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; the core material comprises a fluorine-containing lithium salt, and the particle size of the fluorine-containing lithium 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 realizes the recovery or regulation of the capacity of the sodium ion battery on demand at a fixed time, and also has the performance balance of the cycle life and the efficient transmission of sodium ions.

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] Sodium ions, as an alternative charge carrier, benefit from the natural abundance of their material resources, ensuring a stable mineral supply and enabling economically viable battery systems. Therefore, sodium-ion batteries (SIBs) have broad application prospects in large-scale energy storage and device adaptation. Currently, 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 battery 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 battery lifespan and save energy, time, and costs to some extent.

[0003] 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 (consumption of the SEI film, decomposition of the electrolyte, etc.). For sodium-ion batteries, constructing a stable SEI film significantly improves cycle performance. Currently, most strategies focus on constructing the SEI film at the initial stage. However, the SEI film composition cannot effectively and stably suppress side reactions in the long term. Furthermore, organic species and sodium salts are usually added to the electrolyte to alleviate interfacial failure, making it difficult to guarantee long-term cycle performance with existing electrolyte compositions.

[0004] Therefore, there is very little information available on how to restore or regulate the capacity decay that has already occurred during battery operation, as well as how to balance the performance of both lifespan and efficient sodium ion transport. This has become an urgent problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides a magnetically responsive capsule, its preparation method, and its application.

[0006] 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 a fluorine-containing lithium salt; The particle size of the core material is larger than the aperture of the tip of the tapered through hole.

[0007] To address the capacity decay issue that occurs in sodium-ion batteries after long-term operation, this disclosure presents a magnetically responsive capsule. By adding the magnetically responsive capsule to the sodium-ion battery, capacity can be restored or regulated on a timed and demand-driven basis, while simultaneously achieving a balance between cycle life and efficient sodium-ion transport. Furthermore, the magnetically responsive capsule is not affected by the operation of the sodium-ion battery under all-weather temperatures.

[0008] 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 (SEI structure modifier). 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.

[0009] The released core material decomposes during normal battery charging and discharging, generating inorganic lithium salts. Following a protective interface layer strategy with inorganic phase dotting, this improves the formation kinetics of the SEI film, optimizing and controlling both the positive and negative electrode interfaces. For the positive electrode, its introduction stabilizes the surface and acts as a "pillar" of the transition metal layer during cycling, suppressing oxygen release and lattice collapse caused by structural instability. For the interface where hard carbon acts as the negative electrode, its introduction reduces SEI film solubility, effectively suppressing sodium ion and electron leakage and mitigating electrolyte decomposition on the hard carbon electrode surface. For the interface where sodium metal acts as the negative electrode, its introduction ensures a uniform distribution of highly conductive inorganic sites throughout the outer and inner layers of the SEI film, reducing interfacial impedance and the transport barrier for active ions within the SEI film, forming Na+. + The fast transport domain and high-throughput nucleation sites, while blocking electron tunneling and preventing electrolyte decomposition, enable the formation of a thinner SEI film during the reversible deposition-stripping process of sodium, thereby achieving Na… + Uniform deposition and rapid transport of the core material. It can be fully converted within the normal battery voltage window without additional steps, maintaining battery integrity and eliminating the need for disassembly.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] As a preferred technical solution of this disclosure, the particle size of the core material is 100-1000nm, such as 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm or 1000nm, but is not limited to the listed values. Other values ​​not listed above are also applicable, preferably 200-400nm.

[0014] Furthermore, under a magnetic field strength of ≥0.05T, the aperture of the tip of the conical through hole is larger than the particle size of the core material.

[0015] 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.

[0016] Preferably, the aperture of the tip of the tapered through-hole is 30-80nm, such as 30nm, 40nm, 50nm, 60nm, 70nm or 80nm; the aperture of the coarse end is 1-3μm, such as 1μm, 1.5μm, 2μm, 2.5μm or 3μm, but is not limited to the listed values, and other values ​​not listed above are also applicable.

[0017] In this disclosure, the size of the tapered through-hole is influenced by many 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 second-level response and smooth release.

[0018] As a preferred technical solution of this disclosure, the thickness of the elastic shell is 1-20μm, such as 1μm, 2μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm or 20μm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0019] Preferably, the diameter of the elastic shell is 100μm-2mm, such as 100μm, 200μm, 300μm, 500μm, 800μm, 900μm, 1mm or 2mm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0020] Preferably, the thickness of the magnetic film layer is 100-1500nm, such as 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm or 1500nm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0021] 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, and the uniformity of the thickness will be difficult to control, leading to wasted costs.

[0022] As a preferred technical solution of this disclosure, the core material includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, or lithium bis(difluorosulfonyl)imide, preferably lithium bis(trifluoromethanesulfonyl)imide.

[0023] Preferably, the material of the elastic shell includes one or more of polyethylene terephthalate-1,4-cyclohexanediol, acrylonitrile-butadiene-styrene, polylactic acid, polyvinyl alcohol, polyacrylic acid, polyisoprene, or polyurethane, and is preferably polyethylene terephthalate-1,4-cyclohexanediol.

[0024] Preferably, the magnetic film layer comprises a mixture of magnetic particles and a dispersant, wherein the magnetic particles account for 40%-80% of the mass of the mixture.

[0025] 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 second-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, it will lead to uneven dispersion, obvious aggregation, and dispersed force.

[0026] Preferably, the magnetic particles include nano-sized carbonyl iron powder and nano-sized iron(III) oxide. Preferably, the dispersant comprises polydimethylsiloxane.

[0027] 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.

[0028] The protective film layer can prevent the magnetic response capsule from contacting the battery casing or the main body of the cell, ensuring battery safety and reducing battery self-discharge caused by magnetic materials, without affecting the release of the core material.

[0029] Preferably, the pore diameter of the protective film layer is 2-4 μm, such as 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0030] Preferably, the thickness of the protective film is 500-2000nm, such as 500nm, 1000nm, 1500nm or 2000nm, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0031] 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.

[0032] Preferably, the protective film layer is made of polypropylene film or polyethylene film.

[0033] As a preferred technical solution of this disclosure, the electrolyte further includes film-forming additives, including fluorocarbonates.

[0034] In this disclosure, the synergistic effect of the core material and the film-forming additive can further improve the capacity recovery effect and extend the cycle life.

[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 intermediate containing a core material is prepared by 3D printing technology, and the elastic shell intermediate has a primary conical through hole; Then, the primary tapered through-hole is processed using ion trajectory etching technology to obtain an elastic shell layer; (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] As a preferred technical solution of this disclosure, in step (1), the step of preparing an elastic shell intermediate containing the core material using 3D printing technology, the nozzle temperature is 220-260℃, for example, 220℃, 230℃, 240℃, 250℃ or 260℃; the heated bed temperature is 70-85℃, for example, 70℃, 75℃, 80℃ or 85℃; 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; 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.

[0038] This disclosure describes a method for preparing an elastic shell intermediate containing a core material using 3D micro / nano stepwise printing technology.

[0039] As a preferred technical solution of this disclosure, the step of processing the primary tapered through hole using ion trajectory etching technology in step (1) includes: bombarding the primary tapered through hole with a heavy ion linear accelerator and then irradiating it with a single gold ion.

[0040] Preferably, the ion energy of each gold ion is 2.0-3.0 GeV / u, such as 2.0 GeV / u, 2.2 GeV / u, 2.4 GeV / u, 2.6 GeV / u, 2.8 GeV / u or 3.0 GeV / u, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0041] 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.

[0042] As a preferred technical solution of this disclosure, the method of coating the protective film layer in step (2) includes any one of thermal bonding, thermal spraying or 3D printing.

[0043] Preferably, in the step of coating the protective film layer using the thermal bonding method, the thermal bonding temperature is 80-120℃ and the thermal bonding pressure is 0.5-5MPa.

[0044] 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.

[0045] Preferably, in the step of coating the protective film layer using 3D printing, the nozzle temperature is 210-240℃; the heated bed temperature is 60-80℃; the fan speed percentage is 10%-15%; the retraction distance is 1-2mm, such as 1mm, 1.5mm or 2mm; and the retraction speed is 20-30mm / s.

[0046] 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 a magnetic response capsule prepared by the preparation method described in the second aspect.

[0047] 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%.

[0048] Preferably, the total mass of the core material in the magnetic response capsule is 1%-5% of the mass of the electrolyte, such as 1%, 2%, 3%, 4% or 5%, but is not limited to the listed values. Other unlisted values ​​mentioned above are also applicable.

[0049] 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; if the amount added is too large, the cycle performance will not be further improved, and it will also lead to an excessively high lithium salt content in the SEI membrane, affecting the transport of sodium ions.

[0050] 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 0.05-0.15T is applied to the outside of the sodium-ion battery for 10-60s, causing the conical through-hole in the magnetic response capsule to undergo elastic deformation and release the core material; then, after being left to stand, it is charged and discharged to restore the capacity.

[0051] The time can be selected as 10s, 20s, 30s, 40s, 50s or 60s, but is not limited to the listed values. Other values ​​not listed above are also applicable.

[0052] 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 95%.

[0053] For the magnetically responsive capsule described in this disclosure, a response change on the order of seconds 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 bearing limit of the elastic shell, causing the capsule to twist and affecting the release effect of the core material.

[0054] 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 performing normal charging and discharging; when the capacity begins to decay again, a suitable time can be chosen for a second release, followed by a stand before resuming normal charging and discharging.

[0055] 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 of the sodium-ion battery can be restored or regulated on demand at regular intervals. At the same time, it also achieves a balance between cycle life and efficient sodium-ion transport.

[0056] (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.

[0057] (3) The preparation method described in this disclosure is simple and easy to operate, which is conducive to large-scale production. Attached Figure Description

[0058] 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.

[0059] 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, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0060] 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 the circle represents the local amplification part.

[0061] Figure 2 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.

[0062] Figure 3 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.

[0063] Figure 4 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.

[0064] Figure 5 These are SEM comparison images of the positive electrode active materials of the sodium-ion battery described in Example 1 and Comparative Application Example 1 under different conditions. Wherein, a1 represents the SEM image of the positive electrode active material in the initial state of test ①; wherein, a2 represents the SEM image of the positive electrode active material after 1000 cycles of test ①; wherein, b1 represents the SEM image of the positive electrode active material in the initial state of test ②; wherein, b2 represents the SEM image of the positive electrode active material after 1000 cycles of test ②. Detailed Implementation

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] The following explanation is provided through specific examples.

[0070] Unless otherwise specified, the raw materials, reagents or chemical substances used in the embodiments and comparative examples disclosed herein are all conventional products obtained through commercial channels and can be selected and obtained by those skilled in the art based on known technical knowledge.

[0071] Example 1 This embodiment provides a magnetically responsive capsule and its preparation method. The magnetically responsive capsule described in the specific embodiment differs only in that: The core material 4 is lithium bis(trifluoromethanesulfonyl)imide (purchased from Suzhou Duoduo Chemical Technology Co., Ltd.), with an average particle size of 200 nm and a total mass of 3% of the electrolyte mass; The electrolyte comprises: a mixture of fluoroethylene carbonate and propylene carbonate at a volume ratio of 1:1, followed by the addition of NaClO4 at a concentration of 0.8 mol / L. The amount of electrolyte added exceeds the minimum theoretical amount by 10%, and all subsequent examples and comparative examples are based on this electrolyte. The elastic shell layer 2 has a thickness of 5 μm and is made of polyethylene terephthalate-1,4-cyclohexanediethanol ester (PETG, purchased from China Resources Chemical Materials Technology Co., Ltd., item number: CR-5083); the magnetic film layer 3 has a thickness of 500 nm and includes nano-sized carbonyl iron powder (purchased from Jiangyou Hebao Nanomaterials Co., Ltd., particle size 15-30 nm, purity 99.7%) and polydimethylsiloxane, wherein the mass of the nano-sized carbonyl iron powder accounts for 60% of the total mass of the nano-sized carbonyl iron powder and polydimethylsiloxane; the pore diameter at the tip of the tapered through hole 2-1 is 50 nm, and the pore diameter at the coarse end is 2 μm; The protective film layer 1 is a PP film with a pore diameter of 3μm and a thickness of 500nm.

[0072] The preparation method includes: (1) Select the material of the elastic shell 2 (PETG) and use 3D printing technology to prepare an elastic shell intermediate that contains the core material. The elastic shell intermediate has a primary conical through hole. The nozzle temperature is 240℃, the heated bed temperature is 80℃, the fan speed percentage is 15%, the retraction distance is 1.5mm, and the retraction speed is 25mm / s.

[0073] The primary conical through-hole was bombarded using a heavy ion linear accelerator and then irradiated with a single gold ion (2.2 GeV / u) to obtain an elastic shell 2 with a tip diameter of 50 nm and a coarse end diameter of 2 μm for the conical through-hole 2-1. (2) The raw material of the magnetic film layer 3 is sprayed onto the outer surface of the elastic shell layer 2 by spot spraying, and then cured at 90°C for 1 hour to form the magnetic film layer 3. (3) A protective film layer 1 is coated on the surface of the magnetic film layer 3 using 3D printing to obtain a magnetic response capsule; During the 3D printing process, the nozzle temperature is 220℃, the heated bed temperature is 70℃, the fan speed percentage is 13%, the retraction distance is 1mm, and the retraction speed is 25mm / s.

[0074] Example 2 This embodiment provides a magnetically responsive capsule and its preparation method. The magnetically responsive capsule described in the specific embodiment differs only in that: The core material 4 is lithium bis(trifluoromethanesulfonyl)imide (purchased from Suzhou Duoduo Chemical Technology Co., Ltd.), with an average particle size of 500 nm and a total mass of 1% of the electrolyte mass; The elastic shell 2 is made of polyethylene terephthalate-1,4-cyclohexanediethanol ester (PETG) with a thickness of 1 μm; the magnetic film 3 has a thickness of 100 nm and includes nano-sized carbonyl iron powder and polydimethylsiloxane, wherein the mass of the nano-sized carbonyl iron powder accounts for 60% of the total mass of the nano-sized carbonyl iron powder and polydimethylsiloxane; the pore diameter at the tip of the tapered through-hole 2-1 is 60 nm, and the pore diameter at the coarse end is 2.5 μm; The protective film layer 1 is a PP film with a pore diameter of 3μm and a thickness of 1000nm.

[0075] The preparation method includes: (1) Select the material of the elastic shell 2 (PETG) and use 3D printing technology to prepare an elastic shell intermediate that contains the core material. The elastic shell intermediate has a primary conical through hole. The nozzle temperature is 220℃, the heated bed temperature is 70℃, the fan speed percentage is 10%, the retraction distance is 2mm, and the retraction speed is 30mm / s.

[0076] The primary conical through-hole was bombarded using a heavy ion linear accelerator and then irradiated with a single gold ion (2.2 GeV / u) to obtain an elastic shell 2 with a tip diameter of 60 nm and a coarse end diameter of 2.5 μm for the conical through-hole 2-1. (2) The raw material of the magnetic film layer 3 is sprayed onto the outer surface of the elastic shell layer 2 by spot spraying, and the magnetic film layer 3 is formed after curing at 80°C for 1.5h. (3) A protective film layer 1 is coated on the surface of the magnetic film layer 3 using 3D printing to obtain a magnetic response capsule; During the 3D printing process, the nozzle temperature is 230℃, the heated bed temperature is 70℃, the fan speed percentage is 15%, the retraction distance is 2mm, and the retraction speed is 25mm / s.

[0077] Example 3 This embodiment provides a magnetically responsive capsule and its preparation method. The magnetically responsive capsule described in the specific embodiment differs only in that: No protective film layer 1 was provided; The core material 4 is lithium bis(trifluoromethanesulfonyl)imide (purchased from Suzhou Duoduo Chemical Technology Co., Ltd.), with an average particle size of 800 nm and a total mass of 5% of the electrolyte mass; The elastic shell 2 is made of polyethylene terephthalate-1,4-cyclohexanediethanol ester (PETG) with a thickness of 20 μm; the magnetic film 3 has a thickness of 1200 nm and includes nano-sized carbonyl iron powder and polydimethylsiloxane, wherein the mass of the nano-sized carbonyl iron powder accounts for 50% of the total mass of the nano-sized carbonyl iron powder and polydimethylsiloxane; the diameter of the tip of the tapered through hole 2-1 is 45 nm, and the diameter of the coarse end is 3 μm.

[0078] The preparation method includes: (1) Select the material of the elastic shell 2 (PETG) and use 3D printing technology to prepare an elastic shell intermediate that contains the core material. The elastic shell intermediate has a primary conical through hole. The nozzle temperature is 260℃, the heated bed temperature is 85℃, the fan speed percentage is 20%, the retraction distance is 1mm, and the retraction speed is 20mm / s.

[0079] The primary conical through-hole was bombarded using a heavy ion linear accelerator and then irradiated with a single gold ion (2.2 GeV / u) to obtain an elastic shell 2 with a tip diameter of 45 nm and a coarse end diameter of 3 μm for the conical through-hole 2-1. (2) The raw material of the magnetic film layer 3 is sprayed onto the outer surface of the elastic shell layer 2 by spot spraying, and the magnetic film layer 3 is formed after curing at 100°C for 1 hour to obtain a magnetic response capsule.

[0080] 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 nano-scale carbonyl iron powder accounts for 30% of the total mass of the nano-scale carbonyl iron powder and polydimethylsiloxane.

[0081] 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 nano-scale carbonyl iron powder accounts for 40% of the total mass of the nano-scale carbonyl iron powder and polydimethylsiloxane.

[0082] 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 nano-scale carbonyl iron powder accounts for 80% of the total mass of the nano-scale carbonyl iron powder and polydimethylsiloxane.

[0083] Example 7 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 nano-scale carbonyl iron powder accounts for 90% of the total mass of the nano-scale carbonyl iron powder and polydimethylsiloxane.

[0084] 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 thickness of the elastic shell 2 is 30 μm.

[0085] 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 40 nm.

[0086] Magnetic response time test Test method: The materials of the magnetic response capsules corresponding to Examples 1-8 and Comparative Example 1 were prepared into plates (flat plates: 100×100μm). 2 A flat sample (with each layer thickness consistent with that required in Examples 1-8 and Comparative Example 1) was used as the initial state θ0 = 180°. Then, a magnetic field strength of 0.1T was applied to it, and the sample deformed. The time t 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.

[0087] Table 1

[0088] 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 4-7, a magnetic particle content of 60-80% in the magnetic film layer yields the best results.

[0089] 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 92:2:1:5 to obtain a positive electrode active slurry. The positive electrode active slurry is coated onto 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 90:4:6 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 a negative electrode sheet; wherein, the double-sided areal density is 70 g / m², and 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.

[0090] Application Examples 2-6 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 2-6 is used instead of the magnetic response capsule described in Example 1.

[0091] 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.

[0092] Performance testing (a) Capacity recovery under different magnetic field strengths The capacity recovery effect of the sodium-ion batteries described in Application Example 1 and Comparative Application Example 1 under different magnetic field strengths 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 (1.18A), 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.

[0093] b) Release of core material from magnetic response capsule: After completing step a), the sodium-ion battery is subjected to 1C charge-discharge cycle until the capacity decays to a certain extent (the battery capacity decays to about 91%). The sodium-ion battery is then placed under the corresponding external magnetic fields (0.03T, 0.05T, 0.1T, 0.15T, 0.18T) for 20 seconds to ensure the release of core material, and then left to stand for 48 hours.

[0094] c) After completing step b), charge the sodium-ion battery at a constant current and constant voltage of 1C (1.18A) to 3.65V, cut off the current at 0.1C, discharge at 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.

[0095] The test results are shown in Table 2.

[0096] Table 2

[0097] (ii) Ratio performance Two sodium-ion batteries described in Application Example 1 were selected and labeled as Test I and Test II, respectively. A sodium-ion battery described in Comparative Application Example 1 was selected and labeled as Test III.

[0098] For Test I: First, place it under an external magnetic field of 0.10T for 20 seconds, release the core material, let it stand for 48 hours, and then perform a rate performance test after 500 cycles. Test conditions: In a 25℃ environment, charge the battery at a constant current and constant voltage of 1C (1.18A) to 3.65V, cut off the current at 0.1C, and discharge it at a constant current of 1C to 2.0V. The discharge capacity is recorded as C0, and the voltage range is 2.0-3.65V. Then, charge the battery at a constant current and constant voltage of 1C (1.18A) to 3.65V, cut off the current at 0.1C, and discharge it at a constant current of 30C to 2.0V. The discharge capacity is recorded as C0. x Then the rate discharge capacity retention rate = C x / C0×100%.

[0099] For Test II: Refer to the test conditions of Test I, after 500 cycles, place it under an external magnetic field of 0.10T for 20 seconds, release the core material, let it stand for 48 hours, and then conduct a rate performance test under the same test conditions.

[0100] For Test III: Refer to the test conditions of Test I and conduct the rate performance test.

[0101] Test results are as follows Figure 2 As shown. According to Figure 2 It is known that the introduction of core materials can effectively improve the SEI film formation kinetics and achieve certain optimization and control of the positive and negative electrode interfaces. After cycling, the rate performance of the battery is not affected and may even be improved.

[0102] (III) Impedance performance Two sodium-ion batteries described in Application Example 1 were selected and labeled as Test a and Test b, respectively. A sodium-ion battery described in Comparative Application Example 1 was selected and labeled as Test c.

[0103] For test a: First, place it under an external magnetic field of 0.10T for 20 seconds, release the core material, let it stand for 48 hours, and then perform a 1C standard cycle (voltage range 2.0-3.65V). After 500 cycles, discharge the battery at a constant current of the fixed capacity for 30 minutes, adjust it to 50% SOC, and start testing its impedance.

[0104] For test b: Refer to the cyclic conditions of test a, after 500 cycles, place it under an external magnetic field of 0.10T for 20 seconds, release the core material, let it stand for 48 hours, then perform 3 cycles of 1C standard constant capacity discharge, discharge with constant current at constant capacity for 30 minutes, adjust to 50% SOC, and test its impedance.

[0105] For test c: Refer to the cycling conditions of test a, cycle 500 times, then set the battery to 1C standard capacity for 3 cycles, discharge at constant current for 30 minutes at the constant capacity, adjust to 50% SOC, and start testing its impedance.

[0106] Test results are as follows Figure 3 As shown. By Figure 3 It can be seen that test a released the core material in the initial stage, and its membrane impedance decreased significantly after 500 cycles. Test b also showed a certain degree of reduction compared to test c. This indicates that the introduction of the core material effectively improved the formation kinetics of the SEI film and could achieve certain optimization and control of the positive and negative electrode interfaces. After cycling, the battery SEI was thinner after the introduction of the core material, the interface impedance and the transport barrier of active ions inside the SEI were reduced, and the internal resistance was effectively improved and reduced.

[0107] (iv) Cyclic performance Take two sodium-ion batteries as described in Application Example 1, and label them Test A and Test B respectively. Take a sodium-ion battery as described in Comparative Application Example 1, and label it Test C.

[0108] For test A: First, place it under an external magnetic field of 0.10T for 20s, release the core material, let it stand for 48h, and then perform constant current charge and discharge cycles at 1C in a 25℃ environment, with a voltage range of 2.0-3.65V.

[0109] For test B: Refer to the cyclic conditions of test A, after 500 cycles, place it under an external magnetic field of 0.10T for 20 seconds, release the core material, let it stand for 48 hours, and then continue the cycle.

[0110] For test C: loop according to the loop condition of test A.

[0111] Test results are as follows Figure 4 As shown. By Figure 4 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.

[0112] (v) Changes in positive electrode active materials The sodium-ion battery described in Application Example 1 is designated as Test ①, and the sodium-ion battery described in Comparative Application Example 1 is designated as Test ②.

[0113] For test ①: constant current charge and discharge cycle at 1C (voltage range is 2.0-3.65V), after 500 cycles, place it under an external magnetic field of 0.10T for 20s, release the core material, let it stand for 48h, and then continue to cycle for 500 cycles.

[0114] For test ②: perform 1000 constant current charge-discharge cycles at 1C (voltage range: 2.0-3.65V).

[0115] Comparing the SEM images of the positive electrode active material in the initial state (i.e., before any cycling) and after 1000 cycles in tests ① and ②, as shown below. Figure 5 As shown in the figure, after 500 cycles, the core material in test ① was released, followed by another 500 cycles. Compared with test ② (without the magnetic response capsule), the surface of the positive electrode active material in test ① showed almost no change, with no obvious cracks. This indicates that the release of the core material optimized the interface of the positive electrode CEI film, suppressing oxygen release and lattice collapse caused by structural instability. In contrast, the surface of the positive electrode active material in test ② showed microcracks and structural instability defects, which could further lead to lattice collapse and accelerated cycle decay.

[0116] 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.

[0117] 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 a fluorine-containing lithium 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 100-1000nm, preferably 200-400nm; Furthermore, under a magnetic field strength of ≥0.05T, 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 30-80 nm, and the diameter of the coarse end is 1-3 μm; Preferably, the thickness of the elastic shell is 1-20 μm; Preferably, the diameter of the elastic shell is 100 μm-2 mm; Preferably, the thickness of the magnetic film is 100-1500 nm.

3. The magnetically responsive capsule according to claim 1 or 2, characterized in that, The core material includes one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonylimide), lithium tetrafluoroborate, or lithium bis(difluorosulfonylimide), preferably lithium bis(trifluoromethanesulfonylimide). The material of the elastic shell includes one or more of polyethylene terephthalate-1,4-cyclohexanediol, acrylonitrile-butadiene-styrene, polylactic acid, polyvinyl alcohol, polyacrylic acid, polyisoprene, or polyurethane, preferably polyethylene terephthalate-1,4-cyclohexanediol. Preferably, the magnetic film comprises a mixture of magnetic particles and a dispersant, wherein the magnetic particles account for 40%-80% of the mass of the mixture. Preferably, the magnetic particles comprise nano-sized carbonyl iron powder and / or nano-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 2-4 μm; Preferably, the thickness of the protective film is 500-2000 nm; 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 intermediate containing a core material is prepared by 3D printing technology, and the elastic shell intermediate has a primary conical through hole; Then, the primary tapered through-hole is processed using ion trajectory etching technology to obtain an elastic shell layer; (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), the nozzle temperature is 220-260℃, the heated bed temperature is 70-85℃, the fan speed percentage is 10%-20%, the retraction distance is 1-2mm, and the retraction speed is 20-30mm / s. Preferably, step (1) of processing the primary tapered through-hole using ion trajectory etching technology includes: bombarding the primary tapered through-hole with a heavy ion linear accelerator and then irradiating it with a single gold ion; Preferably, the ion energy of each gold ion is 2.0-3.0 GeV / u.

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%-5% 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 0.05-0.15T is applied to the outside of the sodium-ion battery for 10-60s, causing the conical through-hole in the magnetic response capsule to undergo elastic deformation and release the core material; then, after being left to stand, it is charged and discharged to restore the capacity.

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