The invention belongs to the field of material chemistry and relates to a preparation method of a positive electrode material for a lithium-sulfur battery. According to the method, a composite material of which the effective loading amount of sulfur is significantly increased and the "shuttle effect" of polysulfides is reduced is obtained through three steps of preparing a graphene oxide aqueous solution, preparing a foamed graphene/carbon nanotube composite material and preparing a sulfur/foamed graphene/carbon nanotube composite positive electrode material. The material is used as a positiveelectrode material for a lithium battery, so that volume expansion of the lithium-sulfur battery can be effectively reduced, the electrochemical stability of the battery is improved, the first discharge capacity can reach 1529mAh/g and the discharge capacity is still 859mAh/g after 200 charge-discharge cycles.

Preparation method of positive electrode material for lithium-sulfur battery

The invention belongs to the technical field of electrode materials, in particular relates to a three-dimensional selenium/graphene foam meshed porous self-supporting flexible electrode material, a preparation method and an application. The three-dimensional selenium/graphene foam meshed porous self-supporting flexible electrode material is prepared by using a simple chemical vapor deposition technique and an impregnation method. The obtained positive electrode material is composed of elemental selenium and graphene foams; the elemental selenium is an active substance and is coated in the graphene foams to provide an active site; the electrical conductivity of the composite material is improved by the graphene foams so as to alleviate the shuttle of polyselenides; the synergistic action ofthe two components makes the self-supporting flexible electrode material exhibit high capacity and high cycle stability. The chemical vapor deposition technique and the impregnation method utilized by the invention are easy and effective, and the large-scale preparation and low-cost industrialization of the three-dimensional selenium/graphene foam meshed porous self-supporting flexible electrodematerial are easily realized.

Three-dimensional selenium/graphene foam meshed porous self-supporting flexible electrode material, preparation method and application

A method for manufacturing a graphene foam positive electrode for a lithium-sulfur battery. The method comprises the followings steps: step (1) adding a graphite oxide and a polyacrylonitrile into a ball mill to perform ball milling for 30-60 minutes, then adding a ball-milled mixture into a mixed solution of an ethanol and water for ultrasonic dispersion to form a suspension with a concentration of 1-20 g/L; step (2) immersing a nickel foam in the suspension for 10-60 minutes, steam-drying the solvent and adding a gas mixture of hydrogen and nitrogen to protect a reaction within a muffle furnace for 1-10 hours at 800-1,100°C, then reacting to completion followed by natural cooling; step (3) immersing a product from the previous step in a 1-3 mol/L hydrochloric acid, performing a reaction for 5-10 hours at 60-80°C, then reacting to completion to obtain a graphene foam; and step (4) coating an elemental sulfur powder on a surface of the graphene foam, placing the foam in a sealed container, reacting for 1-5 hours at 120-180°C, cooling, then rolling to obtain an electrode. The manufacturing method is easy to perform and directly provides a positive electrode for a lithium-sulfur battery, thereby simplifying a technique for manufacturing positive electrodes.

Method for manufacturing graphene foam positive electrode for lithium-sulfur battery

The invention discloses a binder-free positive plate preparation method for a lithium-sulfur battery. The method comprises the following steps: placing pre-processed foamed nickel in a graphene oxideand sulfur mixture, and carrying out low-speed centrifugation and freeze drying to obtain foamed nickel loaded with the graphene oxide and sulfur mixture; using the obtained foamed nickel loaded withthe graphene oxide and sulfur mixture as a working electrode to carry out electrochemical reduction reaction, and carrying out washing with deionized water and freeze drying after the reaction is completed; and carrying out heating in hydrochloric acid to etch the foamed nickel, and carrying out washing with deionized water and freeze drying to obtain an electrochemically reduced graphene oxide and sulfur positive plate. The method provided by the invention has the advantages that a sulfur positive electrode without a binder, a conductive additive and a current collector is prepared through the electrochemical method, the preparation method is simple, and mixing, coating and other processes are avoided; and an electrochemically reduced graphene oxide and sulfur mixture that is obtained canbe directly used as the positive plate, and masses of inactive substances in the plate are reduced, so that the energy density of the lithium-sulfur battery is increased.

Binder-free positive plate preparation method for lithium-sulfur battery

The invention discloses a lithium-sulfur battery with nitrogen-doped porous carbon nanorod-covered foamed graphene sheets as the intermediate layer. The lithium-sulfur battery with the nitrogen-dopedporous carbon nanorod-covered foamed graphene sheets as the intermediate layer comprises a positive electrode, a negative electrode and electrolytes; a diaphragm is arranged between the positive electrode and the negative electrode; the nitrogen-doped porous carbon nanorod-covered foamed graphene sheets are arranged between the positive electrode and the diaphragm. By means of the nanopore structures on the surface of the nanorods growing on the surface of graphene as well as a large number of carbon-oxygen active sites generated by nitrogen doping, not only transmission and exchange of materials during battery charging and discharging processes can be greatly enhanced, but also electron transmission capacity of the surface of the positive electrode can be greatly improved; meanwhile, thecarbon-oxygen active sites generated by nitrogen doping and the nanopores can effectively absorb polysulfide generated by the positive electrode to prevent the polysulfide from migrating to and dissolving in electrolyte solution, thereby greatly improving the cycling stability of the lithium-sulfur battery.

Lithium-sulfur battery with nitrogen-doped porous carbon nanorod-covered foamed graphene sheets as intermediate layer

The invention provides a preparation method of a foamed graphene lithium-sulfur battery positive plate. The preparation method comprises the steps of (1) adding graphite oxide and polyacrylonitrile into a ball mill for ball-milling for 30-60 min, then adding the mixture after the ball-milling into a mixed solution of ethanol and water for ultrasonic dispersion so as to form a suspension liquid with the concentration of 1-20 g/L; (2) soaking foamed nickel in the suspension liquid for 10-60 min, drying a solvent by distillation and then placing the processed foamed nickel in a muffle furnace which is protected by a hydrogen-nitrogen mixed gas for reaction for 1-10 h at 800-1100 DEG C, and cooling naturally after the reaction is finished; (3) soaking the product obtained in the step (3) in 1-3 mol/L hydrochloric acid for reaction for 5-10 h at 60-80 DEG C, and obtaining the foamed graphene after the reaction is finished; and (4) painting elemental sulfur powder on the surface of the foamed graphene, then placing the foamed graphene in a sealed container for reaction for 1-5 h at 120-180 DEG C, cooling the product and then rolling the product to obtain the electrode plate. The preparation method of the foamed graphene lithium-sulfur battery positive plate is simple, the lithium-sulfur battery positive plate can be obtained directly, and the preparation process of the positive electrode is simplified.

Preparation method of foamed graphene lithium-sulfur battery positive plate

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Preparation method of foamed graphene lithium-sulfur battery positive plate