WO2017139941A1 - Method for preparing graphene / polyanthraquinone thioether / sulfur-composite anode material - Google Patents

Abstract

The present invention provides a method for preparing a polyanthraquinone thioether / graphene / sulfur-composite anode material, comprising the following steps: (1) dissolving sodium sulfide and elemental sulfur in distilled water to obtain an orange solution, and adding Triton X-100 and adding concentrated hydrochloric acid to gradually form a yellow suspension; (2) adding graphite oxide to the distilled water and subjecting to ultrasound to obtain a graphene oxide solution; adding the aforementioned yellow suspension to obtain graphene oxysulfide; (3) adding the obtained graphene-oxysulfide composite material to a potassium iodide solution, then adding dilute hydrochloric acid to obtain a sulfur-graphene composite material; (4) adding the obtained sulfur-graphene composite material to N-methyl-2-pyrrolidone and stirring, then adding 1,5-dichloroanthraquinone and stirring, then adding anhydrous sodium sulfide to obtain a polyanthraquinone / graphene / sulfur composite material. In the present invention, sulfur is covered by graphene and polyanthraquinone having flexibility, and can inhibit the dissolution of a discharge product polysulfide and mitigate its volume expansion.

Description

Method for preparing graphene/polyfluorene sulfide/sulfur composite cathode material Technical field

The invention belongs to the field of nano material synthesis, and relates to a preparation method of a cathode material for a lithium sulfur battery, in particular to a method for preparing a graphene/polyfluorene sulfide/sulfur composite cathode material.

Background technique

The lithium-sulfur battery is a battery system in which lithium metal is used as a negative electrode and elemental sulfur is used as a positive electrode. Lithium-sulfur batteries have two discharge platforms (about 2.4V and 2.1V), but their electrochemical reaction mechanism is complicated. Lithium-sulfur batteries have the advantages of high specific energy (2600Wh/kg), high specific capacity (1675mAh/g), low cost, etc., and are considered to be promising new generation batteries. However, at present, there are problems such as low utilization rate of active materials, low cycle life and poor safety, which seriously restricts the development of lithium-sulfur batteries. The main causes of the above problems are as follows: (1) Elemental sulfur is an electron and ionic insulator, and the room temperature conductivity is low (5 × 10 ^{-3 OS} · cm ^-1 ). Since there is no ionic sulfur, it acts as a positive electrode. (1) Lithium polysulfide Li ₂ S _n (8>n≥4) produced during the electrode reaction is easily soluble in the electrolyte, forming a concentration difference between the positive and negative electrodes. The gradient migrates to the negative electrode, and the high poly lithium polysulfide is reduced by the lithium metal to the oligomeric lithium polysulfide. As the above reaction proceeds, the oligomeric lithium polysulfide aggregates at the negative electrode, eventually forming a concentration difference between the two electrodes, and then migrating to the positive electrode to be oxidized to a highly polylithium polysulfide. This phenomenon is known as the shuttle effect, which reduces the utilization of sulfur active substances. At the same time, insoluble Li ₂ S and Li ₂ S _{2 are} deposited on the surface of the lithium negative electrode, which further deteriorates the performance of the lithium-sulfur battery; (3) the final product of the reaction, Li ₂ S, is also an electronic insulator, which is deposited on the sulfur electrode, and lithium The migration speed of ions in solid lithium sulfide is slow, which makes the electrochemical reaction kinetics slower. (4) The density of sulfur and the final product Li ₂ S is different. When the sulfur is lithiated, the volume expands by about 79%, which easily leads to Li _{2 .} The powdering of S causes safety problems in lithium-sulfur batteries. The above-mentioned shortcomings restrict the development of lithium-sulfur batteries, which is also the key issue that needs to be solved in the research of lithium-sulfur batteries.

technical problem

The invention provides a graphene/polyfluorene sulfide/sulfur composite material, the preparation method is simple, the conductive conductive graphene provides a conductive network, and the sulfur particles are coated to limit the movement of the polysulfide, and the outer layer Polysulfide sulfide coated with sulfur nanographene to improve the conductivity of sulfur and prevent the vulcanization of discharge products The dissolution of the substance and the volume expansion are relieved. At the same time, the ultra-high lithium ion conductivity of the polysulfonium sulfide can effectively conduct lithium ions. The composite material is used as the positive electrode of the lithium-sulfur battery, and has the characteristics of high capacity, high magnification and stable cycle performance. .

Problem solution

Technical solution

The specific scheme is as follows: a preparation method of a graphene/polyfluorene sulfide/sulfur composite cathode material, comprising the following steps:

(1) Sodium sulfide and elemental sulfur were ground in an agate mortar in proportion, and then the mixture was dissolved in distilled water to obtain an orange solution. Triton X-100 was added to the above solution, and 37.5% concentrated hydrochloric acid was added while stirring to gradually form. Yellow suspension

(2) Adding graphite oxide to distilled water to obtain a graphene oxide solution, adding the graphene oxide solution to the above yellow suspension, stirring in a water bath, and obtaining a suspension which is centrifuged, washed with water, and freeze-dried to obtain dark gray sulfur oxide graphite. Alkene composite material;

(3) adding the obtained sulfur oxide graphene composite material to potassium iodide solution, then adding 10% hydrochloric acid, sealing, and moving to a dark environment for reaction, centrifugation, water washing, ethanol washing, sulfur graphene composite material;

(4) The obtained sulfur graphene composite material is added to N-methylpyrrolidone to form a suspension of 1 g/L, and then stirred with 1,5-dichloroanthracene, then anhydrous sodium sulfide is added, and the mixture is stirred and refluxed. Set, filter, and vacuum dry to obtain a polysulfide sulfide/graphene/sulfur composite.

Preferably, the mass ratio of sodium sulfide to elemental sulfur in the step (1) is 1:1 to 1:5, the mass fraction of Triton X-100 is 1%, and the sodium sulfide and the mass fraction Triton X- in the step (1) The ratio of 100 solutions is 1-50 g: 1 ml.

Preferably, in the step (2), the mass ratio of the graphite oxide to the sodium sulfide in the step (1) is 1:5-50.

Preferably, in the step (3), the ratio of the amount of the graphite oxide to the potassium iodide solution is 1 mg: 1-5 ml; and the ratio of the amount of hydrochloric acid to the potassium iodide solution is 1:5-10.

Preferably, in the step (4), the mass ratio of ruthenium to sodium sulfide in the step (1) is 1:10-50; the anhydrous sodium sulfide and the 1,5-dichloroguanidine in the step (4) The molar ratio is 1:0.5-2.

Preferably, in the step (1), the mass fraction of concentrated hydrochloric acid is 30%, and in the step (3), the thinning The mass fraction of hydrochloric acid is 10%.

Advantageous effects of the invention

Beneficial effect

The invention has the following beneficial effects: (1) The graphene/polyfluorene sulfide/sulfur composite material prepared by the method prepared by the method has a three-layer structure, the inner layer of sulfur particles, and the intermediate layer is curved graphene coating. The outer layer is a polysulfide sulfide coating; (2) both graphene and polysulfonium sulfide have ultra-high conductivity, and the polysulfonium sulfide also has an ultra-high lithium ion conductivity. The polyfluorene sulfide/graphene/sulfur composite prepared by the method can effectively improve the electronic conductivity and ionic conductivity of the cathode material of lithium-sulfur battery; (3) polyfluorene sulfide/graphene/sulfur composite material Sulfur is coated with flexible graphene and polysulfonium sulfide, which can inhibit the dissolution of polysulfide of the discharge product and relieve volume expansion.

Brief description of the drawing

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an SEM image of a polyfluorene sulfide/graphene/sulfur composite prepared in accordance with the present invention.

Invention embodiment

Embodiments of the invention

The preferred embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

Example 1

(1) 10 g of sodium sulfide and 50 g of elemental sulfur were ground in an agate mortar, and then the mixture was dissolved in distilled water to obtain an orange solution, and 10 ml of a 1% by mass of Triton X-100 was added to the above solution, and stirred for 3 hours, and then Continuously add 30% concentrated hydrochloric acid, stir for 3 h, and gradually form a yellow suspension.

(2) 2 g of graphite oxide was added to distilled water for 30 min to form a 1 g/L graphene oxide solution, and the graphene oxide solution was added to the above yellow suspension, and stirred in a water bath at 70 ° C for 1 h, and the obtained suspension was centrifuged and washed with water. After lyophilization, a dark gray sulfur oxide graphene composite material was obtained.

(3) Add the obtained sulfur oxide graphene composite material to 2L of 2mol/L potassium iodide solution, then quickly add 0.4L of 10% hydrochloric acid, seal, and move to dark environment for 1h, centrifuge, wash. , ethanol wash, sulfur graphene composite.

(4) Adding the obtained sulfur graphene composite material to N-methylpyrrolidone and stirring for 10 minutes to form 1 g/L. The suspension was stirred with 1 g of 1,5-dichloropurine for 1 h, then 0.141 g of anhydrous sodium sulfide was added, stirred under reflux for 10 h, allowed to stand, filtered, and dried in vacuo to obtain polysulfonium sulfide/graphene/ Sulfur composites.

Example 2

(1) 50 g of sodium sulfide and 50 g of elemental sulfur were ground in an agate mortar, and then the mixture was dissolved in distilled water to obtain an orange solution, and 1 ml of a 1% by mass of Triton X-100 was added to the above solution, and stirred for 3 hours, and then continuously A 30% concentrated hydrochloric acid was added and stirred for 3 hours to gradually form a yellow suspension.

(2) 1 g of graphite oxide was added to distilled water for 30 min to form a 1 g/L graphene oxide solution, and the graphene oxide solution was added to the above yellow suspension, and stirred in a water bath at 70 ° C for 1 h, and the obtained suspension was centrifuged and washed with water. After lyophilization, a dark gray sulfur oxide graphene composite material was obtained.

(3) Add the obtained sulfur oxide graphene composite material to 5L of 2mol/L potassium iodide solution, then quickly add 0.5L of 10% hydrochloric acid, seal, and transfer to dark environment for 1h, centrifuge, wash. , ethanol wash, sulfur graphene composite.

(4) The obtained sulfur graphene composite material was added to N-methylpyrrolidone and stirred for 10 minutes to form a suspension of 1 g/L, and 1 g of 1,5-dichloroanthracene was added for stirring for 5 hours, and then 0.564 g of anhydrous sulfurized was added. The sodium was stirred under reflux for 24 hours, allowed to stand, filtered, and vacuum dried to obtain a polyfluorene sulfide/graphene/sulfur composite.

Example 3

(1) 10 g of sodium sulfide and 20 g of elemental sulfur were ground in an agate mortar, and then the mixture was dissolved in distilled water to obtain an orange solution, and 1 ml of a 1% by mass of Triton X-100 was added to the above solution, and stirred for 3 hours, and then continuously A 30% concentrated hydrochloric acid was added and stirred for 3 hours to gradually form a yellow suspension.

(2) 1 g of graphite oxide was added to distilled water for 30 min to form a 1 g/L graphene oxide solution, and the graphene oxide solution was added to the above yellow suspension, and stirred in a water bath at 70 ° C for 1 h, and the obtained suspension was centrifuged and washed with water. After lyophilization, a dark gray sulfur oxide graphene composite material was obtained.

(3) Add the obtained sulfur oxide graphene composite material to 2L of 2mol/L potassium iodide solution, then quickly add 0.3L of 10% hydrochloric acid, seal, and move to dark environment for 1h, centrifuge, wash. , ethanol wash, sulfur graphene composite.

(4) The obtained sulfur graphene composite material was added to N-methylpyrrolidone and stirred for 10 minutes to form a suspension of 1 g/L, 0.5 g of 1,5-dichloroanthracene was added for stirring for 4 hours, and then 0.141 g of anhydrous was added. Sodium sulfide, stirred under reflux for 15 h, allowed to stand, filtered, and vacuum dried to obtain a polysulfide sulfide/graphene/sulfur composite.

Example 4

(1) 10 g of sodium sulfide and 30 g of elemental sulfur were ground in an agate mortar, and then the mixture was dissolved in distilled water to obtain an orange solution, 0.5 ml of a 1% portion of Triton X-100 was added to the above solution, and stirred for 3 hours, and then Continuously add 30% concentrated hydrochloric acid, stir for 3 h, and gradually form a yellow suspension.

(2) 0.5 g of graphite oxide was added to distilled water for 30 min to form a 1 g/L graphene oxide solution, and the graphene oxide solution was added to the above yellow suspension, and stirred in a water bath at 70 ° C for 1 h, and the obtained suspension was centrifuged and washed. After lyophilization, a dark gray sulfur oxide graphene composite material is obtained.

(3) Add the obtained sulfur oxide graphene composite material to 1.5 L of a 2 mol/L potassium iodide solution, and then quickly add 0.2 L of 10% hydrochloric acid, seal, and transfer to a dark environment for 1 h, and centrifuge. Washed, washed with ethanol, sulfur graphene composite.

(4) The obtained sulfur graphene composite material was added to N-methylpyrrolidone and stirred for 10 minutes to form a suspension of 1 g/L, and 0.35 g of 1,5-dichloroanthracene was added and stirred for 2 hours, and then 0.148 g of anhydrous was added. Sodium sulfide, stirred under reflux for 20 h, allowed to stand, filtered, and vacuum dried to obtain a polysulfide sulfide/graphene/sulfur composite material.

Example 5

(1) 10 g of sodium sulfide and 40 g of elemental sulfur were ground in an agate mortar, and then the mixture was dissolved in distilled water to obtain an orange solution, and 0.25 ml of a 1% by mass of Triton X-100 was added to the above solution, and stirred for 3 hours. Then, a mass fraction of 30% concentrated hydrochloric acid was continuously added, and the mixture was stirred for 3 hours to gradually form a yellow suspension.

(2) 0.25 g of graphite oxide was added to distilled water for 30 min to form a 1 g/L graphene oxide solution, and the graphene oxide solution was added to the above yellow suspension, and stirred in a water bath at 70 ° C for 1 h, and the obtained suspension was centrifuged and washed. After lyophilization, a dark gray sulfur oxide graphene composite material is obtained.

(3) Add the obtained sulfur oxide graphene composite material to 1L concentration of 2mol/L potassium iodide solution, then quickly add 0.12L of 10% hydrochloric acid, seal, and transfer to dark environment for 1h, centrifuge, wash. , ethanol wash, sulfur graphene composite.

(4) The obtained sulfur graphene composite material was added to N-methylpyrrolidone and stirred for 10 minutes to form a suspension of 1 g/L, and 0.25 g of 1,5-dichloroanthracene was added for stirring for 3 hours, and then 0.084 g of anhydrous was added. Sodium sulfide, stirred under reflux for 18 h, allowed to stand, filtered, and vacuum dried to obtain a polysulfide sulfide/graphene/sulfur composite.

Electrode preparation and performance test; electrode material, acetylene black and PVDF were mixed in NMP at a mass ratio of 80:10:10, coated on aluminum foil as electrode film, lithium metal plate as counter electrode, CELGARD 2400 as separator, 1 mol /L LiTFSI/DOL-DME (volume ratio 1:1) is an electrolyte, 1 mol/L LiNO ₃ is an additive, assembled into a button-type battery in a filled glove box, and a constant current charge and discharge is performed using a Land battery test system. test. The charge and discharge voltage range is 1-3V, the current density is 0.01C, and the performance is shown in Table 1.

Table 1

[Table 1]

As shown in Figure 1, the SEM image of the graphene/polysulfide sulfide/sulfur composite shows that the graphene is bent and wrapped on the surface of the nano-sulfur particles instead of the usual lamellar structure. The ether is also coated on the outer layer of graphene, which can effectively prevent the expansion of sulfur and the shuttle of polysulfide to affect the capacity.

The above is a further detailed description of the present invention in connection with the specific preferred embodiments, and the specific embodiments of the present invention are not limited to the description. It will be apparent to those skilled in the art that the present invention may be made without departing from the spirit and scope of the invention.

Claims (7)

A preparation method of a polyfluorene sulfide/graphene/sulfur composite cathode material, comprising the following steps: (1) Sodium sulfide and elemental sulfur are ground in an agate mortar in proportion, and then the mixture is dissolved in distilled water to obtain an orange solution. Triton X-100 is added to the above solution, and concentrated hydrochloric acid is added while stirring to gradually form a yellow suspension. ; (2) Adding graphite oxide to distilled water to obtain a graphene oxide solution, adding the graphene oxide solution to the above yellow suspension, stirring in a water bath, and obtaining a suspension which is centrifuged, washed with water, and freeze-dried to obtain dark gray sulfur oxide graphite. Alkene composite material; (3) adding the obtained sulfur oxide graphene composite material to a potassium iodide solution, then adding dilute hydrochloric acid, sealing, and moving to a dark environment for reaction, centrifugation, water washing, ethanol washing, and sulfur graphene composite material; (4) The obtained sulfur graphene composite material is added to N-methylpyrrolidone and stirred, and then 1,5-dichloroanthracene is added to stir, then anhydrous sodium sulfide is added, stirred, refluxed, allowed to stand, filtered, and vacuum dried. , obtaining a polysulfide sulfide/graphene/sulfur composite material. The preparation method according to claim 1, wherein the mass ratio of sodium sulfide to elemental sulfur in the step (1) is 1:1 to 1:5, and the mass fraction of Triton X-100 is 1%, the step ( 1) The ratio of sodium sulfide to mass fraction of Triton X-100 solution is 1-50 g: 1 ml. The preparation method according to claim 1, wherein in the step (2), the mass ratio of the graphite oxide to the sodium sulfide in the step (1) is 1:5-50. The preparation method according to claim 1, wherein in the step (3), the ratio of the amount of the graphite oxide to the potassium iodide solution is 1 mg: 1-5 ml; and the volume ratio of the hydrochloric acid to the potassium iodide solution is 1:5 - 10. The preparation method according to claim 1, wherein in the step (4), the mass ratio of the 1,5-dichloroanthracene to the sodium sulfide in the step (1) is 1:10-50; In 4), the molar ratio of anhydrous sodium sulfide to 1,5-dichloroanthracene is 1:0.5-2. The preparation method according to claim 1, wherein in the step (4), The reflux time was stirred for 10-24 h. The preparation method according to claim 1, wherein in the step (1), the mass fraction of concentrated hydrochloric acid is 30%, and in the step (3), the mass fraction of dilute hydrochloric acid is 10%.

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