CN106784548A - Lithium ion battery green, Efficient lignocellulose matrix barrier film and preparation method thereof - Google Patents

Abstract

The invention relates to a green, high-efficiency lignocellulose-based separator for lithium-ion batteries and a preparation method thereof. Ternary blend composite-based diaphragm and its preparation method: coating and electrospinning preparation of pure lignocellulose diaphragm, lignocellulose as the main body and other natural or synthetic polymer material binary or ternary composite diaphragm The pouring, coating and electrospinning preparation of the first. The beneficial effect of the present invention is that the natural macromolecule material aggregate lignocellulose with an annual output of nearly one trillion tons in the world is selected as the matrix, or the lignocellulose is selected as the main body and other natural or synthetic macromolecule composites are used as the matrix to prepare a The diaphragm used in lithium-ion batteries completely solves the problem of "white pollution" of lithium-ion batteries and endows the batteries with high performance. The content of the invention also opens up a new application field of lignocellulose.

Description

Green, high-efficiency lignocellulose-based separator for lithium-ion batteries and preparation method thereof

technical field

The invention relates to a green, high-efficiency lignocellulose matrix diaphragm for lithium ion batteries and a preparation method thereof, belonging to the technical field of lithium ion batteries.

Background technique

Compared with traditional lead-acid batteries, lithium-ion batteries are called green power sources. Currently, liquid electrolytes are widely used in lithium-ion battery products because they have good ion conductivity, compatibility with electrodes, and low cost. In this liquid electrolyte lithium-ion battery, the positive and negative electrodes are separated by an electronically insulating polypropylene film or polyethylene film or a composite film of the two, but these separators are uniformly distributed with holes that allow the liquid electrolyte and lithium salt penetration. In this lithium-ion battery, the positive electrode, negative electrode, liquid electrolyte and separator are the four major components for the battery to work. In terms of mass, the mass of the separator in the liquid electrolyte lithium-ion battery usually accounts for about 30wt.% of the total mass of the battery. Obviously, when the battery is disposed of at the end of its life, a large amount of polypropylene or polyethylene or both composite wastes will be produced. pollute". At this level, this lithium-ion battery is not really a green power source. In order to solve this problem, it is a very effective means to replace the traditional polypropylene diaphragm or polyethylene diaphragm or the composite diaphragm prepared by using natural high molecular polymer as the matrix. According to literature reports, natural polymers that can be used as a membrane matrix include cellulose, starch, chitosan, agar, pectin, and gelatin. . From the research conclusion, the cellulose separator can only match the traditional polymer separator in some properties, and the performance of the rest of the natural polymer separators is not satisfactory. Therefore, there are very few research reports in this area in the past two years, because the performance of these natural polymer separators is unconvincing, and the cost is higher than traditional separators. Therefore, the present invention is based on the analysis of the liquid electrolyte lithium-ion battery and its diaphragm problem, and selects the natural polymer material aggregate—lignocellulose (lignocellulose), which has the largest annual output (nearly trillion tons) in the world, and uses pure wood Cellulose or its main body and other natural or synthetic polymer blend compounds are used as a matrix to prepare separators that can be used in lithium-ion batteries, solving the problem of "white pollution" in lithium-ion batteries and endowing batteries with high performance. This invention not only solves some problems of lithium-ion batteries, but also opens up a new application field of lignocellulose. Relevant studies have not yet appeared in domestic and foreign reports.

Contents of the invention

technical problem to be solved

In order to prepare a lithium-ion battery with no "white pollution" and high performance, the present invention proposes to use the pure natural polymer material aggregate lignocellulose with the largest annual output in the world or take lignocellulose as the main body and other natural or synthetic polymers The binary or ternary blend compound is used as a matrix to prepare a separator that can be used in a lithium-ion battery, endowing the battery with green and high-performance characteristics.

Technical solutions

The green, high-efficiency lignocellulose-based separator for lithium-ion batteries and its preparation method are characterized in that: five kinds of lignocellulose-based or lignocellulose-based and other natural or synthetic polymer binary or ternary co-polymers have been developed. A diaphragm with a mixed compound as a matrix and a preparation method thereof, the specific process is as follows:

(1) Coating preparation of pure lignocellulose membrane: weigh 900-1000mg of lignocellulose and 35-40ml of deionized water, put them in a beaker; stir at room temperature (25±1°C) for 2 -3h, to obtain a uniform suspension; pour the suspension into a flat-bottomed glass dish, under normal pressure and 60±2°C, until the water evaporates completely, and a uniform pure lignocellulose membrane is obtained.

(2) Preparation of pure lignocellulose membrane by electrospinning: grind and sieve lignocellulose, and collect powder between 100-200 mesh; put the collected powder in a beaker, add solvent, and stir at room temperature for 5-8h , to obtain a uniform electrospinning solution with a concentration range of 5wt.%-10wt.%; put the electrospinning solution into the syringe, set the positive high voltage to 10-12kV, the negative high voltage to -1--2kV, and the injection speed to be 2.5-3ml/h, the drum speed is 20-25rpm, the distance between the fixed positive and negative electrodes is 10-12cm, the electrospinning time is 2-3h, electrospinning, obtain a uniform and flat wet film, dry at room temperature, and obtain pure Lignocellulose membrane.

(3) Pouring preparation of binary or ternary composite diaphragms with lignocellulose as the main body and other natural or synthetic polymer materials: with lignocellulose mass fraction in the range of 65wt.%-95wt.%, other natural or synthetic The mass fraction of the one-element or two-element composite of the polymer material is in the range of 35wt.%-5wt.%, and the corresponding mass is weighed respectively; the weighed pure lignocellulose is prepared according to the above-mentioned process to prepare a diaphragm with uniform thickness; the weighed The natural or synthetic polymer material one-component or two-component compound is placed in a beaker, and a good solvent that can just dissolve the compound at room temperature is added, and stirred until a uniform solution is obtained; the obtained uniform solution is slowly poured on pure lignocellulose On the diaphragm, ensure that the solution is completely immersed in the pores of the lignocellulose diaphragm, and then under the conditions of normal pressure and 25-60 ° C until the solvent evaporates to obtain a uniform lignocellulose main body binary or ternary composite diaphragm.

(4) Coating preparation of lignocellulose as the main body and other natural or synthetic polymer material binary or ternary composite membranes: with lignocellulose mass fraction in the range of 65wt.%-95wt.%, other natural or synthetic polymer materials The mass fraction of synthetic macromolecule material one-element or two-element compound is in the interval range of 35wt.%-5wt.%, weigh the substances of corresponding mass respectively; Put it into a beaker; put the total mass of the mixture in the beaker to the volume ratio of the solvent in the range of 1g: 15ml-1g: 40ml, add a good solvent, and stir at 25-80°C until a uniform suspension is obtained; the obtained uniform The suspension is coated on a glass plate, and then kept under the condition of normal pressure and 25-60° C. until the solvent evaporates completely to obtain a homogeneous lignocellulose main body binary or ternary composite membrane.

(5) Electrospinning preparation of lignocellulose as the main body and other natural or synthetic polymer material binary or ternary composite membranes: grind and sieve lignocellulose, and collect powder between 100-200 mesh; According to the quality range of lignocellulose powder in the range of 65wt.%-95wt.%, weigh the powder and other natural or synthetic macromolecular material one-component or two-component composites, and place them in a beaker; then add solvent and stir at room temperature for 5 -15h, to obtain a uniform electrospinning solution with a solution concentration range of 1wt.%-10wt.%; put the electrospinning solution into the syringe, set the positive high voltage to 10-20kV, and the negative high voltage to -1--5kV, and inject The speed is 0.5-5ml/h, the rotation speed of the drum is 20-100rpm, the distance between the fixed positive and negative electrodes is 10-20cm, the electrospinning time is 2-10h, electrospinning to obtain a uniform and flat wet film, and drying at room temperature. A homogeneous lignocellulosic host binary or ternary composite membrane is obtained.

The green, high-efficiency lignocellulose-based diaphragm for lithium-ion batteries and its preparation method are characterized in that: in the electrospinning preparation of pure lignocellulose diaphragm, the solvent is deionized water, propylene carbonate, One or more of N, N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide and hexafluoroisopropanol.

The green, high-efficiency lignocellulose-based separator for lithium-ion batteries and its preparation method are characterized in that: the pouring, In coating and electrospinning preparation, the natural or synthetic polymer materials are natural polymer materials such as cellulose, starch, chitosan, agar, pectin and gelatin or polyacrylate, polyacrylonitrile, polyether One or a mixture of synthetic polymers such as ether ketone, polyethylene oxide, polyacetate, and polyvinylidene fluoride.

The green, high-efficiency lignocellulose-based diaphragm for lithium-ion batteries and its preparation method are characterized in that: the pouring and tertiary composite diaphragm with lignocellulose as the main body and other natural or synthetic polymer materials In the preparation of coating, the good solvent for dissolving natural or synthetic macromolecular materials one-element or two-element complexes is deionized water, methanol, ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, N,N dimethylformamide, N, One or more of N-dimethylacetamide, dimethyl sulfoxide, tetramethyl urea, trimethyl phosphate and N-methylpyrrolidone.

The green, high-efficiency lignocellulose-based separator for lithium-ion batteries and its preparation method are characterized in that: in the electrospinning of lignocellulose as the main body and other natural or synthetic polymer materials binary or ternary composite separators In silk preparation, the solvents added when configuring the electrospinning solution are deionized water, acetone, tetrahydrofuran, N, N dimethylformamide, dimethyl sulfoxide, ethylene carbonate, propylene carbonate and N-methyl One or a mixture of pyrrolidones.

Beneficial effect

The beneficial effects of the present invention are that the natural macromolecule material aggregate lignocellulose with the largest annual output (nearly one trillion tons) in the world is selected as the matrix or the matrix is selected with lignocellulose as the main body and other natural or synthetic macromolecular composites To prepare a separator that can be used in a lithium-ion battery, while completely solving the problem of "white pollution" of the lithium-ion battery, it can endow the battery with high performance. SUMMARY OF THE INVENTION The present invention not only solves some problems existing in lithium-ion batteries, but also opens up a new application field of lignocellulose.

Description of drawings

Figure 1 is a scanning electron micrograph of a pure lignocellulose membrane prepared by coating method.

Figure 2 is the charge-discharge diagram of the pure lignocellulose separator assembled half-cell Li/S-LE/LFP prepared by the coating method.

Fig. 3 is the charge-discharge diagram of half-cell Li/S-LE/LFP assembled with PEG1000 content of 30wt.% lignocellulose binary composite membrane prepared by casting method.

detailed description

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment:

Example 1

Weigh 1000mg of lignocellulose and 40ml of deionized water and place them in a beaker; stir for 2 hours at room temperature at 25°C to obtain a uniform suspension; Under the condition of 60°C, until the water evaporates, a uniform pure lignocellulose membrane is obtained.

Example 2

Weigh five parts of lignocellulose with a mass of 1000 mg, and then weigh five parts of starch with a mass of 50 mg, 75 mg, 100 mg, 125 mg and 150 mg; put five parts of lignocellulose and five parts of starch into five beakers in turn , and successively add 30ml of deionized water into the beaker; at 80°C, stir for 0.5h to obtain a viscous uniform solution; pour the solution on a glass plate, and dry at normal pressure for 5h at 60°C to obtain a uniform and flat A binary composite membrane with lignocellulose as the main body and starch as the secondary body.

Example 3

Weigh 900mg of lignocellulose and place it in a beaker, add 35ml of deionized water; prepare a pure lignocellulose diaphragm according to the process described in Example 1 above; weigh 385mg of PEG1000 and place it in a beaker, add 20ml of deionized water, and Stir until dissolved to obtain a homogeneous viscous solution; slowly pour the viscous solution on the pure lignocellulose diaphragm, and dry it at normal pressure and 60°C for 10 hours to obtain a uniform and flat lignocellulose as the main body and PEG1000 as the secondary body. Binary complex diaphragm.

Carry out battery assembly and performance test to embodiment:

Assemble various batteries: Punch the obtained separator into a disc with a diameter of 19mm on a punching machine, transfer it to a vacuum oven; dry it in a vacuum at 70±2°C for 5-7 hours, then quickly transfer it into water with an oxygen content of less than 0.5ppm glove box; choose 2032 button battery shell, use stainless steel sheet inert electrode SS, active lithium sheet electrode Li, lithium iron phosphate positive electrode LFP, use the commercialized new Zhoubang company model LBC305-01 as the liquid electrolyte LE, and use The prepared composite membrane is separator S, and SS/S-LE/SS, Li/S-LE/SS, Li/S-LE/Li and Li/S-LE/LFP batteries are assembled;

Performance test: three electrochemical properties of ion conductivity, electrochemical stability window and lithium ion migration number were tested on the electrochemical workstation CHI-660D of Shanghai Chenhua Company in China; tested on the charge and discharge tester of Shenzhen Xinwei Company in China Battery charging performance. The ionic conductivity is calculated by testing the AC impedance of SS/S-LE/SS batteries. The spectrum test conditions are that the scanning frequency range is 0.1Hz to 100kHz, and the exchange signal amplitude is 10mV; to test Li/S-LE/SS linear scanning The method to determine the electrochemical stability window, the test condition is that the scanning rate is 1mV s ^-1 , the lithium sheet is the counter electrode and the reference electrode, and the stainless steel is the working electrode; to test the AC impedance and DC resistance of the Li/S-LE/Li battery Polarization method to determine the number of lithium ion migration, the test conditions are AC impedance frequency range 0.1Hz ~ 100kHz, exchange signal amplitude 10mV, polarization voltage applied by DC polarization is 10mV; test the electrical performance of Li/S-LE/LFP battery charging point , The test conditions are constant current charge and discharge, the charge and discharge cut-off high and low voltages are 4.5V and 2.0V respectively, and the rate range is 0.2-3C.

Test results: Example 1 system: lithium ion conductivity at room temperature is 2.53×10 ^-3 S·cm ^-1 , electrochemical stability window is 6.0V, lithium ion migration number is 0.82, and the charge and discharge capacity at 1.0C rate is 160mAh· g ^-1 and 156mAh·g ^-1 ; the system of Example 2: among the five prepared systems, the system with 50 mg of starch showed the highest performance: the lithium ion conductivity at room temperature was 1.27×10 ^-3 S·cm ^{- 1.} The electrochemical stability window is 6.6V, the lithium ion migration number is 0.79, and the charge and discharge capacities are 169mAh·g ^-1 and 160mAh·g ^-1 at a rate of 0.2C; the system of Example 3: the lithium ion conductivity at room temperature is 1.50 ×10 ^-3 S·cm ^-1 , electrochemical stability window 5.3V, lithium ion transfer number 0.81, charge and discharge capacities of 156mAh·g ^-1 and 152mAh·g ^-1 at a rate of 0.5C, respectively.

Claims (5)

1. Green, high-efficiency lignocellulose-based separator for lithium-ion batteries and its preparation method, characterized in that: five kinds of lignocellulose-based substrates or based on lignocellulose as the main body and other natural or synthetic polymer binary or tertiary membranes have been developed. The element-blend compound is the diaphragm of the matrix and the preparation method thereof, and the specific process is as follows: (1) Coating preparation of pure lignocellulose membrane: weigh 900-1000mg of lignocellulose and 35-40ml of deionized water, put them in a beaker; stir at room temperature (25±1°C) for 2 -3h, to obtain a uniform suspension; pour the suspension into a flat-bottomed glass dish, under normal pressure and 60±2°C, until the water evaporates completely, and a uniform pure lignocellulose membrane is obtained. (2) Preparation of pure lignocellulose membrane by electrospinning: grind and sieve lignocellulose, and collect powder between 100-200 mesh; put the collected powder in a beaker, add solvent, and stir at room temperature for 5-8h , to obtain a uniform electrospinning solution with a concentration range of 5wt.%-10wt.%; put the electrospinning solution into the syringe, set the positive high voltage to 10-12kV, the negative high voltage to -1--2kV, and the injection speed to be 2.5-3ml/h, the drum speed is 20-25rpm, the distance between the fixed positive and negative electrodes is 10-12cm, the electrospinning time is 2-3h, electrospinning, obtain a uniform and flat wet film, dry at room temperature, and obtain pure Lignocellulose membrane. (3) Pouring preparation of binary or ternary composite diaphragms with lignocellulose as the main body and other natural or synthetic polymer materials: with lignocellulose mass fraction in the range of 65wt.%-95wt.%, other natural or synthetic The mass fraction of the one-element or two-element composite of the polymer material is in the range of 35wt.%-5wt.%, and the corresponding mass is weighed respectively; the weighed pure lignocellulose is prepared according to the above-mentioned process to prepare a diaphragm with uniform thickness; the weighed The natural or synthetic polymer material one-component or two-component compound is placed in a beaker, and a good solvent that can just dissolve the compound at room temperature is added, and stirred until a uniform solution is obtained; the obtained uniform solution is slowly poured on pure lignocellulose On the diaphragm, ensure that the solution is completely immersed in the pores of the lignocellulose diaphragm, and then under the conditions of normal pressure and 25-60 ° C until the solvent evaporates to obtain a uniform lignocellulose main body binary or ternary composite diaphragm. (4) Coating preparation of lignocellulose as the main body and other natural or synthetic polymer material binary or ternary composite membranes: with lignocellulose mass fraction in the range of 65wt.%-95wt.%, other natural or synthetic polymer materials The mass fraction of synthetic macromolecule material one-element or two-element compound is in the interval range of 35wt.%-5wt.%, weigh the substances of corresponding mass respectively; Put it into a beaker; put the total mass of the mixture in the beaker to the volume ratio of the solvent in the range of 1g: 15ml-1g: 40ml, add a good solvent, and stir at 25-80°C until a uniform suspension is obtained; the obtained uniform The suspension is coated on a glass plate, and then kept under the condition of normal pressure and 25-60° C. until the solvent evaporates completely to obtain a homogeneous lignocellulose main body binary or ternary composite membrane. (5) Electrospinning preparation of lignocellulose as the main body and other natural or synthetic polymer material binary or ternary composite membranes: grind and sieve lignocellulose, and collect powder between 100-200 mesh; According to the quality range of lignocellulose powder in the range of 65wt.%-95wt.%, weigh the powder and other natural or synthetic macromolecular material one-component or two-component composites, and place them in a beaker; then add solvent and stir at room temperature for 5 -15h, to obtain a uniform electrospinning solution with a solution concentration range of 1wt.%-10wt.%; put the electrospinning solution into the syringe, set the positive high voltage to 10-20kV, and the negative high voltage to -1--5kV, and inject The speed is 0.5-5ml/h, the rotation speed of the drum is 20-100rpm, the distance between the fixed positive and negative electrodes is 10-20cm, the electrospinning time is 2-10h, electrospinning to obtain a uniform and flat wet film, and drying at room temperature. A homogeneous lignocellulosic host binary or ternary composite membrane is obtained. 2. green according to claim 1, high-efficiency lignocellulose matrix diaphragm and preparation method thereof for lithium ion battery, it is characterized in that: in the electrospinning preparation of pure lignocellulose diaphragm, described solvent is deionized One or more of water, propylene carbonate, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide and hexafluoroisopropanol. 3. The green, high-efficiency lignocellulosic matrix separator for lithium ion batteries according to claim 1 and its preparation method, characterized in that: the lignocellulose is used as the main body and other natural or synthetic polymer materials in binary or ternary In the pouring, coating and electrospinning preparation of the composite membrane, the natural or synthetic polymer materials are natural polymer materials such as cellulose, starch, chitosan, agar, pectin and gelatin or polyacrylate, One or a mixture of synthetic polymers such as polyacrylonitrile, polyether ether ketone, polyethylene oxide, polyacetate, and polyvinylidene fluoride. 4. The green, high-efficiency lignocellulosic matrix separator for lithium ion batteries according to claim 1 and its preparation method, characterized in that: it is based on lignocellulose and other natural or synthetic polymer materials in binary or ternary In the pouring and coating preparation of the composite diaphragm, the good solvent for dissolving the natural or synthetic macromolecular material one-component or two-component composite is deionized water, methanol, ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, N, N dimethyl One or more of methyl formamide, N, N dimethyl acetamide, dimethyl sulfoxide, tetramethyl urea, trimethyl phosphate and N-methylpyrrolidone. 5. The green, high-efficiency lignocellulosic matrix separator for lithium ion batteries according to claim 1 and its preparation method, characterized in that: the lignocellulose is used as the main body and other natural or synthetic polymer materials in binary or ternary In the electrospinning preparation of the composite diaphragm, the solvent added when configuring the electrospinning solution is deionized water, acetone, tetrahydrofuran, N, N dimethylformamide, dimethyl sulfoxide, ethylene carbonate, propylene carbonate One or more mixtures of esters and N-methylpyrrolidone.