GRAPHENE POWDER, METHOD FOR PRODUCTION THEREOF AND USE THEREOF Russian patent published in 2024 - IPC C01B32/19 B82Y40/00 

FIELD: nanotechnology.

SUBSTANCE: invention relates to nanotechnology and can be used in making electroconductive or heat-dissipating composite materials, as well as anticorrosion coatings. First, pre-foamed graphite with expansion coefficient of 200-300 is obtained by heating foaming graphite to 800-950 °C and foaming for 10-60 s. Pre-foamed graphite is then mixed with a solvent and a wetting agent, for example, a polyoxyethylene amine fatty ether, having a hydrophilic-lipophilic balance (HLB) value greater than or equal to 12. Weight ratio of pre-foamed graphite to wetting substance is 1:(0.01-0.1). Obtained mixture is homogenised in two steps at high pressure to obtain a suspension containing graphene powder. For example, the first homogenisation is carried out at pressure of 30-40 MPa for 20-60 minutes, and the second one – at pressure of 40-50 MPa for 10-30 minutes. After that suspension is dried by spraying or freezing-drying to obtain graphene powder. At spray drying, temperature of inlet air is 300-350 °C, outlet air temperature 100-130 °C, rotational speed of the centrifugal disc of the spray drying equipment is 20,000-30,000 rpm. During freezing-drying, the temperature of the cold trap is not more than -65 °C, box partition temperature is not more than -55 °C, heating rate 0.1-0.5 °C/min; duration of heating from box partition temperature to 0 °C is not less than 24 hours, degree of vacuum is not more than 10 Pa. Obtained graphene powder has a particle size of 15-35 mcm, is a stack of graphene sheets between which there are voids, and exhibits peaks D and G in the Raman spectrum, with the ratio of heights of said peaks I_D/I_G of 0.10 or less. Carbon content in the obtained graphene powder is equal to or more than 99.50 wt.%, and the oxygen content is 300 ppm or less. Graphene powder is characterized by a specific surface area of 50-300 m²/g, or density after compaction of 0.02-0.04 g/cm³; or specific conductivity of 500-5,000 C/cm. Graphene sheets in graphene powder contain 1-10 graphene layers and have median particle size, preferably 5-15 mcm. Initial temperature of thermal decomposition of graphene sheets during heat treatment in air atmosphere is more than or equal to 600 °C. After thermal treatment of graphene sheets in air atmosphere at 800 °C degree of their weight loss is less than or equal to 10%.

EFFECT: invention enables to obtain high-purity graphene powder using an environmentally friendly method; when used in lithium-ion batteries, this powder can significantly reduce internal resistance of electrodes and improve stability of batteries at any current strength.

14 cl, 22 dwg, 5 ex