CN113140710A - Preparation method of polymer positive electrode material for lithium-sulfur battery - Google Patents

Preparation method of polymer positive electrode material for lithium-sulfur battery Download PDF

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CN113140710A
CN113140710A CN202010057562.5A CN202010057562A CN113140710A CN 113140710 A CN113140710 A CN 113140710A CN 202010057562 A CN202010057562 A CN 202010057562A CN 113140710 A CN113140710 A CN 113140710A
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lithium
tcp
sulfur battery
positive electrode
sodium
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成会明
张笑银
李峰
孙振华
胡广剑
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Institute of Metal Research of CAS
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    • H—ELECTRICITY
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    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H—ELECTRICITY
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    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • 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
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Abstract

The invention discloses a preparation method of a polymer positive electrode material for a lithium-sulfur battery, and belongs to the technical field of lithium-sulfur batteries. The present invention prepares a polymer positive electrode material for a lithium sulfur battery having stable electrochemical activity by using sodium polysulfide and a chlorine-containing organic monomer as polymerization reaction monomers and completing polymerization reaction through a phase transfer catalyst, and uses it as a positive electrode material for a lithium sulfur battery. The polymer anode material for the lithium-sulfur battery, prepared by the invention, has the characteristics of faster electrochemical kinetics, high conductivity and stable cycle performance when being used in the anode of the lithium-sulfur battery. The preparation process is simple in flow, mild in preparation conditions and good in application prospect.

Description

Preparation method of polymer positive electrode material for lithium-sulfur battery
The technical field is as follows:
the invention relates to the technical field of lithium batteries, in particular to a preparation method of a polymer positive electrode material for a lithium-sulfur battery.
Background art:
the lithium-sulfur battery has high energy density (2500Wh kg)-1) Can meet the requirement of future storageEnergy density requirements of the device. Meanwhile, the sulfur is used as a byproduct in the petroleum industry, has wide source and low price, and is a positive electrode material suitable for large-scale production. However, sulfur has problems as a positive electrode material for lithium-sulfur batteries. Sulfur is an insulating material and has poor electronic and ionic conductivity, resulting in low utilization of sulfur in the electrode. Meanwhile, sulfur generates intermediate lithium polysulfide (Li) during charging and discharging2Sx, 3 is more than or equal to X is less than or equal to 8). These lithium polysulfides are soluble in organic electrolytes, diffuse from the positive electrode to the negative electrode under the action of electric field force and concentration gradient, and react with the negative electrode, resulting in loss of active material, fading of battery capacity, reduction in coulombic efficiency, deterioration of the negative electrode, and the like. In view of the problems of the sulfur positive electrode, a widely used method is to increase the conductivity of the sulfur positive electrode by compounding a conductive material with sulfur, and modify the conductive material to suppress the shuttle effect generated by lithium polysulfide. However, this approach has two insurmountable drawbacks. First, the conductive material other than the conductive agent may lower the energy density, particularly the volume energy density, of the entire positive electrode. Second, the modified conductive material only mitigates the shuttling effect, but does not completely eliminate it. Thus, the application of sulfur anodes has met with significant challenges.
In order to solve the problem when sublimed sulfur is used as a positive electrode, a sulfur-rich polymer is proposed as a new positive electrode material. The sulfur-rich polymer is a material with simple preparation process, low price and environmental protection. Meanwhile, in the sulfur-rich polymer, active sulfur chains are uniformly dispersed in the organic framework through covalent bonds, so that active substance agglomeration is avoided. In addition, through molecular structure design, the sulfur chain of the sulfur-rich polymer and the organic part without active sulfur can be adjusted, thereby realizing different electrochemical properties and electrochemical behaviors. The molecular orbit of the whole material can be adjusted by adjusting the organic part without active sulfur in the sulfur-rich polymer, so that the material has the characteristics of better electronic conductivity, quicker electrochemical dynamics, higher discharge voltage and the like. Therefore, the electrochemical performance of the sulfur-rich polymer can be optimized by regulating the organic part of the sulfur-rich polymer without active sulfur.
The invention content is as follows:
the invention aims to provide a preparation method of a polymer cathode material for a lithium-sulfur battery, wherein when the cathode material is used for the lithium-sulfur battery, a lithium polysulfide intermediate product is not generated, and the reduction of electrochemical performance caused by a lithium polysulfide shuttle effect is avoided. In addition, the benzoquinone group contained in the positive electrode material improves the conductivity of the material and accelerates the electrochemical reaction kinetics of the material. Therefore, the material has better electrochemical performance.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a preparation method of a polymer cathode material for a lithium-sulfur battery comprises the following steps:
(1) adding sodium sulfide and sulfur powder into water according to a certain proportion, and reacting to obtain an aqueous solution of sodium polysulfide;
(2) adding an aqueous solution of sodium polysulfide, 1,2, 3-trichloropropane (1,2,3-TCP), a phase transfer catalyst and 2, 5-dichloro-1, 4-p-benzoquinone (2,5-DCBQ) into water according to the concentration requirement. And reacting the mixed solution at a proper temperature for a period of time to obtain the polymer cathode material for the lithium-sulfur battery.
The reaction process of steps (1) to (2) needs to be carried out in an inert gas.
In the step (1), the sodium sulfide is sodium sulfide nonahydrate or anhydrous sodium sulfide; after the sodium sulfide is added into water, the concentration range of the sodium sulfide is 0.1mol L-1～3mol L-1。
In the step (1), the molar ratio of the sodium sulfide to the sulfur powder is 0.3-1.2.
In the step (1), sodium sulfide and sulfur powder are added into water and then react for 3-48 hours at 20-80 ℃ to obtain an aqueous solution of sodium polysulfide; the sodium polysulfide synthesized by the reaction is one or more of sodium disulfide, sodium trisulfide and sodium tetrasulfide.
In the step (2), the phase transfer catalyst is one of Cetyl Trimethyl Ammonium Bromide (CTAB), sodium dodecyl sulfate and 4- (1,1,3, 3-tetramethyl butyl) phenyl-polyethylene glycol; wherein the concentration range of the phase transfer catalyst in the mixed solution is 10mmol L-1～100mmol L-1。
In the step (2), the reaction time of the step (2) is 3-48 hours, and the reaction temperature is 20-80 ℃.
In the process of preparing the polymer cathode material for the lithium-sulfur battery in the step (2), firstly, dissolving 2,5-DCBQ in 1,2,3-TCP to prepare a 1,2,3-TCP solution of the 2,5-DCBQ, wherein the molar ratio of the 2,5-DCBQ to the 1,2,3-TCP is 0.01-0.1; then adding the 1,2,3-TCP solution of 2,5-DCBQ into water for reaction.
In the step (2), the concentration of the 1,2,3-TCP solution of 2,5-DCBQ in the mixed solution is 0.01mol L-1～0.5mol L-1The concentration of sodium polysulfide in the mixed solution is 0.01mol L-1～0.5mol L-1。
The design principle of the invention is as follows:
the invention can synthesize sodium polysulfide (NaS) with different sulfur atom numbers by controlling the molar ratio of sodium sulfide nonahydrate (or anhydrous sodium sulfide) to sublimed sulfurxAnd X is 2-4). The 2,5-DCBQ and 1,2,3-TCP were then configured as a 1,2,3-TCP solution of 2, 5-DCBQ. Wherein the molar ratio of the 2,5-DCBQ to the 1,2,3-TCP is 0.01 to 0.1. And (3) carrying out polymerization reaction on the 1,2,3-TCP solution of the 2,5-DCBQ and sodium polysulfide by using a phase transfer catalyst to obtain the cathode material. The benzoquinone group in the polymer material can change the molecular orbit of the polymer material, so that the lower electronic conductance and slow electrochemical kinetics of the polymer material are improved, and the benzoquinone group can improve the diffusion rate of lithium ions, so that the electrochemical performance of the intrinsic insulating polymer material is greatly improved, and the better electrochemical capacity exertion is realized. Meanwhile, the polymer does not generate lithium polysulfide in the charging and discharging processes, so that capacity fading caused by lithium polysulfide shuttling is eliminated. The lithium-sulfur battery is assembled by using the polymer positive electrode material for the lithium-sulfur battery, and the voltage is between 1.7V and 2.8V (vs+) Within the potential, the high electrochemical capacity exertion, the stable cycle performance and the good rate performance are realized.
The polymer anode material for the lithium-sulfur battery, prepared by the invention, realizes the simultaneous improvement of electronic and ionic conductivity, and can avoid the use of conductive materials except conductive agents. When the polymer cathode material for the lithium-sulfur battery is used as an active material, sulfur chains with lithium storage activity in the material are uniformly dispersed in an organic framework, which is beneficial to exerting the electrochemical capacity of the active component. In the positive electrode, the polymer positive electrode material for the lithium-sulfur battery and lithium ions generate solid-solid reaction, lithium polysulfide which can be dissolved in electrolyte is not generated, the shuttle effect of the lithium polysulfide is eliminated, and the capacity attenuation of the battery is inhibited. Therefore, the lithium-sulfur battery cathode material prepared by the invention can realize higher capacity exertion and better cycle stability.
The invention has the following advantages and beneficial effects:
1. the polymer cathode material for the lithium-sulfur battery prepared by the invention does not use a conductive material except a conductive agent, so that the energy density of the whole electrode material is improved.
2. The polymer anode material electrode for the lithium-sulfur battery prepared by the invention is 1.7V-2.8V (vs. Li/Li)+) When charge and discharge reactions occur within the potential, lithium polysulfide which is soluble in the electrolyte is not generated, and better cycle stability can be realized.
3. In the polymer cathode material for the lithium-sulfur battery, the sulfur chains for storing lithium are uniformly dispersed in the organic framework, so that the rapid conversion of active substances is facilitated, and the utilization rate of sulfur is improved. Meanwhile, the in-situ doped benzoquinone group increases the conductivity of the material and accelerates the electrochemical kinetics of the material. Therefore, the lithium-sulfur battery assembled by using the cathode material prepared by the invention as an electrode is between 1.7V and 2.8V (vs. Li/Li)+) High specific capacity, good cycling stability and better rate capability can be realized in the potential.
4. The synthesis strategy provided by the invention has universality, and sodium polysulfide and more organic monomers can be used for carrying out polymerization reaction to generate the polymer cathode material for the lithium-sulfur battery with more diversified functional groups.
5. The preparation method has the advantages of simple preparation process, mild preparation conditions, wide sources and low price of raw materials required by preparation, and can be used for large-scale production.
Description of the drawings:
FIG. 1 is a process flow of the present invention for preparing a polymer positive electrode material for a lithium-sulfur battery; in the figure: (a) a process flow diagram for the preparation of sodium polysulfide; (b) a process flow chart of the preparation of the polymer cathode material for the lithium-sulfur battery.
FIG. 2 is a graph of the electrochemical performance of a polytriasuifoxidate material (3S-TCP) where the electrochemical capacity is based on the entire polymer material; in the figure: (a) CV curve of 3S-TCP; (b) at 100mA g-1Under the current density, the charge-discharge curve of the 3S-TCP; (c) at 1000mAh g-1Specific capacity of 3S-TCP and coulombic efficiency under current density.
FIG. 3 is a graph of the electrochemical performance of poly (trimethylene sulfide) and carbon nanotube composites (3S-TCP/CNTs), where the electrochemical capacity is based on the entire composite; in the figure: (a) CV curve of 3S-TCP/CNTs; (b) at 100mA g-1Under the current density, the charge-discharge curve of 3S-TCP/CNTs; (c) at 1000mAh g-1Specific capacity of 3S-TCP/CNTs and coulombic efficiency under current density.
FIG. 4 is a graph of the electrochemical performance of a benzoquinone doped polytriphenylene sulfide material-1 (BP-3S-TCP-1), where the electrochemical capacity is based on the entire polymer material; in the figure: (a) CV curve of BP-3S-TCP-1; (b) at 100mA g-1Under the current density, the charge-discharge curve of BP-3S-TCP-1; (c) at 1000mAh g-1Specific capacity of BP-3S-TCP-1 and coulombic efficiency under current density. (d) Specific capacity and coulombic efficiency of BP-3S-TCP-1 under different multiplying power.
FIG. 5 is a graph of the electrochemical performance of a benzoquinone doped polytriphenylene sulfide material-2 (BP-3S-TCP-2), where the electrochemical capacity is based on the entire polymer material; in the figure: (a) at 100mA g-1Under the current density, the charge-discharge curve of BP-3S-TCP-2; (b) at 1000mAh g-1Specific capacity of BP-3S-TCP-2 and coulombic efficiency under current density.
FIG. 6 is a graph of the electrochemical performance of a benzoquinone doped polytriathiopropane material-3 (BP-3S-TCP-3), where the electrochemical capacity is based on the entire polymer material; in the figure: (a) at 100mA g-1Under the current density, the charge-discharge curve of BP-3S-TCP-2; (b) at 1000mAh g-1Specific capacity and coulombic efficiency of BP-3S-TCP-2 at current densityFigure (a).
The specific implementation mode is as follows:
the invention is illustrated below with reference to comparative examples and examples, but the content of the patent protection is not limited to the following examples.
Comparative example 1
Comparative example 1 the process for preparing 3S-TCP was carried out in three steps. In the first step, sodium sulfide trisulfide can be obtained by controlling the molar ratio of sodium sulfide nonahydrate to sublimed sulfur to be 0.5. In the second step, a CTAB aqueous solution with a concentration of 20mM was prepared. Thirdly, sodium polysulfide and TCP in the prepared sodium polysulfide solution are added into a CTAB aqueous solution with the molar ratio of 0.5, and then reacted for more than 12 hours at 30 ℃ to obtain 3S-TCP through polymerization.
3S-TCP is used as a working electrode (60 wt.% of 3S-TCP, 30 wt.% of conductive additive and 10 wt.% of binder are uniformly mixed and then coated on a carbon-containing aluminum foil current collector), a lithium sheet is used as a reference electrode and a counter electrode, and the electrolyte adopts 1M LiTFSI + DOL/DME (volume ratio of 1:1) +0.2M LiNO3And the diaphragm adopts Celgard2400 diaphragm. The working electrode is a circular sheet with the diameter of 12 mm, the lithium sheet is a circular sheet with the diameter of 15 mm, the diaphragm is a circular sheet with the diameter of 19 mm, the volume of the electrolyte is 40 microliter, and the battery case is a 2025 stainless steel battery case. During discharge test, the potential interval is 1.7V-2.8V (vs. Li/Li)+). As shown in FIG. 2a, 3S-TCP shows a reduction peak at 2.08V during the discharge process. As shown in FIG. 2b, 3S-TCP is at 100mA g-1Under the current density, a discharge platform appears at about 2.1V, and 175mAh g is realized-1Specific discharge capacity of (2). The difference between the charging voltage platform and the discharging voltage platform of the 3S-TCP is large, about 0.15V, and the voltage platform is unstable, which shows large electrode polarization. As shown in fig. 2c, at 1000mA g-1Current density and 1.7V-2.8V (vs. Li/Li)+) The potential is charged and discharged, the electrochemical capacity of the 3S-TCP is extremely low, and the specific capacity is about 50mAh g-1And after 250 long cycles, about 42mAh g was maintained-1The specific capacity of (A). Therefore, the original 3S-TCP shows poor electrochemical performance and is not suitable for direct use as a positive electrode active material.
Comparative example 2
Comparative example 2 the process for the preparation of 3S-TCP/CNTs was carried out in three steps. In the first step, sodium sulfide trisulfide can be obtained by controlling the molar ratio of sodium sulfide nonahydrate to sublimed sulfur to be 0.5. And secondly, preparing a CTAB Carbon Nano Tube (CNTs) dispersion liquid with the concentration of 20 mM. Thirdly, adding the prepared sodium polysulfide solution and TCP into carbon nano tube dispersion liquid of 20mM CTAB according to the mol ratio of 0.5, and then reacting for more than 12 hours at 30 ℃ to obtain 3S-TCP/CNTs through polymerization reaction.
Sodium sulfide nonahydrate and sublimed sulfur are synthesized into sodium trisulfide according to the molar ratio of 1: 2. Subsequently, a carbon nanotube dispersion of CTAB was prepared. Then, the prepared sodium trisulfide solution and TCP are added into carbon nano tube dispersion liquid of CTAB, and poly-trisulfide propane and carbon nano tube composite material (3S-TCP/CNTs) are obtained through polymerization reaction. 3S-TCP/CNTs is used as a working electrode (70 wt.% of 3S-TCP/CNTs, 20 wt.% of conductive additive and 10 wt.% of binder are uniformly mixed and then coated on a carbon-containing aluminum foil current collector), a lithium sheet is used as a reference electrode and a counter electrode, and the electrolyte adopts 1M LiTFSI + DOL/DME (volume ratio of 1:1) +0.2M LiNO3And the diaphragm adopts Celgard2400 diaphragm. The working electrode is a circular sheet with the diameter of 12 mm, the lithium sheet is a circular sheet with the diameter of 15 mm, the diaphragm is a circular sheet with the diameter of 19 mm, the volume of the electrolyte is 40 microliter, and the battery case is a 2025 stainless steel battery case. During discharge test, the potential interval is 1.7V-2.8V (vs. Li/Li)+). As shown in FIG. 3a, 3S-TCP/CNTs showed a reduction peak at 2.08V during the discharge. As shown in FIG. 3b, 3S-TCP/CNTs was at 100mA g-1Under the current density, a discharge platform appears at about 2.1V, and 425mAh g is realized-1Specific discharge capacity of (2). As shown in FIG. 3c, at 1000mA g-1Current density and 1.7V-2.8V (vs. Li/Li)+) The 3S-TCP/CNTs can realize more than 300mAh g by charge and discharge in the potential-1And after 250 long cycles, about 110mAh g was maintained-1The specific capacity of (A). The introduction of the carbon nanotube conductive material improves the electrochemical performance of 3S-TCP, but reduces the energy density of the whole electrode. Moreover, the carbon nanotube material itself is expensive, which is not suitable for large-scale commercializationAnd (4) producing.
Example 1
Example 1 the process for the preparation of BP-3S-TCP-1 was carried out in three steps. In the first step, sodium sulfide trisulfide can be obtained by controlling the molar ratio of sodium sulfide nonahydrate to sublimed sulfur to be 0.5. Thirdly, mixing the 2,5-DCBQ and the 1,2,3-TCP according to the molar ratio of 0.01 to prepare a 1,2,3-TCP solution of the 2, 5-DCBQ. The fourth step was to add the prepared sodium polysulfide solution and 1,2,3-TCP solution containing 2,5-DCBQ in a molar ratio of 0.5 to an aqueous solution of CTAB 20mM, followed by reaction at 30 ℃ for 24 hours to obtain BP-3S-TCP-1.
BP-3S-TCP-1 is used as a working electrode (60 wt.% of BP-3S-TCP-1, 30 wt.% of conductive additive and 10 wt.% of binder are uniformly mixed and then coated on a carbon-containing aluminum foil current collector), a lithium sheet is used as a reference electrode and a counter electrode, and the electrolyte adopts 1M LiTFSI + DOL/DME (volume ratio of 1:1) +0.2M LiNO3And the diaphragm adopts Celgard2400 diaphragm. The working electrode is a circular sheet with the diameter of 12 mm, the lithium sheet is a circular sheet with the diameter of 15 mm, the diaphragm is a circular sheet with the diameter of 19 mm, the volume of the electrolyte is 40 microliter, and the battery case is a 2025 stainless steel battery case. During discharge test, the potential interval is 1.7V-2.8V (vs. Li/Li)+). As shown in FIG. 4a, a reduction peak of BP-3S-TCP-1 appeared at 2.05V during the discharge. As shown in FIG. 4b, BP-3S-TCP-1 is at 100mA g-1Under the current density, a discharge platform appears at about 2.1V, and about 630mAh g is realized-1Specific discharge capacity of (2). Meanwhile, the charge-discharge curve of BP-3S-TCP-1 shows that the difference between the charge voltage plateau and the discharge voltage plateau is very small, about 0.05V, which is much smaller than the voltage difference of the material in comparative example 1 (FIG. 2 b). This demonstrates that the benzoquinone group in BP-3S-TCP-1 improves electrochemical kinetics. In addition, in FIGS. 4a and b, the unique discharge peak or discharge plateau can demonstrate that BP-3S-TCP-1 undergoes a solid-solid reaction during discharge, and does not produce lithium polysulfide that is soluble in the electrolyte. As shown in FIG. 4c, at 1000mA g-1Current density and 1.7V-2.8V (vs. Li/Li)+) The potential is charged and discharged, BP-3S-TCP-1 can realize the approximate 300mAh g-1And after 250 long cycles, about 190mAh g was maintained-1The specific capacity is better than that of 3S-The cycle performance of TCP/CNTs (FIG. 3c) is much higher than the comprehensive electrochemical performance of 3S-TCP (FIG. 2 c). As shown in FIG. 4d, at 2000mA g-1BP-3S-TCP-1 can still maintain 250mAh g at the current density of-1The specific capacity of (A). In conclusion, the electrochemical performance of the non-conductive polymer active material is greatly improved by doping the benzoquinone group into the 3S-TCP. And, this achieves electrochemical capacity exertion and better cycle stability similar to those of electrodes using expensive carbon nanotube conductive materials.
Example 2
Example 2 below the procedure for the preparation of BP-3S-TCP-2 was carried out in three steps. In the first step, sodium sulfide trisulfide can be obtained by controlling the molar ratio of sodium sulfide nonahydrate to sublimed sulfur to be 0.5. Thirdly, mixing the 2,5-DCBQ and the 1,2,3-TCP according to the molar ratio of 0.01 to prepare a 1,2,3-TCP solution of the 2, 5-DCBQ. The fourth step was to add the prepared sodium polysulfide solution and 1,2,3-TCP solution containing 2,5-DCBQ in a molar ratio of 0.5 to an aqueous solution of 18mM CTAB, followed by reaction at 30 ℃ for 24 hours to obtain BP-3S-TCP-2.
Sodium sulfide nonahydrate and sublimed sulfur are synthesized into sodium trisulfide according to the molar ratio of 1: 2. Subsequently, an aqueous solution of CTAB was prepared. Then, the prepared sodium trisulfide solution and the 1,2,3-TCP solution of 2,5-DCBQ are added into a CTAB aqueous solution, and a benzoquinone doped polytriasulfide propane material-2 (BP-3S-TCP-2) is obtained through a polymerization reaction. BP-3S-TCP-2 is used as a working electrode (60 wt.% of BP-3S-TCP-2, 30 wt.% of conductive additive and 10 wt.% of binder are uniformly mixed and then coated on a carbon-containing aluminum foil current collector), a lithium sheet is used as a reference electrode and a counter electrode, and the electrolyte adopts 1M LiTFSI + DOL/DME (volume ratio of 1:1) +0.2M LiNO3And the diaphragm adopts Celgard2400 diaphragm. The working electrode is a circular sheet with the diameter of 12 mm, the lithium sheet is a circular sheet with the diameter of 15 mm, the diaphragm is a circular sheet with the diameter of 19 mm, the volume of the electrolyte is 40 microliter, and the battery case is a 2025 stainless steel battery case. During discharge test, the potential interval is 1.7V-2.8V (vs. Li/Li)+). As shown in FIG. 5a, BP-3S-TCP-2 is at 100mA g-1Under the current density, a discharge platform appears at about 2.1V, and about 445mAh g is realized-1Specific discharge capacity of (2). Of, at the same time, BP-3S-TCP-2The charge and discharge curves show a very small difference between the charge voltage plateau and the discharge voltage plateau, about 0.05V, much smaller than the voltage difference of the material of comparative example 1 (fig. 2 b). This demonstrates that the benzoquinone group in BP-3S-TCP-2 improves electrochemical kinetics. In addition, in FIG. 5a), a single discharge plateau can demonstrate that BP-3S-TCP-2 undergoes a solid-solid reaction during discharge, and does not produce lithium polysulfide that is soluble in the electrolyte. As shown in FIG. 5(b), g was set at 1000mA-1Current density and 1.7V-2.8V (vs. Li/Li)+) The BP-3S-TCP-2 can realize 291mAh g-1The specific capacity of the resin is high, and 184mAh g is kept after 250 times of long circulation-1The specific capacity is superior to the cycle performance of 3S-TCP/CNTs (figure 3c) and is far higher than the comprehensive electrochemical performance of 3S-TCP (figure 2 c). The reduction in the concentration of the phase transfer catalyst does not affect the effect of the benzoquinone groups in the resulting polymeric material. Example 2 still achieves a better exertion of electrochemical properties.
Example 3
Example 3 below the procedure for the preparation of BP-3S-TCP-3 was carried out in three steps. In the first step, sodium sulfide trisulfide can be obtained by controlling the molar ratio of sodium sulfide nonahydrate to sublimed sulfur to be 0.5. In the second step, a CTAB aqueous solution with a concentration of 20mM was prepared. Thirdly, mixing the 2,5-DCBQ and the 1,2,3-TCP according to the molar ratio of 0.01 to prepare a 1,2,3-TCP solution of the 2, 5-DCBQ. The fourth step was to add the prepared sodium polysulfide solution and 1,2,3-TCP solution containing 2,5-DCBQ in a molar ratio of 0.5 to an aqueous solution of 20mM CTAB, followed by reaction at 30 ℃ for 12 hours to obtain BP-3S-TCP-3.
Sodium sulfide nonahydrate and sublimed sulfur are synthesized into sodium trisulfide according to the molar ratio of 1: 2. Subsequently, an aqueous solution of CTAB was prepared. Then, the prepared sodium trisulfide solution and the 1,2,3-TCP solution of 2,5-DCBQ are added into a CTAB aqueous solution, and a benzoquinone doped polytriasulfide propane material-3 (BP-3S-TCP-3) is obtained through a polymerization reaction. BP-3S-TCP-3 is used as a working electrode (60 wt.% of BP-3S-TCP-2, 30 wt.% of conductive additive and 10 wt.% of binder are uniformly mixed and then coated on a carbon-containing aluminum foil current collector), a lithium sheet is used as a reference electrode and a counter electrode, and the electrolyte adopts 1M LiTFSI + DOL/DME (volume ratio of 1:1) +0.2M LiNO3And the diaphragm adopts Celgard2400 diaphragm. The working electrode is a circular sheet with the diameter of 12 mm, the lithium sheet is a circular sheet with the diameter of 15 mm, the diaphragm is a circular sheet with the diameter of 19 mm, the volume of the electrolyte is 40 microliter, and the battery case is a 2025 stainless steel battery case. During charge and discharge test, the potential range is 1.7V-2.8V (vs. Li/Li)+). As shown in FIG. 5a, BP-3S-TCP-3 is at 100mA g-1Under the current density, a discharge platform appears at about 2.1V, and about 490mAh g is realized-1Specific discharge capacity of (2). Meanwhile, the charge-discharge curve of BP-3S-TCP-3 shows that the difference between the charge voltage platform and the discharge voltage platform is very small, about 0.05V, and is much smaller than the voltage difference of the material in comparative example 1 (FIG. 2b), which proves that the quinone group in BP-3S-TCP-3 improves electrochemical kinetics. In addition, in FIG. 6a, a single discharge plateau can demonstrate that BP-3S-TCP-2 undergoes a solid-solid reaction during discharge, and does not produce lithium polysulfide that is soluble in the electrolyte. As shown in fig. 6b, at 1000mA g-1Current density and 1.7V-2.8V (vs. Li/Li)+) The potential is charged and discharged, and the BP-3S-TCP-3 can realize 360mAh g-1And after 250 long cycles, about 238mAh g was maintained-1The specific capacity of the composite is better than the electrochemical performance of 3S-TCP/CNTs (figure 3c) and is far higher than the electrochemical performance of 3S-TCP (figure 2 c). The reduction of the reaction time does not affect the doping effect of benzoquinone in the obtained polymer material, but improves the electrochemical capacity of the material. Among them, the electrochemical stability of the material is slightly poor, but the material is still not output to the 3S-TCP/CNTs electrode.
Thus, based on the above examples and comparative examples, we have adopted a novel process of in situ doping of the polymer material with a benzoquinone group. The method greatly improves the electrochemical capacity exertion of the polymer material and realizes better cycle performance and rate performance. At the same time, this avoids the use of expensive non-conductive carbon materials. Moreover, the preparation method is simple, the preparation conditions are mild, the expanded production is facilitated, and the method has a wide commercial prospect.
Furthermore, the above-described embodiments are merely illustrative descriptions of the present patent and are not to be construed as limitations of the present patent. Any improvements and modifications that may be made based on the principles and techniques of this patent are intended to be covered by this patent.

Claims (9)

1. A preparation method of a polymer positive electrode material for a lithium-sulfur battery is characterized by comprising the following steps: the method comprises the following steps:
(1) adding sodium sulfide and sulfur powder into water according to a certain proportion, and reacting to obtain an aqueous solution of sodium polysulfide;
(2) adding an aqueous solution of sodium polysulfide, 1,2, 3-trichloropropane (1,2,3-TCP), a phase transfer catalyst and 2, 5-dichloro-1, 4-benzoquinone (2,5-DCBQ) into water according to the concentration requirement; and reacting the mixed solution at a proper temperature for a period of time to obtain the polymer cathode material for the lithium-sulfur battery.
2. The method of preparing a polymer positive electrode material for a lithium sulfur battery according to claim 1, characterized in that: the reaction process of steps (1) to (2) needs to be carried out in an inert gas.
3. The method of preparing a polymer positive electrode material for a lithium sulfur battery according to claim 1, characterized in that: in the step (1), the sodium sulfide is sodium sulfide nonahydrate or anhydrous sodium sulfide; after the sodium sulfide is added into water, the concentration range of the sodium sulfide is 0.1mol L-1～3mol L-1。
4. The method of preparing a polymer positive electrode material for a lithium sulfur battery according to claim 1, characterized in that: in the step (1), the molar ratio of the sodium sulfide to the sulfur powder is 0.3-1.2.
5. The method of preparing a polymer positive electrode material for a lithium sulfur battery according to claim 1, characterized in that: in the step (1), sodium sulfide and sulfur powder are added into water and then react for 3-48 hours at 20-80 ℃ to obtain an aqueous solution of sodium polysulfide; the sodium polysulfide synthesized by the reaction is one or more of sodium disulfide, sodium trisulfide and sodium tetrasulfide.
6. The method of preparing a polymer positive electrode material for a lithium sulfur battery according to claim 1, characterized in that: in the step (2), the phase transfer catalyst is one of cetyl trimethyl ammonium bromide, sodium dodecyl sulfate and 4- (1,1,3, 3-tetramethyl butyl) phenyl-polyethylene glycol; wherein the concentration range of the phase transfer catalyst in the mixed solution is 10mmol L-1～100mmol L-1。
7. The method of preparing a polymer positive electrode material for a lithium sulfur battery according to claim 1, characterized in that: the reaction time of the step (2) is 3-48 hours, and the reaction temperature is 20-80 ℃.
8. The method of preparing a polymer positive electrode material for a lithium sulfur battery according to claim 1, characterized in that: in the process of preparing the polymer cathode material for the lithium-sulfur battery in the step (2), firstly, dissolving 2,5-DCBQ in 1,2,3-TCP to prepare a 1,2,3-TCP solution of the 2,5-DCBQ, wherein the molar ratio of the 2,5-DCBQ to the 1,2,3-TCP is 0.01-0.1; then adding the 1,2,3-TCP solution of 2,5-DCBQ into water for reaction.
9. The method of preparing a polymer positive electrode material for a lithium sulfur battery according to claim 8, characterized in that: in the step (2), the concentration of the 1,2,3-TCP solution of 2,5-DCBQ in the mixed solution is 0.01mol L-1～0.5mol L-1The concentration of sodium polysulfide in the mixed solution is 0.01mol L-1～0.5mol L-1。
CN202010057562.5A 2020-01-19 2020-01-19 Preparation method of polymer positive electrode material for lithium-sulfur battery Pending CN113140710A (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105885048A (en) * 2014-12-12 2016-08-24 中国人民解放军63971部队 Polythioquinone and preparation method thereof
CN108258213A (en) * 2018-01-05 2018-07-06 中国科学院金属研究所 A kind of organic polymer sulphur/nano carbon-base composite material and its application in lithium-sulfur cell

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105885048A (en) * 2014-12-12 2016-08-24 中国人民解放军63971部队 Polythioquinone and preparation method thereof
CN108258213A (en) * 2018-01-05 2018-07-06 中国科学院金属研究所 A kind of organic polymer sulphur/nano carbon-base composite material and its application in lithium-sulfur cell

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Application publication date: 20210720