Electrode materials with high volumetric capacity are highly desired to improve the energy storage performance for the next generation supercapacitor. The loading density of active materials and potential window are the two keys to realizing the maximization of volumetric capacity. Herein, carbon aerogel microspheres (CAMs) with uniform spherical structure and high loading density are prepared by an emulsion polymerization without freeze/supercritical drying step. The CAMs are further treated with H3PO4, which not only optimize their pore structure for facilitating ion diffusion but also introduce phosphorus species to carbon skeleton for blocking active oxidation sites. Owing to the high loading density and the suppressed formation of unstable oxygen species by phosphorus, the optimal sample shows a good volume energy density of 48.1 Wh L-1 under a high applied potential difference of 3.3 V in 1M TEABF(4)/PC electrolyte. Our work presents a new direction for the developing of high volumetric energy density supercapacitors. (C) 2019 Elsevier Ltd. All rights reserved.