CN110752349A - Preparation method of lithium-sulfur battery positive electrode - Google Patents

Preparation method of lithium-sulfur battery positive electrode Download PDF

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CN110752349A
CN110752349A CN201911005678.8A CN201911005678A CN110752349A CN 110752349 A CN110752349 A CN 110752349A CN 201911005678 A CN201911005678 A CN 201911005678A CN 110752349 A CN110752349 A CN 110752349A
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electrode
lithium
sulfur
sulfur battery
positive electrode
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谢勇
李洒
伽龙
黄云辉
潘国宇
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Tongji University
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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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • 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
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention provides a preparation method of a lithium-sulfur battery anode, which comprises the following steps: uniformly mixing an active substance sulfur, a conductive agent and a binder to obtain a mixture, adding a dispersing solvent into the mixture, and uniformly mixing to obtain electrode slurry; uniformly coating the electrode slurry on a positive current collector to obtain a wet electrode coated with the slurry; freezing the wet electrode coated with the slurry for 1-5 h in a low-temperature environment at-80 to-5 ℃ until the wet electrode is frozen and molded, and solidifying and crystallizing the dispersion solvent in the wet electrode to obtain a solidified electrode; placing the solidification electrode in a vacuum environment with the vacuum degree of 0.1-100 Pa for 1-5 h, so that ice crystals in the solidification electrode are sublimated in a solid phase manner to obtain an electrode with the sublimated solid phase; and (3) rolling the electrode subjected to solid phase sublimation, and controlling the porosity of the electrode to be between 50 and 70 percent to obtain the lithium-sulfur battery anode. The preparation method is simple, and effectively solves the problem of electrode cracking in the preparation of the high-sulfur-carrying anode by adopting the traditional hot drying method.

Description

Preparation method of lithium-sulfur battery positive electrode
Technical Field
The invention belongs to the field of lithium batteries, and particularly relates to a preparation method of a lithium-sulfur battery anode.
Background
With the development of portable electronic products, energy storage technologies and new energy automobiles, the modern society puts higher demands on the energy density of batteries. Lithium ion batteries are limited by the intercalation/deintercalation reaction mechanism of the electrode material, and their energy density has hardly been able to be increased. And the anode material of the current lithium ion battery mainly consists of transition metal oxide, and the cost of the raw material is always high. The development of a new generation of novel battery systems with high energy density and low cost is imminent. The lithium-sulfur battery has high specific capacity (1672 mAhg)-1) And energy density (2600Wh kg)-1) And the elemental sulfur of the anode material is rich in resource, low in price and environment-friendly. Is a high-energy battery system with great development potential and application prospect.
However, despite the recent numerous research reports on lithium sulfur batteries, the way to commercialize lithium sulfur batteries is not smooth. The reason for this is that the sulfur positive electrode mainly includes the following two aspects:
1) the preparation technology of the high-load lithium-sulfur battery positive electrode is still a difficult problem. In order to obtain a high energy density of the battery, the surface capacity of the electrode must be increased. The electrode surface capacity of the current commercial lithium ion battery is about 4mAh cm-2On the other hand, considering that the average discharge voltage of the lithium-sulfur battery is lower than that of the lithium-ion battery (2.1V for the lithium-sulfur battery and 3.7V for the lithium-ion battery), the electrode surface capacity of the lithium-sulfur battery needs to reach 7mAh cm-2And the above. The actual specific capacity per sulfur is 1000mAh g-1Calculating to require that the sulfur carrying capacity of the anode of the lithium-sulfur battery reaches 7mg cm-2. However, the areal loadings of lithium-sulfur batteries have been mostly concentrated in the 1-4mg cm range in literature reports-2。
2) Excessive electrolyte addition severely dilutes the theoretical energy density of a lithium sulfur battery. The addition amount of the electrolyte in the current lithium-sulfur battery is far excessive, and in part of literatures, the addition amount of the electrolyte exceeds the active substance sulfur by ten times (10 mu Lmg)-1And only 0 in lithium ion batteries.3μL mg-1). Such a large amount of electrolyte severely dilutes the theoretical energy density of a lithium-sulfur battery, resulting in an actual energy density that is not even comparable to that of a lithium-ion battery.
At present, lithium ion batteries are mostly used as a preparation method of a positive electrode of a lithium sulfur battery, namely, an active substance, a conductive agent and a binder are uniformly mixed in a solvent, then the mixture is coated on a current collector, and finally the solvent in an electrode is volatilized at a certain temperature to obtain a battery pole piece. However, since sulfur has much lower conductivity than lithium ion electrode material batteries, a relatively large amount of conductive additives (about 30% and about 5% for lithium ion batteries) are often added in the preparation of the positive electrode, and most of these conductive additives have high specific surface area and pore volume (for higher sulfur loading and polysulfide adsorption). The addition of excessive conductive additives causes huge surface tension and volume shrinkage in the solvent volatilization process in the electrode pole piece, thereby causing the electrode cracking phenomenon and limiting the preparation of the high-capacity lithium-sulfur battery anode. Although the area loading of the lithium-sulfur battery electrode can be improved by adopting a three-dimensional current collector at present, the three-dimensional electrode can reduce the volume energy density of the lithium-sulfur battery due to the developed pore structure of the three-dimensional electrode, and can also require more electrolyte to fill the pores so as to reduce the mass energy density of the battery. Therefore, in order to obtain a lithium sulfur battery with high energy density, a new method for preparing a positive electrode of the lithium sulfur battery is urgently needed.
Disclosure of Invention
The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a positive electrode for a lithium-sulfur battery.
The invention provides a preparation method of a lithium-sulfur battery positive electrode, which is characterized by comprising the following steps: step 1, uniformly mixing an active substance sulfur, a conductive agent and a binder to obtain a mixture, adding a dispersing solvent into the mixture, and uniformly mixing to obtain electrode slurry; step 2, uniformly coating the electrode slurry on a positive current collector to obtain a wet electrode coated with the slurry; step 3, freezing the wet electrode coated with the slurry for 1-5 h in a low-temperature environment at-80-5 ℃, and freezing and molding the wet electrode to solidify and crystallize the dispersion solvent in the wet electrode to obtain a solidified electrode; step 4, placing the solidification electrode in a vacuum environment with the vacuum degree of 0.1-100 Pa for 1-5 h, so that ice crystals in the solidification electrode are sublimated in a solid phase manner, and obtaining an electrode after the solid phase is sublimated; and 5, performing rolling treatment on the electrode subjected to solid phase sublimation, and controlling the porosity of the electrode to be between 50 and 70 percent to obtain the lithium-sulfur battery anode.
In the method for preparing the positive electrode of the lithium-sulfur battery provided by the invention, the method can also have the following characteristics: wherein, the mass ratio of the active substance sulfur in the mixture in the step 1 is 50-75%, the mass ratio of the conductive agent is 10-30%, and the mass ratio of the adhesive is 2-20%.
In the method for preparing the positive electrode of the lithium-sulfur battery provided by the invention, the method can also have the following characteristics: in the step 1, active substance sulfur and a conductive agent are uniformly mixed in advance, heated for 12 hours at the temperature of 155 ℃ in an inert atmosphere, and then mixed with a binder to obtain a mixture, or the active substance sulfur is directly mixed with the conductive agent and the binder to obtain the mixture.
In the method for preparing the positive electrode of the lithium-sulfur battery provided by the invention, the method can also have the following characteristics: wherein the inert atmosphere is argon or nitrogen.
In the method for preparing the positive electrode of the lithium-sulfur battery provided by the invention, the method can also have the following characteristics: in the step 1, the active substance sulfur is directly and uniformly mixed with the conductive agent and the binding agent to obtain the mixture.
In the method for preparing the positive electrode of the lithium-sulfur battery provided by the invention, the method can also have the following characteristics: wherein the particle size range of the active substance sulfur in the step 1 is 50 nm-50 μm.
In the method for preparing the positive electrode of the lithium-sulfur battery provided by the invention, the method can also have the following characteristics: the conductive agent in the step 1 is one or a mixture of more of Ketjen black, conductive graphite, conductive carbon black, carbon nanotubes, carbon nanofibers and graphene.
In the method for preparing the positive electrode of the lithium-sulfur battery provided by the invention, the method can also have the following characteristics: wherein, the binder in the step 1 is one or a mixture of more of styrene-butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, polyacrylate, acrylonitrile multipolymer LA133 and acrylonitrile multipolymer LA 132.
In the method for preparing the positive electrode of the lithium-sulfur battery provided by the invention, the method can also have the following characteristics: wherein, the mixing mode of the mixture and the dispersing solvent in the step 1 is ball milling stirring or mechanical stirring, and the stirring time is 1-5 h.
In the method for preparing the positive electrode of the lithium-sulfur battery provided by the invention, the method can also have the following characteristics: and 2, the positive current collector in the step 2 is one of a two-dimensional metal current collector and a three-dimensional metal network.
Action and Effect of the invention
According to the preparation method of the lithium-sulfur battery positive electrode, the freezing crystallization and vacuum sublimation of the solvent in the electrode slurry are adopted to dry the electrode, so that the problem of electrode cracking in the preparation of the high-sulfur-loading positive electrode by adopting the traditional hot drying method is effectively solved, and the sulfur loading of the positive electrode piece can be increased to 10mg cm-2Therefore, the practical production requirements of the lithium-sulfur battery are completely met. The nucleation shape of the ice crystals in the electrode can be effectively adjusted under certain freezing temperature and freezing time, so that an ideal electrode pore structure and electrochemical performance are obtained, the speed of the ice crystals during sublimation and the generated volume strain can be effectively adjusted under certain vacuum degree and vacuum time, the lithium-sulfur battery anode with a complete structure can be obtained, and the electrode prepared by the preparation method provided by the invention has high specific capacity even under high loading capacity.
In addition, the lithium-sulfur battery positive electrode prepared by the preparation method of the lithium-sulfur battery positive electrode effectively avoids the situations of local material agglomeration, uneven components and structures in the electrode and the like generated in the electrode preparation by the traditional hot drying method, and has very good electrode structure and component uniformity, so that the electrode prepared by the preparation method can effectively improve the consistency in the battery production process, improves the yield, and is very important for reducing the cost in commercial production.
Furthermore, the lithium-sulfur battery anode prepared by the preparation method provided by the invention has a hierarchical porous structure, the vertical and low-tortuosity large channels of the lithium-sulfur battery anode are favorable for rapid diffusion of lithium ions, the mutually communicated small-size capillary structures are favorable for promoting dissolution and reaction of polysulfide, and the hierarchical porous structure can enable the lithium-sulfur battery to work normally under low electrolyte (even if the electrolyte does not completely fill electrode pore channels).
Therefore, the preparation method is simple, the raw materials are low in price, and the method is close to the production and preparation process of the lithium ion battery electrode, and is easy to implement industrially and produce in large batch.
Drawings
FIG. 1 is a digital photograph of the surface of an electrode sheet prepared by a conventional method for preparing an electrode for a lithium-sulfur battery according to comparative example 1 of the present invention;
FIG. 2 is an SEM photograph of the surface of an electrode sheet prepared by a conventional preparation method of an electrode for a lithium-sulfur battery in comparative example 1 of the present invention;
FIG. 3 is a digital photograph of the surface of an electrode plate of a lithium-sulfur battery prepared by the preparation method of the present invention in example 1 of the present invention;
FIG. 4(a) is a SEM photograph of the surface of an electrode plate of a lithium-sulfur battery prepared by the preparation method of the invention in example 1 of the invention;
FIG. 4(b) is an SEM photograph of the surface of an electrode plate of a lithium-sulfur battery prepared by the preparation method of the invention in example 1 of the invention;
FIG. 5 is a charge-discharge curve of four lithium-sulfur batteries in parallel test assembled by electrode plates prepared by the preparation method of the invention in example 1 of the invention;
FIG. 6(a) is a photograph of an electrode sheet prepared by the preparation method of the present invention in example 2 of the present invention;
fig. 6(b) is a photograph of a lithium sulfur pouch battery assembled with an electrode plate prepared by the preparation method of the present invention in example 2 of the present invention;
FIG. 6(c) is an electrode sheet prepared by the preparation method of the present invention in example 2 of the present inventionThe assembled soft package lithium-sulfur battery is 1.2 mu Lmg-1Discharge performance and energy density curve.
Detailed Description
In order to make the technical means and functions of the present invention easy to understand, the present invention is specifically described below with reference to the embodiments and the accompanying drawings.
In the examples of the present invention, the required materials other than the self-made materials were purchased through general commercial routes.
The preparation method of the lithium-sulfur battery positive electrode provided by the invention comprises the following steps:
step 1, uniformly mixing an active substance sulfur, a conductive agent and a binder to obtain a mixture, adding a dispersing solvent into the mixture, and uniformly mixing to obtain electrode slurry;
step 2, uniformly coating the electrode slurry on a positive current collector to obtain a wet electrode coated with the slurry;
step 3, freezing the wet electrode coated with the slurry for 1-5 hours in a low-temperature environment of-80-5 ℃ until the wet electrode is frozen and molded, so that the dispersion solvent in the wet electrode is solidified and crystallized to obtain a solidified electrode;
step 4, placing the solidification electrode in a vacuum environment with the vacuum degree of 0.1-100 Pa for 1-5 h to sublimate the ice crystal solid phase in the solidification electrode;
and 5, performing rolling treatment on the electrode after solid phase sublimation, and controlling the porosity of the electrode to be between 50 and 70 percent to obtain the lithium-sulfur battery anode.
In step 1 of the invention, active substance sulfur and a conductive agent are uniformly mixed in advance, heated for 12 hours at the temperature of 155 ℃ in an inert atmosphere, and then mixed with a binder to obtain a mixture, or the active substance sulfur is directly mixed with the conductive agent and the binder to obtain the mixture.
The inert atmosphere in the present invention is argon or nitrogen.
In the step 1 of the invention, the active substance sulfur has a particle size range of 50 nm-50 μm, and the dispersion solvent is water.
The conductive agent in step 1 of the invention is one or a mixture of more of Ketjen black, conductive graphite, conductive carbon black, carbon nanotubes, carbon nanofibers, graphene and other conductive additives.
The binder in step 1 of the invention is one or a mixture of more of styrene-butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, polyacrylate, acrylonitrile multipolymer LA133, acrylonitrile multipolymer LA132 or other aqueous binders and organic solvent binders.
The mixing mode of the mixture and the dispersing solvent in the step 1 is ball milling stirring or mechanical stirring, and the stirring time is 1-5 h.
The positive current collector in step 2 of the invention is one of a two-dimensional metal current collector and a three-dimensional metal network or a current collector made of other two-dimensional conductive materials and a current collector made of a three-dimensional conductive network.
In the step 4 of the invention, the mass ratio of the active substance sulfur in the positive electrode of the lithium-sulfur battery is 50-75%, the mass ratio of the conductive agent is 10-30%, and the mass ratio of the binder is 2-20%.
< comparative example 1>
2g of commercial sublimed sulfur powder, 0.53g of Ketjen black (ECP 200JD), 2.66g of mixed binder aqueous solution of styrene-butadiene rubber and carboxymethyl cellulose (the mass ratio of the styrene-butadiene rubber to the carboxymethyl cellulose is 1:1, and the solid content of the binder aqueous solution is 5%), sequentially adding the mixture into a 50ml ball milling tank (sulfur, Ketjen black, the mass ratio of the binder is 75:20:5), adding a proper amount of ball milling beads and 8g of water into the ball milling tank, ball milling the mixture at a rotating speed of 350 revolutions per minute for 2 hours, uniformly and flatly coating electrode slurry with uniform ball milling on a current collector by using an automatic coating machine, controlling the coating thickness to be 200 microns to obtain a wet electrode, quickly placing the prepared wet electrode into a vacuum drying oven at-60 ℃ below zero for drying for 12 hours, taking out the wet electrode to obtain the electrode with the sulfur content of 75%, and the sulfur loading amount of-2The lithium sulfur battery electrode of (1).
FIG. 1 is a digital photograph of the surface of an electrode sheet prepared by a conventional method for preparing an electrode for a lithium-sulfur battery in comparative example 1 of the present invention.
As can be seen from fig. 1, the electrode prepared by the conventional method for preparing a positive electrode for a lithium sulfur battery of this comparative example had severe surface cracks.
FIG. 2 is an SEM photograph of the surface of an electrode sheet prepared by a conventional preparation method of an electrode for a lithium-sulfur battery in comparative example 1 of the present invention.
As can be seen from fig. 2, the electrode prepared by the conventional method for preparing the positive electrode for a lithium-sulfur battery according to the comparative example has a dense surface and an unevenly distributed microstructure in cross section, and the inside of the electrode has a closed pore structure.
< example 1>
Adding 2g of commercial sublimed sulfur powder, 0.53g of Ketjen black (ECP 200JD), 2.66g of styrene butadiene rubber and carboxymethyl cellulose mixed binder aqueous solution (the mass ratio of SBR to CMC is 1:1, and the solid content of the binder aqueous solution is 5%), adding the mixture into a 50ml ball milling tank (sulfur, Ketjen black, and the mass ratio of the binder is 75:20:5), adding a proper amount of ball milling beads and 8g of water into the mixture, performing ball milling at the rotating speed of 350 revolutions per minute for 2 hours, uniformly and flatly coating electrode slurry subjected to ball milling on an aluminum foil collector by using an automatic coating machine, controlling the coating thickness to be 200 microns to obtain a wet electrode, rapidly placing the prepared wet electrode in a freezing environment of 40 ℃ below zero to solidify an aqueous solvent into ice crystals, performing freezing for 2 hours, taking out the frozen solidified electrode, placing the frozen electrode in a vacuum environment with the vacuum degree of 0.1Pa for 1 hour, sublimating the previously solidified ice crystals, and taking out to obtain the product with 75% of sulfur content and 4mg cm of sulfur carrying capacity-2The lithium sulfur battery electrode of (1).
FIG. 3 is a digital photograph of the surface of an electrode plate of a lithium-sulfur battery prepared by the preparation method of the present invention in example 1 of the present invention.
As can be seen from fig. 3, the surface of the positive electrode of the lithium-sulfur battery prepared by the method of the present invention according to this example does not crack even at a relatively high loading amount.
Fig. 4(a) is an SEM photograph of the surface of the electrode sheet of the lithium-sulfur battery prepared by the preparation method of the present invention in example 1 of the present invention, and fig. 4(b) is an SEM photograph of the surface of the electrode sheet of the lithium-sulfur battery magnified and prepared by the preparation method of the present invention in example 1 of the present invention.
As can be seen from fig. 4(a) and 4(b), the positive electrode of the lithium-sulfur battery prepared by the method of the present invention of this embodiment has a well-defined hierarchical pore structure and mostly has an interconnected open pore structure.
The lithium-sulfur battery electrode and the lithium negative electrode prepared in this example were assembled into a button cell, and four batteries were used as parallel test batteries to perform constant current charging and discharging at 0.1C at room temperature within the voltage range of 1.7 to 2.8V, and the results are shown in fig. 5.
Fig. 5 is a charge-discharge curve of four lithium-sulfur batteries in parallel tests assembled by electrode plates prepared by the preparation method of the invention in example 1 of the invention.
As shown in fig. 5, the abscissa represents the specific capacity, and the ordinate represents the battery voltage.
As can be seen from FIG. 5, the four parallel test cells were all charged and discharged at constant current of 0.1C within the voltage range of 1.7 to 2.8V at room temperature, and the average discharge capacity of the four parallel test cells reached 1200mAh g-1Standard deviation of capacity of only 33mAh g-1The consistency is very good.
< example 2>
Adding 2g of commercial sublimed sulfur powder, 0.875g of Ketjen black (ECP 600JD) and 1.66g of LA133 binder aqueous solution (the solid content of the binder aqueous solution is 15%) into a 50ml ball milling tank (sulfur, Ketjen black, the mass ratio of the binder is 64:28:8), adding a proper amount of ball milling beads and 8g of water into the ball milling tank, performing ball milling at the rotating speed of 350 revolutions per minute for 2 hours, uniformly and flatly coating the uniform electrode slurry obtained by ball milling on a current collector aluminum foil by using an automatic coating machine, controlling the coating thickness to be 300 microns to obtain a wet electrode, rapidly placing the prepared wet electrode in a freezing environment of minus 30 ℃ to solidify a water solvent into ice crystals, wherein the freezing time is 2 hours, finally taking out the frozen electrode, placing the frozen electrode in a vacuum environment with the vacuum degree of 0.1Pa for 2 hours, subliming the previously solidified ice crystals, taking out the ice crystals to obtain the sulfur content of 64%, the sulfur loading was 8mg cm-2The lithium sulfur battery electrode of (1).
Then, the lithium-sulfur battery electrode and the lithium cathode prepared in the embodiment are assembled into a button cell, and 0.1C constant current charging and discharging are performed at room temperature within a voltage range of 1.7 to 2.8V, and four flat cells are formedThe average discharge capacity of the battery reaches 1156mAh g in the row test-1Standard deviation of capacity of only 35mAh g-1。
FIG. 6(a) is a photograph of an electrode plate prepared by the preparation method of the present invention, FIG. 6(b) is a photograph of a lithium sulfur soft package battery assembled by the electrode plate prepared by the preparation method of the present invention, and FIG. 6(c) is a photograph of a soft package lithium sulfur battery assembled by the electrode plate prepared by the preparation method of the present invention, wherein the diameter of the soft package lithium sulfur battery is 1.2 mu Lmg-1Discharge performance and energy density curve.
As shown in fig. 6(c), the abscissa represents the battery capacity, and the ordinate represents the battery voltage.
As can be seen from fig. 6(c), the soft pack battery assembled by the lithium sulfur battery electrode and the lithium negative electrode prepared in this example can be added in the electrolyte solution with an amount of 1.2 μ Lmg-1Working under the condition of low electrolyte, the first discharge capacity of the lithium ion battery can reach 1200mAh g-1Above, the overall energy density of the lithium-sulfur battery can reach 481Wh kg-1。
< example 3>
Grinding 2g of commercial sublimed sulfur powder and 0.66 g of Ketjen black (ECP 600JD) in a mortar for half an hour until the mixture is uniform, and then heating the mixture for 12 hours at 155 ℃ under an inert atmosphere (argon or nitrogen) to obtain a sulfur/carbon composite material; the sulfur/carbon composite was then mixed with LA133 in a 95: 5, adding a proper amount of water and ball milling beads into a ball milling tank, performing ball milling for 2 hours at a rotating speed of 350 revolutions per minute by adding a proper amount of water and the ball milling beads to prepare uniform electrode slurry, then uniformly coating the electrode slurry on a current collector aluminum foil by using an automatic coating machine, wherein the coating thickness is respectively 500 micrometers and 700 micrometers, then rapidly placing the prepared wet electrode in a freezing environment of-30 ℃ to solidify a water solvent into ice crystals, the freezing time is 2 hours, finally taking out the frozen electrode, placing the frozen electrode in a vacuum environment with a vacuum degree of 0.1Pa for 2 hours to sublimate the previously solidified ice crystals, and then taking out the frozen electrode to obtain the electrode with the sulfur content of 64 percent and the sulfur carrying capacity of 8.2mg cm-2And 14.2mg cm-2The lithium sulfur battery electrode of (1).
The sulfur loadings obtained in this example were 14.2mg cm each-2The lithium-sulfur battery electrode and the lithium cathode are assembled into a button batteryAnd 0.5mA cm at room temperature in a voltage range of 1.7 to 2.8V-2Constant current charging and discharging, the first discharge capacity can reach 1400mAh g-1And the cycle performance is stable.
Effects and effects of the embodiments
According to the preparation method of the lithium-sulfur battery positive electrode, the freezing crystallization and vacuum sublimation of the solvent in the electrode slurry are adopted to dry the electrode, so that the problem of electrode cracking in the preparation of the high-sulfur-loading positive electrode by adopting the traditional hot drying method is effectively solved, and the sulfur loading of the positive electrode piece can be increased to 10mg cm-2Therefore, the practical production requirements of the lithium-sulfur battery are completely met. The nucleation shape of the ice crystals in the electrode can be effectively adjusted at a certain freezing temperature and freezing time, so that an ideal electrode pore structure and electrochemical performance are obtained, the speed of the ice crystals during sublimation and the generated volume strain can be effectively adjusted at a certain vacuum degree and vacuum time, and the lithium-sulfur battery anode with a complete structure is favorably obtained. In addition, the button cell is assembled by the lithium-sulfur battery anode and the lithium cathode prepared by the invention, and the anode loading is 14.2mgcm at room temperature-2The amount of electrolyte added was 7. mu.L mg-1When using, 0.5mA cm-2Discharge with first discharge capacity up to 1400mAh g-1The sulfur utilization rate exceeds 85%, and the electrode prepared by the preparation method has higher specific capacity even under high loading.
In addition, the lithium-sulfur battery positive electrode prepared by the preparation method of the lithium-sulfur battery positive electrode provided by the embodiment of the invention effectively avoids the situations of local material agglomeration, nonuniform components and structures in the electrode and the like generated in the electrode preparation by the traditional hot drying method, has very good electrode structure and component uniformity, and is assembled into a button battery together with a lithium metal negative electrode when the positive electrode loading capacity is 4mg cm-2In this case, the standard deviation of the discharge capacity of 4 parallel test cells was 37mAh g-1And the standard deviation of the discharge capacity of 4 parallel test batteries of the electrode prepared by the traditional thermal dry method reaches 490mAh g-1It can be seen that the electrodes prepared by the present invention can haveThe consistency in the production process of the battery is effectively improved, and the yield is improved, which is very important for reducing the cost in commercial production.
Furthermore, the lithium-sulfur battery anode prepared by the preparation method provided by the invention has a hierarchical porous structure, the vertical and low-tortuosity large channels of the lithium-sulfur battery anode are favorable for rapid diffusion of lithium ions, the mutually communicated small-size capillary structures are favorable for promoting dissolution and reaction of polysulfide, and the hierarchical porous structure can enable the lithium-sulfur battery to work normally under low electrolyte (even if the electrolyte does not completely fill electrode pore channels). The prepared positive electrode of the lithium-sulfur battery and the lithium metal negative electrode are assembled into the soft package battery, and when the loading capacity of the positive electrode is 8mg cm-2The amount of electrolyte added was 1.2. mu. Lmg-1When the battery is used, the battery can still release more than 1200mAh g-1The specific capacity of the lithium-sulfur battery can also improve the overall energy density of the lithium-sulfur battery to 481Wh kg-1。
In addition, the mixing and stirring time of the mixture and the dispersing solvent is 1-5 h, and the stirring is carried out within the range, so that the mixing uniformity of the sulfur, the conductive agent and the binder is improved, and the damage to a polymer chain of the binder for too long time can be avoided.
In addition, the type and the corresponding mass ratio of the conductive agent are favorable for both the electrochemical performance of the lithium-sulfur battery electrode and the reduction of the consumption of the conductive agent.
Furthermore, the type and the corresponding addition amount of the binder are favorable for resisting the failure of the binder material at low temperature, so that the electrode structure stability is improved.
Therefore, the preparation method is simple, the raw materials are low in price, and the method is close to the production and preparation process of the lithium ion battery electrode, and is easy to implement industrially and produce in large batch.
The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.

Claims (10)

1. A preparation method of a lithium-sulfur battery positive electrode is characterized by comprising the following steps:
step 1, uniformly mixing an active substance sulfur, a conductive agent and a binder to obtain a mixture, adding a dispersing solvent into the mixture, and uniformly mixing to obtain electrode slurry;
step 2, uniformly coating the electrode slurry on a positive current collector to obtain a wet electrode coated with the slurry;
step 3, freezing the wet electrode coated with the slurry for 1-5 hours in a low-temperature environment of-80-5 ℃ until the wet electrode is frozen and molded, so that the dispersion solvent in the wet electrode is solidified and crystallized to obtain a solidified electrode;
step 4, placing the solidification electrode in a vacuum environment with the vacuum degree of 0.1-100 Pa for 1-5 h, so that ice crystals in the solidification electrode are sublimated in a solid phase manner, and obtaining an electrode after sublimation of the solid phase;
and 5, performing rolling treatment on the electrode after solid phase sublimation, and controlling the porosity of the electrode to be between 50 and 70 percent to obtain the lithium-sulfur battery anode.
2. The method of manufacturing a positive electrode for a lithium-sulfur battery according to claim 1, characterized in that:
wherein, the mass ratio of the active substance sulfur in the mixture in the step 1 is 50-75%, the mass ratio of the conductive agent is 10-30%, and the mass ratio of the binder is 2-20%.
3. The method of manufacturing a positive electrode for a lithium-sulfur battery according to claim 1, characterized in that:
in the step 1, the active substance sulfur and the conductive agent are uniformly mixed in advance, heated at 155 ℃ for 12 hours in an inert atmosphere, and then mixed with the binder to obtain the mixture.
4. The method of manufacturing a positive electrode for a lithium-sulfur battery according to claim 3, characterized in that:
wherein the inert atmosphere is argon or nitrogen.
5. The method of manufacturing a positive electrode for a lithium-sulfur battery according to claim 1, characterized in that:
in the step 1, the active substance sulfur is directly and uniformly mixed with the conductive agent and the binder to obtain the mixture.
6. The method of manufacturing a positive electrode for a lithium-sulfur battery according to claim 1, characterized in that:
wherein the particle size range of the active substance sulfur in the step 1 is 50 nm-50 μm.
7. The method of manufacturing a positive electrode for a lithium-sulfur battery according to claim 1, characterized in that:
the conductive agent in the step 1 is one or a mixture of more of Ketjen black, conductive graphite, conductive carbon black, carbon nanotubes, carbon nanofibers and graphene.
8. The method of manufacturing a positive electrode for a lithium-sulfur battery according to claim 1, characterized in that:
wherein, the binder in the step 1 is one or a mixture of more of styrene-butadiene rubber, carboxymethyl cellulose, polytetrafluoroethylene, polyacrylate, acrylonitrile multipolymer LA133 and acrylonitrile multipolymer LA 132.
9. The method of manufacturing a positive electrode for a lithium-sulfur battery according to claim 1, characterized in that:
wherein the mixing mode of the mixture and the dispersion solvent in the step 1 is ball milling stirring or mechanical stirring, and the stirring time is 1-5 h.
10. The method of manufacturing a positive electrode for a lithium-sulfur battery according to claim 1, characterized in that:
wherein, the positive current collector in the step 2 is one of a two-dimensional metal current collector and a three-dimensional metal network current collector.
CN201911005678.8A 2019-10-22 2019-10-22 Preparation method of lithium-sulfur battery positive electrode Pending CN110752349A (en)

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Publication number Priority date Publication date Assignee Title
CN111420853A (en) * 2020-03-27 2020-07-17 天目湖先进储能技术研究院有限公司 Pole piece drying method for inhibiting adhesive migration, pole piece and battery
CN112701302A (en) * 2020-12-28 2021-04-23 武汉理工氢电科技有限公司 Gas diffusion layer, membrane electrode assembly, fuel cell and preparation method
CN112909217A (en) * 2021-01-25 2021-06-04 北京理工大学 Regulating and controlling method for positive electrode pore structure of lithium-sulfur battery
CN113948678A (en) * 2021-09-07 2022-01-18 长沙矿冶研究院有限责任公司 Preparation method of porous high-capacity electrode for lithium-sulfur battery
CN113948678B (en) * 2021-09-07 2023-09-26 长沙矿冶研究院有限责任公司 Preparation method of porous high-load electrode for lithium-sulfur battery
CN114335532A (en) * 2021-12-14 2022-04-12 华中科技大学 Lithium ion battery anode lithium supplementing method based on freeze drying and product

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