Reversible thermal response switch material for battery thermal safety protection and preparation method and application thereof

Abstract

The application discloses a reversible thermal response switch material for battery thermal safety protection and a preparation method and application thereof, and comprises the following steps: taking two different organic silicon polymers with the same mass as polymer matrix, sufficiently grinding and uniformly mixing to prepare an organic silicon mixture, weighing a certain amount of nickel powder, adding the nickel powder into the organic mixture in batches, uniformly mixing the nickel and the organic matter after each addition, and then adding, until all the nickel is uniformly mixed with the organic matter to become a gray-black viscous slurry, transferring the ground viscous slurry to a carbon-coated aluminum foil, and using a scraper to scrape the slurry into a sheet with uniform thickness from top to bottom. The application directly prepares a thermal response switch electrode material by using a mixing coating method, does not need to add any other additives in the preparation process, reduces the reaction steps, and saves the preparation cost. Moreover, the prepared material has excellent thermal response performance.

Description

Technical Field

[0001] This invention belongs to the field of electrode material preparation technology, and relates to a reversible thermally responsive switching material for battery safety protection, its preparation method and application. Background Technology

[0002] Lithium-ion batteries are gaining popularity in electronic devices and new energy vehicles, but recent fires and explosions in electric vehicles have raised serious concerns about their safety. Lithium-ion batteries are susceptible to fire and even explosion under dangerous conditions such as impacts, compression, rapid charging and discharging, short circuits, and high temperatures, making their safety a major obstacle to their development. Safety hazards in lithium-ion batteries can be prevented through external and internal protection designs. External protection designs can only improve safety to a certain extent and cannot completely eliminate safety risks. Internal strategies involve adding flame-retardant solvents to the electrolyte; however, a sufficient amount of flame retardant is required to achieve a flame-retardant effect, inevitably affecting battery performance, such as reducing specific capacity and coulombic efficiency. Therefore, this temporary strategy cannot completely solve the safety hazards of lithium-ion batteries. Some researchers have studied improving the melting point of the separator to address lithium-ion battery safety issues. While modified separators can withstand high temperatures, excessively high temperatures can damage the battery.

[0003] Recently, there have been increasing reports on thermally responsive switching materials, primarily prepared by adding conductive fillers to an insulating polymer matrix. The mechanism by which these thermally responsive switching materials protect lithium-ion batteries is as follows: when the internal temperature of the battery rises, the polymer expands, increasing the battery's internal resistance and stopping discharge. Once the internal temperature returns to normal, the battery can resume operation. In other words, the battery is immediately shut down when the internal temperature is abnormal but before it rises further, thus preventing damage. However, current thermal protection technologies are all one-time applications; once the battery is shut down, it cannot be restarted. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a reversible thermal response switch material for battery safety protection, its preparation method and application, so as to solve the technical problem that existing thermal response switch materials cannot achieve reversible restart.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention discloses a method for preparing a reversible thermally responsive switching material for battery safety protection, comprising the following steps:

[0007] 1) Take two different organosilicon polymers of equal mass as polymer matrices, grind them thoroughly and evenly to obtain an organosilicon mixture;

[0008] 2) Add nickel powder to the organosilicon mixture in batches. Each time the nickel powder is added, it is thoroughly mixed with the mixture before it is added again until all the nickel powder is completely mixed with the organosilicon mixture to obtain a viscous slurry.

[0009] 3) The viscous slurry is evenly coated onto the substrate to obtain a reversible thermal response switch material for battery safety protection.

[0010] Preferably, the two different organosilicon polymers are organosilicon A and organosilicon B, both of which are two-component organosilicones purchased from Guangzhou Tinci Advanced Materials Co., Ltd., with product batch numbers TCS-120L(A) and TCS-120L(B), respectively.

[0011] Preferably, in step 1), the grinding time is 5 minutes.

[0012] Preferably, in step 2), the mass of the added nickel powder is 3% to 15% of the total mass of the polymer matrix.

[0013] Preferably, in step 3), the substrate is carbon-coated aluminum foil.

[0014] More preferably, the carbon-coated aluminum foil is cut to a length of 20cm and a width of 7cm, and the cut carbon-coated aluminum foil is pasted onto the glass plate.

[0015] Preferably, a viscous slurry is uniformly applied to the substrate using a scraper with a thickness of 120 micrometers.

[0016] The present invention also discloses a reversible thermally responsive switch material for battery safety protection prepared by the above-described preparation method. The impedance of the reversible thermally responsive switch material increases significantly by several orders of magnitude when the temperature is above 90°C, and decreases significantly when cooled to below 30°C.

[0017] This invention also discloses the application of the above-mentioned reversible thermally responsive switch material for battery safety protection in the preparation of lithium-ion battery cathodes.

[0018] Preferably, the specific capacity of the lithium-ion battery positive electrode is 150 mAh g when charged and discharged at a current density of 0.1C. -1 After 100 charge-discharge cycles at a current density of 0.2C, the specific capacity remained at 120 mAh g. -1 .

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention discloses a method for preparing a reversible thermally responsive switching material for battery safety protection. The method uses equal masses of two-component organosilicon polymers mixed as an insulating polymer matrix. Conductive nickel with a unique spike structure is added to each component of this insulating polymer matrix, and then the mixture is coated to obtain the target product, i.e., a reversible thermally responsive switching polymer material. This method eliminates the need for any other additives during preparation, reducing reaction steps and saving on preparation costs.

[0021] The impedance of the reversible thermally responsive switch material prepared by the method of this invention was measured at different temperatures, proving that it has a thermal switching function. It can achieve switch opening at a specific temperature (greater than 90°C) and maintain the battery's electrical performance after cooling. Good reversibility is a major feature of this temperature-sensitive switch material.

[0022] The reversible thermally responsive switch material prepared according to this invention was applied to the preparation of the positive electrode of a lithium-ion battery, and the specific capacity was 150 mAh g when charged and discharged at a current density of 0.1C. -1 After 100 charge-discharge cycles at a current density of 0.2C, the specific capacity still remains at 120 mAh g. -1 . Attached Figure Description

[0023] Figure 1 SEM image of the nickel ball with spike structure in Example 1;

[0024] Figure 2 EIS diagrams of the thermally responsive switch material in Example 1 at different temperatures are shown; where (a) is the EIS spectrum and (b) is the impedance evolution based on the spectrum.

[0025] Figure 3 This is a graph showing the charge-discharge curves of the button battery assembled with the thermally responsive switch material in Example 1 at different temperatures;

[0026] Figure 4 EIS diagrams of the thermally responsive switch material in Example 2 at different temperatures, where (a) EIS spectrum; (b) impedance evolution based on the spectrum;

[0027] Figure 5 EIS diagrams of the thermally responsive switch material in Example 3 at different temperatures, where (a) EIS spectrum; (b) impedance evolution based on the spectrum;

[0028] Figure 6 EIS diagrams of the thermally responsive switch material in Example 4 at different temperatures, where (a) EIS spectrum; (b) impedance evolution based on the spectrum;

[0029] Figure 7The following are EIS diagrams of the thermally responsive switch material in Example 5 at different temperatures, where (a) is the EIS spectrum and (b) is the impedance evolution based on the spectrum. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] The present invention will now be described in further detail with reference to the accompanying drawings:

[0033] The raw materials organosilicon A and organosilicon B used in the following embodiments of the present invention are two two-component organosilicones, purchased from Guangzhou Tinci Advanced Materials Co., Ltd., with product batch numbers TCS-120L(A) and TCS-120L(B), respectively.

[0034] The nickel powder used in the following embodiments of the present invention is nickel nanoparticles with a spiked structure, and the preparation method is as follows:

[0035] At 50°C, 4g of nickel acetate tetrahydrate was dissolved in 20-50mL of deionized water. Then, 10mL of 80% hydrazine hydrate solution was added to the solution, and the mixture was further heated to 65-80°C for 1-5 hours. The solution was then cooled to 50°C, and under mechanical stirring, 30mL of 5M sodium hydroxide solution was added dropwise to the nickel acetate and hydrazine hydrate mixture using a dropper. After the addition was complete, the solution was heated to 70-90°C for 3-6 hours to allow the nickel acetate to be fully reduced to nickel nanoparticles. After the reaction was complete, the nickel nanoparticles were aged for 24-48 hours, and the synthesized nickel nanoparticles were collected by filtration. The nanoparticles were washed three times each with deionized water, ethanol, and toluene to remove residual impurities. Finally, the nickel nanoparticles were vacuum dried overnight at 50°C.

[0036] The obtained nickel nanoparticles were placed in a tube furnace, and an argon-hydrogen mixture containing 5% hydrogen was introduced. The temperature was increased to 350-500℃ at a rate of 5℃ per minute, and then held for 120 minutes. Finally, the temperature was allowed to cool naturally to obtain the desired nickel nanoparticles with spiked structures. SEM images of these nanoparticles are shown below. Figure 1 As shown.

[0037] Example 1

[0038] A method for preparing a thermally responsive switching material includes the following steps:

[0039] Step 1: Take a clean mortar and use a dropper to take 0.2125g of organosilicon A;

[0040] Step 2: Take a new dropper and draw 0.2125g of organosilicon B, then squeeze it into the mortar containing organosilicon A.

[0041] Step 3: Add equal amounts of organosilicon A and organosilicon B to the mortar and grind for 5 minutes to ensure that organosilicon A and organosilicon B are evenly mixed.

[0042] Step 4: Weigh 0.075g of nickel powder on a balance and add it to the organic matter in batches. Each batch of nickel should be thoroughly mixed with the organic matter before adding more, until all the nickel is evenly mixed with the organic matter, forming a grayish-black viscous slurry.

[0043] Step 5: Cut a piece of carbonized aluminum foil 7cm wide and 20cm long using a cutter. Secure the top and bottom edges of the foil to the glass plate with tape. Transfer the ground slurry onto the carbonized aluminum foil and use a 90-micron scraper to scrape the slurry into a sheet of uniform thickness from top to bottom.

[0044] Step 6: Place the scraped electrode sheet into a 60℃ oven and keep it at that temperature for 1 hour to allow organosilicon A and organosilicon B to fully polymerize. Then it can be taken out for testing.

[0045] The prepared electrode sheets were used as electrode materials to test their performance in a coin cell. The dried membrane was cut into 19mm diameter electrode sheets using a manual cutting machine. The electrode sheets were then transferred to a glove box filled with argon gas (water and oxygen levels ≤0.01ppm) for subsequent battery assembly. The CR2016 battery was assembled in the glove box. The battery structure, from bottom to top, is: positive electrode shell - gasket - membrane - gasket - negative electrode shell. The gasket in contact with the positive electrode shell is 15.8mm in diameter and 1mm thick, and the gasket in contact with the negative electrode shell is 15.8mm in diameter and 0.5mm thick. After battery assembly, it was placed in an electric sealing machine for sealing, with a sealing pressure of 0.85T. The assembled device was then used to test impedance and other performance characteristics at different temperatures using a Princeton electrochemical workstation. The test results are as follows:

[0046] The EIS diagrams and charge-discharge curves of the thermally responsive switching material prepared in this embodiment at different temperatures are shown below. Figure 2 and 3 As shown, when the temperature exceeds 90℃, the impedance of the material increases by several orders of magnitude compared to room temperature. We fabricated the material into electrode sheets and assembled them into a battery for temperature testing. When the battery temperature abnormally increased to 90℃, the voltage dropped linearly and the discharge stopped, indicating excellent thermal response performance. Upon further cooling to 30℃, the impedance decreased significantly, demonstrating good reversible switching characteristics.

[0047] Example 2

[0048] The process in this embodiment is the same as in embodiment 1, except that some process parameters have been changed: the mass of nickel powder is 0.025g.

[0049] The prepared electrode sheets were used as electrode materials to test their performance in a coin cell. The dried membrane was cut into 19mm diameter electrode sheets using a manual cutting machine. The electrode sheets were then transferred to a glove box filled with argon gas (water and oxygen levels ≤0.01ppm) for subsequent battery assembly. The CR2016 battery was assembled in the glove box. The battery structure, from bottom to top, is: positive electrode shell - gasket - membrane - gasket - negative electrode shell. The gasket in contact with the positive electrode shell is 15.8mm in diameter and 1mm thick, and the gasket in contact with the negative electrode shell is 15.8mm in diameter and 0.5mm thick. After battery assembly, it was placed in an electric sealing machine for sealing, with a sealing pressure of 0.85T. The assembled device was then used to test impedance and other performance characteristics at different temperatures using a Princeton electrochemical workstation. The test results are as follows:

[0050] The EIS diagrams of the low-nickel content thermally responsive switch material prepared in this embodiment at different temperatures are shown below. Figure 4 As shown, by Figure 4It can be seen that changing the nickel content can change the performance of the electrode material, which reflects the controllable preparation of the electrode material.

[0051] Example 3

[0052] The process in this embodiment is the same as in embodiment 1, except that some process parameters have been changed: the mass of nickel powder is 0.04g.

[0053] The prepared electrode sheets were used as electrode materials to test their performance in a coin cell. The dried membrane was cut into 19mm diameter electrode sheets using a manual cutting machine. The electrode sheets were then transferred to a glove box filled with argon gas (water and oxygen levels ≤0.01ppm) for subsequent battery assembly. The CR2016 battery was assembled in the glove box. The battery structure, from bottom to top, is: positive electrode shell - gasket - membrane - gasket - negative electrode shell. The gasket in contact with the positive electrode shell is 15.8mm in diameter and 1mm thick, and the gasket in contact with the negative electrode shell is 15.8mm in diameter and 0.5mm thick. After battery assembly, it was placed in an electric sealing machine for sealing, with a sealing pressure of 0.85T. The assembled device was then used to test impedance and other performance characteristics at different temperatures using a Princeton electrochemical workstation. The test results are as follows:

[0054] The EIS diagrams of the thermally responsive switching material prepared in this embodiment at different temperatures are shown below. Figure 5 As shown in the figure, increasing the nickel content can change the performance of the electrode material.

[0055] Example 4

[0056] The process in this embodiment is the same as in embodiment 1, except that some process parameters have been changed: the mass of nickel powder is 0.05g.

[0057] The prepared electrode sheets were used as electrode materials to test their performance in a coin cell. The dried membrane was cut into 19mm diameter electrode sheets using a manual cutting machine. The electrode sheets were then transferred to a glove box filled with argon gas (water and oxygen levels ≤0.01ppm) for subsequent battery assembly. The CR2016 battery was assembled in the glove box. The battery structure, from bottom to top, is: positive electrode shell - gasket - membrane - gasket - negative electrode shell. The gasket in contact with the positive electrode shell is 15.8mm in diameter and 1mm thick, and the gasket in contact with the negative electrode shell is 15.8mm in diameter and 0.5mm thick. After battery assembly, it was placed in an electric sealing machine for sealing, with a sealing pressure of 0.85T. The assembled device was then used to test impedance and other performance characteristics at different temperatures using a Princeton electrochemical workstation. The test results are as follows:

[0058] The EIS diagrams of the thermally responsive switching material prepared in this embodiment at different temperatures are shown below. Figure 6As shown in the figure, increasing the nickel content can improve the thermal response performance of the electrode material.

[0059] Example 5

[0060] The process in this embodiment is the same as in embodiment 1, except that some process parameters have been changed: the mass of nickel powder is 0.1g.

[0061] The prepared electrode sheets were used as electrode materials to test their performance in a coin cell. The dried membrane was cut into 19mm diameter electrode sheets using a manual cutting machine. The electrode sheets were then transferred to a glove box filled with argon gas (water and oxygen levels ≤0.01ppm) for subsequent battery assembly. The CR2016 battery was assembled in the glove box. The battery structure, from bottom to top, is: positive electrode shell - gasket - membrane - gasket - negative electrode shell. The gasket in contact with the positive electrode shell is 15.8mm in diameter and 1mm thick, and the gasket in contact with the negative electrode shell is 15.8mm in diameter and 0.5mm thick. After battery assembly, it was placed in an electric sealing machine for sealing, with a sealing pressure of 0.85T. The assembled device was then used to test impedance and other performance characteristics at different temperatures using a Princeton electrochemical workstation. The test results are as follows:

[0062] The EIS diagrams of the thermally responsive switching material prepared in this embodiment at different temperatures are shown below. Figure 7 As shown in the figure, excessive nickel content has a negative impact on the thermal response performance of the electrode material.

[0063] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a reversible thermally responsive switching material for battery safety protection, characterized in that, Includes the following steps: 1) Take two different organosilicon polymers of equal mass as polymer matrices, grind them thoroughly and evenly to obtain an organosilicon mixture; both different organosilicon polymers are two-component organosilicon. 2) Add nickel powder to the organosilicon mixture in batches, mixing thoroughly with the mixture before each addition, until all the nickel powder is completely and evenly mixed with the organosilicon mixture to obtain a viscous slurry; the mass of the added nickel powder is 3% to 15% of the total mass of the polymer matrix; 3) The viscous slurry is evenly coated onto the substrate to obtain a reversible thermal response switch material for battery safety protection.

2. The method for preparing the reversible thermally responsive switching material for battery safety protection according to claim 1, characterized in that, In step 1), the grinding time is 5 minutes.

3. The method for preparing the reversible thermally responsive switching material for battery safety protection according to claim 1, characterized in that, In step 3), the substrate is carbon-coated aluminum foil.

4. The method for preparing the reversible thermally responsive switching material for battery safety protection according to claim 3, characterized in that, The carbon-coated aluminum foil is cut to a length of 20 cm and a width of 7 cm, and then the cut carbon-coated aluminum foil is pasted onto a glass plate.

5. The method for preparing the reversible thermally responsive switching material for battery safety protection according to claim 1, characterized in that, A viscous slurry with a thickness of 120 micrometers was used to evenly coat the substrate.

6. A reversible thermally responsive switch material for battery safety protection, prepared by the method according to any one of claims 1 to 5, characterized in that, The impedance of this reversible thermally responsive switch material increases significantly by several orders of magnitude when the temperature is above 90°C, and decreases significantly when cooled to below 30°C.

7. The application of the reversible thermally responsive switch material for battery safety protection as described in claim 6 in the preparation of lithium-ion battery cathodes.

8. The application as described in claim 7, characterized in that, The specific capacity of this lithium-ion battery cathode is 150 mAh g when charged and discharged at a current density of 0.1 C. -1 After 100 charge-discharge cycles at a current density of 0.2 C, the specific capacity remained at 120 mAh g. -1 .

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