1. Conical through hole; 3. Magnetic film layer; 4. Core material. S / N represents the applied magnetic field, and circle A represents the local amplification part.

[0067] Figure 2 This is a comparison chart of the discharge capacity of the sodium-ion batteries described in Application Examples 1, 8-12 and Comparative Application Example 1 of this disclosure.

[0068] Figure 3 This is a comparison chart of the rate performance of the sodium-ion battery described in Application Example 1 and Comparative Application Example 1 under different conditions.

[0069] Figure 4 This is a comparison diagram of the impedance of the sodium-ion battery described in Example 1 and Comparative Application Example 1 under different conditions.

[0070] Figure 5 This is a comparison graph showing the cycle performance of the sodium-ion battery described in Practical Example 1 and Comparative Application Example 1 under different conditions. Detailed Implementation

[0071] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0072] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0073] This disclosure provides a magnetically responsive capsule, the working principle of which is shown in the figure below. Figure 1 As shown, the magnetic response capsule includes a protective film layer 1, an elastic shell layer 2, a magnetic film layer 3, and a core material 4. The elastic shell layer 2 has an internal accommodating space, and the core material 4 is located in the accommodating space. The magnetic film layer 3 covers the outer surface of the elastic shell layer 2, and the protective film layer 1 covers the outer surface of the magnetic film layer 3. The elastic shell 2 is provided with a tapered through hole 2-1, and the tip of the tapered through hole 2-1 faces the inner surface of the elastic shell 2; The core material 4 includes a fluorine-containing lithium salt; The particle size of the core material 4 is larger than the aperture of the tip of the tapered through hole 2-1; The protective film layer 1 has pores, and the diameter of the pores is larger than the particle size of the core material 4.

[0074] Its working principle is as follows: When no magnetic field is applied (B=0), the core material 4 is located within the containment space of the elastic shell layer 2. When a magnetic field is applied (B≠0), the conical through hole 2-1 expands, thereby releasing the core material 4.

[0075] Example 1 This embodiment provides a magnetically responsive capsule and its preparation method. The difference between this embodiment and the magnetically responsive capsule described in the specific implementation is only that: The core material 4 is sodium trifluoromethane sulfinate, with an average particle size of 2 μm and a total mass of 1.65% of the electrolyte mass. The electrolyte comprises: a mixture of ethylene carbonate and dimethyl carbonate at a volume ratio of 4:6, followed by the addition of NaPF6 and NaClO4 at a mass ratio of 95:5, with a sodium salt concentration of 1 mol / L. The amount of electrolyte added exceeds the minimum theoretical addition amount by 10%. All subsequent examples and comparative examples are based on this electrolyte. The elastic shell layer 2 has a thickness of 60 μm and is made of polyethylene terephthalate (purchased from DuPont, product number: 530); the magnetic film layer 3 has a thickness of 15 μm and includes micron-sized carbonyl iron powder (purchased from Alfaisa (China) Chemical Co., Ltd., particle size 1-2 μm, purity 99.5%) and polydimethylsiloxane, wherein the mass of the micron-sized carbonyl iron powder accounts for 80% of the total mass of the micron-sized carbonyl iron powder and polydimethylsiloxane; the pore diameter at the tip of the tapered through-hole 2-1 is 150 nm, and the pore diameter at the coarse end is 12 μm; The protective film layer 1 is a PP film with a pore diameter of 6μm and a thickness of 2μm.

[0076] The preparation method includes: (1) Preparation of core material: In a round-bottom flask, trifluoromethanesulfonyl chloride, sodium bicarbonate, and sodium sulfite were mixed with deionized water (200 ml) in a molar ratio of 1:2.2:2.2 to obtain a mixture; The mixture was stirred at 90°C for 4 hours and then concentrated by heating. The concentrated crude product was dissolved in 0.1 L of anhydrous ethanol and stirred until homogeneous. Insoluble impurities were removed by filtration. The filtrate was dried with magnesium sulfate and then concentrated by rotary evaporator. The concentrated product was recrystallized with ethanol and then pulverized to obtain sodium trifluoromethanesulfinate. (2) Select the material of the elastic shell 2 and use 3D printing technology to prepare the elastic shell that contains the core material. The elastic shell has a primary conical through hole. The nozzle temperature is 240℃, the heated bed temperature is 85℃, the fan speed percentage is 15%, the retraction distance is 1.5mm, and the retraction speed is 25mm / s. (3) The material of the magnetic film layer 3 is sprayed onto the outer surface of the elastic shell layer 2 by dot spraying, and then cured at 90°C for 1 hour to form the magnetic film layer 3; (4) A protective film layer 1 is coated onto the surface of the magnetic film layer 3 using 3D printing to obtain a magnetically responsive capsule; In the 3D printing process, the nozzle temperature is 230℃, the heated bed temperature is 75℃, the fan speed percentage is 15%, the retraction distance is 2mm, and the retraction speed is 30mm / s.

[0077] Example 2 This embodiment provides a magnetically responsive capsule and its preparation method. The difference between this embodiment and the magnetically responsive capsule described in the specific implementation is only that: The core material 4 is sodium trifluoromethane sulfinate, with an average particle size of 800 nm and a total mass of 1% of the electrolyte mass. The elastic shell 2 is made of polyethylene terephthalate and has a thickness of 10 μm; the magnetic film 3 has a thickness of 4 μm and includes micron-sized carbonyl iron powder and polydimethylsiloxane, wherein the mass of the micron-sized carbonyl iron powder accounts for 80% of the total mass of the micron-sized carbonyl iron powder and polydimethylsiloxane; the diameter of the tip of the tapered through hole 2-1 is 100 nm and the diameter of the coarse end is 10 μm; The protective film layer 1 is a PP film with a pore diameter of 7μm and a thickness of 3μm.

[0078] The preparation method includes: (1) Preparation of core material: Referring to step (1) of Example 1, the obtained sodium trifluoromethane sulfinate was pulverized to the required particle size; (2) Select the material of the elastic shell 2 and use 3D printing technology to prepare an elastic shell intermediate body that contains the core material. The elastic shell intermediate body has a primary conical through hole. Among them, the nozzle temperature is 230℃, the heated bed temperature is 80℃, the fan speed percentage is 10%, the retraction distance is 1mm, and the retraction speed is 20mm / s; (3) The material of the magnetic film layer 3 is sprayed onto the outer surface of the elastic shell layer 2 by dot spraying, and then cured at 80°C for 1.5h to form the magnetic film layer 3; (4) A protective film layer 1 is coated onto the surface of the magnetic film layer 3 using 3D printing to obtain a magnetically responsive capsule; In the 3D printing process, the nozzle temperature is 250℃, the heated bed temperature is 75℃, the fan speed percentage is 25%, the retraction distance is 1.5mm, and the retraction speed is 25mm / s.

[0079] Example 3 This embodiment provides a magnetically responsive capsule and its preparation method. The difference between this embodiment and the magnetically responsive capsule described in the specific implementation is only that: No protective film layer 1 was provided; The core material 4 is lithium bis(trifluoromethanesulfonyl)imide, with an average particle size of 8 μm and a total mass of 3.1% of the electrolyte mass. The elastic shell 2 is made of polyethylene terephthalate and has a thickness of 200 μm; the magnetic film 3 has a thickness of 50 μm and includes micron-sized carbonyl iron powder and polydimethylsiloxane, wherein the mass of the micron-sized carbonyl iron powder accounts for 60% of the total mass of the micron-sized carbonyl iron powder and polydimethylsiloxane; the diameter of the tip of the tapered through hole 2-1 is 300 nm and the diameter of the coarse end is 15 μm.

[0080] The preparation method includes: (1) Preparation of core material: Referring to step (1) of Example 1, the obtained sodium trifluoromethane sulfinate was pulverized to the required particle size; (2) Select the material of the elastic shell 2 and use 3D printing technology to prepare the elastic shell that contains the core material. The elastic shell has a primary conical through hole. Among them, the nozzle temperature is 250℃, the heated bed temperature is 90℃, the fan speed percentage is 10%, the return distance is 1mm, and the return speed is 20mm / s; (3) The material of the magnetic film layer 3 is sprayed onto the outer surface of the elastic shell layer 2 by dot spraying, and the magnetic film layer 3 is formed after curing at 100°C for 1 hour to obtain a magnetic response capsule.

[0081] Example 4 This embodiment provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule described in Embodiment 1, except that: In the magnetic film layer 3, the mass of the micron-sized carbonyl iron powder accounts for 50% of the total mass of the micron-sized carbonyl iron powder and polydimethylsiloxane.

[0082] Example 5 This embodiment provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule described in Embodiment 1, except that: In the magnetic film layer 3, the mass of the micron-sized carbonyl iron powder accounts for 60% of the total mass of the micron-sized carbonyl iron powder and polydimethylsiloxane.

[0083] Example 6 This embodiment provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule described in Embodiment 1, except that: In the magnetic film layer 3, the mass of the micron-sized carbonyl iron powder accounts for 90% of the total mass of the micron-sized carbonyl iron powder and polydimethylsiloxane.

[0084] Example 7 This embodiment provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule described in Embodiment 1, except that: The thickness of the elastic shell 2 is 300 μm.

[0085] Example 8 This embodiment provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule described in Embodiment 1, except that: The total mass of the core material 4 is 1% of the mass of the electrolyte.

[0086] Example 9 This embodiment provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule described in Embodiment 1, except that: The total mass of the core material 4 is 2.1% of the mass of the electrolyte.

[0087] Example 10 This embodiment provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule described in Embodiment 1, except that: The total mass of the core material 4 is 2.6% of the mass of the electrolyte.

[0088] Example 11 This embodiment provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule described in Embodiment 1, except that: The total mass of the core material 4 is 3.1% of the mass of the electrolyte.

[0089] Example 12 This embodiment provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule described in Embodiment 1, except that: The total mass of the core material 4 is 3.5% of the mass of the electrolyte.

[0090] Comparative Example 1 This comparative example provides a magnetically responsive capsule, which is the same as the magnetically responsive capsule in Example 1, except that the through hole on the elastic shell 2 is a straight cylindrical through hole with a diameter of 150 nm.

[0091] Magnetic response time test Test method: The materials of the magnetic response capsules corresponding to Examples 1-7 and Comparative Example 1 were prepared into plates (flat plates: 2×2mm). 2 A flat sample (with each layer thickness consistent with that required in Examples 1-7 and Comparative Example 1) was used as the initial state θ0 = 180°. Then, a magnetic field strength of 0.16T was applied to it, and the sample deformed. The time from the flat state to the maximum deformation was recorded, which is the magnetic response time. The change process of the sample was recorded using an ultra-high-speed camera. The average aperture of the through hole tip was measured at the point of maximum deformation. The test results are shown in Table 1.

[0092] Table 1

[0093] As shown in Table 1, the magnetic response capsule described in this disclosure can improve the magnetic response time by controlling factors such as the proportion of magnetic particles and the thickness of the elastic shell. According to Examples 1 and 4-6, a magnetic particle content of 60-90% in the magnetic film layer yields the best results.

[0094] Application Example 1 This disclosure also provides a test sodium-ion battery, comprising: Positive electrode sheet: Sodium vanadium phosphate (NVP), conductive carbon black (SP), carbon nanotubes (CNTs), and polyvinylidene fluoride (PVDF) binder are dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 93:1.5:1:4.5 to obtain a positive electrode active slurry. The positive electrode active slurry is coated on the upper and lower surfaces of an aluminum foil, then dried and rolled to obtain the positive electrode sheet; wherein the double-sided areal density is 200 g / m². 2 The compacted density is 1.7 g / cm³. 3 ; Negative electrode sheet: Hard carbon, conductive carbon black (SP), and binder polyvinylidene fluoride (PVDF) are dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 91:3.5:5.5 to obtain a negative electrode active slurry; the negative electrode active slurry is coated on the upper and lower surfaces of aluminum foil, and then dried and rolled to obtain the negative electrode sheet; wherein, the double-sided areal density is 70 g / m². 2 The compacted density is 0.92 g / cm³. 3 ; Membrane: 16μm PP base membrane with a porosity of 50%; Electrolyte: Refer to Example 1; The positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes, and then wound to obtain a battery cell. The battery cell is placed in a battery casing, electrolyte is injected, the magnetic response capsule described in Example 1 is added, the battery cell is encapsulated, and after a formation and capacity testing process, a sodium-ion battery is obtained.

[0095] Application Examples 2-12 provide a sodium-ion battery, which is the same as the sodium-ion battery in Application Example 1, except that the magnetic response capsule described in Examples 2-12 is used instead of the magnetic response capsule described in Example 1.

[0096] Comparative Application Example 1 This comparative application example provides a sodium-ion battery, which is the same as the sodium-ion battery described in Application Example 1, except that a magnetic response capsule is not added.

[0097] Performance testing (i) Effects of different magnetic field strengths and different amounts of core material on capacity recovery The capacity recovery effect of the sodium-ion batteries described in Application Example 1 and Comparative Application Example 1 under different magnetic field strengths and different core material contents was determined. Test conditions: a) At 25°C, the sodium-ion battery is charged to 3.65V with a constant current and constant voltage of 1C (1.3A), and the cutoff current is 0.1C. Then, it is discharged to 2.0V with a constant current of 1C. The battery is then charged for 3 cycles, with a voltage range of 2.0-3.65V. The discharge capacity of the 3rd cycle is recorded as C1 (reference discharge capacity).

[0098] b) Release of core material in magnetic response capsule: After completing step a), perform 1C charge-discharge cycle on the sodium-ion battery until the capacity decays to a certain extent (the battery capacity decays to about 89%). Place the sodium-ion battery under the corresponding external magnetic field for 80 seconds to ensure the release of core material. Then let it stand for 48 hours and charge the battery to 4.0V at 45℃.

[0099] c) After completing step b), charge the sodium-ion battery with a constant current and constant voltage of 1C (1.3A) to 3.65V, cut off the current at 0.1C, discharge with a constant current of 1C to 2.0V, and maintain the capacity for 3 cycles. The voltage range is 2.0-3.65V. The discharge capacity of the 3rd cycle is recorded as C2.

[0100] The capacity recovery results under different magnetic field strengths are shown in Table 2.

[0101] Table 2

[0102] The capacity recovery results for different core material contents are shown in Table 3, where the applied magnetic field strength is 0.16T.

[0103] Table 3

[0104] As shown in Table 3, too little core material content has a limited effect on capacity recovery; while too much core material content does not further improve capacity recovery.

[0105] (ii) Ratio performance The sodium-ion battery described in Application Example 1 is designated as Test I, and the sodium-ion battery described in Comparative Application Example 1 is designated as Test II.

[0106] For test I: Test conditions: In a 25℃ environment, the battery was charged at a constant current and constant voltage of 1C (1.3A) to 3.65V, with a cutoff current of 0.1C, and then discharged at a constant current of 1C to 2.0V. The discharge capacity was recorded as C0, and the voltage range was 2.0-3.65V. Then, the battery was charged at a constant current and constant voltage of 1C (1.3A) to 3.65V, with a cutoff current of 0.1C, and then discharged at a constant current of 10C to 2.0V. The discharge capacity was recorded as C0. x Rate discharge capacity retention rate = C x / C0×100%.

[0107] Under the above test conditions, the battery was first cycled 3000 times, then placed under an external magnetic field of 0.16T for 80 seconds to release the core material, left to stand for 48 hours, and then charged to 4.0V at 45℃. After that, the rate performance test was carried out.

[0108] For Test II: The rate performance test is conducted only under the test conditions of Test I (without any operation related to releasing the core material).

[0109] Test results are as follows Figure 3 As shown. According to Figure 3 It can be seen that the rate performance of a battery is not affected after the introduction of core materials after cycling.

[0110] (III) Impedance performance The sodium-ion battery described in Application Example 1 is designated as Test a, and the sodium-ion battery described in Comparative Application Example 1 is designated as Test b.

[0111] For test a: Perform 1C standard cycle (voltage range 2.0-3.65V) for 3000 cycles, then place it under an external magnetic field of 0.16T for 80s, release the core material, let it stand for 48h, charge the battery to 4.0V at 45℃, then perform 1C standard constant capacity cycle for 3 cycles, discharge at constant capacity current for 30min, adjust to 50% SOC, and test its impedance.

[0112] For test b: Refer to the cyclic conditions of test a, and start testing its impedance after 3000 cycles (without any operation related to releasing the core material).

[0113] Test results are as follows Figure 4 As shown. By Figure 4 It can be seen that after cycling, the internal resistance of the sodium-ion battery remains stable after the introduction of core materials.

[0114] (iv) Cyclic performance The sodium-ion battery described in Application Example 1 is designated as Test A, and the sodium-ion battery described in Comparative Application Example 1 is designated as Test B.

[0115] For test A: constant current charge-discharge cycle at 1C, voltage range of 2.0-3.65V, 3000 cycles, then place it under an external magnetic field of 0.16T for 80s, release the core material, let it stand for 48h, charge the battery to 4.0V at 45℃, and then continue the cycle.

[0116] For test B: Perform the cycle according to the cycle conditions of test A (without any operation related to releasing the core material).

[0117] Test results are as follows Figure 5 As shown. By Figure 5 It is understood that the magnetic response capsule provided in this disclosure can release the core material on demand at regular intervals to restore battery capacity and extend cycle life.

[0118] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0119] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A magnetically responsive capsule, characterized in that, The magnetically responsive capsule includes an elastic shell, a magnetic film, and a core material. The elastic shell has an internal accommodating space, and the core material is located within the accommodating space. The magnetic film covers the outer surface of the elastic shell. The elastic shell is provided with a tapered through hole, and the tip of the tapered through hole faces the inner surface of the elastic shell. The core material includes sodium salt; The particle size of the core material is larger than the aperture of the tip of the tapered through hole.

2. The magnetically responsive capsule according to claim 1, characterized in that, The particle size of the core material is 500nm-8μm, preferably 1-3μm; Furthermore, under a magnetic field strength of ≥0.12T, the aperture of the tip of the conical through hole is larger than the particle size of the core material. Preferably, the diameter of the tip of the tapered through hole is 100-300 nm, and the diameter of the coarse end is 10-15 μm; Preferably, the thickness of the elastic shell is 10-200 μm; Preferably, the diameter of the elastic shell is 1mm-1cm; Preferably, the thickness of the magnetic film is 4-50 μm.

3. The magnetically responsive capsule according to claim 1 or 2, characterized in that, The core material includes one or more of sodium oxalate, sodium squartz, sodium citrate or sodium trifluoromethanesulfonate, preferably sodium trifluoromethanesulfonate; Preferably, the material of the elastic shell includes one or more of polyethylene terephthalate, polyethylene-methyl methacrylate ionomer, polycaprolactone, polylactic acid, polyvinyl alcohol, polyacrylic acid, polyisoprene, or polyurethane. Preferably, the magnetic film layer comprises magnetic particles and a dispersant, wherein the magnetic particles account for 60%-90% of the total mass of the magnetic particles and the dispersant; Preferably, the magnetic particles comprise micron-sized carbonyl iron powder and / or micron-sized iron(III) oxide; Preferably, the dispersant comprises polydimethylsiloxane.

4. The magnetically responsive capsule according to any one of claims 1-3, characterized in that, The magnetic response capsule further includes a protective film layer, which covers the outer surface of the magnetic film layer. The protective film layer has pores, and the diameter of the pores is larger than the particle size of the core material. Preferably, the pore diameter of the protective film is 5-10 μm; Preferably, the thickness of the protective film layer is 1-5 μm; Preferably, the protective film layer is made of polypropylene film or polyethylene film.

5. A method for preparing a magnetically responsive capsule as described in any one of claims 1-4, characterized in that, The preparation method includes the following steps: (1) An elastic shell containing a core material is prepared by using any one or a combination of at least two of 3D printing technology, ion trajectory etching technology, mask technology, in-situ polymerization method or nano-micro jet method, wherein the elastic shell has a tapered through hole; (2) The magnetic film layer components are sprayed onto the outer surface of the elastic shell by dot spraying, and a magnetic film layer is formed after curing; optionally, a protective film layer is coated on the surface of the magnetic film layer to obtain a magnetic response capsule.

6. The preparation method according to claim 5, characterized in that, In step (1), when the 3D printing technology is used to prepare the elastic shell layer that contains the core material, the nozzle temperature is 230-250℃, the heated bed temperature is 80-90℃, the fan speed percentage is 10%-25%, the retraction distance is 1-2mm, and the retraction speed is 20-30mm / s.

7. The preparation method according to claim 5 or 6, characterized in that, The curing temperature in step (2) is 80-100℃ and the time is 1-2h.

8. The preparation method according to any one of claims 5-7, characterized in that, Step (2) The method of coating the protective film layer includes any one of thermal lamination, thermal spraying or 3D printing.

9. A sodium-ion battery, characterized in that, The battery includes an electrode assembly, an electrolyte, a magnetic response capsule, and a battery casing. The electrode assembly includes a positive electrode, a separator, and a negative electrode, with the separator located between the positive and negative electrode. The magnetic response capsule is housed in the space formed by the battery casing and the electrode assembly. The magnetic response capsule is the magnetic response capsule as described in any one of claims 1-4 or the magnetic response capsule prepared by the preparation method as described in any one of claims 5-8; Preferably, the total mass of the core material in the magnetic response capsule is 1%-3.1% of the mass of the electrolyte.

10. A method of applying the sodium-ion battery as described in claim 9, characterized in that, The application method includes: A magnetic field with an intensity of 0.12-0.23T is applied to the outside of the sodium-ion battery for 50-300s, causing the conical through-hole in the magnetic response capsule to undergo elastic deformation and release the core material; then, after standing, the battery is charged at 40-50℃ to restore the capacity of the sodium-ion battery.

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