Preparation and application methods of high-heat-resistance lithium ion battery diaphragm composite coating

Abstract

The invention provides a preparation and use method of a high-heat-resistance lithium ion battery diaphragm composite coating. The preparation and use method comprises the following steps: step S01, mixing Al2O3 powder with epoxy resin; s02, the Al2O3 powder and epoxy resin are fully fused, and a mixed solution is obtained; and S03, the mixed solution is put into a drying box to be defoamed under the vacuum condition, then an epoxy resin curing agent is added, the epoxy resin and the curing agent are fully stirred to be uniform, internal bubbles are removed, and preparation of the composite coating is completed. Compared with a chemical coating method, the treatment time is short, the treatment process is safe, and no waste liquid is generated to pollute the environment; the method is efficient in treatment, the compatibility between the electrode material and the diaphragm can be improved, the interface impedance is reduced, and the overall performance of the lithium ion battery is improved; the composite coating prepared by the invention has good flame retardant property, can reduce or prevent the combustion of electrolyte when the battery is short-circuited or overcharged, and can obviously improve the high heat resistance of the lithium ion battery diaphragm.

Description

Technical Field

[0001] The present invention belongs to the field of lithium battery separators and relates to a preparation and use method of a high heat-resistant lithium ion battery separator composite coating. Background Art

[0002] As one of the four key components of lithium-ion batteries, lithium-ion battery separators can prevent the positive and negative electrodes of the battery from directly contacting each other and causing short circuits, and allow ions to pass freely and quickly during charging and discharging. The performance of the separator will affect the internal resistance and interface structure of the battery, and thus affect the battery's capacity, rate charge and discharge, and cycle performance.

[0003] In order to solve the thermal stability problem of polyolefin separators, ceramic coating technology has gradually become an effective means to improve the performance of lithium-ion battery separators. Ceramic coating technology can significantly improve the thermal stability and flame retardant properties of the separator by applying a layer of ceramic coating on the surface of the polyolefin separator. Ceramic materials, such as aluminum oxide and lithium ceramics, have excellent thermal stability and strength, and can form a protective layer to prevent heat conduction, thereby reducing the risk of deformation of the separator at high temperatures. In addition, ceramic coating can also improve the interfacial compatibility of the separator, promote the effective conduction of lithium ions, and thus improve the overall performance of the battery. However, ceramic coating technology requires a high-temperature processing step, which may cause thermal shrinkage and deformation of the separator.

[0004] The wet stretching method forms a uniform polymer film by dissolving polyethylene or polypropylene in a solvent. Subsequently, the wet stretching process is used to form a nanoscale microporous structure in the solvent. Finally, the microporous structure is fixed by heating and cooling to obtain a diaphragm with high porosity and good mechanical properties. After the dry stretching melts the polyolefin, it is formed into a multilayer structure through rolling and stretching processes, and then annealing is performed at high temperature to crystallize the polymer to form a microporous structure with high porosity, which is conducive to the transmission of ions. However, the wet process involves the use of solvents and complex stretching processes, and the preparation process is complicated and the cost is high. Compared with wet stretching, dry stretching is simpler and less expensive. However, the porosity of the diaphragm prepared by the dry method is relatively low, which may lead to poor ion transmission performance and poor dimensional stability under high temperature conditions; The composite film valve mixes the polymer matrix with inorganic fillers (such as aluminum oxide, silicon oxide, etc.) to form a uniform mixture. This mixture is then coated on the surface of the diaphragm and processed into a composite diaphragm through a casting or extrusion process on the surface of the diaphragm. The high flexibility of the polymer and the high heat resistance of the inorganic material have good comprehensive performance, but there may be interface bonding problems in the process, affecting the performance of the diaphragm. Summary of the invention

[0005] 1. Technical problems to be solved: How to evenly coat the composite separator, ensure good interfacial bonding between the inorganic particles and the organic substrate, and maintain the stability of the coating and the separator 2. Technical solution: In order to solve the above problems, the present invention provides a method for preparing a high heat-resistant lithium-ion battery separator composite coating, comprising the following steps: Step S01: Al2O3 powder is mixed with epoxy resin; the mass ratio of epoxy resin to Al2O3 powder is 1:0.2 to 1:1.

[0006] Step S02: Fully blend Al2O3 powder and epoxy resin to obtain a mixed solution.

[0007] Step S03: placing the obtained mixed solution into a drying oven for degassing under vacuum conditions, then adding an epoxy resin curing agent, fully stirring the epoxy resin and the curing agent, and removing the internal bubbles to complete the preparation of the composite coating.

[0008] In step S01, Al2O3 powder is processed by a plasma processing device, which includes a box. A metal mesh plate is in close contact with the box, dividing the box into two parts, with liquid above the metal mesh plate. The metal mesh plate is connected to a high-voltage power supply to become a high-voltage electrode, and the bottom of the box is connected to a ground electrode. An air gap space is formed between the metal mesh plate and the bottom of the box, and Al2O3 powder is placed in the air gap space. The working gas and the medium gas converge in the air gap space.

[0009] The working gas is Ar, HMDSO or APTES is used as a modifying medium, and the medium vapor is brought into the air gap space by a bubbling method.

[0010] The working gas flow rate adjustment range is 0-10 L / min, and the medium flow rate adjustment range is 0-100 mL / min.

[0011] The high-voltage power supply is a nanosecond pulse power supply with a voltage output peak of 15 kV, a frequency peak of 15 kHz, a pulse width adjustment range of 0 ns-1 ms, a rising edge and falling edge time adjustment range of 50 ns-250 ns, and a voltage amplitude of 3.0-10.0 kV and a power supply frequency of 5.0-8.0 kHz.

[0012] In step S01, the plasma treated Al2O3 powder is ultrasonically dispersed for 28-32 min and then mixed with epoxy resin. In step S02, the epoxy resin mixture of step S01 is physically stirred for 3.6-4.4 hours and ultrasonicated for 0.9-1.1 hours in sequence to fully fuse the Al2O3 powder and the epoxy matrix.

[0013] In step S03, the specific method is: put the mixed solution obtained in step S02 into a drying oven for degassing under vacuum conditions for 0.9-1.1 hours, and then add epoxy resin curing agent, and the mass ratio of mixed solution: curing agent is 10:3. Use a stirring degassing machine to mix and stir at a speed of 900-1100 r / min for 5-6 minutes, and then degas at a speed of 1800-2100 r / min for 1.8-2.5 minutes, so that the epoxy resin and the curing agent are fully mixed and evenly mixed, and the internal bubbles are removed.

[0014] The invention also provides a method for using the high heat-resistant lithium-ion battery separator composite coating.

[0015] 3. Beneficial effects: Compared with the chemical coating method, the present invention has a short processing time, a safe processing process, and will not generate waste liquid to pollute the environment; the present invention has high processing efficiency, can improve the compatibility between the electrode material and the diaphragm, reduce the interface impedance, and improve the overall performance of the lithium ion battery; the composite coating prepared by the present invention has good flame retardant properties, reduces or prevents the combustion of the electrolyte when the battery is short-circuited or overcharged, and can significantly improve the high heat resistance of the lithium ion battery diaphragm. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the preparation process of high heat-resistant lithium-ion battery separator.

[0017] Figure 2 Schematic diagram of plasma treatment of materials. DETAILED DESCRIPTION

[0018] The present invention is described in detail below with reference to the accompanying drawings.

[0019] like Figure 1 As shown, a method for preparing a high heat-resistant lithium-ion battery separator composite coating comprises the following steps: Step S01: Al2O3 powder is mixed with epoxy resin; the mass ratio of epoxy resin to Al2O3 powder is 1:0.2 to 1:1.

[0020] Step S02: Fully blend Al2O3 powder and epoxy resin to obtain a mixed solution.

[0021] Step S03: placing the obtained mixed solution into a drying oven for degassing under vacuum conditions, then adding an epoxy resin curing agent, fully stirring the epoxy resin and the curing agent, and removing the internal bubbles to complete the preparation of the composite coating.

[0022] In the composite material experiment, the thermal conductivity of the composite material without Al2O3 powder is generally 0.3W / m•K, and the thermal conductivity of the composite material with powder is 0.6W / m•K. After plasma modification, it is increased to 0.7W / m•K. The thermal conductivity of the composite material coating prepared after Al2O3 powder filling is increased by 96.7%. For better effect, Al2O3 powder is plasma treated, such as Figure 2 As shown, the plasma treatment device includes a box, a metal mesh plate is in close contact with the box, and the box is divided into two parts, and the position between the metal mesh plate and the box can be adjusted. Figure 1 As shown, the maximum distance D from the bottom surface.

[0023] There is liquid above the metal mesh, and the metal mesh has solid grids, so the liquid will not enter the metal mesh from the metal mesh. The grid distance of the metal mesh is d.

[0024] The metal mesh is connected to a high-voltage power supply to become a high-voltage electrode, the bottom of the box is a ground electrode, and an air gap is formed between the metal mesh and the bottom of the box. Since the distance between the metal mesh and the bottom is adjustable, the height of the discharge gap of the electrode is also adjustable, and the adjustment range is 2-10 mm, preferably 4 mm. Al2O3 powder is placed in the air gap, and the working gas and the medium gas converge in the air gap.

[0025] In one embodiment, argon is used as the working gas, and the gas flow rate is adjusted in the range of 0-10 L / min, preferably 0.5 L / min. HMDSO or APTES is selected as the modifying medium, and the medium vapor is brought into the air gap space by bubbling, and the medium flow rate is adjusted in the range of 0-100 mL / min, preferably 50 mL / min.

[0026] In one embodiment, the high voltage power supply is a nanosecond pulse power supply voltage with an output peak of 15 kV and a frequency peak of 15 kHz. The pulse width adjustment range is 0 ns-1 ms, preferably 1 µs. The rising edge and falling edge time adjustment range is 50ns-250 ns, preferably 50 ns. In the range of voltage amplitude of 3.0-10.0 kV and power supply frequency of 5.0-8.0 kHz, the powder can obtain a relatively uniform treatment effect. The preferred voltage is 10.0 kV and the frequency is 5.0 kHz.

[0027] In the composite material experiment, the thermal conductivity of the composite coating made from powders treated with plasma coating was improved by 11.3% compared with the composite material made from uncoated powders.

[0028] Best embodiment: A method for preparing a high heat-resistant lithium-ion battery separator composite coating comprises the following steps: Step S01: After the plasma treated Al2O3 powder is ultrasonically dispersed for 28-32 min, it is mixed with epoxy resin. Step S02, the epoxy resin mixture of step S01 is physically stirred for 3.6-4.4 hours and ultrasonicated for 0.9-1.1 hours in sequence to fully fuse the Al2O3 powder and the epoxy matrix.

[0029] Step S03: Place the mixed solution obtained in step S02 in a drying oven for degassing under vacuum conditions for 0.9-1.1 hours, and then add epoxy resin curing agent, with the mixed solution: curing agent mass ratio being 10:3. Use a stirring degassing machine to mix and stir at a speed of 900-1100 r / min for 5-6 minutes, and then degas at a speed of 1800-2100 r / min for 1.8-2.5 minutes to fully mix the epoxy resin and curing agent and remove the bubbles inside.

[0030] The present invention also provides a method for using a high heat-resistant lithium-ion battery separator composite coating, comprising the following steps: Step S91: uniformly coating the high heat-resistant lithium-ion battery separator composite coating on the separator.

[0031] Step S92: Pre-addition: 4-6 min until the mixed solution has no obvious flow on the sample surface.

[0032] Step S93: Place in an oven and heat to 80°C at a rate of 2-5°C / min, cure for 3.6-4.4 hours, and use after natural cooling to obtain an electronic diaphragm with a composite coating.

[0033] In one embodiment, the quality inspection is performed by cutting and shaping the obtained electronic diaphragm with the composite coating.

Claims

1. A method for preparing a high heat-resistant lithium-ion battery separator composite coating, characterized in that: The following steps are involved: Step S01: Al2O3 powder is mixed with epoxy resin, and the mass ratio of epoxy resin to Al2O3 powder is 1:0.2 to 1:1; Step S02: Fully blending Al2O3 powder and epoxy resin to obtain a mixed solution; Step S03: placing the obtained mixed solution into a drying oven for degassing under vacuum conditions, then adding an epoxy resin curing agent, fully stirring the epoxy resin and the curing agent, and removing the internal bubbles to complete the preparation of the composite coating.

2. The preparation method according to claim 1, characterized in that: In step S01, Al2O3 powder is processed by a plasma processing device, which includes a box. A metal mesh plate is in close contact with the box, dividing the box into two parts, with liquid above the metal mesh plate. The metal mesh plate is connected to a high-voltage power supply to become a high-voltage electrode, and the bottom of the box is connected to a ground electrode. An air gap space is formed between the metal mesh plate and the bottom of the box, and Al2O3 powder is placed in the air gap space. The working gas and the medium gas converge in the air gap space.

3. The preparation method according to claim 2, characterized in that: The working gas is Ar, HMDSO or APTES is used as a modifying medium, and the medium vapor is brought into the air gap space by a bubbling method.

4. The preparation method according to claim 2, characterized in that: The working gas flow rate adjustment range is 0-10 L / min, and the medium flow rate adjustment range is 0-100 mL / min.

5. The preparation method according to claim 2, characterized in that: The high-voltage power supply is a nanosecond pulse power supply with a voltage output peak of 15 kV, a frequency peak of 15 kHz, a pulse width adjustment range of 0 ns-1 ms, a rising edge and falling edge time adjustment range of 50 ns-250 ns, and a voltage amplitude of 3.0-10.0 kV and a power supply frequency of 5.0-8.0 kHz.

6. The preparation method according to any one of claims 2 to 5, characterized in that: In step S01, the plasma treated Al2O3 powder is ultrasonically dispersed for 28-32 min and then mixed with epoxy resin. The preparation method according to claim 6 is characterized in that: in step S02, the epoxy resin mixture of step S01 is physically stirred for 3.6-4.4 hours and ultrasonicated for 0.9-1.1 hours in sequence to fully fuse the Al2O3 powder and the epoxy matrix.

7. The preparation method according to claim 1, characterized in that: In step S03, the specific method is: putting the mixed solution obtained in step S02 into a drying oven for degassing under vacuum conditions for 0.9-1.1 hours, and then adding epoxy resin curing agent, with the mass ratio of mixed solution: curing agent being 10:

3.

8. Use a stirring and degassing machine to mix and stir at a speed of 900-1100 r / min for 5-6 minutes, and then degas at a speed of 1800-2100 r / min for 1.8-2.5 minutes to fully mix the epoxy resin and curing agent and remove the internal bubbles.

9. A method for using a high heat-resistant lithium-ion battery separator composite coating, characterized in that: The following steps are involved: Step S91: uniformly coating the high heat-resistant lithium-ion battery separator composite coating on the separator; Step S92: pre-addition: 4-6 min until the mixed solution has no obvious flow on the sample surface; Step S93: Place in an oven and heat to 80°C at a rate of 2-5°C / min, cure for 3.6-4.4 hours, and use after natural cooling to obtain an electronic diaphragm with a composite coating.

10. The method for using the high heat-resistant lithium-ion battery separator composite coating according to claim 9, characterized in that: The quality inspection is carried out by cutting and shaping the electronic diaphragm of the obtained composite coating.

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