Separator and method for producing the same, lithium ion battery

Abstract

The application discloses a diaphragm, a preparation method thereof and a lithium ion battery. The diaphragm comprises a polyolefin base film and a functional coating, the functional coating is arranged on at least one side of the polyolefin base film, and the material of the functional coating comprises core-shell structure microspheres, an oxide ceramic and a binder. The core-shell structure microspheres comprise a polymer shell and a core of a conductive hydrogen-absorbing material. Thus, the diaphragm can improve the safety performance of the lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a separator and its preparation method, and a lithium-ion battery. Background Technology

[0002] With the booming development of the electric vehicle industry, battery technology is gradually shifting towards high energy density and fast charging. Consequently, battery safety issues have become particularly prominent. One of the main methods to achieve high energy density is to use high-nickel ternary materials as the cathode. However, its most significant problem is poor thermal stability and structural instability at high temperatures, which greatly deteriorates the intrinsic safety of the battery. Therefore, improving battery safety is a key research task at present.

[0003] There are many strategies for improving the safety of high-nickel ternary lithium batteries, with improvements at the separator level being particularly widespread. Patent CN113078414A provides a composite separator with polyethylene microspheres and a ceramic coating coated on one side of a polypropylene base film. This separator can achieve thermal pore closure at lower temperatures. When thermal runaway occurs in a lithium-ion battery, the low-melting-point polyethylene microspheres melt and fill the micropores of the polypropylene base film, blocking lithium-ion transport and improving the safety performance of the lithium-ion battery. Patent CN116799435A provides a separator with a functional coating. This functional coating is made of core-shell structured microspheres, ceramic oxide, and a binder. When the temperature rises, the outer shell of the microspheres melts at a lower temperature, closing the separator pores and isolating the positive and negative electrodes. Simultaneously, the conductive core is exposed, forming a micro-short circuit between the positive and negative electrodes, causing the battery to slowly self-discharge, reducing the charge capacity, and improving the battery's safety at high temperatures.

[0004] While the technologies disclosed in patents CN113078414A and CN116799435A can improve the safety performance of lithium-ion batteries to some extent, factors inducing battery thermal runaway also include the release of reducing gases (such as hydrogen) from the negative electrode during temperature rise. When the released hydrogen comes into contact with the strongly oxidizing positive electrode or oxygen released from the positive electrode, a violent reaction occurs, releasing a large amount of heat and leading to battery thermal runaway. In the two disclosed technologies, although the melting of low-melting-point microspheres can isolate the positive and negative electrodes over a large area, the release rates of oxygen and hydrogen are relatively fast, and some gases will still diffuse into each other, posing a safety risk. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, one object of this invention is to provide a separator and its preparation method, as well as a lithium-ion battery. The separator provided in this application can improve the safety performance of lithium-ion batteries.

[0006] In a first aspect, the present invention provides a diaphragm, according to an embodiment of the invention, the diaphragm comprising a polyolefin base membrane and a functional coating, the functional coating being disposed on at least one side of the polyolefin base membrane, the material of the functional coating comprising core-shell structured microspheres, oxide ceramics and a binder, wherein the core-shell structured microspheres comprise a polymer shell and a core of conductive hydrogen-absorbing material.

[0007] According to the above embodiments of the present invention, the separator comprises a polyolefin base film and a functional coating, wherein the functional coating is formed on the polyolefin base film. The material of the functional coating includes core-shell structured microspheres, oxide ceramics, and a binder. The core-shell structured microspheres comprise a polymer shell and a core of conductive hydrogen-absorbing material, meaning the polymer can coat the outer surface of the conductive hydrogen-absorbing material. By selecting a polymer to form the shell, when the lithium-ion battery is heated, the polymer melts, causing the separator to close its pores, isolating the positive and negative electrode active layers, blocking lithium-ion transport, and improving the safety performance of the lithium-ion battery. Furthermore, during the melting process of the polymer shell, the conductive hydrogen-absorbing material in the core is exposed. On the one hand, the conductive hydrogen-absorbing material is conductive and can form a micro-short circuit between the positive and negative electrodes, causing the battery to slowly self-discharge, reducing the charge capacity, and improving the battery's safety at high temperatures. On the other hand, the conductive hydrogen-absorbing material can also adsorb hydrogen gas released from the negative electrode of the battery, thereby reducing the accumulation of hydrogen gas inside the battery, reducing the internal pressure of the battery, and further improving the safety performance of the lithium-ion battery. Therefore, the separator of this application can improve the safety performance of lithium-ion batteries.

[0008] In addition, the diaphragm according to the above embodiments of the present invention may have the following additional technical features:

[0009] In some embodiments of the present invention, the mass percentage of the conductive hydrogen-absorbing material is 10%-50%, preferably 20%-30%, based on the total mass of the core-shell structured microspheres. This improves the safety performance of lithium-ion batteries.

[0010] In some embodiments of the present invention, the conductive hydrogen-absorbing material includes Mg2Ni alloy, LaNi5 alloy, FeTi alloy, ZrMn2 alloy, and Mn 1.5 At least one of the Ti alloys. This improves the safety performance of lithium-ion batteries.

[0011] In some embodiments of the present invention, the polymer has a melting point of 100°C-130°C. This improves the safety performance of lithium-ion batteries.

[0012] In some embodiments of the present invention, the polymer includes at least one of polyethylene and polyvinyl chloride.

[0013] In some embodiments of the present invention, based on the total mass of the functional coating, the mass ratio of the core-shell structured microspheres, the oxide ceramic, and the binder is (10%-50%):(50%-85%):(5%-15%). This improves the safety performance of lithium-ion batteries.

[0014] In a second aspect of the invention, this application proposes a method for preparing the above-mentioned separator. According to an embodiment of the invention, the method includes: heating a polymer to form a molten liquid; dispersing a conductive hydrogen-absorbing material into the molten liquid; mixing the materials uniformly and then spray-drying them to obtain core-shell structured microspheres; uniformly dispersing the core-shell structured microspheres, oxide ceramics, and a binder in deionized water to obtain a slurry; and coating the slurry onto at least one side of a polyolefin-based membrane to obtain a separator containing the functional coating. This improves the safety performance of lithium-ion batteries.

[0015] In a third aspect, this application proposes a lithium-ion battery, which, according to embodiments of the invention, comprises the above-described separator or a separator prepared using the above-described method. This improves the safety performance of the lithium-ion battery.

[0016] In a fourth aspect of the present invention, this application proposes a method for preparing the above-mentioned lithium-ion battery. According to an embodiment of the present invention, the method includes: preparing a positive electrode and a negative electrode; heating a polymer to form a molten liquid, dispersing a conductive hydrogen-absorbing material into the molten liquid, mixing it evenly, and then spray-drying it to obtain core-shell structured microspheres; uniformly dispersing the core-shell structured microspheres, oxide ceramics, and binder in deionized water to obtain a slurry; coating the slurry onto at least one side of a polyolefin-based film to obtain a separator containing the functional layer; placing the separator between the positive electrode and the negative electrode and stacking them in a Z-shape to obtain a battery cell; placing the battery cell in a packaging shell and injecting electrolyte to obtain a lithium-ion battery. Thus, a lithium-ion battery with good safety performance can be obtained.

[0017] In some embodiments of the present invention, the method for preparing the positive electrode sheet includes: adding polyvinylidene fluoride, a conductive agent and a positive electrode material in a mass ratio of 1.5%:1.5%:97% sequentially to N-methylpyrrolidone, stirring evenly to obtain a positive electrode slurry, coating the positive electrode slurry onto an aluminum foil current collector, drying, cold pressing and punching to obtain the positive electrode sheet.

[0018] In some embodiments of the present invention, the method for preparing the negative electrode sheet includes: adding sodium carboxymethyl cellulose, styrene-butadiene rubber emulsion, conductive agent and graphite in a mass ratio of 1.5%:1.5%:1.5%:95.5% sequentially to deionized water, stirring evenly to obtain a negative electrode slurry, coating the negative electrode slurry onto a copper foil current collector, drying, cold pressing and punching to obtain the negative electrode sheet.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0021] Figure 1 A schematic diagram of the diaphragm according to one embodiment of this application is shown. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0023] In a first aspect, the present invention provides a diaphragm, according to an embodiment of the invention, with reference to Figure 1 As shown, the membrane comprises: a polyolefin base membrane and a functional coating.

[0024] Polyolefin-based films serve as carriers for functional coatings, enabling them to support and carry the functional coating materials and ensure the safe and stable operation of the battery. As an example, the polyolefin-based films include, but are not limited to, at least one of polyethylene (PE)-based films and polypropylene (PP)-based films.

[0025] According to an embodiment of the present invention, the functional coating is disposed on at least one side of the polyolefin-based film. The material of the functional coating includes core-shell structured microspheres, oxide ceramics, and a binder. The core-shell structured microspheres comprise a polymer shell and a core of conductive hydrogen-absorbing material, meaning the polymer can coat the outer surface of the conductive hydrogen-absorbing material. By selecting a polymer to form the shell, the polymer melts when the lithium-ion battery is heated, causing the separator to close its pores, isolating the positive and negative electrode active layers, blocking lithium-ion transport, and improving the safety performance of the lithium-ion battery. Furthermore, during the melting process of the polymer shell, the core of the conductive hydrogen-absorbing material is exposed. On the one hand, the conductive hydrogen-absorbing material is conductive and can form a micro-short circuit between the positive and negative electrodes, causing the battery to slowly self-discharge, reducing the charge capacity, and improving the battery's safety at high temperatures. On the other hand, the conductive hydrogen-absorbing material can also adsorb hydrogen gas released from the negative electrode of the battery, further improving the safety performance of the lithium-ion battery. Therefore, the separator of this application can improve the safety performance of lithium-ion batteries.

[0026] According to some specific embodiments of the present invention, based on the total mass of the core-shell structured microspheres, the mass percentage of the conductive hydrogen-absorbing material is 10%-50%. For example, it can be 10%, 20%, 30%, 40%, 50%, etc. By limiting the mass percentage of the conductive hydrogen-absorbing material within the above range, on the one hand, it is beneficial to improve the conductivity of the conductive hydrogen-absorbing material, enabling the formation of a micro-short circuit between the positive and negative electrodes, causing the battery to slowly self-discharge, reducing the charge, and improving the battery's safety at high temperatures. On the other hand, it can enhance the ability of the conductive hydrogen-absorbing material to adsorb hydrogen, thereby adsorbing hydrogen released from the negative electrode of the battery, further improving the safety performance of the lithium-ion battery. Further, the mass percentage of the conductive hydrogen-absorbing material is preferably 20%-30%.

[0027] As examples, conductive hydrogen-absorbing materials include, but are not limited to, Mg2Ni alloy, LaNi5 alloy, FeTi alloy, ZrMn2 alloy, and Mn 1.5 At least one of the Ti alloys.

[0028] According to some specific embodiments of the present invention, the melting point of the polymer is 100°C-130°C. For example, it can be 100°C, 110°C, 120°C, 130°C, etc. By limiting the melting point of the polymer to the above range, the polymer can melt under high temperature conditions, thereby closing the pores of the separator, isolating the positive and negative electrode active layers, blocking lithium-ion transport, and improving the safety performance of the lithium-ion battery.

[0029] As an example, the polymer may be made of at least one of polyethylene and polyvinyl chloride.

[0030] According to some specific embodiments of the present invention, based on the total mass of the functional coating, the mass ratio of the core-shell structured microspheres, the oxide ceramic, and the binder is 10%-50%:50%-85%:5%-15%. For example, it can be 10%:50%:5%, 50%:85%:15%, 20%:70%:10%, etc. By limiting the mass ratio of the core-shell structured microspheres, oxide ceramic, and binder within the above range, the performance of the diaphragm is controlled, and the mechanical strength, thermal stability, and chemical stability of the diaphragm are optimized.

[0031] In a second aspect of the present invention, this application proposes a method for preparing the above-mentioned diaphragm. According to an embodiment of the present invention, the method includes: heating a polymer to form a molten liquid; dispersing a conductive hydrogen-absorbing material into the molten liquid; mixing the materials evenly and then spray-drying them to obtain core-shell structured microspheres; uniformly dispersing the core-shell structured microspheres, oxide ceramics, and binder in deionized water to obtain a slurry; and coating the slurry onto at least one side of a polyolefin-based membrane to obtain a diaphragm containing the functional coating.

[0032] According to an embodiment of the present invention, a polymer is first heated to form a molten liquid, and then a conductive hydrogen-absorbing material is dispersed into the molten liquid. After uniform mixing, the mixture is spray-dried to obtain core-shell microspheres with a polymer outer shell and a conductive hydrogen-absorbing core. The core-shell microspheres are then uniformly dispersed with oxide ceramics and a binder in deionized water to prepare a slurry. The slurry is coated on at least one side of a polyolefin-based membrane to obtain a separator. The functional coating of the separator contains core-shell microspheres with a polymer outer shell and a conductive hydrogen-absorbing core, thereby improving the safety performance of the battery. Specifically, by selecting a polymer to form the outer shell of the core-shell microspheres, the outer shell layer of the core-shell microspheres has a low melting point. When the lithium-ion battery is heated to a higher temperature, the polymer will preferentially melt, causing the separator to close its pores, isolating the positive and negative electrode active layers, blocking lithium-ion transport, and improving the safety performance of the lithium-ion battery. Furthermore, during the melting process of the polymer shell, the core of the conductive hydrogen-absorbing material is exposed. On the one hand, the conductive hydrogen-absorbing material is conductive and can form a micro-short circuit between the positive and negative electrodes, causing the battery to slowly self-discharge, reducing the charge, and improving the battery's safety at high temperatures. On the other hand, the conductive hydrogen-absorbing material can also adsorb hydrogen gas released from the negative electrode of the battery, thereby reducing the accumulation of hydrogen gas inside the battery, reducing the internal pressure of the battery, and further improving the safety performance of lithium-ion batteries.

[0033] In a third aspect, this application proposes a lithium-ion battery, which, according to embodiments of the invention, comprises the separator described above or a separator prepared using the method described above. This separator can improve the safety performance of the lithium-ion battery, resulting in better overall performance.

[0034] In a fourth aspect of the present invention, this application proposes a method for preparing the above-mentioned lithium-ion battery. According to an embodiment of the present invention, the method includes: preparing a positive electrode and a negative electrode; heating a microsphere shell material to form a molten liquid, dispersing a conductive hydrogen-absorbing material into the molten liquid, mixing it evenly, and then spray drying it to obtain core-shell structured microspheres; uniformly dispersing the core-shell structured microspheres, oxide ceramics, and binder in deionized water to obtain a slurry; coating the slurry onto at least one side of a polyolefin-based film to obtain a separator containing the functional layer; placing the separator between the positive electrode and the negative electrode and stacking them in a Z-shape to obtain a battery cell; placing the battery cell in a packaging shell and injecting electrolyte to obtain a lithium-ion battery. Thus, the...

[0035] According to some specific embodiments of the present invention, the specific method for preparing the positive electrode sheet is as follows: polyvinylidene fluoride, conductive agent and positive electrode material are added to N-methylpyrrolidone in a mass ratio of 1.5%:1.5%:97%, and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is coated on an aluminum foil current collector, dried, cold-pressed and punched to obtain the positive electrode sheet.

[0036] It should be noted that there are no special limitations on the materials used for the conductive agent and the positive electrode material; conventional materials in the field can be selected, and those skilled in the art can make flexible choices as needed.

[0037] According to some specific embodiments of the present invention, the specific method for preparing the negative electrode sheet is as follows: sodium carboxymethyl cellulose, styrene-butadiene rubber emulsion, conductive agent and graphite are added to deionized water in a mass ratio of 1.5%:1.5%:1.5%:95.5%, and stirred evenly to obtain a negative electrode slurry. The negative electrode slurry is coated on a copper foil current collector, dried, cold-pressed and punched to obtain the negative electrode sheet.

[0038] It should be noted that there are no special restrictions on the types of conductive agents and negative electrode materials; conventional materials in the field can be selected, and those skilled in the art can make flexible choices as needed.

[0039] The present disclosure will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the disclosure. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0040] Example 1

[0041] (1) Preparation of core-shell structured microspheres: Polyethylene is heated to form a molten liquid, and conductive hydrogen-absorbing material LaNi5 alloy particles are dispersed into the polyethylene molten liquid, mixed evenly, and then spray-dried to obtain LaNi5 alloy@polyethylene core-shell structured microsphere material.

[0042] (2) Preparation method of membrane containing core-shell microsphere structure: Using commercially available polyethylene membrane as polyolefin base membrane, core-shell structure microspheres, oxide ceramics and binder are uniformly dispersed in deionized water and stirred evenly to obtain a uniform slurry. Then, the slurry is coated on the surface of polyethylene base membrane to obtain a membrane containing a functional coating.

[0043] (3) Preparation of positive electrode sheet: Polyvinylidene fluoride (PVDF), conductive agent (SP) and positive electrode material (NCM811) are added to N-methylpyrrolidone (NMP) in a mass ratio of 1.5%:1.5%:97%. After thorough mixing, a positive electrode slurry is obtained. The positive electrode slurry is coated on an aluminum foil current collector, dried, cold-pressed and punched to obtain the positive electrode sheet.

[0044] (4) Preparation of negative electrode sheet: Sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber emulsion (SBR), conductive agent and graphite are added to deionized water in a mass ratio of 1.5%:1.5%:1.5%:95.5% in sequence. After thorough stirring and mixing, a negative electrode slurry is obtained. The negative electrode slurry is coated on a copper foil current collector, dried, cold pressed and punched to obtain a negative electrode sheet.

[0045] (5) Preparation of lithium-ion battery: The separator, positive electrode and negative electrode obtained above are stacked in a "Z" shape, packaged with aluminum-plastic film to obtain the cell to be injected with electrolyte, and then baked and injected with electrolyte to obtain a lithium-ion battery with a nominal capacity of 3Ah to be tested.

[0046] Example 2

[0047] (1) Preparation of core-shell structured microspheres: Polyethylene was heated to form a molten liquid, and conductive hydrogen-absorbing material Mn was added... 1.5 Ti alloy particles are dispersed in molten polyethylene, mixed evenly, and then spray-dried to obtain Mn. 1.5 Ti alloy@polyethylene core-shell structured microspheres.

[0048] (2) Preparation method of membrane containing core-shell microsphere structure: Same as in Example 1, except that the core-shell microspheres are Mn 1.5 Ti alloy@polyethylene core-shell structured microspheres.

[0049] (3) Preparation of positive electrode sheet: Same as in Example 1.

[0050] (4) Preparation of negative electrode sheet: Same as in Example 1.

[0051] (5) Preparation of lithium-ion batteries: Same as in Example 1.

[0052] Comparative Example 1

[0053] (1) Preparation method of the diaphragm: The commercially available polyethylene diaphragm is used as the polyolefin base membrane. The oxide ceramic and binder are uniformly dispersed in deionized water and stirred evenly to obtain a uniform slurry. Then, the slurry is coated on the surface of the polyethylene base membrane to obtain a diaphragm with a coating.

[0054] (2) Preparation of positive electrode sheet: Same as in Example 1.

[0055] (3) Preparation of negative electrode sheet: Same as in Example 1.

[0056] (4) Preparation of lithium-ion batteries: Same as in Example 1.

[0057] Comparative Example 2

[0058] (3) Preparation method of diaphragm containing polyethylene microsphere structure material: Using commercially available polyethylene diaphragm as polyolefin base membrane, low melting point polyethylene microspheres, oxide ceramics and binder are uniformly dispersed in deionized water and stirred evenly to obtain a uniform slurry. Then, the slurry is coated on the surface of polyethylene base membrane to obtain a diaphragm with coating.

[0059] (1) Preparation of positive electrode sheet: Same as comparative example 1.

[0060] (2) Preparation of negative electrode sheet: Same as Comparative Example 1

[0061] (4) Preparation of lithium-ion batteries: Same as in Example 1.

[0062] Testing of lithium-ion batteries:

[0063] Under the same conditions, the lithium-ion batteries prepared in Examples 1-2 and Comparative Examples 1-2 were subjected to gas composition analysis, capacity testing, and thermal chamber testing, respectively. The specific testing methods are as follows:

[0064] Gas composition analysis: Taking Example 1 as an example, the prepared lithium-ion battery was placed in a 100°C oven and heated for 30 minutes. The internal gas was collected and the hydrogen content was detected to obtain hydrogen content data.

[0065] Capacity testing: Taking Example 1 as an example, the prepared battery was charged and discharged at 0.33C and 1C respectively to obtain the capacity data of the lithium-ion battery at 0.33C and 1C.

[0066] Hot box test: Taking Example 1 as an example, a fully charged lithium-ion battery was placed in an explosion-proof oven. The temperature was increased from 25°C to 150°C at a rate of 5°C / min and maintained for 60min. The temperature rise and voltage change of the battery were recorded.

[0067] The test results are shown in Table 1.

[0068] Table 1

[0069]

[0070] As shown in Table 1, the lithium-ion batteries prepared in Examples 1 and 2, Comparative Examples 1 and 2 all have similar 1C / 0.33C capacity ratios. This indicates that the use of a separator containing core-shell microspheres, conventional separators, and separators containing polyethylene microspheres have no significant impact on the capacity of lithium-ion batteries. In other words, lithium-ion batteries can perform normally under normal conditions.

[0071] During the hot box test, the lithium-ion battery was monitored at 130°C. The voltage drop observed showed that in Example 1, the lithium-ion battery using the separator containing LaNi5 alloy@polyethylene core-shell microspheres provided by this invention exhibited a significant voltage reduction, reaching 0.11V. This is because, during the hot box test, when the temperature reached the melting point of the core-shell microspheres, the polyethylene shell material melted, exposing the conductive LaNi5 alloy core material, forming a micro-short circuit inside the lithium-ion battery. This caused the lithium-ion battery to discharge slowly, resulting in a voltage drop. Therefore, when the battery failed at 150°C, the highest temperature was only 167°C. This is because after slow self-discharge, the battery charge decreased, the overall thermal stability of the battery system improved, and the energy decreased. Simultaneously, the gas composition analysis data showed a significant reduction in hydrogen content compared to Comparative Examples 1 and 2. This is because the LaNi5 alloy has hydrogen absorption properties, absorbing most of the hydrogen, further reducing the energy of the reaction system during lithium-ion battery failure. Therefore, the highest temperature at which the entire lithium-ion battery failed was only 167°C. Example 2 is the same, because it contains Mn 1.5 The application of Ti alloy@polyethylene core-shell microsphere material in the separator, as well as the gas composition data after the lithium-ion battery produces gas, also show that most of the hydrogen is absorbed. Under the effect of self-discharge, the lithium-ion battery has a large voltage drop and the system energy is reduced. When it fails at 150℃, the battery temperature is only 172℃, and the safety performance of the lithium-ion battery is improved.

[0072] In Comparative Example 1, the lithium-ion battery used a conventional separator. At 130°C, the voltage drop was very small, and the positive and negative electrodes remained open-circuited. In Comparative Example 2, the separator used a conventional base film with polyethylene microspheres. At 130°C, the polyethylene microspheres melted, closing the separator's pores and effectively disconnecting the positive and negative electrodes, thus exhibiting the smallest voltage drop. Gas composition analysis data showed that both comparative examples had significantly higher hydrogen content, indicating that lithium-ion batteries easily produce hydrogen, a highly dangerous reducing gas, when heated. Therefore, Comparative Examples 1 and 2 exhibited higher maximum temperatures compared to Examples 1 and 2, because fully charged lithium-ion batteries have poor high-temperature stability and release a large amount of energy upon failure. Comparing Comparative Examples 1 and 2, it can be seen that Comparative Example 2's battery, containing a polyethylene microsphere separator, completely isolates the positive and negative electrodes, reducing the reaction intensity to some extent. Therefore, Comparative Example 2 exhibited a relatively lower temperature rise compared to Comparative Example 1.

[0073] Therefore, by applying the separator containing core-shell structured microspheres provided in this application to lithium-ion batteries, the safety performance of lithium-ion batteries can be effectively improved. Specifically, when lithium-ion batteries fail at high temperatures, the battery charge decreases and the temperature rise caused by the release of energy by the battery is significantly reduced.

[0074] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," "some implementations," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0075] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A diaphragm, characterized in that, The diaphragm includes: Polyolefin-based films; A functional coating is disposed on at least one side of the polyolefin-based film. The material of the functional coating includes core-shell structured microspheres, oxide ceramics, and a binder, wherein the core-shell structured microspheres include a polymer shell and a conductive hydrogen-absorbing material core. The conductive hydrogen-absorbing material includes Mg2Ni alloy, LaNi5 alloy, FeTi alloy, ZrMn2 alloy, and Mn 1.5 At least one of the Ti alloys.

2. The diaphragm according to claim 1, characterized in that, Based on the total mass of the core-shell structured microspheres, the mass ratio of the conductive hydrogen-absorbing material is 10%-50%.

3. The diaphragm according to claim 1, characterized in that, The polymer has a melting point of 100℃-130℃.

4. The diaphragm according to claim 1, characterized in that, The polymer includes at least one of polyethylene and polyvinyl chloride.

5. The diaphragm according to claim 1, characterized in that, Based on the total mass of the functional coating, the mass ratio of the core-shell structured microspheres, the oxide ceramic, and the binder is (10%-50%):(50%-85%):(5%-15%).

6. A method for preparing the diaphragm according to any one of claims 1-5, characterized in that, include: The polymer is heated to form a molten liquid, and a conductive hydrogen-absorbing material is dispersed into the molten liquid. After being mixed evenly, the mixture is spray-dried to obtain core-shell structured microspheres. Core-shell structured microspheres, oxide ceramics, and binders were uniformly dispersed in deionized water to obtain a slurry. The slurry is coated on at least one side of a polyolefin-based membrane to obtain a diaphragm containing the functional coating.

7. A lithium-ion battery, characterized in that, The lithium-ion battery comprises the separator according to any one of claims 1-5 or the separator prepared by the method of claim 6.

8. A method for preparing the lithium-ion battery according to claim 7, characterized in that, include: Preparation of positive and negative electrode plates; The microsphere shell material is heated to form a molten liquid, and a conductive hydrogen-absorbing material is dispersed into the molten liquid. After being mixed evenly, the mixture is spray-dried to obtain core-shell structured microspheres. The core-shell structured microspheres, oxide ceramics, and binders are uniformly dispersed in deionized water to obtain a slurry. The slurry is coated on at least one side of a polyolefin-based membrane to obtain a membrane containing a functional layer. The separator is placed between the positive electrode and the negative electrode and stacked in a Z-shape to obtain a battery cell. The battery cell is placed in a packaging shell and injected with electrolyte to obtain a lithium-ion battery.

9. The method according to claim 8, characterized in that, The method for preparing the positive electrode sheet includes: adding polyvinylidene fluoride, conductive agent and positive electrode material in a mass ratio of 1.5%:1.5%:97% to N-methylpyrrolidone, stirring evenly to obtain a positive electrode slurry, coating the positive electrode slurry onto an aluminum foil current collector, drying, cold pressing and punching to obtain the positive electrode sheet; And / or, the method for preparing the negative electrode sheet includes: adding sodium carboxymethyl cellulose, styrene-butadiene rubber latex, conductive agent and graphite in a mass ratio of 1.5%:1.5%:1.5%:95.5% to deionized water, stirring evenly to obtain a negative electrode slurry, coating the negative electrode slurry onto a copper foil current collector, drying, cold pressing and punching to obtain the negative electrode sheet.

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