CN116695429A - Modified sepiolite fiber and preparation method thereof, flame-retardant composite polymer solid electrolyte membrane and preparation method and application thereof - Google Patents

Modified sepiolite fiber and preparation method thereof, flame-retardant composite polymer solid electrolyte membrane and preparation method and application thereof Download PDF

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CN116695429A
CN116695429A CN202310727762.0A CN202310727762A CN116695429A CN 116695429 A CN116695429 A CN 116695429A CN 202310727762 A CN202310727762 A CN 202310727762A CN 116695429 A CN116695429 A CN 116695429A
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sepiolite fiber
electrolyte membrane
sepiolite
preparation
fiber
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严伟
王奎
黄伟江
张姣姣
田琴
杨春林
涂春云
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Guiyang University
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Guiyang University
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Abstract

The invention provides a modified sepiolite fiber and a preparation method thereof, and a flame-retardant composite polymer solid electrolyte membrane and a preparation method and application thereof, and relates to the technical field of lithium ion batteries. The sepiolite fiber, aluminum hydroxide, phosphoric acid and water are mixed and subjected to heterogeneous precipitation reaction under the condition that the pH value is 4-5, so that aluminum phosphate coated sepiolite fiber is obtained; and carrying out surface modification on the aluminum phosphate coated sepiolite fiber by using calcium stearate in an alcohol solvent to obtain the modified sepiolite fiber. To prepare the modified sepiolite fiberThe composite polymer solid electrolyte membrane prepared from vitamin and polyethylene oxide has better electrochemical performance, and the ion conductivity can reach 2.39X10 at most ‑5 S·cm ‑1 Meanwhile, the flame retardant property of the composite polymer solid electrolyte membrane is improved, namely the obtained polyoxyethylene composite solid electrolyte membrane has good electrochemical property and flame retardant property, and is a high-safety composite polymer solid electrolyte membrane.

Description

Modified sepiolite fiber and preparation method thereof, flame-retardant composite polymer solid electrolyte membrane and preparation method and application thereof
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a modified sepiolite fiber and a preparation method thereof, a flame-retardant composite polymer solid electrolyte membrane and a preparation method and application thereof.
Background
In recent years, solid polymer electrolytes have been attracting attention because of their convenience in processing, good flexibility and low contact resistance, but they have low yields, high costs, low ionic conductivity, and flammability of organic components, leading to potential safety hazards. Polyethylene oxide (PEO) is an ideal matrix material for constructing composite polymer electrolytes because of being nontoxic, strong in cathode stability of ether groups and difficult to react with negative ions in lithium salts. However, PEO is used as a polymer matrix material, and the problems of low ionic conductivity, narrow electrochemical stability window, poor mechanical strength and the like still exist; the main component is polyether chain forging, and the Limiting Oxygen Index (LOI) of PEO is about 17.5% through theoretical calculation, so that the PEO is a flammable organic polymer, and the application range of the PEO is severely limited.
Disclosure of Invention
In view of the above, the present invention aims to provide a modified sepiolite fiber and a preparation method thereof, and a flame-retardant composite polymer solid electrolyte membrane and a preparation method and application thereof. The polyethylene oxide solid electrolyte membrane prepared from the modified sepiolite fiber provided by the invention has good electrochemical performance and flame retardant performance, and is high in safety.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of modified sepiolite fiber, which comprises the following steps:
mixing sepiolite fiber, aluminum hydroxide, phosphoric acid and water, and carrying out heterogeneous precipitation reaction under the condition that the pH value is 4-5 to obtain aluminum phosphate coated sepiolite fiber;
mixing the aluminum phosphate coated sepiolite fiber, calcium stearate and an alcohol solvent for surface modification reaction to obtain the modified sepiolite fiber.
Preferably, the mass ratio of the sepiolite fiber to the aluminum hydroxide to the phosphoric acid is (4-10): (0.5-1): (5-15).
Preferably, the homogeneous precipitation reaction is specifically performed by:
mixing sepiolite fibers with water to obtain sepiolite fiber dispersion;
dropwise adding hydrochloric acid into the sepiolite fiber dispersion liquid to adjust the pH value to 2-3, so as to obtain acidified sepiolite fiber dispersion liquid;
mixing aluminum hydroxide, phosphoric acid and water, and adding the obtained mixed solution to the acidified sepiolite fiber dispersion; then ammonia water is added dropwise, and heterogeneous precipitation reaction is carried out under the condition that the pH value is 4-5.
Preferably, the heterogeneous precipitation reaction time is 30-50 min; the heterogeneous reaction is carried out under the condition of stirring, and the stirring speed is 800-1000 r/min.
Preferably, the mass ratio of the aluminum phosphate coated sepiolite fiber to the calcium stearate is (4-5): (0.02-0.1).
Preferably, the temperature of the surface modification reaction is 70-80 ℃ and the time is 30-50 min; the surface modification reaction is carried out under the condition of stirring, and the stirring speed is 500-800 r/min.
The invention provides the modified sepiolite fiber prepared by the preparation method in the technical scheme, wherein the modified sepiolite fiber is calcium stearate modified coated sepiolite fiber, and the coated sepiolite fiber is aluminum phosphate coated sepiolite fiber.
The invention provides a flame-retardant composite polymer solid electrolyte membrane, which comprises modified sepiolite fibers, lithium salt and polyethylene oxide, wherein the modified sepiolite fibers are prepared by the technical scheme;
the ratio of EO mole number in the polyethylene oxide to lithium ion mole number in the lithium salt is 16-20: 0.5 to 1; the mass of the modified sepiolite fiber is 1-20% of the mass of the polyethylene oxide.
The invention provides a preparation method of a flame-retardant composite polymer solid electrolyte membrane, which comprises the following steps:
mixing the modified sepiolite fiber, lithium salt, polyethylene oxide and an organic solvent to obtain a glue solution;
and (3) forming a film from the glue solution to obtain the flame-retardant composite polymer electrolyte membrane.
The invention provides the application of the flame-retardant composite polymer solid electrolyte membrane in lithium ion batteries, which is prepared by the technical scheme or the preparation method.
The invention provides a preparation method of modified sepiolite fiber, which comprises the following steps: mixing sepiolite fiber, aluminum hydroxide, phosphoric acid and water, and carrying out heterogeneous precipitation reaction under the condition that the pH value is 4-5 to obtain aluminum phosphate coated sepiolite fiber; mixing the aluminum phosphate coated sepiolite fiber, calcium stearate and an alcohol solvent for surface modification reaction to obtain the modified sepiolite fiber. In the invention, the sepiolite fiber has a large ion channel, on one hand, the filler interacts with the polymer, especially nano particles can be dispersed among polymer molecules, so that the phase composition of the polymer electrolyte at room temperature is influenced, the amorphous phase content of the system is increased, and the peristaltic capability of a molecular chain segment is improved; on the other hand, filler as Lewis acid and lithium salt anion X - And Lewis base such as O in PEO react to reduce Li + -X - Ion pairs, increase the number of free carriers and also weaken O-Li + Interaction to make lithium ion more easily transported, thereby increasing ion conductivityThe ionic conductivity of the polyethylene oxide solid electrolyte membrane is effectively improved; the sepiolite fiber has the excellent performances of high temperature resistance and flame retardance, and can obviously improve the flame retardance of the polymer composite material; however, the sepiolite has poor compatibility with polyethylene, and the surface of the aluminum phosphate coated sepiolite fiber is organically modified by calcium stearate, so that the compatibility of the sepiolite fiber and the polyethylene is improved.
The invention provides the modified sepiolite fiber prepared by the preparation method in the technical scheme, wherein the modified sepiolite fiber is calcium stearate modified coated sepiolite fiber, and the coated sepiolite fiber is aluminum phosphate coated sepiolite fiber. The solid electrolyte membrane of polyethylene oxide polymer prepared by the modified sepiolite fiber provided by the invention has better electrochemical performance, and the highest ionic conductivity can reach 2.39X10 -5 S·cm -1 Meanwhile, the flame retardant property of the composite polymer electrolyte membrane is improved, namely the obtained polyethylene oxide polymer solid electrolyte membrane has good electrochemical property and flame retardant property, and is a high-safety composite polymer solid electrolyte membrane. The button type lithium ion battery assembled by using the solid electrolyte membrane of the polyethylene oxide polymer has higher initial capacity, high charge and discharge efficiency and better cycle performance. The invention provides a new way and thought for preparing the solid electrolyte and the lithium ion battery with high safety.
Drawings
FIG. 1 shows a pure sepiolite fiber (SEP) and an aluminum phosphate coated sepiolite fiber (SEP@AlPO) prepared in example 1 4 ) Scanning Electron Microscope (SEM), transmission Electron Microscope (TEM), and elemental analysis map; in FIG. 1, (a) is an SEM image of pure SEP and (b) is SEP@AlPO 4 (c) is SEP@AlPO 4 (d) is SEP@AlPO 4 Is an elemental analysis map of (a);
FIG. 2 shows a pure sepiolite fiber (SEP) and aluminum phosphate coated sepiolite prepared in example 1Fiber (SEP@AlPO) 4 ) XPS profile of (a);
FIG. 3 shows different Al (OH) groups of examples 1 to 3 3 And H 3 PO 4 XRD profile of mass ratio coated sepiolite fiber;
FIG. 4 shows pure SEP, calcium stearate (CaSt 2 ) SEP@AlPO before and after calcium stearate modification in example 6 4 Is a infrared spectrogram of (2);
FIG. 5 is a graph of pure PEO film in comparative example 1, PEO/LiTFSI composite film in comparative example 2, PEO/LiTFSI/m-SEP@AlPO in examples 7-10 4 XRD spectrum and DSC curve of the composite electrolyte membrane, in fig. 5, (a) is XRD spectrum, and (b) is DSC curve;
fig. 6 shows ac impedance spectra of electrolyte membranes prepared in examples 7 to 10 and comparative example 2, where (a) in fig. 6 shows ac impedance spectra of a blocked cell and (b) shows ac impedance spectra of a full cell;
FIG. 7 is a microcalorimeter plot of PEO electrolyte membranes prepared in examples 7-10 and comparative examples 1-2;
FIG. 8 is a PEO/LiTFSI electrolyte membrane prepared in comparative example 2 and PEO/LiTFSI/m-SEP@AlPO prepared in example 8 4 10 SEM photograph of electrolyte membrane, (a) in FIG. 8 is SEM photograph of PEO/LiTFSI electrolyte membrane, (b) is PEO/LiTFSI/m-SEP@AlPO 4 SEM photograph of 10 electrolyte film, (c) PEO/LiTFSI/m-SEP@AlPO 4 10 cross-sectional photographs of electrolyte membranes.
Detailed Description
The invention provides a preparation method of modified sepiolite fiber, which comprises the following steps:
mixing sepiolite fiber, aluminum hydroxide, phosphoric acid and water, and carrying out heterogeneous precipitation reaction under the condition that the pH value is 4-5 to obtain aluminum phosphate coated sepiolite fiber;
mixing the aluminum phosphate coated sepiolite fiber, calcium stearate and an alcohol solvent for surface modification reaction to obtain the modified sepiolite fiber.
In the present invention, unless otherwise specified, all the materials involved are commercially available products well known to those skilled in the art.
The sepiolite fiber, aluminum hydroxide, phosphoric acid and water are mixed, and heterogeneous precipitation reaction is carried out under the condition that the pH value is 4-5, so that the aluminum phosphate coated sepiolite fiber is obtained. In the present invention, the specification of the phosphoric acid is preferably analytically pure; the mass ratio of the sepiolite fiber to the aluminum hydroxide to the phosphoric acid is preferably (4-10): (0.5-1): (5 to 15), more preferably (4 to 8.5): 1: (6-8).
In the present invention, the specific operation of the heterogeneous precipitation reaction is preferably:
(a) Mixing sepiolite fibers with water to obtain sepiolite fiber dispersion;
(b) Dropwise adding hydrochloric acid into the sepiolite fiber dispersion liquid to adjust the pH value to 2-3, so as to obtain acidified sepiolite fiber dispersion liquid;
(c) Mixing aluminum hydroxide, phosphoric acid and water, and adding the obtained mixed solution to the acidified sepiolite fiber dispersion; then ammonia water is added dropwise, and heterogeneous precipitation reaction is carried out under the condition that the pH value is 4-5.
In the present invention, the sepiolite fiber is preferably washed with water, dried and ground in sequence before use; the washing is preferably carried out by adopting deionized water under the condition of ultrasonic oscillation to remove impurities; the drying temperature is preferably 50-60 ℃, and the drying time is based on the drying to constant weight; the grinding is based on grinding to powder. In the present invention, the sepiolite fiber to water usage ratio in step (a) is preferably 10g:160mL of the sepiolite fiber is preferably mixed with water at room temperature under stirring, based on uniform dispersion of the sepiolite fiber in water. In the present invention, the mass fraction of hydrochloric acid in the step (b) is preferably 37%. In the present invention, the ratio of the total mass of aluminum hydroxide and phosphoric acid to the volume of water in the step (c) is preferably (9.84 to 19.66) g:10mL; the mixing of the aluminum hydroxide, phosphoric acid and water is preferably performed at room temperature with stirring. In the present invention, the time of the heterogeneous precipitation reaction is preferably 30 to 50 minutes, more preferably 30 to 40 minutes; the heterogeneous precipitation reaction is preferably carried out under the condition of stirring, and the stirring speed is preferably 800-1000 r/min. According to the invention, by utilizing the characteristic that P-OH in the molecular structure of aluminum phosphate is easy to condense and dehydrate, a heterogeneous precipitation method is adopted to coat aluminum phosphate precipitate on the outer surface of nanofiber sepiolite.
In the invention, after the heterogeneous precipitation reaction is completed, the obtained reaction system is preferably subjected to solid-liquid separation, solid-phase washing, drying and grinding in sequence; the solid-liquid separation method is preferably vacuum filtration, the water washing is preferably deionized water, and the drying temperature is preferably 60-80 ℃; the grinding is based on grinding to powder.
After the aluminum phosphate coated sepiolite fiber is obtained, the aluminum phosphate coated sepiolite fiber, calcium stearate and an alcohol solvent are mixed for surface modification reaction, so that the modified sepiolite fiber is obtained. In the present invention, the alcohol solvent is preferably absolute ethanol; the mass ratio of the aluminum phosphate coated sepiolite fiber to the calcium stearate is preferably (4-5): (0.02 to 0.1), more preferably 4: (0.02-0.08); the mass ratio of the aluminum phosphate coated sepiolite fiber to the alcohol solvent is preferably 4g:30mL. In the present invention, the temperature of the surface modification reaction is preferably 70 to 80 ℃, more preferably 70 to 75 ℃, and the time is preferably 30 to 50min, more preferably 30 to 40min; the surface modification reaction is carried out under stirring, and the stirring speed is preferably 500-800 r/min. After the surface modification reaction, the invention preferably carries out solid-liquid separation, solid-phase alcohol washing, drying and grinding on the obtained modified liquid in sequence to obtain modified sepiolite fibers; the solid-liquid separation method is preferably suction filtration; the alcohol reagent used in the alcohol washing is preferably absolute ethyl alcohol, and the times of the alcohol washing are preferably 2-3 times; the drying temperature is preferably 50-70 ℃, more preferably 60 ℃, and the drying time is preferably 10-15 h, more preferably 12h; the grinding is performed until the powder is ground into fine powder.
The invention provides the modified sepiolite fiber prepared by the preparation method in the technical scheme, wherein the modified sepiolite fiber is calcium stearate modified coated sepiolite fiber, and the coated sepiolite fiber is aluminum phosphate coated sepiolite fiber. In the present invention, the sepioliteThe fiber has a large ion channel, on one hand, the filler interacts with the polymer, and particularly, nanoscale particles can be dispersed among polymer molecules, so that the phase composition of the polymer electrolyte at room temperature is influenced, the amorphous phase content of a system is increased, and the peristaltic capacity of a molecular chain segment is improved; on the other hand, filler as Lewis acid and lithium salt anion X - And Lewis base such as O in PEO react to reduce Li + -X - Ion pairs, increase the number of free carriers and also weaken O-Li + The interaction enables lithium ions to be more easily transmitted, thereby increasing the ionic conductivity, effectively improving the ionic conductivity of the solid electrolyte membrane of the polyethylene oxide polymer, and the sepiolite fiber has the excellent performances of high temperature resistance and flame retardance, and can obviously improve the flame retardance of the polymer composite material; according to the invention, the sepiolite fiber is coated with aluminum phosphate, so that the flame retardant property can be further improved, and the excellent properties of the aluminum phosphate and the sepiolite fiber are fully exerted; however, the sepiolite has the characteristics of hydrophilicity, oleophobicity and poor compatibility with polyethylene oxide, and the surface of the aluminum phosphate coated sepiolite fiber is organically modified through calcium stearate, so that the compatibility of the sepiolite fiber and the polyethylene oxide is improved.
The invention provides a flame-retardant composite polymer solid electrolyte membrane which comprises modified sepiolite fibers, lithium salt and polyethylene oxide. In the present invention, the lithium salt is preferably lithium bistrifluoromethane sulfonyl imide; the ratio of EO mole number in the polyethylene oxide to lithium ion mole number in the lithium salt is 16-20: 0.5 to 1, preferably 20:1, a step of; the mass of the modified sepiolite fiber is 1 to 20%, preferably 5 to 20%, more preferably 10 to 15% of the mass of the polyethylene oxide. The solid electrolyte membrane of polyethylene oxide polymer has better electrochemical performance, and the ion conductivity can reach 2.39X10 at most -5 S·cm -1 Meanwhile, the solid electrolyte membrane of the polyethylene oxide polymer has improved flame retardant property, namely the solid electrolyte membrane of the polyethylene oxide polymer has good electrochemical property and flame retardant property, and is a high-safety composite solid electrolyte membrane of the polymer.
The invention provides a preparation method of the flame-retardant composite polymer electrolyte membrane, which comprises the following steps:
mixing the modified sepiolite fiber, lithium salt, polyethylene oxide and an organic solvent to obtain a glue solution;
and (3) forming a film from the glue solution to obtain the flame-retardant composite polymer electrolyte membrane.
In the present invention, the organic solvent is preferably acetonitrile; the mixing is preferably: firstly mixing the modified sepiolite fiber with an organic solvent, and adding lithium salt and polyethylene oxide into the obtained dispersion liquid for second mixing; the first mixing is preferably carried out under ultrasonic conditions; the second mixing is preferably performed under stirring, and uniform glue solution is obtained through the second mixing. In the present invention, the film forming method is preferably: pouring the glue solution into a polytetrafluoroethylene mould, standing until the organic solvent is completely volatilized, and demoulding to obtain the flame-retardant composite polymer electrolyte membrane. In the present invention, the thickness of the flame retardant composite polymer electrolyte membrane is preferably 50 to 80 μm, more preferably 70 to 80 μm.
The invention provides an application of the flame-retardant composite polymer electrolyte membrane prepared by the technical scheme or the preparation method in a lithium ion battery. The invention has no special requirements on the type of the lithium ion battery; the method of application of the present invention is not particularly limited, and may be applied by methods well known to those skilled in the art. The lithium ion battery assembled by the flame-retardant composite polymer electrolyte membrane has high initial capacity, high charge and discharge efficiency and good cycle performance.
The modified sepiolite fiber and the preparation method thereof, and the flame-retardant composite polymer solid electrolyte membrane and the preparation method and application thereof provided by the present invention are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Preparation of aluminum phosphate coated sepiolite fiber:
weighing a certain amount of sepiolite fibers, uniformly dispersing the sepiolite fibers by using deionized water through ultrasonic oscillation, and carrying out suction filtration and washing for several times to remove part of impurities; the washed sepiolite is dried in a 60 ℃ oven and then ground to powder for standby. Weighing 10g of sepiolite powder, dispersing in 160mL of deionized water, and magnetically stirring to uniformly disperse the sepiolite powder to obtain sepiolite fiber dispersion; then, the pH value of the dispersion is adjusted to about 2 by hydrochloric acid with the concentration of 37 percent to obtain acidified sepiolite fiber dispersion liquid for standby. 2.33g of Al (OH) are weighed out separately 3 And 17.33g H 3 PO 4 Pouring into a beaker, adding 10mL of ultrapure water, adding the obtained mixed solution into the acidified sepiolite fiber dispersion, then dropwise adding an ammonia water solution through magnetic stirring, adjusting the pH value to be about 4.8 to generate phosphate precipitation, carrying out suction filtration, washing with deionized water, drying at 60 ℃, and grinding to obtain aluminum phosphate coated sepiolite fiber (marked as SEP@AlPO) 4 Ⅰ)。
The aluminum phosphate coated sepiolite fiber prepared in example 1 was subjected to Scanning Electron Microscopy (SEM), transmission Electron Microscopy (TEM), elemental analysis and X-ray photoelectron spectroscopy (XPS), and the test results are shown in fig. 1 and 2.
Pure sepiolite fiber (SEP) and aluminum phosphate coated sepiolite fiber sep@alpo prepared in example 1 4 As shown in (a) and (b) of FIG. 1, SEP@AlPO 4 A Transmission Electron Microscope (TEM) is shown in fig. 1 (c). As can be seen from fig. 1 (a), sepiolite is fibrous and has a smoother surface; after the introduction of aluminum phosphate, it is apparent from fig. 1 (b) and (c) that a large amount of aluminum phosphate particles are uniformly dispersed on the surface of SEP, indicating that aluminum phosphate successfully coats sepiolite fibers. SEP@AlPO 4 As shown in FIG. 1 (c), alPO is also present on the surface of SEP by elemental analysis 4 The content of Al and P elements in the particles is 19 percent. At the same time, from FIG. 2 pure SEP and SEP@AlPO 4 The XPS spectrum of (C) shows that SEP@AlPO 4 Peaks of electron spectra of P2P (134 eV) and Al2P (75 eV) appear, indicating AlPO 4 Successfully coated on sepiolite fiber.
Example 2
Preparation of aluminum phosphate coated sepiolite fiber:
weighing a certain amount of sepiolite fiber, uniformly dispersing the sepiolite fiber by using deionized water through ultrasonic oscillation, and carrying out suction filtration and washing for a plurality of times to remove part of impurities. The washed sepiolite is dried in a 60 ℃ oven and then ground to powder for standby. Weighing 10g of sepiolite powder, dispersing in 160mL of deionized water, and magnetically stirring to uniformly disperse the sepiolite powder to obtain sepiolite fiber dispersion; then, the pH value of the dispersion was adjusted to about 2 with hydrochloric acid having a concentration of 37% to obtain an acidified sepiolite fiber dispersion for use. 1.75g of Al (OH) are weighed out respectively 3 And 13g H 3 PO 4 Pouring into a beaker, adding 10mL of ultrapure water, adding the obtained mixed solution into the acidified sepiolite fiber dispersion, then dropwise adding an ammonia water solution through magnetic stirring, adjusting the pH value to be about 4.8 to generate phosphate precipitation, carrying out suction filtration, washing with deionized water, drying at 60 ℃, and grinding to obtain aluminum phosphate coated sepiolite fiber (marked as SEP@AlPO) 4 Ⅱ)。
Example 3
Weighing a certain amount of sepiolite fiber, uniformly dispersing the sepiolite fiber by using deionized water through ultrasonic oscillation, and carrying out suction filtration and washing for a plurality of times to remove part of impurities. The washed sepiolite is dried in a 60 ℃ oven and then ground to powder for standby. Weighing 10g of sepiolite powder, dispersing in 160mL of deionized water, and magnetically stirring to uniformly disperse the sepiolite powder to obtain sepiolite fiber dispersion; then, the pH value of the dispersion was adjusted to about 2 with hydrochloric acid having a concentration of 37% to obtain an acidified sepiolite fiber dispersion for use. 1.17g of Al (OH) are weighed out separately 3 And 8.67g H 3 PO 4 Pouring into a beaker, adding 10mL of ultrapure water, adding the obtained mixed solution into the acidified sepiolite fiber dispersion, then dropwise adding an ammonia water solution through magnetic stirring, adjusting the pH value to be about 4.8 to generate phosphate precipitation, carrying out suction filtration, washing with deionized water, drying at 60 ℃, and grinding to obtain the sepiolite fiber coated with aluminum phosphate (noted as SEP@AlPO 4 Ⅲ)。
FIG. 3 shows different Al (OH) in example 1, example 2 and example 3 3 And H 3 PO 4 XRD profile of mass ratio coated sepiolite fiber. As can be seen from fig. 3, SEP has a characteristic diffraction peak at 2θ=10.5°, alPO 4 The characteristic diffraction peak is 2θ=13.7°, and follows AlPO 4 Corresponding to the increase of SEP@AlPO 4 To more explain the increase in peak intensity of AlPO 4 The particles were successfully coated on the surface of SEP.
Example 4
Preparation of modified coated sepiolite fiber:
4g of SEP@AlPO prepared in example 1 were weighed out 4 Adding 30mL of absolute ethyl alcohol and 0.02g of calcium stearate into a three-neck flask, then placing the three-neck flask into an oil bath pot, stirring and reacting for 30min at 70 ℃, cooling to room temperature, taking out and vacuum filtering, washing a filter cake with absolute ethyl alcohol for 2-3 times, placing the filter cake into a 60 ℃ oven for drying for 12h, grinding the filter cake into fine powder by a mortar after drying, and obtaining the modified coated sepiolite fiber (marked as m-SEP@AlPO) 4 ) Placing into a sealed bag for sealing and preserving.
Example 5
4g of SEP@AlPO prepared in example 1 were weighed out 4 Adding 30mL of absolute ethyl alcohol and 0.04g of calcium stearate into a three-neck flask, then placing the three-neck flask into an oil bath pot, stirring and reacting for 30min at 70 ℃, cooling to room temperature, taking out and vacuum filtering, washing a filter cake with absolute ethyl alcohol for 2-3 times, placing the filter cake into a 60 ℃ oven for drying for 12h, grinding the filter cake into fine powder by a mortar after drying, and obtaining the modified coated sepiolite fiber (marked as m-SEP@AlPO) 4 ) Placing into a sealed bag for sealing and preserving.
Example 6
4g of SEP@AlPO prepared in example 1 were weighed out 4 Adding 30mL of absolute ethyl alcohol and 0.08g of calcium stearate into a three-neck flask, then placing the three-neck flask into an oil bath pot, stirring and reacting for 30min at 70 ℃, cooling to room temperature, taking out and vacuum filtering, washing a filter cake with absolute ethyl alcohol for 2-3 times, placing the filter cake into a 60 ℃ oven for drying for 12h, grinding the filter cake into fine powder by a mortar after drying, and obtaining the modified coated sepiolite fiber (marked as m-SEP@AlPO) 4 ) Placing into a sealed bag for sealing and preserving.
FIG. 4 shows pure SEP, calcium stearate (CaSt 2 ) SEP@AlPO before and after calcium stearate modification in example 6 4 Is a spectrum of infrared light of (a) is obtained. As can be seen from FIG. 4, pure sepiolite was found at 3673cm -1 The sepiolite hydroxyl (-OH) stretching vibration peak appears; 900cm -1 ～1100cm -1 1030cm of band -1 、972cm -1 、930cm -1 Asymmetric stretching diffraction peaks of Si-O-Si bonds appear; at 765cm -1 And 798cm -1 The symmetrical stretching vibration of Si-O-Si bonds occurs. Calcium stearate at 1541cm -1 、1575cm -1 At which a characteristic peak of carbonyl (-c=o) appears. By comparing the spectrograms before and after coating, the aluminum phosphate coated sepiolite is found to be 3673cm after coating -1 The characteristic peak intensity of the sepiolite-OH and Si-O-Si bonds is reduced to a certain extent, and the modified sep@AlPO 4 1541cm of calcium stearate -1 、1575cm -1 Characteristic peaks at the positions, showing that the calcium stearate is successful on SEP@AlPO 4 The modification is performed.
Example 7
Preparation of a composite polymer electrolyte membrane:
0.025g (5%) of the modified coated sepiolite fiber prepared in example 6 was weighed and dispersed in 20mL of acetonitrile solution, after shaking ultrasonically for 0.5h, transferred to a glove box and stirred continuously for 1h, then 0.16g of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), 0.5g (n (EO): n (Li) of polyethylene oxide (PEO) were weighed + ) =20: 1) Adding the mixture into the solution, and stirring for 5 hours to form uniform glue solution; pouring the obtained glue solution into a polytetrafluoroethylene mould, standing for 12h until acetonitrile is completely volatilized, taking down the prepared electrolyte membrane from the mould, and recording the thickness of the electrolyte membrane as PEO/LiTFSI/m-SEP@AlPO of about 70-80 mu m 4 5。
Example 8
Preparation of a composite polymer electrolyte membrane:
0.05g (10%) of the modified coated sepiolite fiber prepared in example 6 was weighed, dispersed in 20mL of acetonitrile solution, after shaking ultrasonically for 0.5h, transferred into a glove box and stirred continuously for 1h, then 0.16g of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), 0.5g of polyethylene oxide (PEO) were weighed (n (EO): n (Li) + ) =20: 1) Adding the mixture into the solution, and stirring for 5 hours to form uniform glue solution; pouring the obtained glue solution into a polymerStanding for 12h on a tetrafluoroethylene mold until acetonitrile is completely volatilized, taking the prepared electrolyte membrane out of the mold, and recording the electrolyte membrane as PEO/LiTFSI/m-SEP@AlPO, wherein the thickness of the electrolyte membrane is about 70-80 mu m 4 10。
Example 9
Preparation of a composite polymer electrolyte membrane:
0.075g (15%) of the modified coated sepiolite fiber prepared in example 6 was weighed, dispersed in 20mL of acetonitrile solution, ultrasonically oscillated for 0.5h, transferred to a glove box and continuously stirred for 1h, then 0.16g of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), 0.5g (n (EO): n (Li) of polyethylene oxide (PEO) were weighed + ) =20: 1) Adding the mixture into the solution, and stirring for 5 hours to form uniform glue solution; pouring the obtained glue solution into a polytetrafluoroethylene mould, standing for 12h until acetonitrile is completely volatilized, taking down the prepared electrolyte membrane from the mould, and recording the thickness of the electrolyte membrane as PEO/LiTFSI/m-SEP@AlPO of about 70-80 mu m 4 15。
Example 10
Preparation of a composite polymer electrolyte membrane:
0.1g (20%) of the modified coated sepiolite fiber prepared in example 6 was weighed and dispersed in 20mL of acetonitrile solution, after shaking ultrasonically for 0.5h, transferred into a glove box and stirred continuously for 1h, then 0.16g of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), 0.5g of polyethylene oxide (PEO) and (n (EO): n (Li) + ) =20: 1) Adding the mixture into the solution, and stirring for 5 hours to form uniform glue solution; pouring the obtained glue solution into a polytetrafluoroethylene mould, standing for 12h until acetonitrile is completely volatilized, taking down the prepared electrolyte membrane from the mould, and recording the thickness of the electrolyte membrane as PEO/LiTFSI/m-SEP@AlPO of about 70-80 mu m 4 20。
Comparative example 1
Preparation of PEO film:
weighing 0.5g of polyethylene oxide (PEO), adding into 20mL of acetonitrile, and stirring for 5 hours in a glove box to form uniform glue solution; pouring the obtained glue solution into a polytetrafluoroethylene mould, standing for 12 hours until acetonitrile is completely volatilized, taking down the prepared electrolyte membrane from the mould, and placing the electrolyte membrane into a sealing bag and placing the sealing bag into a glove box for standby.
Comparative example 2
Preparation of PEO/LiTFSI composite film:
weighing 0.16g of lithium bistrifluoromethane sulfonyl imide (LiTFSI), 0.5g of polyethylene oxide (PEO) (n (EO): n (Li) + ) =20: 1) Adding the mixture into 20mL of acetonitrile, and stirring the mixture in a glove box for 5 hours to form uniform glue solution; pouring the obtained glue solution into a polytetrafluoroethylene mould, standing for 12 hours until acetonitrile is completely volatilized, and taking down the prepared electrolyte membrane from the mould, wherein the thickness is about 70-80 mu m.
The electrolyte membranes prepared in examples 7 to 10 and comparative example 2 were assembled into a button cell:
and (5) filling the electrolyte membrane into a sealing bag by using a manual sheet punching machine, and placing the electrolyte membrane into a glove box for standby. In a glove box, the positive electrode shell is horizontally placed on an insulating table top, the positive electrode plate is placed on the upper layer of the positive electrode shell, the electrolyte membrane is placed on the positive electrode plate, the metal lithium sheet is placed on the electrolyte membrane, and then the steel sheet and the spring piece are sequentially placed, and finally the negative electrode shell is covered. And testing the surface of the battery by using a paper towel , finally clamping the positive electrode of the battery upwards into a die of a battery sealing machine by using tweezers, adjusting the pressure to 900Pa, pressing for 5 seconds, and clamping the assembled battery out by using the tweezers to obtain the CR2032 full battery. And simultaneously, placing the cut electrolyte membrane between gaskets, packaging by using anode and cathode shells to obtain a blocked battery, and storing the assembled battery in a glove box for later use. And carrying out electrochemical performance, charge and discharge characterization test on the assembled blocking battery and the full battery.
In the examples and comparative examples in the preparation process of the composite polymer electrolyte membrane and the button cell thereof, the positive electrode material of the lithium ion battery is lithium iron phosphate (LiFePO) 4 ) The assembly sequence is as follows: negative electrode shell/elastic sheet/stainless steel sheet/lithium sheet/polyoxyethylene-based solid electrolyte/LiFePO 4 Positive electrode case.
Ion conductivity was tested by ac impedance method: performing alternating current impedance testing at 60 ℃ by using an electrochemical workstation; the ion conductivity σ of the polyoxyethylene-based solid electrolyte was calculated by testing the resulting ac impedance spectrum using the formula σ=t/RA. Wherein t is the thickness of the electrolyte membrane, R is the resistance value of the electrolyte membrane, and A is the cross-sectional area of the electrolyte membrane.
FIG. 5 is a graph of pure PEO film in comparative example 1, PEO/LiTFSI composite film in comparative example 2, PEO/LiTFSI/m-SEP@AlPO in examples 7-10 4 XRD spectrum and DSC curve of the composite electrolyte membrane are shown in fig. 5, where (a) is the XRD spectrum and (b) is the DSC curve. As can be seen from fig. 5 (a), PEO molecular chains are arranged in a spiral form to form a single crystal, and PEO characteristic peaks of pure PEO and a lithium salt film are substantially consistent, and are present at 2θ=19°,23 °, where 19 ° corresponds to the (120) crystal plane, 23 ° corresponds to the (032) and (112) crystal planes, which indicates that the PEO structure is unchanged. By comparing PEO/LiTFSI with different m-SEP@AlPO 4 The XRD pattern of the electrolyte membrane with the content can be found that stronger sepiolite characteristic diffraction peaks appear at 2 theta = 10.3 degrees, 11.5 degrees, 28.3 degrees and 30.8 degrees after the inorganic filler is added, and the XRD pattern is the main component Mg of the sepiolite 4 Si 6 O 15 (OH) 2 ·6H 2 O diffraction peaks associated with m-sep@alpo 4 The content is increased to be enhanced. Meanwhile, it can be found that with m-sep@alpo at 2θ=19°,23° 4 The characteristic peak here decays with increasing loading, which indicates that m-SEP@AlPO 4 Interaction with PEO reduces the peak intensity characteristic of PEO, and m-SEP@AlPO is additionally added 4 The increase in relative content does not cause a significant change in the peak position characteristic of PEO. In conclusion, m-SEP@AlPO 4 The introduction of (a) significantly alters the crystallization characteristics of PEO, which may lead to changes in the physicochemical properties of the film.
FIG. 5 (b) and Table 1 are respectively different m-SEP@AlPO 4 Content PEO/LiTFSI/m-SEP@AlPO 4 DSC curves and data for composite electrolyte membranes. As can be seen from FIG. 5 (b), the glass transition temperature of each composite film was about-50℃and the melting temperature was about 60 ℃; the difference between the composite film with the lithium salt added and the composite film without the lithium salt added is obvious. Adding m-SEP@AlPO 4 The melting temperature of the composite film is partially reduced, and the melting temperature is partially reduced along with m-SEP@AlPO 4 The melting temperature does not change much with increasing content. As can be seen from the crystallinity data in Table 1, when m-SEP@AlPO 4 When the addition content is 10%, m-SEP@AlPO 4 The inhibition of crystallization of the composite film is most remarkable. m-SEP@AlPO 4 The addition of the catalyst plays a certain role in inhibiting the crystallization of the composite film.
TABLE 1 DSC data for composite Polymer electrolyte separator
Fig. 6 and table 2 show the ac impedance spectra and the ionic conductivity of the electrolyte membranes prepared in examples 7 to 10 and comparative example 2 at 60 ℃, and fig. 6 (a) shows the ac impedance spectrum of a blocked cell and (b) shows the ac impedance spectrum of a full cell. As can be seen from FIG. 6 (a) and Table 2, different amounts of m-SEP@AlPO are added 4 The impedance value of the post-blocking battery tends to decrease within a certain range, thereby improving the ion conductivity. By comparing with PEO/LiTFSI, it is not difficult to see that the ionic conductivity of the composite electrolyte film is effectively improved after the inorganic filler is added. When m-SEP@AlPO 4 When the addition amount of (2) is increased to 10%, the ionic conductivity of the composite electrolyte membrane is maximized. In addition, from a full cell impedance spectroscopy analysis of PEO composite membrane assembly in FIG. 6 (b) and Table 2, it was found that m-SEP@AlPO was added 4 After that, the overall impedance value of the full cell has a tendency to decrease, and the ionic conductivity is improved compared to PEO/LiTFSI, which is consistent with the conclusion drawn from a blocked cell. It can be seen that the addition of m-SEP@AlPO 4 And then effectively improves the ion conductivity of the composite electrolyte film. The increase of the content of the coated sepiolite fiber in a certain range is beneficial to reducing the impedance of the composite electrolyte membrane, so that the ionic conductivity is improved, the resistance of lithium ion transmission in the electrolyte is effectively reduced, and the internal resistance of the battery is reduced.
TABLE 2PEO/LiTFSI/m-SEP@AlPO 4 Blocking cell impedance and ion conductivity
Constant current charge and discharge cycle tests were performed on CR2032 coin cells (sequentially designated as cells 1 to 5) assembled with electrolyte membranes prepared in examples 7 to 10 and comparative example 2, with a discharge rate of 0.2C, and the test results are shown in table 3. As shown in Table 3, the lithium ion battery prepared by the solid state electrolyte of polyethylene oxide provided by the invention has higher initial capacity, high charge and discharge efficiency and better cycle performance.
Table 3 results of constant current charge and discharge cycle test of the batteries prepared in examples 7 to 10 and comparative example 2
Fig. 7 and table 4 are microcalorimeter curves and values for the PEO electrolyte membranes prepared in examples 7 to 10 and comparative examples 1 to 2. As can be seen from FIG. 7, the Peak Heat Release Rate (PHRR) of the PEO composite membrane after the addition of lithium salt and m-SEP@AlPO 4 There was a significant decrease in Total Heat Release (THR) with lithium salt and m-SEP@AlPO 4 The addition showed some decrease, indicating that the coated sepiolite fibers improved the flame retardancy of PEO, and the peak heat release rate Temperature (TPHRR) was measured at the addition of lithium salt and m-SEP@AlPO 4 The flame retardant properties of the PEO film are improved by a part of the improvement, 5% and 10% of the flame retardant properties are effective, but with m-SEP@AlPO 4 The flame retardant property of the electrolyte membrane is reduced by increasing the addition amount, which indicates that the proper addition of m-SEP@AlPO 4 Is favorable for improving the flame retardant property of the electrolyte membrane and provides a new thought and theoretical basis for the high-safety composite polymer electrolyte membrane.
TABLE 4 micro calorimetric data for electrolyte membranes of examples 7 to 10 and comparative examples 1 to 2
FIG. 8 is a PEO/LiTFSI electrolyte membrane prepared in comparative example 2 and PEO/LiTFSI/m-SEP@AlPO prepared in example 8 4 10 SEM photograph of electrolyte membrane, (a) in FIG. 8 is SEM photograph of PEO/LiTFSI electrolyte membrane, (b) is PEO/LiTFSI/m-SEP@AlPO 4 SEM photograph of 10 electrolyte film, (c) PEO/LiTFSI/m-SEP@AlPO 4 10 cross-sectional photographs of electrolyte membranes. As can be seen from FIGS. 8 (a) and (b), the PEO/LiTFSI electrolyte membrane was smooth and relatively uniform in surface, and 10% of m-SEP@AlPO was added 4 After that, fibrous sepiolite appears on the surface of the electrolyte membrane, and the distribution is more uniform, and at the same time, a more uniform and flat surface is also presented. It can also be seen from fig. 8 (c) that the electrolyte membrane interface is uniform and the electrolyte membrane is prepared to have a thickness of about 70 μm.
From the above examples, it can be seen that the solid electrolyte membrane of polyethylene oxide polymer prepared from the modified sepiolite fiber provided by the invention has good electrochemical performance and flame retardant property, and high safety.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (10)

1. The preparation method of the modified sepiolite fiber is characterized by comprising the following steps of:
mixing sepiolite fiber, aluminum hydroxide, phosphoric acid and water, and carrying out heterogeneous precipitation reaction under the condition that the pH value is 4-5 to obtain aluminum phosphate coated sepiolite fiber;
mixing the aluminum phosphate coated sepiolite fiber, calcium stearate and an alcohol solvent for surface modification reaction to obtain the modified sepiolite fiber.
2. The preparation method according to claim 1, wherein the mass ratio of sepiolite fiber, aluminum hydroxide and phosphoric acid is (4 to 10): (0.5-1): (5-15).
3. The preparation method according to claim 1 or 2, wherein the heterogeneous precipitation reaction is specifically performed by:
mixing sepiolite fibers with water to obtain sepiolite fiber dispersion;
dropwise adding hydrochloric acid into the sepiolite fiber dispersion liquid to adjust the pH value to 2-3, so as to obtain acidified sepiolite fiber dispersion liquid;
mixing aluminum hydroxide, phosphoric acid and water, and adding the obtained mixed solution to the acidified sepiolite fiber dispersion; then ammonia water is added dropwise, and heterogeneous precipitation reaction is carried out under the condition that the pH value is 4-5.
4. The method according to claim 3, wherein the heterogeneous precipitation reaction is carried out for 30 to 50 minutes; the heterogeneous reaction is carried out under the condition of stirring, and the stirring speed is 800-1000 r/min.
5. The preparation method according to claim 1, wherein the mass ratio of the aluminum phosphate coated sepiolite fiber to the calcium stearate is (4-5): (0.02-0.1).
6. The method according to claim 1 or 5, wherein the surface modification reaction is carried out at a temperature of 70 to 80 ℃ for 30 to 50 minutes; the surface modification reaction is carried out under the condition of stirring, and the stirring speed is 500-800 r/min.
7. The modified sepiolite fiber prepared by the preparation method of any one of claims 1 to 6, wherein the modified sepiolite fiber is a calcium stearate modified coated sepiolite fiber, and the coated sepiolite fiber is an aluminum phosphate coated sepiolite fiber.
8. A flame retardant composite polymer solid electrolyte membrane, characterized in that the components comprise modified sepiolite fibers, lithium salt and polyethylene oxide, wherein the modified sepiolite fibers are the modified sepiolite fibers of claim 7;
the ratio of EO mole number in the polyethylene oxide to lithium ion mole number in the lithium salt is 16-20: 0.5 to 1; the mass of the modified sepiolite fiber is 1-20% of the mass of the polyethylene oxide.
9. The method for preparing a flame retardant composite polymer solid electrolyte membrane according to claim 8, comprising the steps of:
mixing the modified sepiolite fiber, lithium salt, polyethylene oxide and an organic solvent to obtain a glue solution;
and (3) forming a film from the glue solution to obtain the flame-retardant composite polymer electrolyte membrane.
10. The application of the flame-retardant composite polymer solid electrolyte membrane of claim 8 or the flame-retardant composite polymer solid electrolyte membrane prepared by the preparation method of claim 9 in lithium ion batteries.
CN202310727762.0A 2023-06-19 2023-06-19 Modified sepiolite fiber and preparation method thereof, flame-retardant composite polymer solid electrolyte membrane and preparation method and application thereof Pending CN116695429A (en)

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