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• A brand-new two-step reaction mechanism of ONA electrode is proposed in AIB. • The π-π stacking structures of π-COCs can contribute capacity directly. • The ONA show the co-existence of high capacity and excellent cycle stability in AIB. Π-conjugated organic compounds (π-COCs), as a potential electrode material, mainly emphasized the effects of functional groups and intramolecular π-conjugated system on charge storage in the past studies. In this work, we discovered a brand-new two step energy storage mechanism for π-COCs using oligomeric naphthalene (ONA) with intermolecular π-π stacking structure as electrode material in Al ion battery system. The electrochemical reaction of ONA is identified as the synergistic work of the chemical-adsorption of AlCl 4 - anions at low potential and the π···[AlCl 4 ]···π interaction at high potential. Based on this, the Al-ONA battery exhibits an excellent electrochemical performance (high specific capacity of 450 mAh/g at 0.1 A/g, long cycle life without attenuation for 4000 cycles at 1 A/g). This discovery of the energy storage mechanism, especially for the π···anion···π interaction, for π-COCs materials opens the door to exploring high performance organic electrode materials in energy storage field. [ABSTRACT FROM AUTHOR]

N-doping can endow carbon materials with high electrochemical activity. Besides the widely validated sp 2 -hybridized nitrogen doping, sp -hybridized nitrogen (sp - N) atoms are also expected to be new active sites. However, both sp - N atoms and cyano (CN) groups containing sp - N are rarely produced in carbon materials presently. In this work, the first cyano groups-modified carbon materials are synthesized firstly via an interesting struggle between the chemical etching of KOH and the catalytic graphitization of Co nanoparticles in carbon frameworks. The theoretical calculations and experimental results manifest that the stronger electronegativity of CN groups renders carbon materials a higher electrochemical activity. As K+ storage anodes, the CN−modified carbon materials exhibit an obvious boost in potassium storage performance in both ester- and ether-based electrolytes. Therefore, as a new N doping form, the successful introduction of CN groups into carbon materials opens a door for exploring sp -N doped carbon materials for applications in energy storage and other fields. [Display omitted] • The first cyano-modified carbon materials are prepared. • As K+ storage anodes, the CN-modified carbon exhibits the impressive performance. • The storage mechanism of CN was explored by theoretical calculation and test. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultrasonic induced rGO self-encapsulation of S, N dual-doped carbon spheres. • The rGO acts as a protective shield and a filter. • Pseudocapacitance contribution of high S, N co-doped carbon spheres. • Up to 60% Initial Coulomb Efficiency. Pseudocapacitance points out a new direction for the recent research and development of potassium ion anode materials because of its fast energy storage kinetics, which has yielded lots of successful pseudocapacitance-rich examples by introducing more active sites such as doped heteroatoms. However, the negative reactions with the electrolyte in electrochemical process often cause the serious inactivation of active sites, giving a hit for seeking higher pseudocapacitance. In this work we proposed a new strategy to wrap the protective shield for the pseudocapacitance-rich materials to alleviate this matter. By the ultrasonic-induced rGO self-encapsulation of S, N dual-doped carbon spheres, the directional contact between active sites and the electrolyte is blocked, while the rGO films with enlarged interlayer spacing and lots of defects also like filter membrane, accelerate the K+ desolvation and fast diffusion into carbon matrix. Benefiting from the synergistic effect of rGO shielding and filtrating, the pseudocapacitance of S, N dual-doping carbon spheres is fully activated. As the potassium-ion battery anode, the obtained S, N dual-doping carbon sphere@rGO delivers a state-of-the-art capacity of 596 mAh g−1, which achieves a 52.5 % capacity enhancement in contrast to that without rGO shield. As a proof of application, the resultant high-pseudocapacitance carbon anode is incorporated into a potassium ion hybrid capacitor, showing the most favorable capacity-cyclability combinations with the high energy–density of 83 Wh kg−1 after 6500 cycles at 5A g−1. [ABSTRACT FROM AUTHOR]