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Lithium-ion capacitors (LIC) have problems such as the imbalance of electrochemical kinetics between the battery-type anode and the capacitive cathode, and the large change in the working potential of the hard carbon anode during charge and discharge, which limit the improvement of electrochemical performance for LIC. To solve these problems, CoSe 2 nanoparticles embedded nitrogen-doped hard carbon microspheres (NCS-CoSe 2) are synthesized and used as the anode material of LIC. Electrochemical tests show that NCS-CoSe 2 has a reversible specific capacity of as high as 500 mAh g−1 at a current density of 1 A g−1, which can effectively stabilize the working potential of the anode. At a high working voltage window of 2.2–4.5 V, the potential change of the NCS-CoSe 2 anode is as low as 0.35 V, significantly smaller than that of the pure hard carbon (0.87 V). Regarding the electrode kinetics, the NCS-CoSe 2 anode is matched with the active carbon cathode well. When the power density rises sharply from 335 W kg−1 to 6700 W kg−1, the energy density of NCS-CoSe 2 //AC LIC can attain 82 Wh kg−1 (56.9% of initial energy density). Image, graphical abstract [ABSTRACT FROM AUTHOR]

Polythiophene (Pth) is a good candidate cathode material for aluminum ion battery (AIB) because of its lightness, safety, plasticity and flexibility. However, it always manifests inferior stability. Herein, a stable Pth-based cathode is realized through the anchoring effect between Pth and carboxyl. Pth with a thin film morphology is in situ synthesized on the surface of carboxylated carbon nanotubes (CNT-COOH). As a support, CNT-COOH not only alleviates the agglomeration of Pth that provides abundant transport channels for ions and electrons simultaneously, but also enhances the stability of Pth through the anchoring effect. As a result, the prepared Pth/CNT-COOH composite exhibits high discharge capacity (113 mAh g−1 at 1 A g−1), outstanding rate performance (95 mAh g−1 at 5 A g−1) and stable cycle stability (10,000 cycles with 0.001% decay per cycle). This work realizes a promising Pth-based AIBs with high capacity and long lifespan, which paves the way to the applications of organic materials in AIBs. [ABSTRACT FROM AUTHOR]