CN106207060A - Lithium ion-containing ceramic coating diaphragm and preparation method and application thereof - Google Patents

Abstract

The invention discloses a ceramic coated diaphragm containing lithium ions, which comprises a substrate diaphragm and a ceramic coating, the ceramic coating is made by uniformly coating the surface of the substrate diaphragm with a water-based ceramic slurry, and the water-based ceramic slurry The following components are included in parts by weight: 10-50 parts of Li-α-sialon containing lithium ions, 0.5-3 parts of binder, 0.2-1.0 parts of additives, and 0.01-0.1 parts of auxiliary agents. The ceramic coating of the present invention contains lithium ions, which is especially suitable for the conduction of lithium ions in the high and low temperature cycle process; the bonding force between the ceramic coating and the diaphragm is enhanced, especially the thermal shrinkage performance, which can inhibit the ceramic diaphragm from falling off; the ceramic coating has a good Strong ability to absorb and maintain the electrolyte, the coating will not fall off in the electrolyte, and still maintain the bonding ability; the ceramic coating is conducive to the improvement of the capacity retention rate of the battery, and improves the cycle life and safety performance.

Description

A kind of ceramic coated separator containing lithium ions and its preparation method and application

technical field

The invention belongs to the technical field of lithium batteries, in particular to a ceramic coated separator containing lithium ions, a preparation method and application thereof.

Background technique

In the "Energy Saving and New Energy Vehicle Industry Plan (2011-2020)" promulgated by the State Council, it is clearly stated that the energy density of power batteries will reach 300Wh/kg in 2020, the cruising range: 300km, and the battery cost: 1.5 yuan/Wh. Lithium-ion batteries and nickel-metal hydride batteries are considered to be two types of power batteries suitable for electric vehicles and hybrid electric vehicles. In the structure of lithium batteries, the separator is one of the key inner components. The performance of the separator determines the interface structure and internal resistance of the battery, which directly affects the capacity, cycle and safety performance of the battery. A separator with excellent performance plays an important role in improving the overall performance of the battery. At present, the commonly used polyolefin-based separators are mainly polyethylene microporous membranes and polypropylene microporous membranes. The melting points of these two types of membranes are about 130 ° C and 150 ° C, respectively, so they are easy to shrink or melt at higher temperatures, causing positive and negative electrodes. The direct contact between the negative electrodes leads to the occurrence of short circuit, which leads to accidents, such as battery explosion caused by discharge. The ceramic diaphragm is also an organic/inorganic composite membrane. It is a protective layer composed of ceramic microparticles coated on one or both sides on the surface of the existing polyolefin microporous membrane substrate to form a porous and safe membrane. Sexual function diaphragm. On the basis of ensuring the original basic characteristics of the polyolefin microporous separator, the separator is endowed with a high heat resistance function, which reduces the thermal shrinkage of the separator, thereby more effectively reducing the internal short circuit of the lithium-ion battery and preventing the battery from heat caused by the internal short circuit of the battery. out of control.

At present, ceramic separators for lithium-ion batteries are gradually appearing on the market. The ceramics used in common ceramic coatings are nano-alumina particles. However, some ceramic diaphragms have problems such as powder falling and low uniformity. The main reason is that on the one hand, the ultrafine alumina powder has a large specific surface energy and high surface activity, and a single ultrafine particle is often in an unstable state. Attract each other and agglomerate, and its surface is generally hydrophilic, while polyolefin membrane is a hydrophobic material. Therefore, according to most research reports, the uniformity of ceramic powder coating is poor, and there is obvious "powder drop" phenomenon, which will greatly affect the performance of ceramic separators in lithium-ion batteries. Therefore, the existing ceramic diaphragms are in urgent need of improvement in terms of improving the wettability and safety of the electrolyte.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention proposes a ceramic coated diaphragm containing lithium ions and its preparation method and application. Coating a new type of ceramic on the base film can not only effectively improve the thermal stability of the diaphragm, but also maintain The original porous performance of the polyene separator has achieved good results in both adhesion and electrolyte wettability. In the process of high and low temperature cycling, the frame structure has the ability to regulate lithium ions, thereby improving the overall performance and stability of the ceramic separator, and improving the safety of the electrochemical device.

The purpose of the present invention can be achieved through the following technical solutions:

A ceramic coated diaphragm containing lithium ions, characterized in that it comprises a substrate diaphragm and a ceramic coating, the ceramic coating is made by uniformly coating the surface of the substrate diaphragm with a water-based ceramic slurry, and the water-based ceramic slurry The material includes the following components in parts by weight: 10-50 parts of Li-α-sialon containing lithium ions, 0.5-3 parts of binder, 0.2-1.0 parts of additives, and 0.01-0.1 parts of auxiliary agents.

The particle size distribution of the first type of powder in the Li-α-sialon is that the D50 is greater than 5nm and less than 1.0um, and the content is 10% to 60% of the total mass of Li-α-sialon; the particle size distribution of the second type of powder is The D50 is less than 10nm, and the content is 40%-90% of the total mass of Li-α-sialon; the ratio of the particle size of the second type to the first type powder is 0.1-0.5.

The thickness of the ceramic coating coated on the surface of the substrate separator is 2.0-5.0um.

The base material diaphragm is a polyethylene diaphragm or a polypropylene diaphragm.

The binder in the water-based ceramic slurry includes polystyrene-butadiene emulsion, polymethyl methacrylate-butyl acrylate emulsion, polystyrene-butyl acrylate emulsion, polytetrafluoroethylene emulsion, polyvinylidene One or more of vinyl fluoride emulsions.

The additives in the water-based ceramic slurry are water-soluble macromolecules, including sodium carboxymethyl cellulose, cross-linked sodium carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hypromellose, One or more of polyvinyl alcohol, polyethylene glycol and polyacrylamide.

The additives in the water-based ceramic slurry include tertiary alkyl polyol polyvinyl ether, sodium diisooctyl sulfonate, alkylnaphthalene sulfonate, polyether modified silicone oil, polypropylene glycol-ethylene oxide, One or more of polyether stearate dimethyl siloxane, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene glycylether, polyoxyethylene polyoxypropanolamine ether.

The invention also discloses a method for preparing a ceramic coating diaphragm containing lithium ions, comprising the following steps:

(1) Take Li-α-sialon whose particle size ratio between the second type and the first type powder is 0.1-0.5:1, and disperse it in deionized water to prepare Li-α-sialon aqueous solution and Li-α-sialon aqueous solution The solid content is 10-50%;

(2) Mixing the Li-α-sialon aqueous solution with binders, additives and auxiliary agents to prepare water-based ceramic slurry, wherein the mass ratio of Li-α-sialon to binder is 3-50:1;

(3) The water-based ceramic slurry is evenly coated on the surface of the substrate diaphragm, and the ceramic coated diaphragm is obtained after drying.

The Li-α-sialon aqueous solution in the step (1) also includes 0.1 to 1.0 wt% of a dispersant, and the dispersant includes sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, dodecyl One or more of sodium sulfonate, sodium hexametaphosphate, polyacrylic acid, cetyltrimethylammonium bromide, octylphenol polyoxyethylene, and polyethylene glycol.

Application of a lithium-ion-containing ceramic-coated separator in an electrochemical device.

Beneficial effects of the present invention: the ceramic coating of the present invention contains lithium ions, which is especially suitable for the conduction of lithium ions in the high and low temperature cycle process; the bonding force between the ceramic coating and the diaphragm is enhanced, especially the thermal shrinkage performance, and the powder shedding of the ceramic diaphragm is inhibited ;The ceramic coating has a strong ability to absorb and maintain the electrolyte, the coating will not fall off in the electrolyte, and still maintains the bonding ability; the ceramic coating is conducive to the improvement of the capacity retention rate of the battery, and improves the cycle life and safety performance .

Description of drawings

Figure 1 is a comparison chart of the charge retention rate and capacity recovery rate of the ceramic separator (1#) prepared in Example 1 of the present invention and the common separator (2#) after high-temperature storage.

detailed description

A ceramic coated diaphragm containing lithium ions, characterized in that it comprises a substrate diaphragm and a ceramic coating, the ceramic coating is made by uniformly coating the surface of the substrate diaphragm with a water-based ceramic slurry, and the water-based ceramic slurry The material includes the following components in parts by weight: 10-50 parts of Li-α-sialon containing lithium ions, 0.5-3 parts of binder, 0.2-1.0 parts of additives, and 0.01-0.1 parts of auxiliary agents. The particle size distribution of the first type of powder in Li-α-sialon is that D50 is greater than 5nm and less than 1.0um, and the content is 10% to 60% of the total mass of Li-α-sialon; the particle size distribution of the second type of powder is D50 Less than 10nm, the content is 40% to 90% of the total mass of Li-α-sialon; the ratio of the particle size of the second type to the first type of powder is 0.1 to 0.5.

Example 1

1. Take 2g of Li-α-sialon with a particle size D50 of the first type of powder of 50nm, and 8g of Li-α-sialon with a particle size of the second type of powder with a D50 of 5nm, add them to 40g of deionized water, and stir at high speed for 30 minutes , and then ultrasonically dispersed for 30 minutes to obtain a pre-dispersion of Li-α-sialon ceramic powder. Add 0.5wt% dispersant to the pre-dispersion, including: 0.125 g of sodium dodecylbenzenesulfonate, octylphenol polyoxygen Ethylene 0.063g and polyacrylic acid 0.063g, the dosage ratio of the three is 2:1:1, stir the pre-dispersion liquid at high speed for 30min, then add a small amount of hydrochloric acid dilute solution and ammonia solution to adjust the pH value of the dispersion liquid to maintain at 4～ 5. The above-mentioned pre-dispersion was ball-milled in a ball mill for 2 hours to obtain a uniform and stable Li-α-sialon aqueous solution.

2. Add 2 g of polystyrene-butadiene emulsion with a solid content of 50%, 0.15 g of sodium carboxymethyl cellulose and 0.05 g of tert-alkyl polyol polyvinyl ether into Li-α-sialon aqueous solution, and carry out slow After stirring evenly, filter with a 300-mesh stainless steel screen to obtain a water-based ceramic coating slurry.

3. Use a micro-gravure printing machine to evenly coat the above-mentioned water-based ceramic coating slurry on the polyethylene diaphragm, the substrate diaphragm running speed is 0.5m/min, and the hot air drying temperature is 50°C to prepare a single-sided ceramic coating Ceramic diaphragm with a thickness of 3.0±0.5um. Figure 1 shows the high temperature charge retention rate and capacity recovery rate of batteries made with different separators after storage at 55°C for 7 days.

Example 2

1. Take 5g of Li-α-sialon with a particle size D50 of the first type of powder of 18nm, and 5g of Li-α-sialon with a particle size of the second type of powder with a D50 of 9nm, add them to 40g of deionized water, and stir at high speed for 30 minutes , and then ultrasonically dispersed for 30 minutes to obtain a pre-dispersion of Li-α-sialon ceramic powder. The dispersant that adds 0.5wt% in the predispersion liquid comprises: sodium lauryl sulfonate 0.125g, octylphenol polyoxyethylene 0.063g and polyethylene glycol 0.063g, and the consumption ratio of the three is 2:1: 1. Stir the pre-dispersion at high speed for 30 minutes, then add a small amount of dilute hydrochloric acid solution and dilute sodium hydroxide solution to adjust the pH value of the dispersion to 4-5; the above-mentioned pre-dispersion is ball-milled in a ball mill for 2 hours to obtain a uniform and stable Li-α-sialon aqueous solution.

2. Add 2.50 g of polymethyl methacrylate-butyl acrylate emulsion with a solid content of 40%, 0.15 g of polyacrylamide and 0.04 g of polyether stearate dimethyl siloxane into the Li-α-sialon aqueous solution g. After stirring evenly at a slow speed, filter with a 400-mesh stainless steel screen to obtain a water-based ceramic coating slurry.

3. Use a micro-gravure printing machine to evenly coat the above-mentioned water-based ceramic coating slurry on the polyethylene diaphragm. The substrate diaphragm runs at a speed of 1.0m/min, and the hot air drying temperature is 60°C to prepare a single-sided ceramic coating. Ceramic diaphragm with a thickness of 4.0±0.5um.

Example 3

1. Take 4g of Li-α-sialon with a particle size D50 of the first type of powder of 20nm, and 6g of Li-α-sialon with a particle size of the second type of powder with a D50 of 6nm, add them to 40g of deionized water, and stir at high speed for 30 minutes , and then ultrasonically dispersed for 30 minutes to obtain a pre-dispersion of Li-α-sialon ceramic powder. Add 0.5wt% dispersant to the pre-dispersion, including: sodium dodecylbenzenesulfonate 0.125g, octylphenol polyoxyethylene 0.063g and polyacrylic acid 0.063g, the amount ratio of the three is 2:1:1 . Stir the pre-dispersion at high speed for 30 minutes, then add a small amount of dilute hydrochloric acid solution and dilute sodium hydroxide solution to adjust the pH value of the dispersion to 4-5; the above-mentioned pre-dispersion is ball-milled in a ball mill for 2 hours to obtain a uniform and stable Li-α-sialon aqueous solution.

2. Add 2.50g of polyvinylidene fluoride emulsion with a solid content of 20%, 0.17g of polyacrylamide and 0.05g of polyether stearate dimethyl siloxane into the Li-α-sialon aqueous solution, and stir slowly After uniformity, filter with a 400-mesh stainless steel screen to obtain a water-based ceramic coating slurry.

3. Use a micro-gravure printing machine to evenly coat the above-mentioned water-based ceramic coating slurry on the polyethylene diaphragm. The substrate diaphragm runs at a speed of 1.0m/min, and the hot air drying temperature is 60°C to prepare a single-sided ceramic coating. Ceramic diaphragm with a thickness of 4.0±0.5um.

The above content is only an example and description of the structure of the present invention. Those skilled in the art make various modifications or supplements to the described specific embodiments or replace them in similar ways, as long as they do not deviate from the structure of the invention or Anything beyond the scope defined in the claims shall belong to the protection scope of the present invention.

Claims (10)

1. A ceramic coating diaphragm containing lithium ions, characterized in that it comprises a substrate diaphragm and a ceramic coating, and the ceramic coating is made by uniformly coating the surface of the substrate diaphragm by a water-based ceramic slurry, and the water-based The ceramic slurry comprises the following components in parts by weight: 10-50 parts of Li-α-sialon containing lithium ions, 0.5-3 parts of binder, 0.2-1.0 parts of additives and 0.01-0.1 parts of additives. 2. The ceramic coating diaphragm containing lithium ions according to claim 1, characterized in that, the particle size distribution of the first type of powder in the Li-α-sialon is that D50 is greater than 5nm and less than 1.0um, and the content is 10% to 60% of the total mass of Li-α-sialon; the particle size distribution of the second type of powder is D50 less than 10nm, and the content is 40% to 90% of the total mass of Li-α-sialon; the second type and the first The particle size ratio of the powder-like body is 0.1-0.5. 3 . The ceramic-coated diaphragm containing lithium ions according to claim 2 , characterized in that the thickness of the ceramic coating coated on the surface of the substrate diaphragm is 2.0-5.0 um. 4. The ceramic-coated diaphragm containing lithium ions according to claim 3, wherein the substrate diaphragm is a polyethylene diaphragm or a polypropylene diaphragm. 5. The ceramic coating diaphragm containing lithium ions according to claim 1, wherein the binding agent in the water-based ceramic slurry comprises polystyrene-butadiene emulsion, polymethylmethacrylate- One or more of butyl acrylate emulsion, polystyrene-butyl acrylate emulsion, polytetrafluoroethylene emulsion, polyvinylidene fluoride emulsion. 6. The ceramic coating diaphragm containing lithium ions according to claim 1, wherein the additive in the water-based ceramic slurry is a water-soluble macromolecule, including sodium carboxymethyl cellulose, cross-linked carboxymethyl One or more of sodium cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hypromellose, polyvinyl alcohol, polyethylene glycol, and polyacrylamide. 7. the ceramic coating membrane that contains lithium ion according to claim 1, is characterized in that, the auxiliary agent in described water-based ceramic slurry comprises tertiary alkyl polyol polyvinyl ether, sodium sulfonate diisooctyl , alkyl naphthalene sulfonate, polyether modified silicone oil, polypropylene glycol-ethylene oxide, polyether stearate dimethyl siloxane, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene glycylether , one or more of polyoxyethylene polyoxypropanolamine ethers. 8. A preparation method for preparing a ceramic coating diaphragm containing lithium ions according to any one of claims 1-7, characterized in that, comprising the steps of: (1) Take Li-α-sialon whose particle size ratio between the second type and the first type powder is 0.1-0.5:1, and disperse it in deionized water to prepare Li-α-sialon aqueous solution and Li-α-sialon aqueous solution The solid content is 10-50%; (2) Mixing the Li-α-sialon aqueous solution with binders, additives and auxiliary agents to prepare water-based ceramic slurry, wherein the mass ratio of Li-α-sialon to binder is 3-50:1; (3) The water-based ceramic slurry is evenly coated on the surface of the substrate diaphragm, and the ceramic coated diaphragm is obtained after drying. 9. The method according to claim 8, characterized in that, the Li-α-sialon aqueous solution in the step (1) also includes 0.1 to 1.0 wt% of a dispersant, and the dispersant includes dodecylbenzene Sodium Sulfonate, Sodium Lauryl Sulfate, Sodium Lauryl Sulfonate, Sodium Hexametaphosphate, Polyacrylic Acid, Cetyltrimethylammonium Bromide, Octylphenol Polyoxyethylene, Polyethylene Glycol one or more of. 10. Use of a ceramic coated separator containing lithium ions in an electrochemical device.