▎ 摘　　要

NOVELTY - A multilayer cake-like nanographene has diameter of 50-300 nm, thickness of 1/5 to 1/2 of diameter, interlamellar spacing of 0.7-1 nm, small graphene sheet vertical support between layers, and specific surface area of 800-2000 m2/g. USE - Multilayer cake-like nanographene used for preparing electrode material (claimed) of supercapacitor under high voltage. ADVANTAGE - The nanographene is compression-resistant, not easy to overlap, not easily swollen by electrolyte and not easily attenuated; and has high energy density per unit area. Preparation method is simple to operate and has high yield and low cost. The capacitance of electrode material is 130-150 F/g when the nanographene is used as electrode material to encapsulate capacitor and its weight is controlled at 20% of device weight. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation cake-like nanographene by: (A) soaking 5-100 nm kaolin nanosheet, magnesium carbonate hydrate, basic magnesium carbonate and/or aluminum silicate in 0.1-1 mol/L carbohydrate solution for 0.2-3 hours, filtering, and compacting precipitate to obtain nanolamellar precursor; (B) calcining nanolamellar precursor at 200-950 degrees C for 0.2-3 hours while introducing oxygen-containing gas or carbon dioxide-containing gas to form porous oxide template, switching inlet gas to inert gas and introducing carbon source carried by carrier gas, and adjusting temperature to 800-1100 degrees C, decomposing carbon source on porous template surface to prepare graphene, reacting for 0.2-4 hours, stopping carbon source, and naturally cooling; and (C) dissolving graphene-based porous template in acidic or alkaline solution, separating to obtain nanographene, thoroughly washing, and drying.