LU501427B1

LU501427B1 - Cyanoethyl cellulose membrane, cyanoethyl cellulose gel polymer electrolyte and preparation method thereof

Info

Publication number: LU501427B1
Application number: LU501427A
Authority: LU
Inventors: Feijun Wang; Yanhua Liu; Ziqiang Shao; Yinfeng Xia; Zilai Zhou; Kun Du; Miao Yu
Original assignee: Beijing Institute Tech; Chongqing Lihong Fine Chemicals Co Ltd
Priority date: 2022-02-09
Filing date: 2022-02-09
Publication date: 2022-08-11

Abstract

The present disclosure discloses a cyanoethyl cellulose membrane, a cyanoethyl cellulose gel polymer electrolyte and a preparation method thereof. The preparation method comprises the steps of: dissolving cyanoethyl cellulose in a solvent to form a solution, and then drying to form a membrane; immersing the cyanoethyl cellulose membrane into an electrolyte solution to be activated to form gel; and removing the redundant electrolyte on the surface of the gel to obtain a cyanoethyl cellulose gel polymer electrolyte. The cyanoethyl cellulose gel polymer electrolyte provided by the present disclosure has good heat resistance and corrosion resistance, wide raw material sources, renewability and biodegradability; the cyanoethyl cellulose membrane provided by the present disclosure has tensile strength of more than 25 MPa and liquid absorption rate of 700-1,300%; the room temperature ionic conductivity of the cyanoethyl cellulose gel polymer electrolyte reaches 10-3 S/cm level, the lithium ion transference number is more than 0.7, and the electrochemical stability window is more than 4.8 V; the preparation process of the cyanoethyl cellulose gel polymer electrolyte is simple and practical, and is easy to operate.

Description

CYANOETHYL CELLULOSE MEMBRANE, CYANOETHYL CELLULOSE GEL POLYMER ELECTROLYTE AND PREPARATION METHOD THEREOF TECHNICAL FIELD

[01] The present disclosure relates to a battery material, and particularly relates to a cyanoethyl cellulose membrane for a lithium ion secondary battery, a cyanoethyl cellulose gel polymer electrolyte membrane and a preparation method thereof.

BACKGROUND ART

[02] As a new generation of green high-energy rechargeable batteries, compared with conventional lead-acid batteries, nickel-metal hydride batteries and other secondary batteries, lithium-ion batteries have the advantages of have higher voltage of battery cell, larger specific energy, no memory effect, no pollution, small self-discharge, and long cycle time, etc., and have been widely used in portable electronic products such as notebook computers, smart phones, digital cameras, etc., and also have a broad development space in the field of power batteries. Traditional commercial lithium-ion batteries generally utilize flammable organic liquid electrolytes, and there are safety risks such as liquid leakage and combustion and explosion during use. As a research hotspot in recent years, polymer lithium-ion batteries have the advantages of low cost, simple processing and controllable shape. Compared with liquid lithium-ion batteries, polymer lithium-ion batteries can effectively solve safety problems such as liquid leakage and combustion explosion, so they have broad application prospects in the fields of portable electronics, electric vehicles and aerospace, etc.

[03] Polymer electrolytes can be divided into solid polymer electrolytes (SPE) and gel polymer electrolytes (GPE) according to their morphology and composition. The SPE only consists of polymers and lithium salts, and has the defects of low ionic conductivity at room temperature, making it difficult to meet practical needs. Generally, by adding small molecular plasticizers to lower the glass transition temperature of the polymer and improve the flexibility of the molecular chain, gel polymer electrolytes are obtained. GPEs can achieve room temperature ionic conductivity similar to liquid electrolytes, which facilitates to preserve electrolytes, reduce the risk of electrolyte leakage, and improve safety performance. In addition, GPEs have the advantages of plasticity, strong processing, and controllable shape. Currently, more researches are conducted on polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF) and the copolymers gel polymer electrolytes. Although these gel polymer electrolytes have good properties, they are derived from non-renewable fossil energy, with complex preparation and poor biodegradability. With the depletion of fossil energy and people's attention to environmental protection, it is of great significance to find a renewable, non-polluting polymer electrolyte material.

[04] Cellulose derivatives have many advantages such as wide source of raw materials, renewable, non-toxic, and degradable, and have good application prospects in 1 polymer electrolytes. Highly substituted cyanoethyl cellulose (CEC) is an organic LU501427 soluble cellulose derivative with high dielectric constant. The high dielectric constant is conducive to promoting the dissolution of lithium salts and increasing the carrier concentration, thereby improving the ionic conductivity, weakening the phenomenon of concentration polarization, reducing the formation of lithium dendrites; moreover, CEC has good heat resistance and corrosion resistance, which has positive significance for improving the performance of polymer lithium-ion batteries. Cyanoethyl cellulose gel polymer electrolyte materials are rarely reported.

SUMMARY

[05] The present disclosure aims to provide a cyanoethyl cellulose membrane for a lithium ion secondary battery, a cyanoethyl cellulose gel polymer electrolyte membrane and a preparation method thereof, wherein the cyanoethyl cellulose membrane has good mechanical property, high liquid absorption rate and excellent electrical property.

[06] The present disclosure is implemented through the following technical solution:

[07] A method for preparing a cyanoethyl cellulose gel polymer electrolyte for a lithium ion secondary battery comprises the following steps:

[08] A, dissolving cyanoethyl cellulose in a solvent to form a solution, and then drying to form a membrane;

[09] B, immersing the cyanoethyl cellulose membrane into an electrolyte solution to be activated to form gel; and

[10] C, removing the redundant electrolyte on the surface of the gel to obtain the cyanoethyl cellulose gel polymer electrolyte membrane.

[11] Further, in the method for preparing the cyanoethyl cellulose gel polymer electrolyte, the electrolyte in the step B is an organic solution of the following lithium salt.

[12] Further, in the method for preparing the cyanoethyl cellulose gel polymer electrolyte, the lithium salt is one of or a mixture of more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate and lithium hexafluoroarsenate.

[13] Further, in the method for preparing the cyanoethyl cellulose gel polymer electrolyte, the organic solvent for dissolving the lithium salt is one of or a mixture of more of ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate and propylene carbonate.

[14] Further, in the method for preparing the cyanoethyl cellulose gel polymer electrolyte, the substitution degree of cyanoethyl cellulose in the step A is not less than

2.2.

[15] Further, in the method for preparing the cyanoethyl cellulose gel polymer electrolyte, the solvent in the step A is N,N-dimethylformamide, N,N- dimethylacetamide and dimethyl sulfoxide.

[16] The present disclosure also provides a cyanoethyl cellulose gel polymer electrolyte and a cyanoethyl cellulose membrane which are prepared according to the above preparation method.

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[17] The present disclosure has the following beneficial effects: LU501427

[18] 1, the cyanoethyl cellulose gel polymer electrolyte provided by the present disclosure has good heat resistance and corrosion resistance, wide raw material sources, renewability and biodegradability;

[19] 2, the cyanoethyl cellulose membrane provided by the present disclosure has tensile strength of more than 25 MPa and liquid absorption rate of 700-1,300%; the room temperature ionic conductivity of the cyanoethyl cellulose gel polymer electrolyte provided by the present disclosure reaches 10-3 S/cm level, the lithium ion transference number is more than 0.7, and the electrochemical stability window is more than 4.8 V;

[20] 3, the cyanoethyl cellulose gel polymer electrolyte provided by the present disclosure is only composed of cyanoethyl cellulose and lithium salt electrolyte and has simple components;

[21] 4, the cyanoethyl cellulose membrane prepared in the step 1 of the present disclosure has the advantages of room temperature environment preservation and storage, the cyanoethyl cellulose gel polymer electrolytes with different mechanical strengths and different ionic conductivities can be obtained by regulating and controlling the activation time of the membrane in the electrolyte, and the flexibility of cyanoethyl cellulose gel polymer electrolytes is improved; and

[22] 5, the preparation process is simple and practical, does not need to relate to polymerization crosslinking reaction and is beneficial to reducing the cost and improving the efficiency.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[23] The present disclosure will be further described below with reference to specific embodiments. The embodiments are only preferred embodiments of the present disclosure, and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall fall within the scope of protection of the present disclosure.

[24] Example 1

[25] 1 g of CEC with a degree of substitution of 2.25 was dissolved in 50 g of N, N-dimethylformamide (DMF) to form a transparent solution, 25 g of the solution was poured into a petri dish with a diameter of 9 cm, and put in an oven at 80 °C for 12 h to obtain a CEC membrane with a thickness of about 85 um. After the CEC membrane was cut to a suitable size, the dried CEC membrane was immersed in an electrolyte (lithium perchlorate (LiClO,): ethylene carbonate (EC): propylene carbonate (PC) = 1:1:1) in a glove box to activate for 2 h to a gel state, and the excess electrolyte on the surface was gently wiped off with filter paper to obtain a CEC gel polymer electrolyte.

[26] Example 2

[27] 1 g of CEC with a degree of substitution of 2.35 was dissolved in 50 g of N, N- dimethylacetamide (DMAc) to form a transparent solution, 25 g of the solution was poured into a petri dish with a diameter of 9 cm, and put in an oven at 80 °C for 12 h to obtain a CEC membrane with a thickness of about 85 um. After the CEC membrane 3 was cut to a suitable size, the dried CEC membrane was immersed in an electrolyte LU501427 (lithium hexafluorophosphate(LiPFg): ethylene carbonate(EC): dimethyl carbonate(DMC): ethyl methyl carbonate(EMC)=1: 1: 1: 1) in a glove box to activate for 6 h to a gel state, and the excess electrolyte on the surface was gently wiped off with filter paper to obtain a CEC gel polymer electrolyte.

[28] Example 3

[29] 1 g of CEC with a degree of substitution of 2.5 was dissolved in 50 g of N, N- dimethylformamide (DMF) to form a transparent solution, 25 g of the solution was poured into a petri dish with a diameter of 9 cm, and put in an oven at 80 °C for 12 h to obtain a CEC membrane with a thickness of about 85 um. After the CEC membrane was cut to a suitable size, the dried CEC membrane was immersed in an electrolyte (lithium tetrafluoroborate(LIBF4): ethylene carbonate(EC): dimethyl carbonate(DMC) =1: 1: 1) in a glove box to activate for 6 h to a gel state, and the excess electrolyte on the surface was gently wiped off with filter paper to obtain a CEC gel polymer electrolyte.

[30] Example 4

[31] 1 g of CEC with a degree of substitution of 2.66 was dissolved in 30 g of N, N-dimethylacetamide(DMAc) to form a transparent solution, 15 g of the solution was poured into a petri dish with a diameter of 9 cm, and put in an oven at 80 °C for 12 h to obtain a CEC membrane with a thickness of about 75 um. After the CEC membrane was cut to a suitable size, the dried CEC membrane was immersed in an electrolyte (lithium hexafluorophosphate(LiPFg): ethylene carbonate(EC): dimethyl carbonate(DMC)=1: 1: 1) in a glove box to activate for 6 h to a gel state, and the excess electrolyte on the surface was gently wiped off with filter paper to obtain a CEC gel polymer electrolyte.

[32] Example 5

[33] 1 g of CEC with a degree of substitution of 2.75 was dissolved in 40 g of N, N-dimethylformamide (DMF) to form a transparent solution, 20 g of the solution was poured into a petri dish with a diameter of 9 cm, and put in an oven at 80 °C for 12 h to obtain a CEC membrane with a thickness of about 80 um. After the CEC membrane was cut to a suitable size, the dried CEC membrane was immersed in an electrolyte (lithium hexafluorophosphate(LiPFe): ethylene carbonate(EC): ethyl methyl carbonate (EMC)=1: 1: 1) in a glove box to activate for 6 h to a gel state, and the excess electrolyte on the surface was gently wiped off with filter paper to obtain a CEC gel polymer electrolyte.

[34] The performance of the CEC membranes prepared in Examples 1 to 5 was tested. The results showed that the tensile strength was greater than 25 MPa, and the liquid absorption rate was 700-1300%. The performance of the CEC gel polymer electrolytes prepared in Examples 1 to 5 was tested, and the results showed that the room temperature ionic conductivity reached 10° S/cm level, the lithium ion transference number was greater than 0.7, and the chemical stability window was greater than 4.8V.

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Claims

WHAT IS CLAIMED IS: LUS01427 I. A method for preparing a cyanoethyl cellulose gel polymer electrolyte, comprising the following steps: A, dissolving cyanoethyl cellulose in a solvent to form a solution, and then drying to form a membrane, namely, a cyanoethyl cellulose membrane; B, immersing the cyanoethyl cellulose membrane into an electrolyte solution to be activated to form gel; and C, removing the redundant electrolyte on the surface of the gel to obtain a cyanoethyl cellulose gel polymer electrolyte.
2. The method for preparing a cyanoethyl cellulose gel polymer electrolyte according to claim 1, wherein the electrolyte in the step B is an organic solution of the following lithium salt.
3. The method for preparing a cyanoethyl cellulose gel polymer electrolyte according to claim 2, wherein the lithium salt is one of or a mixture of more of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate and lithium hexafluoroarsenate.
4. The method for preparing a cyanoethyl cellulose gel polymer electrolyte according to claim 2, wherein the organic solvent for dissolving the lithium salt is one of or a mixture of more of ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate and propylene carbonate.
5. The method for preparing a cyanoethyl cellulose gel polymer electrolyte according to claim 1, wherein the substitution degree of cyanoethyl cellulose in the step A is not less than 2.2.
6. The method for preparing a cyanoethyl cellulose gel polymer electrolyte according to claim 1, wherein the solvent in the step A is N, N-dimethylformamide, N, N-dimethylacetamide and dimethyl sulfoxide.
7. A cyanoethyl cellulose gel polymer electrolyte is prepared according to the preparation method of any one of claims 1 to 6.
8. A cyanoethyl cellulose membrane is prepared according to the preparation method of any one of claims 1 to 6.

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