CN116315421A - Preparation method of battery diaphragm with high lithium ion conductivity - Google Patents
Preparation method of battery diaphragm with high lithium ion conductivity Download PDFInfo
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- CN116315421A CN116315421A CN202310250941.XA CN202310250941A CN116315421A CN 116315421 A CN116315421 A CN 116315421A CN 202310250941 A CN202310250941 A CN 202310250941A CN 116315421 A CN116315421 A CN 116315421A
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Abstract
A preparation method of a battery diaphragm with high lithium ion conductivity belongs to the technical field of lithium batteries. The method is characterized in that an electronegative polymer is used as a raw material, a carbonaceous filler is doped, and a non-solvent induced phase separation method is adopted to prepare the large-area diaphragm. Firstly, dissolving a certain electronegative polymer in a solvent, and stirring until uniform precursor liquid slurry is obtained; dissolving a trace of carbonaceous filler in a solvent, and stirring by ultrasonic to obtain a carbonaceous solution with extremely low concentration and uniform dispersion; adding a small amount of carbonaceous solution into the precursor slurry to obtain a mixed solution, and finally preparing the catalyst by using a non-solvent induced phase separation methodA large area diaphragm is obtained. Anion-boosting Li by the negative groups inherent in the electronegative polymer + The added carbonaceous filler is favorable for increasing the porosity of the diaphragm so as to improve the ion conductivity, finally improves the lithium ion conductivity of the diaphragm, regulates and controls the ion transmission, and is hopeful to realize safe and reliable quick charge.
Description
Technical Field
The invention relates to a preparation method of a battery diaphragm with high lithium ion conductivity, and belongs to the technical field of lithium batteries.
Background
Lithium secondary batteries are electrochemical energy storage devices having excellent properties of no pollution, high energy density, long cycle life, low self-discharge, no memory effect, etc., and have been receiving wide attention in various fields by virtue of these advantages. Currently, the market of portable intelligent devices and electric vehicles is vigorous, but various factors still exist to restrict the large-scale use of the portable intelligent devices and electric vehicles, wherein the rapid charging is a key technical barrier to restrict the popularization of the portable intelligent devices and electric vehicles.
The ion transport kinetics inside lithium secondary batteries are a critical factor in determining their fast charge capacity. Ion transport kinetics can be expressed in terms of lithium ion conductivity, which is calculated by the formula: lithium ion conductivity = ion conductivity σx lithium ion migration number t Li + . However, the commercial microporous membrane is a polyolefin membrane at present, and has the function of isolating electron conduction between the anode and the cathode, providing a microporous channel for ion reciprocating transmission, and having no regulation and control function on ion transmission, so the microporous membrane has no contribution to quick charge of a lithium ion battery.
Therefore, it is proposed to prepare a large-area separator by using an electronegative polymer as a raw material and doping a carbonaceous filler, and adopting a non-solvent induced phase separation method. Anion-boosting Li by the negative groups inherent in the electronegative polymer + The added carbonaceous filler is favorable for increasing the porosity of the diaphragm so as to improve the ion conductivity, finally improve the lithium ion conductivity, regulate and control the ion transmission, and is hopeful to realize safe and reliable quick charge, so that the lithium battery is more widely developed in the energy storage field.
Disclosure of Invention
The invention provides a preparation method of a battery diaphragm with high lithium ion conductivity, which takes an electronegative polymer as a raw material, is doped with a carbonaceous filler, and adopts a non-solvent induced phase separation method to prepare a large-area diaphragm. The diaphragm has the function of regulating and controlling ion transmission, and the preparation method is simple and easy to operate and can be used for large-area preparation.
The preparation method of the battery diaphragm with high lithium ion conductivity comprises the following specific steps:
(1) And dissolving the precursor powder of the electronegative polymer (polyvinylidene fluoride and polybenzimidazole) with a certain concentration in a high-solubility solvent (N, N-dimethylacetamide and N, N-dimethylformamide), and stirring for 10-12 h to obtain precursor slurry with good dispersibility.
(2) Dispersing a trace amount of carbonaceous filler (carbon nano tube and carbon nano fiber) in a solvent, carrying out ultrasonic treatment for 20min, and stirring for 10h to obtain a carbonaceous solution with extremely low concentration and uniform dispersion.
(3) Adding a small amount of carbonaceous solution into the precursor slurry, stirring uniformly, standing until defoaming, casting the mixed solution on a smooth glass plate by using a doctor blade coater, immersing a substrate into a non-solvent, and carrying out rapid exchange between the solvent and the non-solvent under the action of a chemical potential gradient driving force to realize a phase conversion process until a phase conversion finishing film automatically floats;
(4) And (3) vacuum drying the obtained diaphragm at a certain temperature to obtain the diaphragm with large area.
The prepared diaphragm is applied to a lithium battery, can play a role in regulating and controlling ion transmission, and is expected to realize safe and reliable rapid charging.
The mass ratio of the electronegative polymer to the carbonaceous filler is (0.5-2) x 10 5 :4。
Compared with the prior art, the invention has the following advantages:
1. the invention provides a preparation method of a battery diaphragm with high lithium ion conductivity, which has simple preparation process and can realize large-area preparation.
2. The invention utilizes the electronegative polymer to fix anions to promote Li + The added carbonaceous filler is beneficial to increasing the porosity of the diaphragm so as to improve the ion conductivity and realize the ion transmission regulation and control function.
Drawings
FIG. 1 is a schematic view of the preparation process of example 1 of the present invention
FIG. 2 is a graph showing the lithium ion migration count versus the PP separator tested in accordance with the present invention and the CNT@PVDF separator obtained in example 1;
FIG. 3 is a graph showing the ionic conductivity of the PP separator obtained by the test of the present invention and the CNT@PVDF separator obtained in example 1, and a histogram of ionic conductivity corresponding to the number of lithium ions transferred from the two separators
Fig. 4 is a graph comparing the rate performance of the full cell of the PP separator obtained by the inventive test and the cnt@pvdf separator obtained in example 1.
Detailed Description
The invention will be further elucidated with reference to the drawings and the detailed description, but the invention is not limited to the following examples.
In the following examples, 1mol/L LiPF was used for the electrolyte 6 /
(ec+dmc+emc) (volume ratio 1:1:1); the battery assembly was completed using the glovebox eteux LAB2000 from itex inert gas systems limited; lithium ion migration number and ion conductivity were tested using a prinston versstat 4 electrochemical workstation: (1) Lithium ion migration number (t) Li + ) The measurement is performed by a combination of direct current potentiostatic polarization measurement and Electrochemical Impedance Spectroscopy (EIS) of Li/Li symmetric cells. The initial current (I) was recorded during potentiostatic polarization with a voltage bias of 10mV 0 ) And steady state current (I SS ). In addition, the initial and steady-state interfacial resistance (R 0 And R is S ) Can be determined by measuring the ac impedance of the cell before and after polarization. Li (Li) + The migration number can be calculated by the formula:
wherein I is SS And I 0 Respectively steady state current and initial state current. R is R 0 And R is S The initial state resistance and the steady state resistance, respectively. DeltaV is the applied polarization voltage (10 mV).
(2) By being in the frequency range 10 on an electrochemical workstation 6 To 1Hz, at an open circuit voltage of 10mVAc impedance measurements, assess ion conductivity (σ) of electrolyte-immersed separator in SS/separator/SS cells. The ionic conductivity was calculated according to the following:
where d is the thickness of the separator, R b Is the volume resistance and S is the effective area of the diaphragm.
And testing the performance of the full battery by adopting a blue charge-discharge tester: the charge-discharge voltage of the battery ranges from 2.5 to 4V.
Example 1
(1) Preparing precursor slurry (0.1 g/ml) from polyvinylidene fluoride (PVDF) raw material: 1g of PVDF powder is weighed and dissolved in 10mL of N, N-dimethylformamide, and stirred for 10 to 12 hours, thus obtaining PVDF slurry with good dispersibility.
(2) 1mg of carbon nanotube is dissolved in 100mL of N, N-dimethylformamide solvent, sonicated for 20min, and then stirred for 10h, thereby obtaining a carbon nanotube solution with extremely low concentration and uniform dispersion.
(3) Adding 4mL of Carbon Nanotube (CNT) solution into PVDF slurry, stirring the mixed solution uniformly, standing until defoaming, casting the precursor solution on a smooth glass plate substrate by using a doctor blade coater, immersing the substrate into deionized water, and carrying out rapid exchange between a solvent and a non-solvent under the action of a chemical potential gradient driving force to realize a phase conversion process until a phase conversion film automatically floats.
(4) And (3) vacuum drying the membrane for 10 hours at 60 ℃ to obtain the CNT@PVDF functional membrane with a large area.
(5) The prepared cnt@pvdf separator was used to assemble lithium batteries (polypropylene separator as a control). And assembling the battery in a glove box filled with argon, sequentially assembling a positive electrode shell, a positive electrode, electrolyte, a diaphragm, electrolyte, a negative electrode, a gasket, a spring piece and a negative electrode shell from bottom to top, pressurizing and sealing the battery by using a tablet press, and standing for 12 hours.
Example 2
(1) Preparing precursor slurry (0.15 g/mL) from Polybenzimidazole (PBI): 1.5g of PBI powder is weighed and dissolved in 10mL of N, N-dimethylacetamide, and the mixture is stirred for 10 to 12 hours to obtain PBI slurry with good dispersibility.
(2) 1mg of carbon nanotube is dissolved in 100mL of N, N-dimethylacetamide solvent, and is subjected to ultrasonic treatment for 20min, and then is stirred for 10h, so that a carbon nanotube solution with extremely low concentration and uniform dispersion is obtained.
(3) Adding 4mL of carbon nanotube solution into PBI slurry, stirring the mixed solution uniformly, standing until defoaming, casting the precursor solution on a smooth glass plate substrate by using a doctor blade coater, immersing the substrate into deionized water, and carrying out rapid exchange between a solvent and a non-solvent under the action of a chemical potential gradient driving force to realize a phase conversion process until a phase conversion finishing film automatically floats.
(4) And (3) vacuum drying the membrane for 12 hours at 100 ℃ to obtain the CNT@PBI functional membrane with a large area.
(5) Step (5) in example 1 is the same.
The large-area CNT@PVDF separator prepared in the above example 1 is selected, and the separator prepared in the above example is assembled into a button cell for performance test, and the structure and performance test are described below with reference to the accompanying drawings.
In fig. 2, it can be seen that the lithium ion migration numbers corresponding to the PP separator and the cnt@pvdf separator are 0.41 and 0.67, respectively, which proves that the prepared cnt@pvdf separator can fix anions and promote the transmission of lithium ions.
It can be seen in FIG. 3 that the ionic conductivities of the PP membrane and the CNT@PVDF membrane are respectively 0.31mS cm -1 、0.81mS cm -1 The higher ionic conductivity of the CNT@PVDF diaphragm is due to the fact that the porosity of the diaphragm is improved by the added carbon nano tube, and the absorption of electrolyte is facilitated, so that the rapid transmission of ions is promoted. By the formula (lithium ion conductivity=ion conductivity σ×lithium ion migration number t Li + ) The lithium ion conductivities corresponding to the PP diaphragm and the CNT@PVDF diaphragm are calculated to be 0.13mS cm respectively -1 ，0.54mS cm -1 。
Fig. 4 is a graph comparing the rate performance of the full cells of PP separator and PVDF separator, and it can be seen that the discharge capacity of the cells using cnt@pvdf separator is all higher than that of the corresponding cells of PP separator. The excellent rate performance of the battery using the CNT@PVDF separator is attributed to the high lithium ion conductivity corresponding to the separator, and safe and reliable quick charge is expected to be realized.
Claims (8)
1. A method for preparing a battery separator with high lithium ion conductivity, comprising the steps of:
(1) Dissolving an electronegative polymer precursor powder material with a certain concentration in a high-solubility solvent, and stirring for 10-12 h to obtain precursor slurry with good dispersibility;
(2) Dissolving a trace amount of carbonaceous filler in a solvent, performing ultrasonic treatment for 20min, and stirring for 10h to obtain a carbonaceous solution with extremely low concentration and uniform dispersion;
(3) Adding a small amount of carbonaceous solution into the precursor slurry, stirring uniformly, standing until defoaming, casting the mixed solution on a smooth glass plate substrate by using a doctor blade coater, immersing the substrate into a non-solvent, and carrying out rapid exchange between the solvent and the non-solvent under the action of a chemical potential gradient driving force to realize a phase conversion process until a phase conversion finishing film automatically floats;
(4) And (5) drying the obtained diaphragm in vacuum to obtain the large-area diaphragm.
2. The method for preparing a battery separator with high lithium ion conductivity according to claim 1, wherein the solvent in the step (1) and the solvent in the step (2) are one or more of N, N-dimethylacetamide and N, N-dimethylformamide.
3. The method of manufacturing a battery separator having high lithium ion conductivity according to claim 1, wherein deionized water is selected as the non-solvent in step (3).
4. The method for preparing a battery separator with high lithium ion conductivity according to claim 1, wherein the solvents used in the step (1) and the step (2) are identical, the concentration of the precursor solution in the step (1) is 0.1-0.2g/mL, and the concentration of the carbonaceous solution in the step (2) is 5-15mg/L.
5. The method of preparing a battery separator having high lithium ion conductivity according to claim 1, wherein the mass ratio of the electronegative polymer precursor to the carbonaceous filler in step (3) is (0.5-2) x 10 5 :4。
6. The method for preparing a battery separator with high lithium ion conductivity according to claim 1, wherein the electronegative polymer is one or more selected from polyvinylidene fluoride and polybenzimidazole;
the carbonaceous filler is selected from one or more of carbon nanotubes and carbon nanofibers.
7. A battery separator having high lithium ion conductivity prepared according to the method of any one of claims 1 to 6.
8. The battery separator with high lithium ion conductivity prepared by the method according to any one of claims 1 to 6 is applied to a lithium secondary battery.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202310250941.XA CN116315421A (en) | 2023-03-15 | 2023-03-15 | Preparation method of battery diaphragm with high lithium ion conductivity |
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| CN202310250941.XA CN116315421A (en) | 2023-03-15 | 2023-03-15 | Preparation method of battery diaphragm with high lithium ion conductivity |
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