CN114927830A - Folded MXene modified diaphragm for lithium ion battery and preparation method thereof - Google Patents

Folded MXene modified diaphragm for lithium ion battery and preparation method thereof Download PDF

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CN114927830A
CN114927830A CN202210589891.3A CN202210589891A CN114927830A CN 114927830 A CN114927830 A CN 114927830A CN 202210589891 A CN202210589891 A CN 202210589891A CN 114927830 A CN114927830 A CN 114927830A
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mxene
folded
diaphragm
pmma
ion battery
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CN114927830B (en
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李帆
张立斌
赵海玉
沈亚定
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Jiangsu Housheng New Energy Technology Co Ltd
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Jiangsu Housheng New Energy Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Composite Materials (AREA)
  • Inorganic Chemistry (AREA)
  • Cell Separators (AREA)

Abstract

The invention provides a folded MXene modified diaphragm for a lithium ion battery and a preparation method thereof, wherein the folded MXene @ Mg (OH) 2 The introduction of the nanosheets greatly improves the mechanical strength and heat resistance of the diaphragm, greatly improves the adhesion of the diaphragm to a pole piece and the wettability of electrolyte, and greatly improves the problem of powder shedding of the PMMA coating in the processes of earlier coating and later cell manufacturing; the wetting agent is branched dodecyl (poly-oxygen isopropene) 8 Sodium sulfate, limiting the concentration of wetting agent in the coating layer to 2.5X 10 ‑5 ‑1.5×10 ‑3 The mol/L improves the mechanical strength of the diaphragm, improves the infiltration viscosity of the base film and prolongs the effective service life of the diaphragm; grafting hyperbranched by adopting a solution blending methodThe preparation method comprises the steps of mixing a multi-arm polymer, an ionic liquid block copolymer and PMMA powder, mixing the PMMA powder, and limiting the mass ratio of the hyperbranched grafted multi-arm polymer, the ionic liquid block copolymer and the PMMA powder to greatly improve the ionic conductivity and the heat shrinkage of the diaphragm, so that the heat resistance of the diaphragm is further improved.

Description

Folded MXene modified diaphragm for lithium ion battery and preparation method thereof
Technical Field
The invention relates to the field of battery diaphragms, in particular to a folded MXene modified diaphragm for a lithium ion battery and a preparation method thereof.
Background
With the rapid development of new energy industries and the vigorous development of lithium batteries, the lithium batteries have the advantages of high energy density and long cycle life, so that the lithium batteries are widely applied to various energy applications. The diaphragm in the lithium battery can effectively prevent the danger of short circuit caused by the contact of the positive electrode and the negative electrode, so that the safety and the usability of the lithium battery are improved, and the performance of the lithium battery diaphragm is required to be higher.
The most widely used lithium battery separator at present is a polyolefin separator, however, the use of the polyolefin separator is frequently accompanied by the following problems: because the single polyolefin diaphragm electrophilic electrolyte has insufficient performance and poor bonding performance to an electrode plate, the lithium battery has poor cycle performance, poor battery hardness, low thermal stability and the like, and the development path of the lithium battery to a super-thin battery is limited; the single polyolefin diaphragm has poor mechanical strength and puncture resistance, and is easy to puncture and form thermal runaway; the melting point of the polyolefin diaphragm is low, and the diaphragm is easy to break when thermal runaway occurs, so that the thermal runaway is aggravated, and the battery is burnt and even exploded.
In the existing market, a single side or double sides of a polyolefin diaphragm are generally coated with a water system PVDF glue layer to solve the problems of poor adhesion of the polyolefin diaphragm to a pole piece and poor electrolyte wettability, but the problem of easy falling exists at the same time; the problem that the polyolefin diaphragm is poor in mechanical performance and heat resistance is solved by coating a high-temperature-resistant ceramic coating on one side or two sides of the polyolefin diaphragm, although the diaphragm can be closed to 150 ℃, the closed pore temperature of 150 ℃ also has the risk of short circuit or spontaneous combustion at high temperature, and therefore, the research focus at present is how to further improve the heat resistance of the diaphragm, reduce the risk of diaphragm rupture and improve the safety of a lithium battery.
Disclosure of Invention
The invention aims to provide a folded MXene modified diaphragm for a lithium ion battery and a preparation method thereof, and aims to solve the problems in the prior art.
In order to solve the technical problems, the invention provides the following technical scheme:
a folded MXene modified diaphragm for a lithium ion battery comprises a base film and a coating layer formed by coating on the surface of the base film; the coating layer comprises the following components in parts by mass: 0.6 to 1.6 percent of dispersant, 15 to 25 percent of PMMA powder, 13 to 23 percent of folded MXene @ Mg (OH) 2 Nano-sheets, 7-10% of thickening agent, 2-4% of binder, 0.2-0.5% of wetting agent, 0.05-0.2% of defoaming agent and the balance of ultrapure water.
According to the invention, MXene nanosheets are selected as coating materials and added into the slurry component, wherein the folded MXene nanosheets have good high temperature resistance and heat conductivity, and are beneficial to improving the heat resistance of the coating, so that the heat resistance of the diaphragm is improved;
further, the preparation of the folded MXene nanosheet comprises the following steps:
(1) mixing titanium hydride, titanium carbide and aluminum powder, ball-milling for 3-4h, calcining for 2h at 1440 ℃ and 1450 ℃ in an argon atmosphere, cooling, ball-milling for 2-3h, and sieving to obtain powdered MAX;
(2) stirring powdered MAX, lithium fluoride and hydrochloric acid at 25-30 ℃ for 22-24h, centrifuging, washing with water until the pH value is more than 6, and freeze-drying to obtain a three-dimensional product MXene;
(3) carrying out ultrasonic treatment on three-dimensional MXene and deionized water for 180min under the argon atmosphere, centrifuging to obtain supernatant, and carrying out freeze drying to obtain stripped MXene nanosheets;
(4) mixing the stripped MXene nanosheet with hydrazine hydrate, transferring the MXene nanosheet into a stainless steel high-pressure kettle with a PTFE lining, keeping the temperature for 5-6h at 90-95 ℃, cooling to 18-25 ℃, filtering, washing with absolute ethyl alcohol and deionized water, placing the mixture in a vacuum environment at 80 ℃ for drying for 24h, and controlling the vacuum degree of vacuum drying at 0.08Mpa to obtain the folded MXene nanosheet.
Further, the mass volume ratio of the powdered MAX to the lithium fluoride to the hydrochloric acid is 1g:1g:20 mL; the mass-volume ratio of the three-dimensional MXene to the deionized water is 1g:15 mL.
Further, the base film is a polyolefin diaphragm; the dispersing agent is aliphatic amide dispersing agent, the thickening agent is sodium carboxymethylcellulose thickening agent, the adhesive is polyacrylic acid adhesive, and the defoaming agent is polyether defoaming agent; the wetting agent is alkyl sulfate wetting agent.
Wherein the fold MXene @ Mg (OH) 2 Due to the introduction of the nanosheets, the mechanical strength of the diaphragm is greatly improved due to the excellent performance of the nanosheets; and the folded MXene nanosheets, PMMA and Mg (OH) with flame retardant property 2 The three components synergistically improve the heat resistance of the diaphragm;
further, wrinkles MXene @ Mg (OH) 2 The preparation of the nano-sheet comprises the following steps:
dissolving magnesium sulfate powder in ultrapure water to prepare a magnesium sulfate solution, adding folded MXene nanosheets under the stirring condition, ultrasonically dispersing for 1-2h, heating to 70-75 ℃, adding 2mol/L ammonia water at the flow rate of 55ml/min, stopping reaction when the pH value is 8-10, filtering, sequentially washing with absolute ethyl alcohol and ultrapure water, and vacuum drying for 10-12h to obtain folded MXene @ Mg (OH) 2 A nanosheet.
Furthermore, the molar concentration and mass ratio of the magnesium sulfate solution, the ammonia water and the folded MXene nanosheets is 1.85mol/L:2mol/L:2.36 g.
MXene@Mg(OH) 2 The fold structure on the surface of the nano sheet enables PMMA particles to be firmly adhered to MXene @ Mg (OH) 2 The surface of the nanosheet greatly improves the adhesion of the diaphragm to the pole piece and the wettability of electrolyte, and greatly improves the problem of powder removal of a PMMA coating in the processes of early coating and later cell manufacturing;
and wrinkles MXene @ Mg (OH) 2 The introduction of the nano sheet is from Mg (OH) 2 The crystal water is decomposed by heat and absorbs heat to form a carbonized layer; when the temperature rises to the decomposition temperature, Mg (OH) 2 The water vapor is decomposed and released, latent heat is absorbed, and the concentration of oxygen and combustible gas near the surface of a combustion object is diluted, so that the surface combustion is difficult to carry out; the carbonized layer formed on the surface can prevent oxygen and heat from entering, and meanwhile, the magnesium oxide generated by decomposition of the carbonized layer is a good refractory material, has good high-temperature resistance and heat conductivity, and can improve the capability of the material for resisting open fire.
A preparation method of a folded MXene modified diaphragm for a lithium ion battery comprises the following steps:
s1: the dispersing agent, the PMMA powder body,folded MXene @ Mg (OH) 2 Premixing the nano-sheets and ultrapure water for 10-30min at the rotation speed of 100-300 rpm; adding the thickening agent and continuing stirring for 20-60min at the rotation speed of 200-500 rpm; adding the adhesive and continuously stirring for 30-50min at the rotation speed of 350-500 rpm; adding a wetting agent, stirring the defoaming agent for 20-40min at the rotation speed of 400-600 rpm; filtering to remove iron to obtain PMMA-coated folded MXene @ Mg (OH) 2 Coating slurry of nanosheets;
s2: and (3) coating the prepared coating slurry on two sides of a base film by adopting a micro gravure roller coating process, drying at 70-75 ℃, and rolling to obtain the folded MXene modified diaphragm for the lithium ion battery.
Branched dodecyl (Poly-O-isopropene) 8 Sodium sulfate (G-C) 12 PO 8 S) is provided by Sasol, south Africa;
wetting agent is branched dodecyl (poly-oxygen isopropene) 8 Sodium sulfate (G-C) 12 PO 8 S), inserting a section of polyoxypropylene chain (PO) between hydrophobic alkyl and hydrophilic polar groups, wherein the PO groups can cause the molecules of the surface wetting agent to present an obvious football shape on a gas-liquid interface, so that the surface wetting agent has excellent interface characteristics, polar groups and non-polar groups are contained in the wetting agent, the polar groups and the non-polar groups can be adsorbed to the surface of the modified PMMA through polar interaction and hydrophobic interaction, and the modified PMMA is improved in wettability and ionic conductivity of the diaphragm through the interaction of adsorption modes such as hydrogen bonds, polar interaction, hydrophobic interaction and the like.
By limiting the concentration of wetting agent in the coating layer to 2.5X 10 -5 -1.5×10 -3 mol/L to further improve the ionic conductivity and heat resistance of the separator because the concentration is 1X 10 -7 -2.5×10 -5 mol/L, along with the increase of concentration, the adsorption capacity of wetting agent molecules on a gas-liquid interface and a solid-liquid interface is increased, the influence on contact angles is mutually offset, so that the change of the contact angles is small, the molecules are adsorbed on the solid-liquid interface by virtue of an ion head, and a hydrophobic tail chain points to a solution; when the concentration is 2.5X 10 -5 -1.5×10 -3 mol/L, the adsorption capacity of the wetting agent molecules on a gas-liquid interface tends to be saturated, so that the contact angle is reduced sharply, and at the moment, the wetting agent molecules interact through hydrophobic interactionThe wetting agent is adsorbed on the surface of PMMA to form an aggregate on a solid-liquid interface, so that the steric hindrance of the wetting agent is reduced by limiting the concentration and the branching degree of the wetting agent, the aggregate is formed, the solid-liquid interface tension is reduced, and the hydrophilic modification capability of the wetting agent is enhanced, so that the ionic conductivity of the diaphragm is greatly improved, and the heat resistance of the diaphragm is improved.
Further, the PMMA powder is modified PMMA, and the preparation method comprises the following steps:
1) under the argon atmosphere, mixing and stirring 2, 2-bipyridyl, cuprous chloride, hyperbranched poly-p-chloromethylstyrene, methyl methacrylate and toluene, and reacting at 65-68 ℃ for 8-9h to obtain hyperbranched grafted multi-arm polymer;
2) under the protection of argon, mixing and stirring S-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate, azodiisobutyronitrile, methyl methacrylate and toluene, and reacting at 65-68 ℃ for 4-5h to obtain trithiocarbonate end-capped polymethyl methacrylate;
3) under the nitrogen environment, mixing and stirring polymethyl methacrylate terminated by trithiocarbonate end groups, azodiisobutyronitrile, vinyl benzyl chloride and toluene, and reacting at 65-68 ℃ for 16-18h to obtain an ionic liquid block copolymer;
4) and mixing and stirring the hyperbranched grafted multi-arm polymer, the ionic liquid block copolymer, PMMA powder and tetrahydrofuran to obtain the modified PMMA.
Further, in the step 1), the molar mass ratio of the 2, 2-bipyridine to the methyl methacrylate to the cuprous chloride to the hyperbranched poly-p-chloromethyl styrene is 0.8 mmol/0.04 mol/0.04 g/0.5 g, and the number average molecular weight of the hyperbranched poly-p-chloromethyl styrene is 2500 g/mol; in the step 2), the molar mass ratio of azodiisobutyronitrile to methyl methacrylate to S-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate is 2mmol:0.07mol:0.37 g; in the step 3), the molar mass ratio of the azodiisobutyronitrile to the trithiocarbonate end-capped polymethyl methacrylate to the vinylbenzyl chloride is 0.011mmol:0.6g:1.54 g.
Further, the mass ratio of the hyperbranched grafted multi-arm polymer, the ionic liquid block copolymer and the PMMA powder in the step 4) is 1 (1-3) to 4.
In the invention, the hyperbranched grafted multi-arm polymer and the ionic liquid block copolymer are blended with PMMA powder by adopting a solution blending method, so that the ionic conductivity of the diaphragm is synergistically improved; the invention modifies the surface of hyperbranched poly (chloromethyl styrene), and grafts PMMA to prepare hyperbranched grafted multi-arm polymer; then preparing a functional block copolymer by using a RAFT (reversible addition-fragmentation chain transfer) method, and then preparing an ionic liquid block copolymer;
the ionic liquid block copolymer polymerized ionic liquid containing both the polymerized ionic liquid chain segment and the general polymer chain segment is prepared to greatly improve the mechanical property of the diaphragm, but the ionic conduction property of the ionic liquid block copolymer can be reduced only by doping the non-conductive general polymer chain segment; therefore, the ionic liquid block copolymer can be modified by utilizing the three-dimensional spherical space structure of the hyperbranched polymer, molecular chains are not easy to tangle, and the ionic liquid block copolymer also has the advantages of high solubility, low melt viscosity, good fluidity and the like, and a polymerized ionic liquid chain segment or an ionic group is introduced into the hyperbranched polymer in a blending mode through a large number of active end groups on the surface of the hyperbranched polymer, so that the migration rate of ions is improved.
The mass ratio of the hyperbranched grafted multi-arm polymer to the ionic liquid block copolymer to the PMMA powder is limited, so that the thermal shrinkage of the diaphragm is improved while the ionic conductivity is greatly improved, and the heat resistance of the diaphragm is further improved.
The invention has the beneficial effects that:
the invention provides a folded MXene modified diaphragm for a lithium ion battery and a preparation method thereof, and the lithium ion battery diaphragm with good heat resistance, high flame retardance and high safety is prepared by component limitation and process adjustment;
wherein the fold MXene @ Mg (OH) 2 Due to the introduction of the nanosheets, the mechanical strength of the diaphragm is greatly improved due to the excellent performance of the nanosheets; and the folded MXene nanosheets, PMMA and Mg (OH) with flame retardant property 2 The three components synergistically improve the heat resistance of the diaphragm; MXene @ Mg (OH) 2 Fold knot on nanosheet surfaceSo that PMMA particles can be relatively firmly adhered to MXene @ Mg (OH) 2 The surface of the nanosheet greatly improves the adhesion of the diaphragm to the pole piece and the wettability of electrolyte, and greatly improves the problem of powder removal of a PMMA coating in the processes of early coating and later cell manufacturing;
and fold MXene @ Mg (OH) 2 Incorporation of nanosheets from Mg (OH) 2 The crystal water is decomposed by heat and absorbs heat to form a carbonized layer; when the temperature rises to the decomposition temperature, Mg (OH) 2 The water vapor is decomposed and released, latent heat is absorbed, and the concentration of oxygen and combustible gas near the surface of a combustion object is diluted, so that the surface combustion is difficult to carry out; the carbonized layer formed on the surface prevents oxygen and heat from entering, and meanwhile, the magnesium oxide generated by decomposition of the carbonized layer is a good refractory material, has good high temperature resistance and heat conductivity, and can improve the capability of the material for resisting open fire;
the wetting agent is branched dodecyl (poly-oxygen isopropene) 8 Sodium sulfate, limiting the concentration of wetting agent in the coating layer to 2.5X 10 -5 -1.5×10 -3 The molecular weight of the wetting agent is absorbed on the surface of PMMA through hydrophobic interaction, an aggregate is formed on a solid-liquid interface, the tension of the solid-liquid interface is reduced, and the hydrophilic modification capacity of the wetting agent is enhanced, so that the ionic conductivity of the diaphragm is greatly improved, the mechanical strength of the diaphragm is improved, the infiltration viscosity of the diaphragm to a base film is improved, and the effective service life of the diaphragm is prolonged;
the hyperbranched grafted multi-arm polymer, the ionic liquid block copolymer and the PMMA powder are blended by adopting a solution blending method, and the PMMA powder is blended to synergistically improve the ionic conduction performance of the diaphragm; the invention modifies the surface of hyperbranched poly (chloromethyl styrene), and grafts PMMA to prepare hyperbranched grafted multi-arm polymer; preparing a functional block copolymer, and then preparing an ionic liquid block copolymer; the mass ratio of the hyperbranched grafted multi-arm polymer to the ionic liquid block copolymer to the PMMA powder is limited, so that the ionic conductivity is greatly improved, and the heat shrinkage of the diaphragm is improved, thereby further improving the heat resistance of the diaphragm.
Detailed Description
The technical solutions in the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
It should be noted that if directional indications such as up, down, left, right, front, and back … … are involved in the embodiment of the present invention, the directional indications are only used to explain a specific posture, such as a relative positional relationship between components, a motion situation, and the like, and if the specific posture changes, the directional indications also change accordingly. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
The technical solutions of the present invention are further described in detail with reference to specific examples, which should be understood that the following examples are only illustrative of the present invention and are not intended to limit the present invention.
Example 1
A preparation method of a folded MXene modified diaphragm for a lithium ion battery comprises the following steps:
s1: dispersing agent, PMMA powder, folded MXene @ Mg (OH) 2 Premixing the nano sheets and ultrapure water for 10min at the rotating speed of 300 rpm; adding the thickening agent, and continuously stirring for 20min at the rotating speed of 500 rpm; adding the binder and continuously stirring for 30min at the rotating speed of 500 rpm; adding a wetting agent and stirring the defoaming agent for 20min at the rotating speed of 600 rpm; filtering and removing iron to obtain PMMA-coated folds MXene @ Mg (OH) 2 Coating slurry of nanosheets;
the coating slurry comprises the following components in parts by mass: 0.6% of dispersant, 15% of PMMA powder, 13% of folded MXene @ Mg (OH) 2 Nanosheet, 7% of a thickening agent, 2% of a binder, 0.2% of a wetting agent,0.05 percent of defoaming agent and the balance of ultrapure water;
the base film is a polyolefin diaphragm; the dispersant is aliphatic amide, the thickener is sodium carboxymethylcellulose, the adhesive is polyacrylic acid, and the defoaming agent is a polyether defoaming agent; wetting agent is branched dodecyl (poly-oxygen isopropene) 8 Sodium sulfate, the concentration of the wetting agent in the coating layer is 2.5 x 10 -5 mol/L；
Fold MXene @ Mg (OH) 2 The preparation of the nanosheet comprises the following steps:
dissolving magnesium sulfate powder in ultrapure water to prepare 250ml of magnesium sulfate solution with the concentration of 1.85mol/L, adding 2.36g of folded MXene nanosheets under the stirring condition, ultrasonically dispersing for 1h, heating to 75 ℃, adding 2mol/L of ammonia water at the flow rate of 55ml/min, stopping reaction when the pH value is 8, filtering, sequentially washing with absolute ethyl alcohol and ultrapure water, and vacuum drying for 10h to obtain folded MXene @ Mg (OH) 2 A nanosheet.
The preparation method of the folded MXene nanosheet comprises the following steps:
(1) 7.1321g of titanium hydride, 17.3623g of titanium carbide and 4.6916g of aluminum powder are mixed and then ball-milled for 3h, calcined for 2h at 1440 ℃ in argon atmosphere, cooled and ball-milled for 2h, and sieved to obtain powdered MAX;
(2) powdered MAX1g, 1g of lithium fluoride and 20mL of 9M hydrochloric acid are stirred at 25 ℃ for 24 hours, washed by centrifugation until the pH value is 7, and freeze-dried to obtain a three-dimensional product MXene;
(3) carrying out ultrasonic treatment on three-dimensional MXene1g and 25mL of deionized water for 160min under the atmosphere of argon, centrifuging to obtain a supernatant, and carrying out freeze drying to obtain a stripped MXene nanosheet;
(4) mixing 1g of stripped MXene nanosheets with 20mL of 80% hydrazine hydrate, transferring the mixture into a stainless steel high-pressure kettle with a PTFE liner, keeping the mixture at 90 ℃ for 6h, cooling to 18 ℃, filtering, washing with absolute ethyl alcohol and deionized water, placing the mixture in a vacuum environment at 80 ℃ for 24h, and controlling the vacuum degree of vacuum drying at 0.08Mpa to obtain folded MXene nanosheets;
s2: and (3) coating the prepared coating slurry on two sides of the base film by adopting a micro gravure roller coating process, drying at 70 ℃, and rolling to obtain the folded MXene modified diaphragm for the lithium ion battery.
Example 2
A preparation method of a folded MXene modified diaphragm for a lithium ion battery comprises the following steps:
s1: dispersing agent, PMMA powder, folded MXene @ Mg (OH) 2 Premixing the nano sheets and ultrapure water for 20min at the rotation speed of 200 rpm; adding the thickening agent and continuing stirring for 40min at the rotating speed of 300 rpm; adding the binder and continuously stirring for 40min at the rotating speed of 400 rpm; adding a wetting agent and stirring a defoaming agent for 30min at the rotating speed of 500 rpm; filtering to remove iron to obtain PMMA-coated folded MXene @ Mg (OH) 2 Coating slurry of the nanosheets;
the coating slurry comprises the following components in parts by mass: 1.2 percent of dispersant, 20 percent of PMMA powder, 15 percent of folded MXene @ Mg (OH) 2 The nano-sheet, 9% of thickening agent, 3% of binder, 0.4% of wetting agent, 0.1% of defoaming agent and the balance of ultrapure water;
the base film is a polyolefin diaphragm; the dispersant is aliphatic amide, the thickener is sodium carboxymethylcellulose, the adhesive is polyacrylic acid, and the defoaming agent is a polyether defoaming agent; wetting agent is branched dodecyl (poly-oxygen isopropene) 8 Sodium sulfate, the concentration of the wetting agent in the coating layer being 5 x 10 -4 mol/L；
Folded MXene @ Mg (OH) 2 The preparation of the nano-sheet comprises the following steps:
dissolving magnesium sulfate powder in ultrapure water to prepare 250ml of magnesium sulfate solution with the concentration of 1.85mol/L, adding 2.36g of folded MXene nanosheets under the stirring condition, and performing ultrasonic dispersion 1. Heating to 72 ℃ for 5h, adding 2mol/L ammonia water at the flow rate of 55ml/min, stopping the reaction when the pH is 9, filtering, washing with absolute ethyl alcohol and ultrapure water in sequence, and drying in vacuum for 11h to obtain a folded MXene @ Mg (OH) 2 A nanosheet.
The preparation method of the folded MXene nanosheet comprises the following steps:
(1) 7.1321g of titanium hydride, 17.3623g of titanium carbide and 4.6916g of aluminum powder are mixed and then ball milled for 3.5h, the mixture is calcined for 2h at 1440 ℃ and 1450 ℃ in the argon atmosphere, the mixture is ball milled for 2.5h after being cooled, and the powder MAX is obtained after sieving;
(2) powdered MAX1g, 1g of lithium fluoride and 20mL of 9M hydrochloric acid are stirred for 23h at 28 ℃, washed by centrifugation until the pH is 7, and freeze-dried to obtain a three-dimensional product MXene;
(3) carrying out ultrasonic treatment on three-dimensional MXene1g and 25mL of deionized water for 170min under the atmosphere of argon, centrifuging to obtain a supernatant, and carrying out freeze drying to obtain a stripped MXene nanosheet;
(4) mixing 1g of peeled MXene nanosheet with 20mL of 80% hydrazine hydrate, transferring the mixture into a stainless steel high-pressure kettle with a PTFE liner, keeping the mixture at 92 ℃ for 5.5h, cooling to 20 ℃, filtering, washing with absolute ethyl alcohol and deionized water, placing the mixture in a vacuum environment at 80 ℃ for drying for 24h, and controlling the vacuum degree of vacuum drying at 0.08Mpa to obtain the folded MXene nanosheet;
s2: and (3) coating the prepared coating slurry on two sides of a base film by adopting a micro gravure roller coating process, drying at 73 ℃, and rolling to obtain the folded MXene modified diaphragm for the lithium ion battery.
Example 3
A preparation method of a folded MXene modified diaphragm for a lithium ion battery comprises the following steps:
s1: dispersing agent, PMMA powder, folded MXene @ Mg (OH) 2 Premixing the nano sheets and ultrapure water for 30min at the rotating speed of 100 rpm; adding the thickening agent, and continuously stirring for 60min at the rotating speed of 200 rpm; adding the binder, and continuously stirring for 50min at the rotation speed of 350 rpm; adding a wetting agent, stirring the defoaming agent for 40min at the rotating speed of 400 rpm; filtering and removing iron to obtain PMMA-coated folds MXene @ Mg (OH) 2 Coating slurry of the nanosheets;
the coating slurry comprises the following components in parts by mass: 1.6% of dispersant, 25% of PMMA powder, 23% of folded MXene @ Mg (OH) 2 Nanosheet, 10% of thickening agent, 4% of binder, 0.5% of wetting agent, 0.2% of defoaming agent and the balance of ultrapure water;
the base film is a polyolefin diaphragm; the dispersant is aliphatic amide, the thickener is sodium hydroxymethyl cellulose, the adhesive is polyacrylic acid, and the defoamer is a polyether defoamer; wetting agent is branched dodecyl (poly-oxygen isopropene) 8 Sodium sulfate, the concentration of the wetting agent in the coating layer being 1.5X 10 -3 mol/L；
Fold MXene @ Mg (OH) 2 The preparation of the nano-sheet comprises the following steps:
dissolving magnesium sulfate powder in ultrapure water to prepare 250ml of magnesium sulfate solution with the concentration of 1.85mol/L, adding 2.36g of folded MXene nanosheets under the stirring condition, ultrasonically dispersing for 2h, heating to 75 ℃, adding 2mol/L of ammonia water at the flow rate of 55ml/min, stopping reaction when the pH value is 10, filtering, sequentially washing with absolute ethyl alcohol and ultrapure water, and vacuum drying for 12h to obtain folded MXene @ Mg (OH) 2 A nanosheet;
the preparation method of the folded MXene nanosheet comprises the following steps:
(1) mixing 7.1321g of titanium hydride, 17.3623g of titanium carbide and 4.6916g of aluminum powder, then carrying out ball milling for 3-4h, calcining for 2h at 1450 ℃ in an argon atmosphere, cooling, then carrying out ball milling for 3h, and sieving to obtain powder MAX;
(2) powder MAX1g, lithium fluoride 1g and 9M hydrochloric acid 20mL are stirred at 30 ℃ for 22h, washed by centrifugal water until the pH value is 7, and freeze-dried to obtain a three-dimensional product MXene;
(3) carrying out ultrasonic treatment on three-dimensional MXene1g and 25mL of deionized water for 180min under the atmosphere of argon, centrifuging to obtain a supernatant, and carrying out freeze drying to obtain a stripped MXene nanosheet;
(4) mixing 1g of peeled MXene nanosheet with 20mL of 80% hydrazine hydrate, transferring the mixture into a stainless steel autoclave with a PTFE liner, keeping the mixture at 95 ℃ for 6h, cooling to 25 ℃, filtering, washing with absolute ethyl alcohol and deionized water, placing the mixture in a vacuum environment at 80 ℃ for drying for 24h, and controlling the vacuum degree of vacuum drying at 0.08MPa to obtain the folded MXene nanosheet;
s2: and (3) coating the prepared coating slurry on two sides of a base film by adopting a micro gravure roller coating process, drying at 75 ℃ and rolling to obtain the folded MXene modified diaphragm for the lithium ion battery.
Example 4
A preparation method of a folded MXene modified diaphragm for a lithium ion battery comprises the following steps:
s1: premixing dispersing agent, PMMA powder, folded MXene @ Mg (OH)2 nanosheets and ultrapure water for 10min at the rotating speed of 300 rpm; adding thickener, stirring for 20min at 500rpm; adding the binder and continuously stirring for 30min at the rotating speed of 500 rpm; adding a wetting agent and stirring a defoaming agent for 20min at the rotating speed of 600 rpm; filtering and removing iron to obtain PMMA-coated folds MXene @ Mg (OH) 2 Coating slurry of the nanosheets;
the coating slurry comprises the following components in parts by mass: 0.6% of dispersing agent, 15% of PMMA powder, 13% of folded MXene @ Mg (OH)2 nanosheet, 7% of thickening agent, 2% of binder, 0.2% of wetting agent, 0.05% of defoaming agent and the balance of ultrapure water;
the base film is a polyolefin diaphragm; the dispersant is aliphatic amide, the thickener is sodium carboxymethylcellulose, the adhesive is polyacrylic acid, and the defoaming agent is a polyether defoaming agent; the wetting agent is branched dodecyl (poly-oxygen isopropene) 8 Sodium sulfate, the concentration of the wetting agent in the coating layer is 2.5 x 10 -5 mol/L；
The preparation of the folded MXene @ Mg (OH)2 nanosheet comprises the following steps:
dissolving magnesium sulfate powder in ultrapure water to prepare 250ml of magnesium sulfate solution with the concentration of 1.85mol/L, adding 2.36g of folded MXene nanosheets under the stirring condition, ultrasonically dispersing for 1h, heating to 75 ℃, adding 2mol/L of ammonia water at the flow rate of 55ml/min, stopping reaction when the pH value is 8, filtering, sequentially washing with absolute ethyl alcohol and ultrapure water, and vacuum drying for 10h to obtain folded MXene @ Mg (OH) 2 A nanosheet.
The preparation method of the folded MXene nanosheet comprises the following steps:
(1) 7.1321g of titanium hydride, 17.3623g of titanium carbide and 4.6916g of aluminum powder are mixed and then ball-milled for 3h, calcined for 2h at 1440 ℃ in argon atmosphere, cooled and ball-milled for 2h, and sieved to obtain powdered MAX;
(2) powdered MAX1g, 1g of lithium fluoride and 20mL of 9M hydrochloric acid are stirred for 24 hours at 25 ℃, washed by centrifugation until the pH value is 7, and freeze-dried to obtain a three-dimensional product MXene;
(3) carrying out ultrasonic treatment on three-dimensional MXene1g and 25mL of deionized water for 160min under the atmosphere of argon, centrifuging to obtain a supernatant, and carrying out freeze drying to obtain a stripped MXene nanosheet;
(4) mixing 1g of peeled MXene nanosheet with 20mL of 80% hydrazine hydrate, transferring the mixture into a stainless steel autoclave with a PTFE liner, keeping the mixture at 90 ℃ for 6h, cooling to 18 ℃, filtering, washing with absolute ethyl alcohol and deionized water, placing the mixture in a vacuum environment at 80 ℃ for drying for 24h, and controlling the vacuum degree of vacuum drying at 0.08Mpa to obtain the folded MXene nanosheet;
s2: coating the prepared coating slurry on two sides of a base film by adopting a micro gravure roller coating process, drying at 70 ℃, and then rolling to obtain a folded MXene modified diaphragm for the lithium ion battery;
the PMMA powder is modified PMMA, and the preparation method comprises the following steps:
1) under the argon atmosphere, mixing and stirring 0.8mmol of 2, 2-bipyridyl, 0.04g of cuprous chloride, 0.5g of hyperbranched poly-p-chloromethyl styrene (with the number average molecular weight of 2500g/mol), 0.04mol of methyl methacrylate and 10mL of toluene, and reacting for 9 hours at 65 ℃ to obtain the hyperbranched grafted multi-arm polymer;
2) under the protection of argon, 0.37g of S-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate, 2mmol of azobisisobutyronitrile, 0.07mol of methyl methacrylate and 9mL of toluene are mixed and stirred, and reacted for 5 hours at 65 ℃ to obtain trithiocarbonate end-capped polymethyl methacrylate;
3) under the nitrogen environment, mixing and stirring 0.6g of trithiocarbonate end-capped polymethyl methacrylate, 0.011mmol of azobisisobutyronitrile, 1.54g of vinyl benzyl chloride and 6mL of toluene, and reacting at 65 ℃ for 18h to obtain an ionic liquid block copolymer;
4) 5g of hyperbranched grafted multi-arm polymer, 5g of ionic liquid block copolymer, 20g of PMMA powder and 10mL of tetrahydrofuran are mixed and stirred to obtain the modified PMMA.
Example 5
A preparation method of a folded MXene modified diaphragm for a lithium ion battery comprises the following steps:
s1: dispersing agent, PMMA powder, folded MXene @ Mg (OH) 2 Premixing the nano sheets and ultrapure water for 20min at the rotation speed of 200 rpm; adding the thickening agent and continuously stirring for 40min at the rotating speed of 300 rpm; adding the binder and continuously stirring for 40min at the rotating speed of 400 rpm; adding a wetting agent and stirring the defoaming agent for 30min at the rotating speed of 500 rpm; filtrationObtaining PMMA-coated folds MXene @ Mg (OH) after iron removal 2 Coating slurry of the nanosheets;
the coating slurry comprises the following components in parts by mass: 1.2% of dispersant, 20% of PMMA powder, 15% of folded MXene @ Mg (OH) 2 Nanosheet, 9% of thickening agent, 3% of binder, 0.4% of wetting agent, 0.1% of defoaming agent and the balance of ultrapure water;
the base film is a polyolefin diaphragm; the dispersant is aliphatic amide, the thickener is sodium hydroxymethyl cellulose, the adhesive is polyacrylic acid, and the defoamer is a polyether defoamer; wetting agent is branched dodecyl (poly-oxygen isopropene) 8 Sodium sulfate, the concentration of the wetting agent in the coating layer being 5 x 10 -4 mol/L；
Fold MXene @ Mg (OH) 2 The preparation of the nano-sheet comprises the following steps:
dissolving magnesium sulfate powder in ultrapure water to prepare 250ml of magnesium sulfate solution with the concentration of 1.85mol/L, adding 2.36g of folded MXene nanosheets under the stirring condition, and performing ultrasonic dispersion 1. Heating to 72 ℃ for 5h, adding 2mol/L ammonia water at the flow rate of 55ml/min, stopping the reaction when the pH is 9, filtering, washing with absolute ethyl alcohol and ultrapure water in sequence, and drying in vacuum for 11h to obtain a folded MXene @ Mg (OH) 2 A nanosheet.
The preparation method of the folded MXene nanosheet comprises the following steps:
(1) 7.1321g of titanium hydride, 17.3623g of titanium carbide and 4.6916g of aluminum powder are mixed and then ball milled for 3.5h, the mixture is calcined for 2h at 1440 ℃ and 1450 ℃ in the argon atmosphere, the mixture is ball milled for 2.5h after being cooled, and the powder MAX is obtained after sieving;
(2) powdered MAX1g, 1g of lithium fluoride and 20mL of 9M hydrochloric acid are stirred at 28 ℃ for 23 hours, washed by centrifugation until the pH value is 7, and freeze-dried to obtain a three-dimensional product MXene;
(3) carrying out ultrasonic treatment on three-dimensional MXene1g and 25mL of deionized water for 170min under the argon atmosphere, centrifuging to obtain a supernatant, and carrying out freeze drying to obtain a stripped MXene nanosheet;
(4) mixing 1g of peeled MXene nanosheet with 20mL of 80% hydrazine hydrate, transferring the mixture into a stainless steel autoclave with a PTFE liner, keeping the mixture at the temperature of 92 ℃ for 5.5h, cooling the mixture to 20 ℃, filtering the mixture, washing the mixture by using absolute ethyl alcohol and deionized water, placing the mixture in a vacuum environment at the temperature of 80 ℃ for drying for 24h, and controlling the vacuum degree of vacuum drying to be 0.08Mpa to obtain the folded MXene nanosheet;
s2: coating the prepared coating slurry on two sides of a base film by adopting a micro gravure roller coating process, drying at 73 ℃, and then rolling to obtain a folded MXene modified diaphragm for the lithium ion battery;
the PMMA powder is modified PMMA, and the preparation method comprises the following steps:
1) under argon atmosphere, mixing and stirring 0.8mmol of 2, 2-bipyridyl, 0.04g of cuprous chloride, 0.5g of hyperbranched poly (p-chloromethyl styrene) (with the number average molecular weight of 2500g/mol), 0.04mol of methyl methacrylate and 10mL of toluene, and reacting for 8.5h at 66 ℃ to obtain the hyperbranched grafted multi-arm polymer;
2) under the protection of argon, 0.37g of S-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate, 2mmol of azobisisobutyronitrile, 0.07mol of methyl methacrylate and 9mL of toluene are mixed and stirred, and react for 4.5 hours at 66 ℃ to obtain trithiocarbonate end-capped polymethyl methacrylate;
3) under the nitrogen environment, mixing and stirring 0.6g of trithiocarbonate end-capped polymethyl methacrylate, 0.011mmol of azobisisobutyronitrile, 1.54g of vinyl benzyl chloride and 6mL of toluene, and reacting for 17h at 65-68 ℃ to obtain an ionic liquid block copolymer;
4) 5g of hyperbranched grafted multi-arm polymer, 10g of ionic liquid block copolymer, 20g of PMMA powder and 10mL of tetrahydrofuran are mixed and stirred to obtain the modified PMMA.
Example 6
A preparation method of a folded MXene modified diaphragm for a lithium ion battery comprises the following steps:
s1: mixing dispersant, PMMA powder, fold MXene @ Mg (OH) 2 Premixing the nano sheets and ultrapure water for 30min at the rotation speed of 100 rpm; adding the thickening agent, and continuously stirring for 60min at the rotating speed of 200 rpm; adding the binder and continuously stirring for 50min at the rotating speed of 350 rpm; adding a wetting agent, stirring the defoaming agent for 40min at the rotating speed of 400 rpm; filtering to remove iron to obtain PMMA-coated folded MXene @ Mg (OH) 2 Coating slurry for nanosheetsPreparing materials;
the coating slurry comprises the following components in parts by mass: 1.6 percent of dispersant, 25 percent of PMMA powder, 23 percent of folded MXene @ Mg (OH) 2 The nano-sheet comprises nano-sheets, 10% of thickening agent, 4% of binder, 0.5% of wetting agent, 0.2% of defoaming agent and the balance of ultrapure water;
the base film is a polyolefin diaphragm; the dispersant is aliphatic amide, the thickener is sodium hydroxymethyl cellulose, the adhesive is polyacrylic acid, and the defoamer is a polyether defoamer; the wetting agent is branched dodecyl (poly-oxygen isopropene) 8 Sodium sulfate, the concentration of the wetting agent in the coating layer is 1.5 x 10 -3 mol/L；
Folded MXene @ Mg (OH) 2 The preparation of the nanosheet comprises the following steps:
dissolving magnesium sulfate powder in ultrapure water to prepare 250ml of magnesium sulfate solution with the concentration of 1.85mol/L, adding 2.36g of folded MXene nanosheets under the stirring condition, performing ultrasonic dispersion for 2 hours, heating to 75 ℃, adding 2mol/L ammonia water at the flow rate of 55ml/min, stopping reaction when the pH value is 10, filtering, sequentially washing with absolute ethyl alcohol and ultrapure water, and performing vacuum drying for 12 hours to obtain folded MXene @ Mg (OH) 2 Nanosheets;
the preparation method of the folded MXene nanosheet comprises the following steps:
(1) mixing 7.1321g of titanium hydride, 17.3623g of titanium carbide and 4.6916g of aluminum powder, then carrying out ball milling for 3-4h, calcining for 2h at 1450 ℃ in an argon atmosphere, cooling, then carrying out ball milling for 3h, and sieving to obtain powder MAX;
(2) powder MAX1g, lithium fluoride 1g and 9M hydrochloric acid 20mL are stirred at 30 ℃ for 22h, washed by centrifugal water until the pH value is 7, and freeze-dried to obtain a three-dimensional product MXene;
(3) carrying out ultrasonic treatment on three-dimensional MXene1g and 25mL of deionized water for 180min under the atmosphere of argon, centrifuging to obtain a supernatant, and carrying out freeze drying to obtain a stripped MXene nanosheet;
(4) mixing 1g of peeled MXene nanosheets with 20mL of 80% hydrazine hydrate, transferring the mixture into a stainless steel high-pressure kettle with a PTFE liner, keeping the mixture at 95 ℃ for 6h, cooling to 25 ℃, filtering, washing with absolute ethyl alcohol and deionized water, placing the mixture in a vacuum environment at 80 ℃ for 24h, and controlling the vacuum degree of vacuum drying at 0.08Mpa to obtain folded MXene nanosheets;
s2: coating the prepared coating slurry on two sides of a base film by adopting a micro gravure roller coating process, drying at 75 ℃ and then rolling to obtain a folded MXene modified diaphragm for the lithium ion battery;
the PMMA powder is modified PMMA, and the preparation method comprises the following steps:
1) under the argon atmosphere, mixing and stirring 0.8mmol of 2, 2-bipyridyl, 0.04g of cuprous chloride, 0.5g of hyperbranched poly-p-chloromethyl styrene (with the number average molecular weight of 2500g/mol), 0.04mol of methyl methacrylate and 10mL of toluene, and reacting for 8h at 68 ℃ to obtain the hyperbranched grafted multi-arm polymer;
2) under the protection of argon, 0.37g of S-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate, 2mmol of azobisisobutyronitrile, 0.07mol of methyl methacrylate and 9mL of toluene are mixed and stirred, and react for 4 hours at 68 ℃ to obtain trithiocarbonate end-capped polymethyl methacrylate;
3) under the nitrogen environment, mixing and stirring 0.6g of trithiocarbonate end-capped polymethyl methacrylate, 0.011mmol of azobisisobutyronitrile, 1.54g of vinyl benzyl chloride and 6mL of toluene, and reacting at 68 ℃ for 16h to obtain an ionic liquid block copolymer;
4) 5g of hyperbranched grafted multi-arm polymer, 15g of ionic liquid block copolymer, 20g of PMMA powder and 10mL of tetrahydrofuran are mixed and stirred to obtain the modified PMMA.
Comparative example 1
Example 3 as a control, without added wrinkles MXene @ Mg (OH) 2 Nanosheet, other processes are normal.
Comparative example 2
The same polypropylene-based film as in examples 1-6, other procedures were normal.
Comparative example 3
Example 6 was used as a control, and the concentration of wetting agent in the coating layer was 2X 10 -5 mol/L, other procedures are normal.
Comparative example 4
Example 6 is used as a control group, and the concentration of the wetting agent in the coating layer is 210 -3 mol/L, other procedures are normal.
Comparative example 5
And taking the example 6 as a control group, wherein the mass ratio of the hyperbranched grafted multi-arm polymer to the ionic liquid block copolymer to the PMMA powder is 1:0.8:4, and other working procedures are normal.
Comparative example 6
Taking the example 6 as a control group, the mass ratio of the hyperbranched grafted multi-arm polymer to the ionic liquid block copolymer to the PMMA powder is 1:3.1:4, and other working procedures are normal.
And (3) performance testing: the performance of the diaphragms prepared in examples 1-6 and comparative examples 1-6 is tested, and the thickness, the air permeability value, the needling strength, the anode-hot pressing stripping, the ionic conductivity and the thermal shrinkage are tested by referring to GB/T36363-2018;
and (3) oxygen index determination: reference IOS4589-2 assay: oxygen-nitrogen mixed gas with the temperature of 22 ℃; when the top surface is ignited, the flame is moved away every 5s, the time for contacting the top surface is 20s, whether the diaphragm burns or not is observed, and the oxygen index is the minimum oxygen concentration just required for maintaining the combustion; the results are shown in Table 1;
Figure BDA0003664691570000151
TABLE 1
By comparing example 3 with comparative examples 1 and 2, the wrinkles MXene @ Mg (OH) 2 Due to the introduction of the nanosheets, the mechanical strength of the diaphragm is greatly improved due to the excellent performance of the nanosheets; and the folded MXene nanosheets, PMMA and Mg (OH) with flame retardant property 2 The three components synergistically improve the heat resistance of the diaphragm; MXene @ Mg (OH) 2 The fold structure on the surface of the nanosheet ensures that PMMA particles can be relatively firmly adhered to MXene @ Mg (OH) 2 The surface of the nanosheet greatly improves the adhesion of the diaphragm to the pole piece and the wettability of electrolyte, and greatly improves the problem of powder removal of a PMMA coating in the processes of early coating and later cell manufacturing;
and wrinkles MXene @ Mg (OH) 2 The introduction of the nano sheet is from Mg (OH) 2 The crystal water is formed by heat decomposition and heat absorptionA carbonized layer of (2); when the temperature rises to the decomposition temperature, Mg (OH) 2 The water vapor is decomposed and released, latent heat is absorbed, and the concentration of oxygen and combustible gas near the surface of a combustion object is diluted, so that the surface combustion is difficult to carry out; the carbonized layer formed on the surface prevents oxygen and heat from entering, and meanwhile, the magnesium oxide generated by decomposition of the carbonized layer is a good refractory material, has good high temperature resistance and heat conductivity, and can improve the capability of the material for resisting open fire;
by comparing example 6 with comparative examples 3 and 4, it can be seen that the wetting agent is branched dodecyl (poly-oxy-isopropenyl) 8 Sodium sulfate, a section of polyoxypropylene chain (PO) is inserted between hydrophobic alkyl and hydrophilic polar groups, the PO groups can cause molecules of the surface wetting agent to present an obvious football shape on a gas-liquid interface, so that the surface wetting agent has excellent interface characteristics, polar groups and non-polar groups are contained in the wetting agent, the molecules can be adsorbed to the surface of the modified PMMA through polar interaction and hydrophobic interaction, and the wetting agent can interact with the surface of the modified PMMA through adsorption modes such as hydrogen bonds, polar interaction, hydrophobic interaction and the like, so that the wettability of the modified PMMA is improved, the mechanical strength of the membrane is improved, the wettability of the membrane is sticky, and the effective service life of the membrane is prolonged;
by limiting the concentration of wetting agent in the coating layer to 2.5X 10 -5 -1.5×10 -3 mol/L to further improve the ionic conductivity of the membrane, because the ionic conductivity is 1 multiplied by 10 -7 -2.5×10 -5 mol/L, along with the increase of concentration, the adsorption capacity of wetting agent molecules on a gas-liquid interface and a solid-liquid interface is increased, the influence on contact angles is mutually offset, so that the change of the contact angles is small, the molecules are adsorbed on the solid-liquid interface by virtue of an ion head, and a hydrophobic tail chain points to a solution; when the concentration is 2.5X 10 -5 -1.5×10 -3 mol/L, the adsorption capacity of the wetting agent molecules on a gas-liquid interface tends to be saturated, so that the contact angle is sharply reduced, at the moment, the wetting agent molecules are adsorbed on the surface of PMMA through hydrophobic interaction, and an aggregate is formed on a solid-liquid interface, so that the steric hindrance of the wetting agent is reduced by limiting the concentration and the branching degree of the wetting agent, the aggregate is formed, the solid-liquid interface tension is reduced, the hydrophilic modification capacity is enhanced, and the separation of the diaphragm is greatly improvedA sub-conductivity;
comparing the example 6 with the example 3, the comparative example 5 and the comparative example 6, it can be known that the hyperbranched grafted multi-arm polymer, the ionic liquid block copolymer and the PMMA powder are blended by adopting a solution blending method, and the PMMA powder is blended to synergistically improve the ion conduction performance of the diaphragm; the invention modifies the surface of hyperbranched poly (chloromethyl styrene), and grafts PMMA to prepare hyperbranched grafted multi-arm polymer; then preparing a functional block copolymer by using a RAFT (reversible addition-fragmentation chain transfer) method, and then preparing an ionic liquid block copolymer; the mass ratio of the hyperbranched grafted multi-arm polymer to the ionic liquid block copolymer to the PMMA powder is limited, so that the thermal shrinkage of the diaphragm is improved while the ionic conductivity is greatly improved, and the heat resistance of the diaphragm is further improved.
In conclusion, the diaphragm prepared by the method has good application prospect in the field of diaphragms.
The above description is only an example of the present invention, and is not intended to limit the scope of the present invention, and all modifications, equivalents and applications made by the present invention or directly/indirectly applied to other related technical fields within the spirit of the present invention are included in the scope of the present invention.

Claims (10)

1. The folded MXene modified diaphragm for the lithium ion battery is characterized by comprising a base film and a coating layer formed by coating the surface of the base film; the coating layer comprises the following components in parts by mass: 0.6 to 1.6 percent of dispersant, 15 to 25 percent of PMMA powder, 13 to 23 percent of folded MXene @ Mg (OH) 2 Nano-sheets, 7-10% of thickening agent, 2-4% of binder, 0.2-0.5% of wetting agent, 0.05-0.2% of defoaming agent and the balance of ultrapure water.
2. The folded MXene modified membrane for the lithium ion battery as claimed in claim 1, wherein the base membrane is a polyolefin membrane; the dispersing agent is an aliphatic amide dispersing agent, the thickening agent is a carboxymethylcellulose sodium thickening agent, the adhesive is a polyacrylic acid adhesive, the defoaming agent is a polyether defoaming agent, and the wetting agent is an alkyl sulfate wetting agent.
3. The folded MXene modified diaphragm for lithium ion battery as claimed in claim 1, wherein the folded MXene @ Mg (OH) 2 The preparation of the nanosheet comprises the following steps:
dissolving magnesium sulfate powder in ultrapure water to prepare a magnesium sulfate solution, adding folded MXene nanosheets under stirring for ultrasonic dispersion for 1-2h, heating to 70-75 ℃, adding ammonia water, stopping reaction at the pH of 8-10, filtering, sequentially washing with absolute ethyl alcohol and ultrapure water, and vacuum drying for 10-12h to obtain folded MXene @ Mg (OH) 2 Nanosheets.
4. The folded MXene modified diaphragm for the lithium ion battery as claimed in claim 3, wherein the molar concentration and mass ratio of the magnesium sulfate solution, the ammonia water and the folded MXene nanosheet is 1.85mol/L:2mol/L:2.36 g.
5. The folded MXene modified diaphragm for the lithium ion battery, according to claim 3, wherein the preparation of the folded MXene nanosheet comprises the following steps:
(1) mixing titanium hydride, titanium carbide and aluminum powder, then ball-milling for 3-4h, calcining for 2h at 1440-1450 ℃ in argon atmosphere, cooling, ball-milling for 2-3h, and sieving to obtain powdered MAX;
(2) mixing powder MAX, lithium fluoride and hydrochloric acid, stirring for 22-24h at 25-30 ℃, centrifuging, washing, and freeze-drying to obtain a three-dimensional product MXene;
(3) carrying out ultrasonic treatment on three-dimensional MXene and deionized water for 180min under the argon atmosphere, centrifuging to obtain supernatant, and carrying out freeze drying to obtain stripped MXene nanosheets;
(4) mixing the stripped MXene nanosheets with hydrazine hydrate, transferring the MXene nanosheets into a stainless steel autoclave with a PTFE liner, keeping the stainless steel autoclave at 90-95 ℃ for 5-6h, cooling to 18-25 ℃, filtering, washing with absolute ethyl alcohol and deionized water, placing the mixture in a vacuum environment at 80 ℃ for drying for 24h, and controlling the vacuum degree of vacuum drying at 0.08MPa to obtain the folded MXene nanosheets.
6. The folded MXene modified diaphragm for the lithium ion battery as claimed in claim 5, wherein the mass volume ratio of the powdered MAX to the lithium fluoride to the hydrochloric acid is 1g:1g:20 mL; the mass-volume ratio of the three-dimensional MXene to the deionized water is 1g:15 mL.
7. A preparation method of a folded MXene modified diaphragm for a lithium ion battery is characterized by comprising the following steps:
s1: dispersing agent, PMMA powder, folded MXene @ Mg (OH) 2 Premixing the nano-sheets and ultrapure water for 10-30min at the rotation speed of 100-300 rpm; adding the thickening agent and continuing stirring for 20-60min at the rotation speed of 200-500 rpm; adding the binder and continuously stirring for 30-50min at the rotation speed of 350-500 rpm; adding a wetting agent, stirring the defoaming agent for 20-40min at the rotation speed of 400-600 rpm; filtering to remove iron to obtain PMMA-coated folded MXene @ Mg (OH) 2 Coating slurry of the nanosheets;
s2: and (3) coating the prepared coating slurry on two sides of the base film by adopting a micro gravure roller coating process, drying at 70-75 ℃, and then rolling to obtain the folded MXene modified diaphragm for the lithium ion battery.
8. The folded MXene modified diaphragm for lithium ion battery of claim 7, wherein the wetting agent is branched dodecyl (poly-oxy-isopropenyl) 8 Sodium sulfate, the concentration of the wetting agent in the coating layer being 2.5X 10 -5 -1.5×10 -3 mol/L。
9. The preparation method of the folded MXene modified diaphragm for the lithium ion battery, according to claim 7, is characterized in that the PMMA powder is modified PMMA, and the preparation method comprises the following steps:
1) under the argon atmosphere, mixing and stirring 2, 2-bipyridyl, cuprous chloride, hyperbranched poly (chloromethyl) styrene, methyl methacrylate and toluene, and reacting at 65-68 ℃ for 8-9h to obtain hyperbranched grafted multi-arm polymer;
2) under the protection of argon, mixing and stirring S-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate, azodiisobutyronitrile, methyl methacrylate and toluene, and reacting at 65-68 ℃ for 4-5h to obtain trithiocarbonate end-capped polymethyl methacrylate;
3) under the nitrogen environment, mixing and stirring polymethyl methacrylate terminated by trithiocarbonate end groups, azodiisobutyronitrile, vinyl benzyl chloride and toluene, and reacting for 16-18h at 65-68 ℃ to obtain an ionic liquid block copolymer;
4) the modified PMMA is obtained by mixing and stirring the hyperbranched grafted multi-arm polymer, the ionic liquid block copolymer, the PMMA powder and tetrahydrofuran in a mass ratio of 1 (1-3) to 4.
10. The method for preparing the folded MXene modified diaphragm for the lithium ion battery according to claim 9, wherein 1) the molar mass ratio of the 2, 2-bipyridine, the methyl methacrylate, the cuprous chloride and the hyperbranched poly-p-chloromethylstyrene is 0.8mmol:0.04mol:0.04g:0.5g, and the number average molecular weight of the hyperbranched poly-p-chloromethylstyrene is 2500 g/mol; 2) the molar mass ratio of azodiisobutyronitrile to methyl methacrylate to S-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate is 2mmol to 0.07mol to 0.37 g; 3) the molar mass ratio of azodiisobutyronitrile to trithiocarbonate end-capped polymethyl methacrylate to vinylbenzyl chloride is 0.011mmol:0.6g:1.54 g.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113871792A (en) * 2021-09-27 2021-12-31 江苏厚生新能源科技有限公司 Folded molybdenum disulfide composite diaphragm for lithium-sulfur battery and preparation method thereof
CN113948816A (en) * 2021-10-18 2022-01-18 江苏厚生新能源科技有限公司 MXene composite material modified diaphragm for lithium-sulfur battery and preparation method thereof
CN114374051A (en) * 2021-11-02 2022-04-19 江苏厚生新能源科技有限公司 High-flame-retardance lithium dendrite growth-inhibiting coating diaphragm and preparation method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113871792A (en) * 2021-09-27 2021-12-31 江苏厚生新能源科技有限公司 Folded molybdenum disulfide composite diaphragm for lithium-sulfur battery and preparation method thereof
CN113948816A (en) * 2021-10-18 2022-01-18 江苏厚生新能源科技有限公司 MXene composite material modified diaphragm for lithium-sulfur battery and preparation method thereof
CN114374051A (en) * 2021-11-02 2022-04-19 江苏厚生新能源科技有限公司 High-flame-retardance lithium dendrite growth-inhibiting coating diaphragm and preparation method thereof

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