Multi-level defense security coating as well as preparation method and application thereof

Abstract

The invention discloses a multi-level defense security coating as well as a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. According to the coating, the mesoporous inorganic material is adopted, harmful gas generated by electrolyte decomposition can be adsorbed, and side reaction is inhibited; the large pore channel guarantees efficient transmission of lithium ions, avoids increase of internal resistance, buffers a large amount of joule heat generated by short circuit, obviously delays the temperature rise rate, and prevents more serious short circuit caused by large-area stripping of active substances. In addition, the coating not only retains high conductivity of a metal material, but also retains high ion properties and stress dispersion of an inorganic material, and is higher in safety. Besides, a thermosensitive blocking agent is introduced, when the battery is subjected to internal short circuit due to puncture and the local temperature rises to a preset trigger point, the thermosensitive blocking agent can be fused or subjected to phase change, an electron conduction channel is filled and blocked, a short-circuit current loop is physically cut off, the safety is further enhanced, the unification of electrochemical performance and safety can be realized, and the compatibility is excellent.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a multi-layered protective safety coating, its preparation method, and its application. Background Technology

[0002] In lithium-ion batteries, the goal is to achieve a high energy density with minimal resources to develop electric vehicles. However, the interfacial contact performance of the positive and negative electrodes directly affects battery characteristics such as capacity, internal resistance, rate capability, cycle life, and self-discharge. Currently, the current collector materials for the positive and negative electrodes of lithium-ion batteries are typically high-purity porous aluminum / copper foil. Traditional electrode fabrication involves directly coating the active material onto the current collector. The current collector and active material physically contact each other to collect and guide electrochemically generated active ions to the external circuit, thus achieving the conversion between chemical and electrical energy. As the battery gradually activates, the temperature rises, increasing the internal resistance between the current collector and active material, leading to self-discharge.

[0003] With the rapid development of new energy vehicles and energy storage systems, the energy density of lithium-ion batteries is constantly improving, but their safety issues are becoming increasingly prominent, especially the frequent occurrence of thermal runaway accidents caused by mechanical abuse (such as puncture and crush). Thermal runaway is a multi-field coupled chain reaction process, mainly including stages such as mechanical damage, internal short circuit, local heat accumulation, electrolyte decomposition, and aluminothermic reaction.

[0004] Currently, to improve the safety of lithium-ion batteries, existing technologies include modifications to the current collector, such as carbon-coated aluminum foil to suppress the aluminothermic reaction, or structural protection measures, such as optimized stacked structure. However, existing technologies still have the following shortcomings: while improvements to the separator and electrolyte can delay thermal runaway, they cannot fundamentally block short-circuit current and the aluminothermic reaction; traditional current collector coatings are mostly single-function (such as insulation or thermal conductivity), making it difficult to achieve multi-functional integration of "conductivity-flame retardancy-thermal insulation-structural reinforcement"; and there is a lack of a synergistic protection mechanism that simultaneously achieves "current blocking, heat buffering, mechanical support, and aluminothermic suppression" at the moment of puncture. Summary of the Invention

[0005] In order to solve one of the above-mentioned technical problems, the present invention provides a multi-layered defensive security coating, its preparation method, and its application. The specific technical solution is as follows: A multi-layered defensive security coating, wherein the multi-layered defensive security coating comprises the following raw materials in parts by weight: 10-80 parts of mesoporous inorganic material, 1-3 parts of stabilizer, 0.1-3 parts of thermosensitive blocking agent, 1-5 parts of binder, 0.1-1 parts of conductivity enhancer, and 15-20 parts of solvent.

[0006] Furthermore, the pore size of the mesoporous inorganic material ranges from 0.5 nm to 500 nm, and the porosity is from 30% to 60%.

[0007] Furthermore, the mesoporous inorganic material adopts an inorganic porous framework, which is a SiO2-Al2O3 composite inorganic material.

[0008] Furthermore, the coating also includes a surface modifier comprising a silane coupling agent and a phosphate ester in a mass ratio of (4~7):(3~6).

[0009] Furthermore, the stabilizer is at least one of silicon carbide nanosheets, boron nitride nanosheets, montmorillonite, and hydrotalcite.

[0010] Furthermore, the heat-sensitive blocking agent is at least one of a heat-sensitive polymer and a thermoplastic polymer.

[0011] Furthermore, the adhesive is at least one of polyvinylidene fluoride and sodium carboxymethyl cellulose.

[0012] Furthermore, the conductive enhancer is at least one of carbon nanotubes, graphene, and conductive carbon black.

[0013] Furthermore, the solvent is at least one of N-methylpyrrolidone and an aqueous solution of ethanol.

[0014] In addition, the present invention also provides a method for preparing a multi-layered defensive security coating, the method comprising the following steps: S1. Add mesoporous inorganic materials, stabilizers, thermosensitive blocking agents, binders and conductivity enhancers to the solvent, and stir at a speed of 50 r / min to 100 r / min for 20 min to 30 min to obtain a slurry; S2. The slurry is uniformly coated onto the surface of the pretreated aluminum or copper foil current collector using a doctor blade coating, micro-gravure coating, or spray coating method. It is then dried at 80℃~120℃, immersed in a surface modifier, and dried again at 80℃~120℃ to form a coating.

[0015] In addition, the present invention also provides an application of a multi-layered defensive safety coating, wherein the multi-layered defensive safety coating is applied to the current collector surface of a lithium-ion battery to improve the battery's puncture resistance and thermal safety performance.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The coating of this invention employs a multi-level porous inorganic framework microporous / mesoporous structure that can adsorb harmful gases (such as HF) generated by electrolyte decomposition, suppressing side reactions; large pores ensure efficient lithium-ion transport, avoiding increased internal resistance; the high specific heat capacity of the inorganic framework can absorb and buffer the large amount of Joule heat generated by short circuits, significantly slowing down the temperature rise rate; simultaneously, the robust porous structure enhances the mechanical bonding strength of the electrode layer, dispersing stress during puncture and preventing large-area peeling of active material leading to more severe short circuits. Furthermore, the coating of this invention retains both the high conductivity of metallic materials and the high ionic properties and stress dispersion of inorganic materials, resulting in higher safety.

[0017] 2. The coating of the present invention incorporates a thermosensitive blocking agent. When the battery experiences an internal short circuit due to puncture and the local temperature rises to a preset trigger point, the thermosensitive blocking agent in the coating can melt or undergo a phase change, filling and blocking the electron conduction channel, physically cutting off the short-circuit current loop, and further enhancing safety.

[0018] 3. This invention introduces functional groups into the surface of porous inorganic materials, which can improve wettability with electrolytes and facilitate the formation of a stable electrode / electrolysis interface. Furthermore, the introduced conductivity enhancer can ensure good electronic conductivity of the coating under normal conditions without affecting the current collector function, thus achieving a balance between electrochemical performance and safety, and exhibiting excellent compatibility. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0021] According to one embodiment of the present invention, a multi-layered defensive security coating comprises the following raw materials in parts by weight: 10-80 parts of mesoporous inorganic material, 1-3 parts of stabilizer, 0.1-3 parts of thermosensitive blocking agent, 1-5 parts of binder, 0.1-1 parts of conductivity enhancer, and 15-20 parts of solvent.

[0022] In one embodiment, the mesoporous inorganic material has a pore size range of 0.5 nm to 500 nm and a porosity of 30% to 60%.

[0023] In one embodiment, the mesoporous inorganic material includes mesoporous inorganic materials with pore sizes < 2 nm, mesoporous inorganic materials with pore sizes between 2 nm and 50 nm, and mesoporous inorganic materials with pore sizes between 100 nm and 500 nm.

[0024] In one embodiment, the mesoporous inorganic material employs an inorganic porous framework, which is a SiO2-Al2O3 composite inorganic material.

[0025] In one embodiment, the coating further includes a surface modifier comprising a silane coupling agent and a phosphate ester in a mass ratio of (4-7):(3-6).

[0026] In one embodiment, the silane coupling agent is at least one selected from vinyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-chloropropyltriethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0027] In one embodiment, the phosphate ester is an alkyl polyoxyethylene ether phosphate ester, wherein the alkyl group contains 4 to 10 carbons and the degree of polymerization of the polyoxyethylene ether is 4 to 20.

[0028] In one embodiment, the stabilizer is at least one of silicon carbide nanosheets, boron nitride nanosheets, montmorillonite, and hydrotalcite.

[0029] In one embodiment, the heat-sensitive blocking agent is at least one of a heat-sensitive polymer and a thermoplastic polymer, preferably a heat-sensitive polymer.

[0030] In one embodiment, the thermosensitive polymer is at least one selected from polycaprolactone-polyethylene glycol, polylactic acid-polyethylene glycol block copolymer, and polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer. Preferably, it is a polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer.

[0031] In one embodiment, the polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer has a number-average molecular weight of 4000 Da for the polyethylene glycol segment and a number-average molecular weight of 2000 Da for the polycaprolactone segment.

[0032] In one embodiment, the adhesive is at least one of polyvinylidene fluoride and sodium carboxymethyl cellulose.

[0033] In one embodiment, the conductive enhancer is at least one of carbon nanotubes, graphene, and conductive carbon black.

[0034] In one embodiment, the solvent is at least one of N-methylpyrrolidone and an aqueous ethanol solution.

[0035] In addition, the present invention also provides a method for preparing a multi-layered defensive security coating, the method comprising the following steps: S1. Add mesoporous inorganic materials, stabilizers, thermosensitive blocking agents, binders and conductivity enhancers to the solvent, and stir at a speed of 50 r / min to 100 r / min for 20 min to 30 min to obtain a slurry; S2. The slurry is uniformly coated onto the surface of the pretreated aluminum or copper foil current collector using a doctor blade coating, micro-gravure coating, or spray coating method. It is then dried at 80℃~120℃, immersed in a surface modifier, and dried again at 80℃~120℃ to form a coating.

[0036] In addition, the present invention also provides an application of a multi-layered defensive safety coating, wherein the multi-layered defensive safety coating is applied to the current collector surface of a lithium-ion battery to improve the battery's puncture resistance and thermal safety performance.

[0037] In one embodiment, the thickness of the coating is 5 μm to 30 μm.

[0038] The coating obtained by the above scheme maintains excellent ionic and electronic conductivity during normal battery operation. When subjected to mechanical damage such as puncture, its porous structure buffers stress, enhances electrode layer adhesion, and prevents low-resistance short circuits caused by large-area shedding of active material. When the local temperature rises abnormally due to a short circuit, the thermistor in the coating responds rapidly, melting and filling the pores to form an insulating barrier, physically blocking the short-circuit current. The high specific heat capacity porous framework in the coating effectively absorbs and disperses the Joule heat generated by the short circuit, slowing down the temperature rise rate. Through surface functional group design, it adsorbs harmful gases (such as HF) generated by electrolyte decomposition and inhibits the aluminothermic reaction between the aluminum foil and the positive electrode material. The coating, by constructing a composite functional layer with multi-level pores, thermosensitive response, and high-temperature stability on the current collector surface, exhibits excellent safety during needle puncture, with no open flame or explosion.

[0039] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0040] Example 1: A method for preparing a multi-layered defensive security coating, the method comprising the following steps: S1. By weight, 55 parts of mesoporous inorganic material, 3 parts of silicon carbide nanosheets, 2 parts of polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer, 3 parts of polyvinylidene fluoride and 0.5 parts of carbon nanotubes are added to 20 parts of N-methylpyrrolidone and stirred at 50 r / min for 30 min to obtain a slurry. The mesoporous inorganic material comprises 15% having a pore size of 1 nm; 45% having a pore size of 2 nm to 50 nm; and 40% having a pore size of 100 nm to 500 nm; with a porosity of 45%; and is a SiO2-Al2O3 composite inorganic material. In the polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer, the number average molecular weight of the polyethylene glycol segment is 4000 Da, and the number average molecular weight of the polycaprolactone segment is 2000 Da. S2. The slurry is uniformly coated onto the surface of the pretreated aluminum or copper foil current collector by means of blade coating, micro-gravure coating or spraying, dried at 100°C, then immersed in a surface modifier, and then dried at 105°C to form a coating with a thickness of 20μm. The surface modifier comprises a mixture of γ-aminopropyltriethoxysilane and alkyl polyoxyethylene ether phosphate in a mass ratio of 7:3, wherein the alkyl group contains 4 to 10 carbons and the degree of polymerization of the polyoxyethylene ether is 4 to 20.

[0041] Example 2: A method for preparing a multi-layered defensive security coating, the method comprising the following steps: S1. By weight, 60 parts of mesoporous inorganic material, 3 parts of silicon carbide nanosheets, 3 parts of polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer, 2 parts of polyvinylidene fluoride and 0.5 parts of carbon nanotubes are added to 20 parts of N-methylpyrrolidone and stirred at 50 r / min for 30 min to obtain a slurry. The mesoporous inorganic material comprises 15% having a pore size of 1 nm; 45% having a pore size of 2 nm to 50 nm; and 40% having a pore size of 100 nm to 500 nm; with a porosity of 45%; and is a SiO2-Al2O3 composite inorganic material. In the polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer, the number average molecular weight of the polyethylene glycol segment is 4000 Da, and the number average molecular weight of the polycaprolactone segment is 2000 Da. S2. The slurry is uniformly coated onto the surface of the pretreated aluminum or copper foil current collector by means of blade coating, micro-gravure coating or spraying, dried at 100°C, then immersed in a surface modifier, and then dried at 110°C to form a coating with a thickness of 20μm. The surface modifier comprises a mixture of γ-aminopropyltriethoxysilane and alkyl polyoxyethylene ether phosphate in a mass ratio of 7:3, wherein the alkyl group contains 4 to 10 carbons and the degree of polymerization of the polyoxyethylene ether is 4 to 20.

[0042] Example 3: A method for preparing a multi-layered defensive security coating, the method comprising the following steps: S1. By weight, 65 parts of mesoporous inorganic material, 2 parts of silicon carbide nanosheets, 2 parts of polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer, 3 parts of polyvinylidene fluoride and 0.7 parts of carbon nanotubes are added to 20 parts of N-methylpyrrolidone and stirred at 100 r / min for 30 min to obtain a slurry. The mesoporous inorganic material comprises 15% having a pore size of 1 nm; 45% having a pore size of 2 nm to 50 nm; and 40% having a pore size of 100 nm to 500 nm; with a porosity of 45%; and is a SiO2-Al2O3 composite inorganic material. In the polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer, the number average molecular weight of the polyethylene glycol segment is 4000 Da, and the number average molecular weight of the polycaprolactone segment is 2000 Da. S2. The slurry is uniformly coated onto the surface of the pretreated aluminum or copper foil current collector by means of blade coating, micro-gravure coating or spraying, dried at 100°C, then immersed in a surface modifier, and then dried at 120°C to form a coating with a thickness of 20μm. The surface modifier comprises a mixture of γ-aminopropyltriethoxysilane and alkyl polyoxyethylene ether phosphate in a mass ratio of 7:3, wherein the alkyl group contains 4 to 10 carbons and the degree of polymerization of the polyoxyethylene ether is 4 to 20.

[0043] Comparative Example 1: The difference between Comparative Example 1 and Example 3 is that the pore size of the mesoporous inorganic material used in Comparative Example 1 is 50 nm, while the rest is the same as in Example 3.

[0044] Comparative Example 2: The difference between Comparative Example 2 and Example 3 is that no silicon carbide nanosheets (stabilizer) were added in Comparative Example 2, while the rest were the same as in Example 3.

[0045] Comparative Example 3: The difference between Comparative Example 3 and Example 3 is that no polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer (thermal blocking agent) was added in Comparative Example 3, while the rest was the same as in Example 3.

[0046] Comparative Example 4: The difference between Comparative Example 4 and Example 3 is that Comparative Example 4 uses a conventional coating, while the rest is the same as Example 3. The conventional coating in Comparative Example 4 is as follows: 0.5 parts carbon nanotubes, 1 part graphite and 1 part conductive carbon black are added to 20 parts N-methylpyrrolidone by weight, and then 2 parts polyvinylidene fluoride are added. The mixture is stirred at 50 r / min for 30 min.

[0047] Comparative Example 5: The difference between Comparative Example 5 and Example 3 is that Comparative Example 5 was not treated with a surface modifier, but otherwise it was the same as Example 3.

[0048] The coating samples prepared in Examples 1-3 and the coating samples prepared in Comparative Examples 1-5 were subjected to performance tests, and the results are shown in Table 1 below.

[0049] The corrosion rate test was conducted in accordance with GB / T19292.3-2018, in which samples were immersed in a composite corrosive medium containing H2S (100ppm), CO2 (20%), and organic acids (5% formic acid and 5% acetic acid) for 72h.

[0050] The thermal shock cycle test conditions were as follows: 50 cycles of holding at 300℃ in a high-temperature furnace for 20 minutes and quenching at room temperature in a rapid cooling device (cooling within 10 seconds). Cracks on the coating surface were observed by SEM, the area of ​​coating peeling was counted, and the coating integrity rate was calculated.

[0051] Sulfide permeation conditions were tested under simulated corrosive media containing H2S (500 ppm) in a dynamic cyclic test (flow rate 5 mL / min, duration 24 h). The sulfur content on the coating surface was detected by Fourier transform infrared spectroscopy (FTIR).

[0052] Table 1: Performance Test Results

[0053] As shown in Table 1, the coating of this invention exhibits a low corrosion rate and excellent corrosion resistance in composite corrosive media containing H2S, CO2, and organic acids. This is attributed to the combined effect of the hierarchical porous structure of the mesoporous inorganic material and the surface modifier, which effectively blocks the penetration of corrosive media and adsorbs harmful gases. This invention successfully constructs a multi-layered defensive safety coating integrating conductivity, corrosion resistance, heat insulation, gas barrier properties, structural reinforcement, and thermal response cutoff through the synergistic effect of a multi-component system consisting of a hierarchical mesoporous inorganic framework, stabilizers, thermosensitive blocking agents, conductivity enhancers, and surface modifiers.

[0054] Compared to Example 3, Comparative Example 1 used only a single-pore-size mesoporous inorganic material with a pore size of 50 nm, resulting in a change in performance. This indicates that the hierarchical pore structure easily causes stress concentration in the coating during thermal shock cycling, making the coating integrity worse than in Example 3. This also shows that the single-pore-size material is less effective in dispersing and adsorbing corrosion factors than in Example 3. Comparative Example 2 did not add silicon carbide nanosheets (stabilizer), resulting in poor thermal stability and coating integrity worse than in Example 3. Corrosive media penetrated, leading to overall performance worse than in Example 3. Comparative Example 3 did not add polycaprolactone-polyethylene glycol-polycaprolactone triblock copolymer (thermosensitive blocker). The lack of a thermosensitive blocker in the melt-filling behavior could further seal the micropores, affecting the coating performance. Comparative Example 4 lacked an inorganic porous framework and surface modification, resulting in the worst corrosion resistance and coating integrity compared to Example 3. Comparative Example 5 was not treated with a surface modifier, and no organic functional groups were introduced to the surface, weakening the inhibition of the aluminothermic reaction. This indicates that the surface modifier can optimize the wettability between the coating and the electrolyte, helping to form a stable, low-resistance solid-liquid interface.

[0055] In addition, the current collectors prepared in Examples 1-3 were used to fabricate pouch cells with a rated capacity of 5Ah (NCM811 / Li system, 100% SOC), and needle penetration tests were conducted according to GB / T 31485-2025 (Φ8mm steel needle, 25mm / s). The results showed that none of the cells from Examples 1-3 caught fire, exhibiting excellent needle penetration resistance and no thermal runaway propagation, demonstrating excellent safety.

[0056] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A multi-layered defensive security coating, characterized in that, The multi-layered defensive security coating comprises the following raw materials in parts by weight: 10-80 parts of mesoporous inorganic material, 1-3 parts of stabilizer, 0.1-3 parts of thermosensitive blocking agent, 1-5 parts of binder, 0.1-1 parts of conductive enhancer, and 15-20 parts of solvent.

2. The multi-layered defensive security coating according to claim 1, characterized in that, The mesoporous inorganic material has a pore size range of 0.5 nm to 500 nm and a porosity of 30% to 60%. The mesoporous inorganic material adopts an inorganic porous framework, which is a SiO2-Al2O3 composite inorganic material.

3. The multi-layered defensive security coating according to claim 1, characterized in that, The coating also includes a surface modifier comprising a silane coupling agent and a phosphate ester in a mass ratio of (4~7):(3~6).

4. The multi-layered defensive security coating according to claim 1, characterized in that, The stabilizer is at least one of silicon carbide nanosheets, boron nitride nanosheets, montmorillonite, and hydrotalcite.

5. The multi-layered defensive security coating according to claim 1, characterized in that, The heat-sensitive blocking agent is at least one of a heat-sensitive polymer and a thermoplastic polymer.

6. The multi-layered defensive security coating according to claim 1, characterized in that, The adhesive is at least one of polyvinylidene fluoride and sodium carboxymethyl cellulose.

7. The multi-layered defensive security coating according to claim 1, characterized in that, The conductive enhancer is at least one of carbon nanotubes, graphene, and conductive carbon black.

8. The multi-layered defensive security coating according to claim 1, characterized in that, The solvent is at least one of N-methylpyrrolidone and an aqueous solution of ethanol.

9. A method for preparing a multi-layered defensive security coating, characterized in that, The preparation method is used to prepare the multi-layered defensive security coating as described in any one of claims 1 to 8, and the preparation method includes the following steps: S1. Add mesoporous inorganic materials, stabilizers, thermosensitive blocking agents, binders and conductivity enhancers to the solvent, and stir at a speed of 50 r / min to 100 r / min for 20 min to 30 min to obtain a slurry; S2. The slurry is uniformly coated onto the surface of the pretreated aluminum or copper foil current collector using a doctor blade coating, micro-gravure coating, or spray coating method. It is then dried at 80℃~120℃, immersed in a surface modifier, and dried again at 80℃~120℃ to form a coating.

10. An application of a multi-layered defensive security coating, characterized in that, The application is the multi-layered defensive safety coating as described in any one of claims 1 to 8, applied to the current collector surface of a lithium-ion battery to improve the battery's puncture resistance and thermal safety performance.

Images