WO2018184156A1

WO2018184156A1 - Preparation method of composite material having nitrogen-doped graphene/manganese dioxide/hollow sulfur particles

Info

Publication number: WO2018184156A1
Application number: PCT/CN2017/079505
Authority: WO
Inventors: 钟玲珑
Original assignee: 深圳市佩成科技有限责任公司
Priority date: 2017-04-05
Filing date: 2017-04-05
Publication date: 2018-10-11

Abstract

Provided in the present invention is a preparation method of a composite material having nitrogen-doped graphene/manganese dioxide/hollow sulfur particles, the method comprising the following steps: step (1), adding sulfur powder into carbon disulfide, and stirring and dissolving the same to obtain a homogeneous solution; step (2), ball milling high purity nickel powder by means of a high energy ball mill, adding the ball-milled product into the aforementioned solution, stirring the same to form a homogeneous suspension, performing mechanical stirring, and spraying and drying to obtain sulfur-coated spherical particles; step (3), adding the spherical particles into a solution added with iron chloride, stirring to react, and rinsing with water and filtering; and step (4), adding the filtered-out precipitate into a solution containing manganese chloride and potassium permanganate, stirring to form a homogeneous suspension, heating and stirring to react, and performing centrifugation and water rinsing to obtain sulfur particles coated with manganese dioxide. The composite material is designed to have a hollow structure to reserve space for volume expansion of the sulfur material during a charging or discharging process, thus effectively improving electrochemical properties.

Description

Title: Preparation method of nitrogen-doped graphene/manganese dioxide/hollow sulfur composite material

[0001] The present invention relates to nanomaterial synthesis, and in particular to a method for preparing a lithium sulfur battery cathode material.

Background technique

[0002] A lithium-sulfur battery is a battery system in which lithium metal is used as a negative electrode and elemental sulfur is a positive electrode. Lithium-sulfur batteries have two discharge platforms (approximately 2.4 V and 2.1 V), but their electrochemical reaction mechanisms are complex. Lithium-sulfur batteries have the advantages of high specific energy (2600 Wh/kg), high specific capacity (1675 mAh/g), and low cost, and are considered to be promising new generation batteries.

technical problem

[0003] 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 ion insulator, and the room temperature conductivity is low (5x10 ^s^m). Since there is no ionic sulfur, it is difficult to activate as a positive electrode material; (2) The highly polylithium polysulfide Li ₂ S _n (8 >n>4) generated during the electrode reaction is easily soluble in the electrolyte, forming a concentration difference between the positive and negative electrodes, under the action of the concentration gradient Upon migration to the negative electrode, the highly polylithium polysulfide is reduced by lithium metal to 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. The same insoluble Li ₂ 8 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. Lithium ions migrate slowly in solid lithium sulfide, which slows the electrochemical reaction kinetics. (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 ₂ The powdering of 8 causes safety problems of 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.

Problem solution

Technical solution

[0004] The technical problem to be solved by the present invention is to provide a nitrogen-rich graphene/manganese dioxide/hollow sulfur composite material. The composite material is composed of a hollow structure of sulfur and sulfur coated manganese dioxide material and a nitrogen-rich graphene network. The conductive layer provides a conductive network in the outer layer of graphene, and the hollow structure of the sulfur-based material provides expansion. The space, the outer layer of sulfur dioxide coated with manganese can adsorb the dissolution of polysulfide in the discharge product and improve the electrochemical performance of the material.

[0005] The present invention provides a method for preparing a nitrogen-rich graphene/manganese dioxide/hollow sulfur composite material as follows

[0006] (1) adding sulfur powder to carbon disulfide and stirring to form a uniform solution;

[0007] (2) The high-purity nickel powder is ball-milled by a high-energy ball mill, ball-milled, added to the above solution, stirred to form a uniform suspension, mechanically stirred, and spray-dried to form sulfur-coated spherical particles;

[0008] (3) The spherical particles are added to the ferric chloride solution, the reaction is stirred, washed with water, and filtered.

[0009] (4) the filtered precipitate is added to the solution containing manganese chloride and potassium permanganate, stirred into a uniform suspension, heated to stir the reaction, centrifuged, washed with water to obtain manganese dioxide coated sulfur particles;

[0010] (5) Nitrogen-rich graphene is added to water to ultrasonically disperse to form a uniform suspension, and then the manganese dioxide-coated sulfur particles are added, stirred, suction filtered, and washed to obtain a composite material.

[0011] Step (1) sulfur concentration of carbon disulfide solution is l-5g / mL;

[0012] Step (2) The nickel powder: the mass ratio of the sulfur powder is 0.05-0.2:1, the ball mill is 0.5-2 吋, and the mechanical stirring is 0.5-1 吋;

[0013] The concentration of the ferric chloride solution in the step (3) is l-2 mol / L, and the stirring reaction time is 1-5 hours;

[0014] Step (4) manganese chloride: potassium permanganate: sulfur mass ratio is 1-2: 1-1.5: 10, heating reaction temperature is 50-70 ° C, reaction time is 5-30 Minute

[0015] The concentration of the nitrogen-rich graphene suspension in the step (5) is 0.5-2 g/L, the nitrogen miscellaneous graphene nitrogen miscellaneous graphene: sulfur mass ratio is 1-2:10, the reaction of stirring reaction It is 5-30 minutes in the daytime.

Advantageous effects of the invention

Beneficial effect

[0016] The present invention has the following beneficial effects: (1) The nitrogen-rich graphene has an ultra-high electrical conductivity, and the nitrogen-doped graphene/manganese dioxide/hollow sulfur composite material prepared by the method can effectively improve lithium. The electronic conductivity and ionic conductivity of the cathode material of the sulfur battery, the nitrogen energy on the graphene chemically adsorbs the polysulfide, and reduces the sulfur loss of the charge and discharge; (2) the coating of manganese dioxide in the composite material Sulphur substrate The material is physically protected, and the same manganese dioxide can also chemically adsorb polysulfide to reduce the shuttle effect.

(3) The design of the hollow structure in the composite material reserves space for the volume expansion of the sulfur material during charge and discharge, which can effectively improve the electrochemical performance.

Brief description of the drawing

DRAWINGS

1 is a process flow diagram of the present invention.

2 is a graph showing the charge and discharge performance of the composite material of the present invention.

Embodiments of the invention

[0019] The preferred embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

Embodiment 1

[0021] (1) 100 g of sulfur powder was added to carbon disulfide and stirred to form a solution of lg / mL;

[0022] (2) 5g of high-purity nickel powder was passed through a high-energy ball mill, ball milled for 0.5 hours, ball milled, added to the above solution, stirred to form a uniform suspension, mechanically stirred for 0.5 hours, spray-dried to form sulfur-coated Spherical particle

[0023] (3) The spherical particles were added to a lmol/L ferric chloride solution, stirred for 5 hours, washed with water, and filtered.

[0024] (4) The filtered precipitate was added to 10 g of manganese chloride and 10 g of potassium permanganate solution, stirred into a uniform suspension, heated to 50 ° C, stirred for 30 minutes, centrifuged, washed with water to obtain dioxide Manganese coated sulfur particles

[0025] (5) 10g of nitrogen-rich graphene was added to water to ultrasonically disperse to form a uniform concentration of 0.5g / L suspension, and then added manganese dioxide coated sulfur particles, stirred, suction filtered, washed to obtain a composite material.

Embodiment 2

[0027] (1) 100 g of sulfur powder was added to carbon disulfide and stirred to form a solution of 5 g / mL;

[0028] (2) 20g of high-purity nickel powder was passed through a high-energy ball mill, ball milled for 2 hours, ball milled, added to the above solution, stirred to form a uniform suspension, mechanically stirred for 1 hour, spray-dried to form sulfur-coated Spherical particle

[0029] (3) adding spherical particles to the addition of 2mol / L ferric chloride solution, stirring reaction for 1 hour, washed, passed Filter.

[0030] (4) The filtered precipitate was added to a solution containing 20 g of manganese chloride and 15 g of potassium permanganate, stirred into a uniform suspension, heated to 70 ° C and stirred for 5 minutes, centrifuged, washed with water to obtain a dioxide Manganese coated sulfur particles

[0031] (5) 20g of nitrogen-rich graphene was added to water to ultrasonically disperse to form a uniform concentration of 2g / L suspension, and then the manganese dioxide coated sulfur particles were added, stirred, suction filtered, washed to obtain a composite material .

Example 3

[0033] (1) 100 g of sulfur powder was added to carbon disulfide and stirred to form a 2 g / mL solution;

[0034] (2) 10g of high-purity nickel powder was passed through a high-energy ball mill, ball milled for 1 hour, ball milled, added to the above solution, stirred to form a uniform suspension, mechanically stirred 0.6 hours, spray-dried to form sulfur-coated Spherical particle

[0035] (3) The spherical particles were added to a 1.5 mol/L ferric chloride solution, stirred for 3 hours, washed with water, and filtered.

[0036] (4) The filtered precipitate was added to a solution containing 15 g of manganese chloride and 12 g of potassium permanganate, stirred into a uniform suspension, heated to 60 ° C and stirred for 15 minutes, centrifuged, washed with water to obtain a dioxide Manganese coated sulfur particles

[0037] (5) 15g of nitrogen-rich graphene was added to water to ultrasonically disperse to form a uniform concentration of lg / L suspension, and then the manganese dioxide coated sulfur particles were added, stirred, suction filtered, washed to obtain a composite material .

Embodiment 4

[0039] (1) 100 g of sulfur powder was added to carbon disulfide and stirred to form a solution of 3 g / mL;

[0040] (2) 15g of high-purity nickel powder was passed through a high-energy ball mill, ball milled for 1.5 hours, ball milled, added to the above solution, stirred to form a uniform suspension, mechanically stirred 0.7 hours, spray-dried to form sulfur-coated Spherical particle

[0041] (3) The spherical particles were added to a 1.2 mol/L ferric chloride solution, stirred for 4 hours, washed with water, and filtered.

[0042] (4) The filtered precipitate was added to a solution containing 12 g of manganese chloride and 1 lg of potassium permanganate, stirred into a uniform suspension, heated to 65 ° C and stirred for 10 minutes, centrifuged, washed to obtain two Manganese oxide coated sulfur particles [0043] (5) 12g of nitrogen-rich graphene was added to water to ultrasonically disperse to form a uniform concentration of 1.5g / L suspension, and then the manganese dioxide coated sulfur particles were added, stirred, suction filtered, washed to obtain a composite material.

Embodiment 5

[0045] (1) 100 g of sulfur powder was added to carbon disulfide and stirred to form a 4 g / mL solution;

[0046] (2) 18g of high-purity nickel powder was passed through a high-energy ball mill, ball milled for 1.6 hours, ball milled, added to the above solution, stirred to form a uniform suspension, mechanically stirred 0.8 hours, spray-dried to form sulfur-coated Spherical particle

[0047] (3) The spherical particles were added to a 1.8 mol/L ferric chloride solution, stirred for 2 hours, washed with water, and filtered.

[0048] (4) The filtered precipitate was added to a solution containing 18 g of manganese chloride and 14 g of potassium permanganate, stirred into a uniform suspension, heated to 55 ° C and stirred for 25 minutes, centrifuged, washed with water to obtain a dioxide Manganese coated sulfur particles

[0049] (5) 18g of nitrogen-rich graphene was added to water to ultrasonically disperse to form a uniform concentration of 1.8g / L suspension, and then the manganese dioxide coated sulfur particles were added, stirred, suction filtered, washed to obtain a composite material.

[0050] Preparation and performance testing of electrodes; composite materials, acetylene black and PVDF

Mixed in NMP by mass ratio 80: 10: 10, coated on aluminum foil as electrode film, metal lithium plate as electrode, CELGARD

2400 is a diaphragm, 1 mol/L of LiTFSI/DOL-DME (volume ratio 1:1) is an electrolyte, and 1 mol/L of LiN03 is an additive. It is assembled into a button-type battery in a filled glove box, and is tested by a Land battery test system. Constant current charge and discharge test. The charge and discharge voltage range is 1-3V, and the current density is 0.5C. The performance is shown in Table 1.

Table 1

[] [Table 1]

2 is a graph showing the charge and discharge performance of a composite material prepared in Example 1 of the present invention as a lithium-sulfur battery. Can be seen from the picture The charge and discharge efficiency can reach more than 99%, the first charge and discharge capacity is 1030 mAh/g, the charge and discharge efficiency is 86.5%, and the second charge and discharge capacity is 1210 mAh/g. After 200 charge and discharge cycles, the capacity is relative to the first The secondary discharge capacity still retains more than 89%, indicating that the structure of the composite material can effectively suppress the shuttle effect and improve the life of the sulfur battery.

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

Claims

Claim

[Claim 1] A method for preparing a nitrogen-rich graphene/manganese dioxide/hollow sulfur composite material, which is characterized by comprising the following steps:

Step (1): adding sulfur powder to carbon disulfide and stirring to form a uniform solution; Step (2): ball milling high-purity nickel powder through a high-energy ball mill, adding to the above solution after ball milling, stirring to form a uniform suspension, mechanical Stirring, spray drying to form sulfur-coated spherical particles;

Step (3): adding spherical particles to the ferric chloride solution, stirring the reaction, washing with water, and filtering;

Step (4): adding the filtered precipitate to the solution containing manganese chloride and potassium permanganate, stirring into a uniform suspension, heating and stirring the reaction, centrifuging and washing to obtain manganese dioxide-coated sulfur particles;

Step (5): adding nitrogen-rich graphene to water to form a uniform suspension by ultrasonic dispersion, and then adding manganese dioxide-coated sulfur particles, stirring, suction filtration, and washing to obtain a composite material.

[Claim 2] The preparation method according to claim 1, wherein the concentration of the sulfur disulfide solution in the step (1) is from 1 to 5 g/mL.

[Claim 3] The preparation method according to claim 1, wherein in the step (2), the mass ratio of the nickel powder: sulfur powder is 0.05-0.2:1, and the ball mill is 0.5-2 hours. , mechanical mixing time is 0.

5-1 hours.

[Claim 4] The preparation method according to claim 1, wherein the concentration of the ferric chloride solution in the step (3) is 1 to 2 mol/L, and the stirring reaction time is 1-5 hours.

[Claim 5] The preparation method according to claim 1, wherein the manganese chloride in the step (4)

: Potassium permanganate: The mass ratio of sulfur is 1-2: 1-1.5: 10, the temperature of the heating reaction is 50-70 °C, and the reaction time is 5-30 minutes.

[Claim 6] The preparation method according to claim 1, wherein the concentration of the nitrogen miscible graphene suspension in the step (5) is 0.5-2 g/L, and the nitrogen miscellaneous graphene nitrogen is miscellaneous. Graphene: The mass ratio of sulfur is 1-2:10, and the reaction time of the stirring reaction is 5-30 minutes.