Supercapacitors represent an important energy storage system for high power applications with carbon electrodes acting as the key component. Design and synthesis of advanced carbon materials with supercapacitive activity (capacitance and rate capability) and stability have been the focus of supercapacitor developments. This study reports a high-performance carbon electrode by in situ doping boron atoms into nanoporous carbon particles, which is achieved by a continuous spraying assisted coassembly process. Boron doping leads to extra oxygen graft into carbon surface, enabling both enhanced wettability and durability for the fabricated carbon electrodes. Density functional theory calculations further suggest that boron doping enhances electrolyte ion penetration and interactions with carbon surface, leading to the improved capacitances and rate capability.The constructed symmetric aqueous supercapacitor exhibits all-round performance improvements including high energy density (9.1 Wh kg −1 ) and power density (24.1 kW kg −1 ) as well as ultralong cycling life (100 000 cycles). This work for the first time provides insights into the role of boron doping in enhancing both supercapacitive activity and stability of carbon materials for high-performance supercapacitors.

Coal features low‐cost and high carbon yield and is considered as a promising precursor for carbon anode of sodium‐ion batteries (SIBs) and sodium‐ion capacitors (SICs). Regulation of microcrystalline state and pore configuration of coal structure during thermal transformation is key to boost Na+ storage behavior. Herein, a facile strategy is reported to create abundant closed pores in anthracite‐derived carbon that greatly improves Na+ plateau storage. An altered thermal transformation pathway of chemical activation followed by high‐temperature carbonization is adopted to achieve the conversion of open nanopores and ordered carbon crystallite into closed pores surrounded by short‐range carbon structures. The optimized sample delivers a large reversible capacity of 308 mAh g–1 that is dominantly contributed by the low‐voltage plateau process. Experimental results reveal the enhanced pore‐filling mechanism in the developed closed pores. Benefitting from the improved plateau behavior, the constructed SIB delivers a high‐energy density of 231.2 Wh kg–1 with an average voltage of 3.22 V; the assembled full‐carbon SIC shows high energy and power densities (101.8 Wh kg–1 and 2.9 kW kg–1). This work provides a universal thermal transformation approach for designing high‐performance carbon anode with closed porosity from low‐cost and highly aromatic precursors.

The combination of the high micropore surface area and the controlled mesopore size and mesopore/micropore ratio is responsible for high specific capacitance and excellent rate capability.

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