▎ 摘　　要

NOVELTY - Preparing a low-layer graphene involves: (1) preparing graphene oxide by (1.1) adding a graphite powder to concentrated sulfuric acid and reacting, where the solution is graphite color, then adding nitric acid, stirring for more than 10 minutes, then adding potassium permanganate to the obtained mixed solution, where the solution is dark green, controlling the temperature of the reaction solution at 35-45 degrees C, and stirring, where the solution is yellow-green, (1.2) increasing the temperature of the mixed solution obtained in step (1.1) to 60-70 degrees C, stirring, and continuously heating, and (1.3) cooling the grayish blue paste obtained in step (1.2) to below room temperature, slowly adding excess absolute ethanol and stirring, where the solution becomes black; and (2) preparing the low-layer graphene by (2.1) repeatedly centrifuging and washing the graphene oxide solution obtained in step (1.3) with water until the pH is neutral, then ultrasonically processing and freeze drying. USE - The method is useful for preparing a low-layer graphene, which is useful in a lithium-ion battery. ADVANTAGE - The method enables simple preparation of the low-layer graphene with high purity and large specific surface area. The low-layer graphene improves the capacity and cycle performance of the battery. DETAILED DESCRIPTION - Preparing a low-layer graphene involves: (1) preparing graphene oxide by (1.1) adding a graphite powder to concentrated sulfuric acid, where the mass ratio of graphite powder to concentrated sulfuric acid is more than 1:161 and reacting for more than 10 minutes, where the solution is graphite color, then adding nitric acid, where the mass ratio of nitric acid and graphite powder is more than 1:14 and stirring for more than 10 minutes, then adding potassium permanganate to the obtained mixed solution, where the mass ratio of potassium permanganate to graphite powder is more than 1:6, and the solution is dark green, controlling the temperature of the reaction solution at 35-45 degrees C, and stirring for more than 20 minutes, where the solution is yellow-green, (1.2) increasing the temperature of the mixed solution obtained in step (1.1) to 60-70 degrees C, stirring for more than 4 hours, where the solution is grayish blue paste, continuously heating at more than 90 degrees C, and continuously stirring for more than 20 minutes, and (1.3) cooling the grayish blue paste obtained in step (1.2) to below the room temperature, slowly adding excess absolute ethanol and continuously stirring for more than 30 minutes, where the solution becomes black, namely graphene oxide solution; and (2) preparing the low-layer graphene by (2.1) repeatedly centrifuging and washing the graphene oxide solution obtained in step (1.3) with water until the pH is neutral, then ultrasonically processing for more than 2 hours and freeze drying and (2.2) putting the sample obtained in step (2.1) after freeze drying into a tubular heating furnace, heating and reducing under the protection of inert gas, where the heating temperature is 200-400 degrees C, and the heating time is more than 2 hours, and collecting the product.