Temperature-responsive sodium supplementing material and preparation method thereof, secondary battery

Abstract

The present disclosure relates to a temperature-responsive sodium supplementing material, a preparation method thereof and a secondary battery, wherein the temperature-responsive sodium supplementing material comprises a temperature-responsive micro-nano material container and a sodium supplementing agent in the temperature-responsive micro-nano material container. The temperature-responsive sodium supplementing material provided by the present disclosure can quickly realize the opening of the temperature-responsive micro-nano material container under a thermal response stimulus signal, and realize the timely and quantitative supplement of sodium source on demand. The process is simple and easy to operate, which is conducive to realizing large-scale production and providing a new idea for subsequent sodium supplementing operation.

Description

Technical Field

[0001] This disclosure relates to the field of sodium-ion battery manufacturing technology, and in particular to a temperature-responsive sodium replenishment material and its preparation method, and a secondary battery. Background Technology

[0002] Lithium-ion batteries dominate the field of large-scale energy storage due to their high energy efficiency, long cycle life, and relatively mature technology. However, the limited and uneven distribution of lithium resources restricts their application. Na and Li both belong to Group IA elements and have similar physicochemical properties. The production processes and equipment for the two types of batteries are also largely compatible. Furthermore, sodium-ion batteries have significant advantages and promising development prospects in large-scale applications due to their abundant raw material resources, low price, and high safety.

[0003] However, the commercialization of sodium-ion batteries is still constrained by their relatively low energy density. The lower the energy density, the higher the proportion of auxiliary materials and manufacturing costs, causing sodium-ion batteries to lose their original price advantage. Therefore, increasing energy density is a crucial way to further reduce the cost of sodium-ion batteries and is key to their commercialization.

[0004] For sodium-ion batteries (SIBs), the cathode material is the only reversible sodium ion (Na+) in the entire battery. + (Source) provides the active Na required for the battery's charging and discharging process. + However, during the initial activation and cycling of the battery, irreversible reactions continuously consume the active Na. + This leads to a decrease in the reversible energy density of the battery and a shortened cycle life. Currently, commonly used methods to avoid Na... + The method to reduce the loss is pre-sodiumization, which can provide additional active Na to the sodium-ion battery system. + To avoid Na + The problem of decreased energy density due to sodium loss is addressed, but current pre-sodiumification methods mostly occur during the initial charge activation stage, focusing on how to improve the initial energy density of sodium-ion batteries. However, the focus remains on how to replenish sodium-ion batteries with sodium in a timely and quantitative manner during operation. + Very little is mentioned.

[0005] Therefore, a new method for sodium supplementation is needed to meet the requirements. Summary of the Invention

[0006] To address the aforementioned technical problems, this disclosure provides a temperature-responsive sodium supplement material and its preparation method.

[0007] In a first aspect, this disclosure provides a temperature-responsive sodium replenishment material, the temperature-responsive sodium replenishment material comprising a temperature-responsive micro / nano material chamber, and a sodium replenishing agent located in the temperature-responsive micro / nano material chamber.

[0008] As a preferred technical solution of this disclosure, the temperature-responsive micro / nano material chamber has a spherical or near-spherical structure below 70°C, and deforms to release the internal sodium replenishing agent at 70-80°C.

[0009] As a preferred embodiment of this disclosure, the temperature-responsive micro / nano material chamber undergoes deformation in a time of 1-60 seconds.

[0010] As a preferred technical solution of this disclosure, at temperatures below 70°C, the size of the temperature-responsive micro / nano material chamber is 5-40 μm, preferably 10-20 μm.

[0011] As a preferred technical solution of this disclosure, the thickness of the temperature-responsive micro / nano material chamber is 0.5-2 μm below 70°C.

[0012] As a preferred technical solution of this disclosure, the material of the temperature-responsive micro / nano material chamber includes any one or a combination of at least two of the following: ethylene-methyl acrylate copolymer, polyethylene-methyl methacrylate ionomer, polycaprolactone, polylactic acid, polynorbornene, polystyrene-butadiene copolymer, polymethyl methacrylate copolymer, polycaprolactone-polydimethylsiloxane-polycaprolactone, polyurethane, or polylactic acid-caprolactone copolymer. More preferably, it is a combination of ethylene-methyl acrylate copolymer and polyethylene-methyl methacrylate ionomer.

[0013] As a preferred embodiment of this disclosure, the temperature-responsive micro / nano material chamber is made of a combination of ethylene-methyl acrylate copolymer and polyethylene-methyl methacrylate ionomer. Based on the total mass of the temperature-responsive micro / nano material chamber as 100%, the content of the ethylene-methyl acrylate copolymer is 10-50%, preferably 30%.

[0014] As a preferred technical solution of this disclosure, the sodium supplement is selected from any one or a combination of at least two of modified or unmodified sodium oxalate, modified or unmodified sodium squartzate, sodium biphenyl, modified or unmodified sodium citrate, or sodium powder, and preferably the modification is conductive carbon coating modification.

[0015] As a preferred embodiment of this disclosure, the average particle size of the sodium supplement is 0.2-2 μm, preferably 0.5-1 μm.

[0016] In a second aspect, this disclosure provides a method for preparing the temperature-responsive sodium supplement material described in the first aspect, the method comprising:

[0017] A slurry for preparing a temperature-responsive micro / nano material container is prepared, and the slurry is processed with a sodium supplementing agent to obtain the temperature-responsive sodium supplementing material.

[0018] As a preferred technical solution of this disclosure, the processing method includes any one or a combination of at least two of solution mixing, thermoplastic processing, melt blending, in-situ polymerization, 3D printing or nano-microjets, preferably a combination of melt blending and 3D printing.

[0019] Thirdly, this disclosure provides a secondary battery including the temperature-responsive sodium-supplementing material described in the first aspect.

[0020] As a preferred embodiment of this disclosure, the temperature-responsive sodium replenishing material is disposed on the surface of the separator or in the electrolyte of the secondary battery.

[0021] As a preferred embodiment of this disclosure, the temperature-responsive sodium replenishing material is a solid, and the temperature-responsive sodium replenishing material is applied to the surface of the separator of the secondary battery by spot coating.

[0022] As a preferred embodiment of this disclosure, the temperature-responsive sodium replenishing material is a liquid, and the temperature-responsive sodium replenishing material is applied to the surface of the separator of the secondary battery and / or added to the electrolyte.

[0023] Fourthly, this disclosure provides a method for replenishing sodium in the secondary battery described in the third aspect, the method comprising: heating the secondary battery to 70-80°C and holding it for 1-60 seconds to complete the replenishment of sodium in the secondary battery.

[0024] Fifthly, this disclosure provides another type of secondary battery, which is a lithium-ion battery (lithium supplement), a potassium-ion battery (potassium supplement), a zinc-ion battery (zinc supplement), or a magnesium-ion battery (magnesium supplement).

[0025] The technical solution provided in this disclosure has the following advantages compared with the prior art:

[0026] (1) The temperature-responsive sodium replenishment material provided in this disclosure can quickly realize the opening of the temperature-responsive micro-nano material chamber under the thermal response stimulus signal, release the sodium replenishment agent, and thus realize the sodium source replenishment on time, in quantity and as needed.

[0027] (2) The temperature-responsive micro-nano material chamber provided in this disclosure has a low thermal response temperature and can achieve a response change in the second level at around 70°C. The high temperature environment has little impact on the performance of the battery itself. At the same time, the material chamber will not be stimulated to open at temperatures below 70°C, and the operation of the battery cell will not be affected by the temperature in all weather conditions. It has obvious practicality.

[0028] (3) The preparation method provided 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

[0029] 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.

[0030] 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.

[0031] Figure 1 This is a simplified schematic diagram illustrating the preparation of the temperature-responsive micro / nano material chamber and the release of the sodium supplement agent as described in this disclosure.

[0032] Figure 2 Charge-discharge curves of the sodium-ion battery before and after sodium release provided in Application Example 3;

[0033] Figure 3 Cyclic comparison diagram of the sodium-ion battery provided in Application Example 3 and the sodium-ion battery provided in Comparative Application Example 1. Detailed Implementation

[0034] 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.

[0035] 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.

[0036] By using pre-sodiumization technology, additional active Na can be provided to the battery system. + This is an effective means to solve the problem of active sodium ion consumption. However, most current pre-sodiuming strategies occur during the initial charge activation stage, focusing on improving the initial energy density of the battery. Very few address the timely, quantitative, and on-demand replenishment of sodium during subsequent battery operation. Therefore, this disclosure provides a temperature-responsive sodium replenishment material, its preparation method, and a secondary battery.

[0037] In a first aspect, this disclosure provides a temperature-responsive sodium replenishment material, the temperature-responsive sodium replenishment material comprising a temperature-responsive micro / nano material chamber, and a sodium replenishing agent located in the temperature-responsive micro / nano material chamber.

[0038] The temperature-responsive sodium replenishment material disclosed herein includes a sodium replenishing agent and a temperature-responsive micro / nano material chamber. The sodium replenishing agent is placed in the temperature-responsive micro / nano material chamber, which includes a material with shape memory function, capable of deformation at a certain temperature. The opening of the chamber can be controlled by temperature response to release the sodium replenishing agent.

[0039] The temperature-responsive micro / nanomaterial chamber described in this disclosure consists of two polymer materials: one serves as the material matrix, typically composed of physical or chemical cross-links to maintain structural integrity; the other serves as a switchable unit, which can typically achieve temporary shape fixation and initial shape recovery under external stimuli. By placing the sodium supplement material inside the temperature-responsive micro / nanomaterial chamber and controlling the proportion of the switchable unit in the matrix, the temperature-responsive micro / nanomaterial chamber can be rapidly activated in response to thermal stimuli, enabling timed, quantitative, and on-demand sodium replenishment.

[0040] A simplified schematic diagram illustrating the preparation of the temperature-responsive micro / nano material chamber and the release of the sodium supplement described in this disclosure is shown below. Figure 1 Through processing programming and cooling curing, it obtains a temporary fixed shape with a spherical or near-spherical shape, which is used to encapsulate the sodium supplement. After receiving a heated thermal stimulus, it undergoes deformation, and the polymer structure changes from curled to flat, restoring to its initial state, thereby releasing the sodium supplement.

[0041] As a preferred technical solution of this disclosure, the temperature-responsive micro / nano material chamber has a spherical or near-spherical structure below 70°C, and deforms to release the internal sodium replenishing agent at 70-80°C.

[0042] The deformation at 70-80℃ mentioned in this disclosure means that the material of the temperature-responsive micro / nano material container can deform at 70-80℃ and return to its initial state, rather than that the material can only deform between 70-80℃. For example, it can be 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, etc.

[0043] This disclosure specifically selects temperature-responsive micro / nanomaterials capable of deformation at 70-80℃. When applied to secondary batteries, the sodium battery using this temperature-responsive sodium replenishment material exhibits a low thermal response temperature. This battery can achieve a response change within seconds in the 70-80℃ range. The response time is very short at high temperatures, minimizing the impact on the battery's performance. Since the polymer's initial melting peak is around 70℃, the micro / nanomaterial chamber inside the battery will not be stimulated to open below 70℃, ensuring the cell's operation remains unaffected under all-weather temperatures, demonstrating significant practicality. The process disclosed is simple and easy to operate, facilitating large-scale production and providing a new approach for subsequent sodium replenishment operations.

[0044] As a preferred technical solution of this disclosure, the time for deformation of the temperature-responsive micro / nano material chamber is 1-60s, such as 2s, 5s, 10s, 18s, 40s, 45s, 50s, 55s, 59s, etc.

[0045] As a preferred technical solution of this disclosure, at temperatures below 70°C, the size of the temperature-responsive micro / nano material chamber is 5-40 μm, preferably 10-20 μm, such as 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, etc.

[0046] As a preferred technical solution of this disclosure, the thickness of the temperature-responsive micro / nano material chamber is 0.5-2μm at temperatures below 70℃, for example, 0.6μm, 0.7μm, 0.9μm, 1.1μm, 1.4μm, 1.5μm, 1.8μm, 1.9μm, etc.

[0047] As a preferred technical solution of this disclosure, the material of the temperature-responsive micro / nano material chamber includes any one or a combination of at least two of the following: ethylene-methyl acrylate copolymer, polyethylene-methyl methacrylate ionomer, polycaprolactone, polylactic acid, polynorbornene, polystyrene-butadiene copolymer, polymethyl methacrylate copolymer, polycaprolactone-polydimethylsiloxane-polycaprolactone, polyurethane, or polylactic acid-caprolactone copolymer. More preferably, it is a combination of ethylene-methyl acrylate copolymer and polyethylene-methyl methacrylate ionomer.

[0048] As a preferred embodiment of this disclosure, the temperature-responsive micro / nanomaterial container is made of a combination of ethylene-methyl acrylate copolymer and polyethylene-methyl methacrylate ionomer. Based on the total mass of the temperature-responsive micro / nanomaterial container as 100%, the content of the ethylene-methyl acrylate copolymer is 10-50%, for example, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc., preferably 30%. When the proportion of ethylene-methyl acrylate copolymer is less than 10%, the shape recovery of the temperature-responsive micro / nanomaterial container is poor, which is not conducive to the release of sodium supplement; when the proportion of ethylene-methyl acrylate copolymer is higher than 50%, the temporary shape fixation of the temperature-responsive micro / nanomaterial container is poor, which is not conducive to the storage of sodium supplement.

[0049] As a preferred technical solution of this disclosure, the sodium supplement is selected from any one or a combination of at least two of modified or unmodified sodium oxalate, modified or unmodified sodium squartzate, sodium biphenyl, modified or unmodified sodium citrate, or sodium powder, and preferably the modification is conductive carbon coating modification.

[0050] As a preferred embodiment of this disclosure, the average particle size of the sodium supplement is 0.2-2 μm, preferably 0.5-1 μm, such as 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, etc.

[0051] In a second aspect, this disclosure provides a method for preparing the temperature-responsive sodium supplement material described in the first aspect, the method comprising:

[0052] A slurry for preparing a temperature-responsive micro / nano material container is prepared, and the slurry is processed with a sodium supplementing agent to obtain the temperature-responsive sodium supplementing material.

[0053] As a preferred technical solution of this disclosure, the processing method includes any one or a combination of at least two of solution mixing, thermoplastic processing, melt blending, in-situ polymerization, 3D printing or nano-microjets, preferably a combination of melt blending and 3D printing, which can achieve shape control at the micro-nano scale.

[0054] As a preferred embodiment of this disclosure, the preparation of temperature-responsive sodium supplementation materials includes:

[0055] The ethylene-methyl acrylate copolymer and polyethylene-methyl methacrylate ionomer particles were pre-dried in a vacuum for 12 hours, and then stirred at 180°C and 50 rpm for 10 min using a dual-rotor close mixer.

[0056] As a preferred technical solution of this disclosure, the preparation method of temperature-responsive sodium supplement material includes: using 3D printing to obtain a rolled spherical chamber of a certain size and thickness by slurry of ethylene-methyl acrylate copolymer and polyethylene-methyl methacrylate ionomer particles and sodium supplement particles, and then cooling it to 10°C to fix it, thereby obtaining a temperature-responsive sodium supplement material containing sodium supplement particles.

[0057] Thirdly, this disclosure provides a secondary battery including the temperature-responsive sodium-supplementing material described in the first aspect.

[0058] As a preferred embodiment of this disclosure, the secondary battery is a sodium-ion battery. When applied to sodium-ion batteries, its application is extremely portable.

[0059] The sodium-ion battery disclosed herein can achieve different temperature responses of the chamber by controlling the proportion of switchable cells (shape memory materials) in the temperature-responsive micro / nano material chamber. This disclosure allows the temperature-responsive sodium replenishment material to be fixed onto the separator surface via spot spraying, and then assembled into a battery along with the separator. The process disclosed herein is simple and easy to operate, facilitating large-scale production and providing a new approach for subsequent sodium replenishment operations.

[0060] As a preferred embodiment of this disclosure, the temperature-responsive sodium replenishing material is disposed on the surface of the separator or in the electrolyte of the secondary battery.

[0061] As a preferred embodiment of this disclosure, the temperature-responsive sodium replenishing material is a solid, and the temperature-responsive sodium replenishing material is applied to the surface of the separator of the secondary battery by spot coating.

[0062] As a preferred embodiment of this disclosure, the temperature-responsive sodium replenishing material is a liquid, and the temperature-responsive sodium replenishing material is applied to the surface of the separator of the secondary battery and / or added to the electrolyte.

[0063] As a preferred technical solution of this disclosure, the temperature-responsive sodium-supplementing material is coated onto the surface of the separator by spot spraying, and then the positive electrode, negative electrode, separator and electrolyte are assembled. The assembly method can be at least one of stacking, winding and other combinations thereof, to obtain the sodium-ion battery.

[0064] In this disclosure, an exemplary method for preparing a secondary battery is provided, which includes the following steps:

[0065] Preparation of the positive electrode sheet:

[0066] A positive electrode active material, conductive agent, and binder are mixed and stirred in a ratio of (90-97%):(1.5-5%):(1.5-5%) to prepare a positive electrode active slurry;

[0067] The positive electrode active slurry is uniformly coated onto the positive electrode current collector, with a double-sided surface density of 70-500 g / m². 2 ;

[0068] The positive electrode sheet is rolled to achieve a compaction density of 1.3-3.1 g / cm³. 3 ;

[0069] Preparation of negative electrode sheet:

[0070] A negative electrode active material, conductive agent and binder are mixed and stirred in a ratio of (87-96%):(1-5%):(3-8%) to prepare a negative electrode active slurry;

[0071] The negative electrode active slurry is uniformly coated onto the negative electrode current collector, with a double-sided surface density of 30-190 g / m². 2 ;

[0072] The negative electrode sheet is rolled to achieve a compaction density of 0.8-1.3 g / cm³. 3 ;

[0073] Assemble the battery:

[0074] Temperature-responsive sodium-supplementing material is coated onto the surface of a separator by spot spraying. The separator separates the positive electrode and the negative electrode. The materials are arranged in a regular pattern and then stacked or wound multiple times.

[0075] A positive electrode tab is connected to the positive current collector, and a negative electrode tab is connected to the negative current collector;

[0076] The sodium-ion battery is obtained by assembling the positive electrode, negative electrode, separator, and electrolyte.

[0077] Fourthly, this disclosure provides a method for replenishing sodium in the secondary battery described in the third aspect. The method includes: heating the secondary battery to 70-80°C, such as 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C, etc., and maintaining the temperature for 1-60 seconds, such as 2 seconds, 5 seconds, 10 seconds, 18 seconds, 40 seconds, 45 seconds, 50 seconds, 52 seconds, 59 seconds, etc., to complete the sodium replenishment in the secondary battery.

[0078] When the battery needs sodium replenishment, the temperature is raised to around 70°C. At this temperature, when the polymer material is reheated above its transition temperature, the molecular chain mobility can be reactivated without any external load. Furthermore, due to the favorable thermodynamic trend of increasing entropy, the deformed molecular chain conformation will return to a flat state. In other words, when the temperature-responsive micro / nanomaterial chamber is stimulated by a heat signal, the polymer structure changes from coiled to flattened, the chamber opens, and the sodium replenishment agent is released.

[0079] Fifthly, this disclosure provides another type of secondary battery, which is a lithium-ion battery (lithium supplement), a potassium-ion battery (potassium supplement), a zinc-ion battery (zinc supplement), or a magnesium-ion battery (magnesium supplement).

[0080] As a preferred embodiment of this disclosure, the secondary battery is a lithium-ion battery, using a temperature-responsive lithium replenishment material. The temperature-responsive lithium replenishment material includes a temperature-responsive micro / nano material chamber and a lithium replenishing agent located in the temperature-responsive micro / nano material chamber.

[0081] As a preferred embodiment of this disclosure, the secondary battery is a potassium-ion battery, using a temperature-responsive potassium replenishment material. The temperature-responsive potassium replenishment material includes a temperature-responsive micro / nano material chamber and a potassium replenishing agent located in the temperature-responsive micro / nano material chamber.

[0082] As a preferred embodiment of this disclosure, the secondary battery is a zinc-ion battery, using a temperature-responsive zinc supplementation material. The temperature-responsive zinc supplementation material includes a temperature-responsive micro / nano material chamber and a zinc supplement agent located in the temperature-responsive micro / nano material chamber.

[0083] As a preferred embodiment of this disclosure, the secondary battery is a magnesium-ion battery, using a temperature-responsive magnesium supplementing material. The temperature-responsive magnesium supplementing material includes a temperature-responsive micro / nano material chamber and a magnesium supplementing agent located in the temperature-responsive micro / nano material chamber.

[0084] In the following examples, the ethylene-methyl acrylate copolymer (EMA, [model 1609] containing 9 wt% methyl acrylate (MA)) and the polyethylene-methyl methacrylate ionomer (E / MMA, [model 8940] containing 5.4 mol.% methacrylic acid (MAA) groups, 30% neutralized by sodium salt) were both purchased from DuPont.

[0085] Examples 1-5

[0086] This embodiment provides a temperature-responsive sodium supplementation material and its preparation method, as follows:

[0087] Ethylene-methyl acrylate copolymer and polyethylene-methyl methacrylate ionomer particles were combined in mass ratios of 0:100 (Example 1), 10:90 (Example 2), 30:70 (Example 3), 50:50 (Example 4), and 60:40 (Example 5). The mixture was pre-dried in a vacuum for 12 hours and then stirred at 180°C and 50 rpm for 10 minutes using a dual-rotor mixer to obtain a slurry.

[0088] The obtained slurry and sodium supplement particles (sodium squartz particles, purchased from Fangli Technology) were 3D printed to obtain a rolled spherical chamber with a size of 10μm and a thickness of 1μm. Then, the chamber was cooled to 10℃ to fix it, resulting in a temperature-responsive sodium supplement material containing sodium supplement particles.

[0089] Application Examples 1-5

[0090] This application example provides a sodium-ion battery, the preparation method of which is as follows:

[0091] (1) Preparation of the positive electrode sheet:

[0092] The polyanionic cathode material NFPP, conductive agent SP, CNTs and binder PVDF are mixed in a ratio of 92:2:1:5. The CNTs are mixed with the adhesive solution first. The CNTs are fully expanded by high-speed stirring and ultrasound. Then SP is added and the mixture is stirred and centrifuged at high speed to obtain a uniform conductive slurry. The active material is added and the above materials are mixed by ultrasonic oscillation and vacuum stirring to obtain the cathode active slurry.

[0093] The positive electrode active slurry is uniformly coated onto the positive electrode current collector, and the surface density of the coating on both sides of the positive electrode active slurry is 200 g / m². 2 The positive electrode sheet is rolled to achieve a compaction density of 2.0 g / cm³. 3 ;

[0094] (2) Preparation of negative electrode sheet:

[0095] A negative electrode active slurry was prepared by mixing hard carbon, conductive agent SP and binder PVDF in a ratio of 90:3:7 and stirring.

[0096] The negative electrode active slurry is uniformly coated onto the negative electrode current collector, and the surface density of the coating on both sides of the negative electrode active slurry is 70 g / m². 2 The negative electrode sheet is rolled to achieve a compaction density of 0.92 g / cm³. 3 ;

[0097] (3) Assembly:

[0098] The temperature-responsive sodium-supplementing materials provided in Examples 1-5 are coated onto the surface of the separator by spot spraying. The positive and negative electrode sheets are separated by the separator and arranged in a regular manner and then stacked or wound multiple times.

[0099] Connect the positive electrode tab to the positive current collector and the negative electrode tab to the negative current collector;

[0100] A sodium battery with temperature-controlled sodium replenishment was prepared by injecting electrolyte (1.5 mol / L NaPF6, EC (ethylene carbonate): DMC (dimethyl carbonate): EMC (ethyl methyl carbonate) = 1:1:1 vol%), sealing, formation, aging, and capacity testing.

[0101] Comparative Application Example 1

[0102] This comparative application example provides a sodium-ion battery.

[0103] The difference from the application example is that no temperature-responsive sodium replenishment material is used on the diaphragm surface in this comparative application example.

[0104] Performance testing

[0105] The performance of the temperature-responsive metallization digestion materials provided in Examples 1-5 and the sodium-ion batteries provided in the application examples and comparative application examples was tested using the following methods:

[0106] (1) Shape recovery rate and recovery time:

[0107] The temperature-responsive micro / nano material bins corresponding to Examples 1-5 were prepared into plates (flat plates, 20×2×1μm). 3 A flat sample (denoted as the initial state θ0 = 180°) was placed in water at 70°C for 2 minutes. Subsequently, the sample was folded into a U-shape (θ1 = 0°) under external force and temporarily fixed in water at 10°C for 2 minutes. Finally, the sample with the temporary shape was placed back into water at 70°C to restore its initial shape; the final restored angle is denoted as θ. r The recovery time is denoted as t. r The shape recovery rate R r =θ r / (θ0-θ1)×100%.

[0108] The test results are shown in Table 1:

[0109] Table 1

[0110] type Shape recovery rate / % Shape recovery time / s Example 1 (EMA-0) 20 70 Example 2 (EMA-10) 60 30 Example 3 (EMA-30) 90 10 Example 4 (EMA-50) 75 7 Example 5 (EMA-60) 30 3

[0111] Performance tests show that the temperature-responsive micro / nano material chamber provided in this disclosure can recover to its initial state at temperatures above 70°C, with a recovery time in the order of seconds. Therefore, the temperature-responsive sodium replenishment material provided in this disclosure can release sodium replenishment agent under temperature stimulation of 70-80°C, thereby replenishing the active sodium ions in the battery.

[0112] As can be seen from the comparison of Examples 1-5, when the mass ratio of ethylene-methyl acrylate copolymer in the temperature-responsive micro / nano material container is 30% (Example 3), the shape recovery rate is high and the shape recovery time is fast, which is beneficial to the release of sodium supplement.

[0113] (2) Discharge capacity: (The sodium-ion battery provided in Application Example 3 was used for testing, and the release of sodium replenishment was determined by the discharge capacity.)

[0114] a) Activation of micro-nano material chamber: The battery was placed in the corresponding temperature environment (25℃, 45℃, 55℃, 70℃) for 2 minutes to activate the micro-nano material chamber;

[0115] b) Activation of sodium supplement: Charge the battery at a constant current and constant voltage of 0.5C (0.6A) to 4.15V, cut off current of 0.05C, and discharge at a constant current of 0.5C to 2.0V.

[0116] c) Discharge performance: In a 25℃ environment, the battery is charged to 3.65V with a constant current and constant voltage of 1C (1.2A), the cutoff current is 0.1C, and discharged to 2.0V with a constant current of 1C. The battery is then charged for 3 cycles with a constant current of 2.0-3.65V. The discharge capacity of the 3rd cycle is recorded as C1.

[0117] The test results are shown in Table 2.

[0118] Table 2

[0119] type Discharge capacity / Ah 25℃ 1.25 45℃ 1.25 55℃ 1.25 70℃ 1.40

[0120] Performance tests show that the temperature-responsive sodium replenishing material provided in this disclosure can release sodium replenishing agent at temperatures above 70°C, thereby restoring capacity.

[0121] (3) Electrochemical performance: (The effect of the sodium supplement was characterized by the following electrochemical performance tests using the sodium-ion batteries provided in Application Example 3 and Comparative Application Example 1.)

[0122] a) Sodium supplementation activation: Charge the battery at a constant current and constant voltage of 0.5C (0.6A) to 4.15V, cut off current of 0.05C, and discharge at a constant current of 0.5C to 2.0V.

[0123] b) Cyclic stability: Under constant current charge-discharge cycling at 2C (2.4A) in a 25℃ environment, with a voltage range of 2.0-3.65V, for n cycles. Capacity retention rate on the nth cycle = discharge capacity on the nth cycle / discharge capacity on the first cycle.

[0124] c) Charge and discharge test: In an environment of 25℃, the battery is charged to 3.65V with a constant current and constant voltage of 1C (1.2A), and the cutoff current is 0.1C. It is then discharged to 2.0V with a constant current of 1C.

[0125] Figure 2 The figure shows the charge-discharge curves of the sodium-ion battery (cell containing temperature-responsive sodium replenishing material) provided in Application Example 3 before and after the release of the sodium replenishing material. As can be seen from the figure, the temperature-responsive sodium replenishing material provided in this disclosure can release sodium replenishing agent to supplement the battery capacity.

[0126] Figure 3 The diagram shows a cycle comparison between the sodium-ion battery (cell containing temperature-responsive sodium replenishment material) provided in Application Example 3 and the sodium-ion battery (cell without temperature-responsive sodium replenishment material) provided in Comparative Application Example 1. As can be seen from the diagram, the sodium replenishment agent released during operation of the sodium-ion battery can replenish sodium ions, thereby replenishing the battery capacity and increasing cycle life.

[0127] 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.

[0128] 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 temperature-responsive sodium supplement material, characterized by, The temperature-responsive sodium supplementing material comprises a temperature-responsive micro-nano material container and a sodium supplementing agent in the temperature-responsive micro-nano material container; the material of the temperature-responsive micro-nano material container is a combination of ethylene-methyl acrylate copolymer and polyethylene-methyl methacrylate ionomer. The temperature-responsive micro-nano material container is in a spherical or spherical-like structure below 70℃, and deforms to release the internal sodium supplementing agent at 70-80℃.

2. The temperature-responsive sodium-supplementing material according to claim 1, wherein The deformation time is 1-60s.

3. The temperature-responsive sodium-supplementing material according to claim 1 or 2, characterized by, The thickness of the temperature-responsive micro-nano material container is 0.5-2μm below 70℃.

4. The temperature-responsive sodium-supplementing material according to claim 1, wherein The content of the ethylene-methyl acrylate copolymer is 10-50% based on the total mass of the temperature-responsive micro-nano material container.

5. The temperature-responsive sodium-supplementing material according to claim 4, wherein The content of the ethylene-methyl acrylate copolymer is 30% based on the total mass of the temperature-responsive micro-nano material container.

6. The temperature-responsive sodium-supplementing material according to any one of claims 1, 2, 4, or 5, wherein, The sodium supplementing agent is selected from any one or a combination of at least two of modified or unmodified sodium oxalate, modified or unmodified sodium hypophosphite, sodium diphenyl, modified or unmodified sodium citrate, or sodium powder; The average particle size of the sodium supplementing agent is 0.2-2μm.

7. The temperature-responsive sodium-supplementing material according to claim 6, wherein The modification is conductive carbon coating modification. The average particle size of the sodium supplementing agent is 0.5-1μm.

8. A method for producing the temperature-responsive sodium-supplementing material according to any one of claims 1 to 7, characterized by, The preparation method comprises: Preparation of a slurry of a temperature-responsive micro-nano material container, processing of the slurry with a sodium supplementing agent to obtain the temperature-responsive sodium supplementing material.

9. The method of claim 8, wherein the temperature-responsive sodium-supplementing material is prepared by the steps of: The processing method comprises a combination of at least two of solution mixing, melt blending, in-situ polymerization, 3D printing, and nanomicrojet.

10. The method for preparing the temperature-responsive sodium-supplementing material according to claim 9, characterized in that, The processing method is a combination of melt blending and 3D printing.

11. A secondary battery characterized by comprising: The temperature-responsive sodium supplementing material according to any one of claims 1-7.

12. The secondary battery according to claim 11, characterized by The temperature-responsive sodium supplementing material is arranged on the surface of the separator of the secondary battery or in the electrolyte.

13. The secondary battery according to claim 12, characterized by The temperature-responsive sodium supplementing material is a solid, and is arranged on the surface of the separator of the secondary battery by spot coating.

14. A method of supplementing sodium to the secondary battery according to any one of claims 11 to 13, characterized by, The method comprises: heating the secondary battery to 70-80℃, maintaining for 1-60s, and completing the sodium supplementing of the secondary battery.

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