阅读说明：本技术 环保型纤维素基隔膜的制备方法及其在锂电池中的应用 (Preparation method of environment-friendly cellulose-based diaphragm and application of environment-friendly cellulose-based diaphragm in lithium battery ) 是由 胡伟 吴磊 张德顺 李汪洋 徐凤锦 孙小华 郭浩 贺云 徐文杰 张少强 于 2020-12-07 设计创作，主要内容包括：本发明公开了一种环保型纤维素基隔膜的制备方法,涉及锂电池隔膜技术领域,本发明先以乙烯(氯甲基)二甲氧基硅烷作为单体,经聚合反应制备聚[乙烯(氯甲基)二甲氧基硅烷],属于新型聚合物,再与羧甲基纤维素钠经取代反应在该新型聚合物的结构中引入纤维素,制得纤维素基隔膜；该纤维素基隔膜由于纤维素分子的引入使其环保性提高,具有良好的生物降解性能,能够加速隔膜废弃后在环境中的降解；并且该纤维素基隔膜的力学强度高,耐电解液腐蚀,对电解液的浸润性好,具有足够的吸液保湿能力。(The invention discloses a preparation method of an environment-friendly cellulose-based diaphragm, which relates to the technical field of lithium battery diaphragms and is characterized in that ethylene (chloromethyl) dimethoxysilane is used as a monomer, poly [ ethylene (chloromethyl) dimethoxysilane ] is prepared through a polymerization reaction, which belongs to a novel polymer, and then the poly [ ethylene (chloromethyl) dimethoxysilane ] and sodium carboxymethyl cellulose are introduced into the structure of the novel polymer through a substitution reaction to prepare the cellulose-based diaphragm; due to the introduction of cellulose molecules, the cellulose-based diaphragm has improved environmental protection property, good biodegradability and capability of accelerating the degradation of the diaphragm in the environment after being discarded; the cellulose-based diaphragm has high mechanical strength, electrolyte corrosion resistance, good wettability to electrolyte and enough liquid absorption and moisture retention capacity.)

1. The preparation method of the environment-friendly cellulose-based diaphragm is characterized by comprising the following steps: comprises the following preparation steps:

(1) synthesis of poly [ ethylene (chloromethyl) dimethoxysilane ]: adding ethylene (chloromethyl) dimethoxysilane and an initiator into the solvent I, heating for polymerization reaction, distilling to recover the solvent I after the reaction is finished, and drying distilled residues after water washing to obtain poly [ ethylene (chloromethyl) dimethoxysilane ];

(2) synthesis of poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ]: adding sodium carboxymethylcellulose into a solvent II, adding poly [ ethylene (chloromethyl) dimethoxysilane ] dissolved in the solvent I after completely dissolving, heating for substitution reaction, distilling and recovering the solvent I and the solvent II after the reaction is finished, and drying distilled residues after water is washed to obtain poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ];

(3) adding poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ] into a solvent III, heating for dissolving, carrying out filtration and defoaming, then carrying out blade coating on a coating machine to form a uniform film, and drying to obtain the cellulose-based diaphragm.

2. The method for preparing an environment-friendly cellulose-based separator according to claim 1, wherein: the solvent I is at least one of methanol, ethanol and acetone.

3. The method for preparing an environment-friendly cellulose-based separator according to claim 1, wherein: the initiator is an organic peroxide initiator or an azo initiator.

4. The method for preparing an environment-friendly cellulose-based separator according to claim 1, wherein: the dosage of the initiator is 0.1-0.5% of the mass of the ethylene (chloromethyl) dimethoxysilane.

5. The method for preparing an environment-friendly cellulose-based separator according to claim 1, wherein: the solvent II is water.

6. The method for preparing an environment-friendly cellulose-based separator according to claim 1, wherein: the substitution degree of the sodium carboxymethyl cellulose is 0.3-1.2.

7. The method for preparing an environment-friendly cellulose-based separator according to claim 1, wherein: the mass ratio of the sodium carboxymethylcellulose to the poly [ ethylene (chloromethyl) dimethoxysilane ] is 10-100: 10-100.

8. The method for preparing an environment-friendly cellulose-based separator according to claim 1, wherein: the solvent III is at least one of tetrahydrofuran, N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide and ethyl acetate.

9. Use of the environment-friendly cellulose-based separator prepared according to any one of claims 1 to 8 in a lithium battery.

The technical field is as follows:

the invention relates to the technical field of lithium battery diaphragms, in particular to a preparation method of an environment-friendly cellulose-based diaphragm and application of the environment-friendly cellulose-based diaphragm in a lithium battery.

Background art:

in the construction of lithium batteries, the separator is one of the key internal layer components. The performance of the diaphragm determines the interface structure, internal resistance and the like of the battery, directly influences the capacity, circulation, safety performance and other characteristics of the battery, and the diaphragm with excellent performance plays an important role in improving the comprehensive performance of the battery. The separator has a main function of separating the positive electrode and the negative electrode of the battery to prevent short circuit due to contact between the two electrodes, and also has a function of allowing electrolyte ions to pass therethrough. The separator material is non-conductive, and the physical and chemical properties of the separator have a great influence on the performance of the battery.

At present, lithium battery separators are generally made of polypropylene or polyethylene, and although the separators have good mechanical properties, the separators are not easily biodegradable, so that the separators are easy to cause environmental pollution after being discarded. In addition, when the polypropylene or polyethylene is prepared by adopting a tape casting method, the problems of non-uniform aperture and low mechanical strength exist, so that the use performance of the lithium battery diaphragm is influenced. In order to solve the problems, the present invention prepares an environment-friendly cellulose-based separator by synthesis of a novel polymer.

The invention content is as follows:

the technical problem to be solved by the invention is to provide a preparation method of an environment-friendly cellulose-based diaphragm, wherein the prepared cellulose-based diaphragm not only meets the performance use requirements of a lithium battery on the diaphragm, but also has biodegradability due to the introduction of cellulose molecules.

The technical problem to be solved by the invention is realized by adopting the following technical scheme:

the preparation method of the environment-friendly cellulose-based diaphragm comprises the following preparation steps:

(1) synthesis of poly [ ethylene (chloromethyl) dimethoxysilane ]: adding ethylene (chloromethyl) dimethoxysilane and an initiator into the solvent I, heating for polymerization reaction, distilling to recover the solvent I after the reaction is finished, and drying distilled residues after water washing to obtain poly [ ethylene (chloromethyl) dimethoxysilane ];

(2) synthesis of poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ]: adding sodium carboxymethylcellulose into a solvent II, adding poly [ ethylene (chloromethyl) dimethoxysilane ] dissolved in the solvent I after completely dissolving, heating for substitution reaction, distilling and recovering the solvent I and the solvent II after the reaction is finished, and drying distilled residues after water is washed to obtain poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ];

(3) adding poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ] into a solvent III, heating for dissolving, carrying out filtration and defoaming, then carrying out blade coating on a coating machine to form a uniform film, and drying to obtain the cellulose-based diaphragm.

The structural formula of ethylene (chloromethyl) dimethoxysilane:CAS number 1314981-48-0.

The solvent I is at least one of methanol, ethanol and acetone.

The initiator is an organic peroxide initiator or an azo initiator.

The dosage of the initiator is 0.1-0.5% of the mass of the ethylene (chloromethyl) dimethoxysilane.

The solvent II is water.

The substitution degree of the sodium carboxymethyl cellulose is 0.3-1.2.

The mass ratio of the sodium carboxymethylcellulose to the poly [ ethylene (chloromethyl) dimethoxysilane ] is 10-100: 10-100.

The solvent III is at least one of tetrahydrofuran, N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide and ethyl acetate.

In the technical scheme, ethylene (chloromethyl) dimethoxysilane generates poly [ ethylene (chloromethyl) dimethoxysilane ] through polymerization reaction under the action of an initiator, then generates poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ] through substitution reaction with sodium carboxymethyl cellulose, takes the poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ] as a raw material for preparing the diaphragm, and prepares the cellulose-based diaphragm through a coating method.

The environment-friendly cellulose-based diaphragm prepared by the technical scheme is applied to a lithium battery.

The cellulose-based diaphragm prepared by the technical scheme is applied to the lithium battery, so that the use requirement of the lithium battery on the diaphragm can be met, the pollution problem of the diaphragm to the environment after abandonment can be improved, and sustainable development is realized.

The invention has the beneficial effects that: the preparation method comprises the steps of firstly, taking ethylene (chloromethyl) dimethoxysilane as a monomer, preparing poly [ ethylene (chloromethyl) dimethoxysilane ] through polymerization reaction, wherein the poly [ ethylene (chloromethyl) dimethoxysilane ] belongs to a novel polymer, and then introducing cellulose into the structure of the novel polymer through substitution reaction of the poly [ ethylene (chloromethyl) dimethoxysilane ] and sodium carboxymethylcellulose to prepare the cellulose-based diaphragm; due to the introduction of cellulose molecules, the cellulose-based diaphragm has improved environmental protection property, good biodegradability and capability of accelerating the degradation of the diaphragm in the environment after being discarded; the cellulose-based diaphragm has high mechanical strength, electrolyte corrosion resistance, good wettability to electrolyte and enough liquid absorption and moisture retention capacity.

The specific implementation mode is as follows:

in order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

Sodium carboxymethylcellulose was purchased from soviet, bogey chemical technology ltd with a degree of substitution of 0.8.

Polyethylene was purchased from medium petroleum compliant PP-FC 709M.

Example 1

(1) Synthesis of poly [ ethylene (chloromethyl) dimethoxysilane ]: 10g of ethylene (chloromethyl) dimethoxysilane and 0.05g of azobisisobutyronitrile are added into 350mL of ethanol, the mixture is heated to 70 ℃ for polymerization reaction for 4 hours, the ethanol is distilled and recovered after the reaction is finished, and the distilled residue is dried after being washed, so that poly [ ethylene (chloromethyl) dimethoxysilane ] is obtained.

(2) Poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane]The synthesis of (2): 18g of sodium carboxymethylcellulose are added to 500mL of water and after complete dissolution 25g of poly [ ethylene (chloromethyl) dimethoxysilane dissolved in 500mL of ethanol are added]Heating to 55 ℃ for substitution reaction for 5h, distilling to recover ethanol and water after the reaction is finished, and drying distilled residual water to obtain poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane]. FT-IR infrared spectrum analysis of the product at 1738cm^-1The peak is the C ═ O stretching vibration absorption peak in the ester group, and the peak is 1210cm^-1The position is a C-O stretching vibration absorption peak in the ester group.

(3) Adding 15g of poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ] into 500mL of ethyl acetate, heating for dissolving, filtering, defoaming, then blade-coating on a coating machine to form a uniform film, and drying to obtain the cellulose-based diaphragm with the thickness of 25 μm.

Example 2

Example 2 the same separator preparation method as in example 1 was used except that the mass ratio of sodium carboxymethylcellulose to poly [ ethylene (chloromethyl) dimethoxysilane ] was adjusted.

(1) Synthesis of poly [ ethylene (chloromethyl) dimethoxysilane ]: 10g of ethylene (chloromethyl) dimethoxysilane and 0.05g of azobisisobutyronitrile are added into 350mL of ethanol, the mixture is heated to 70 ℃ for polymerization reaction for 4 hours, the ethanol is distilled and recovered after the reaction is finished, and the distilled residue is dried after being washed, so that poly [ ethylene (chloromethyl) dimethoxysilane ] is obtained.

(2) Synthesis of poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ]: adding 15g of sodium carboxymethylcellulose into 500mL of water, adding 25g of poly [ ethylene (chloromethyl) dimethoxysilane ] dissolved in 500mL of ethanol after complete dissolution, heating to 55 ℃ for substitution reaction, reacting for 5h, distilling and recovering ethanol and water after the reaction is finished, and drying distilled residues after water is washed to obtain poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ].

(3) Adding 15g of poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ] into 500mL of ethyl acetate, heating for dissolving, filtering, defoaming, then blade-coating on a coating machine to form a uniform film, and drying to obtain the cellulose-based diaphragm with the thickness of 25 μm.

Example 3

Example 3 the same separator preparation method as in example 1 was used, except that the mass ratio of sodium carboxymethylcellulose to poly [ ethylene (chloromethyl) dimethoxysilane ] was adjusted.

(1) Synthesis of poly [ ethylene (chloromethyl) dimethoxysilane ]: 10g of ethylene (chloromethyl) dimethoxysilane and 0.05g of azobisisobutyronitrile are added into 350mL of ethanol, the mixture is heated to 70 ℃ for polymerization reaction for 4 hours, the ethanol is distilled and recovered after the reaction is finished, and the distilled residue is dried after being washed, so that poly [ ethylene (chloromethyl) dimethoxysilane ] is obtained.

(2) Synthesis of poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ]: adding 18g of sodium carboxymethylcellulose into 500mL of water, adding 30g of poly [ ethylene (chloromethyl) dimethoxysilane ] dissolved in 500mL of ethanol after complete dissolution, heating to 55 ℃ for substitution reaction, wherein the reaction time is 5h, distilling and recovering ethanol and water after the reaction is finished, and drying distilled residues after water is washed to obtain poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ].

(3) Adding 15g of poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ] into 500mL of ethyl acetate, heating for dissolving, filtering, defoaming, then blade-coating on a coating machine to form a uniform film, and drying to obtain the cellulose-based diaphragm with the thickness of 25 μm.

Comparative example 1

Comparative example 1 the same separator preparation method as in example 1 was used, except that poly [ ethylene (chloromethyl) dimethoxysilane ] and sodium carboxymethylcellulose were not used to synthesize poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ].

(1) Synthesis of poly [ ethylene (chloromethyl) dimethoxysilane ]: 10g of ethylene (chloromethyl) dimethoxysilane and 0.05g of azobisisobutyronitrile are added into 350mL of ethanol, the mixture is heated to 70 ℃ for polymerization reaction for 4 hours, the ethanol is distilled and recovered after the reaction is finished, and the distilled residue is dried after being washed, so that poly [ ethylene (chloromethyl) dimethoxysilane ] is obtained.

(2) 15g of poly [ ethylene (chloromethyl) dimethoxysilane ] is added into 500mL of ethyl acetate, heated and dissolved, filtered, defoamed, then blade-coated on a coating machine to form a uniform film, and dried to obtain the diaphragm with the thickness of 25 μm.

Comparative example 2

Comparative example 2 the same separator preparation method as in example 1 was used, except that polyethylene was used instead of poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ].

Adding 15g of polyethylene into 500mL of ethyl acetate, heating for dissolving, filtering, defoaming, then carrying out blade coating on a coating machine to form a uniform film, and drying to obtain the diaphragm with the thickness of 25 μm.

The performance tests were performed on the separators prepared in the above examples and comparative examples, and the test methods and results were as follows:

tensile strength: the standard GB/T1040.3-2006 is adopted;

puncture strength: the standard GB/T21302-2007 is adopted;

liquid absorption rate: mass m₀Soaking the diaphragm in electrolyte (purchased from Shanghai Tongbo materials science and technology Co., Ltd.), taking out after 2h, sucking the electrolyte on the surface of the diaphragm by using filter paper, weighing m₁Calculating the liquid absorption rate K ═ m [ (- ]₁-m₀)/m₀]×100％。

The test was performed in triplicate and the average was taken.

TABLE 1

Item	Tensile strength/MPa	Puncture Strength/N	Imbibition rate/%)
				Example 1	82.2	71.7	395
Example 2	81.4	69.5	412
				Example 3	83.5	73.6	383
Comparative example 1	85.1	75.3	267
				Comparative example 2	60.3	52.8	232

As can be seen from table 1, in the examples, the tensile strength, puncture strength and liquid absorption rate of the separator can be significantly improved through the synthesis of poly [ ethylene (chloromethyl) dimethoxysilane ] and poly [ ethylene (carboxymethyl cellulose methyl ester) dimethoxysilane ], so that the use performance of the separator is optimized.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.