Capacitance loss with the increase of mass loading represents an outstanding challenge for supercapacitors. Here we demonstrate for the first time a mm-thick, 3D printed graphene aerogel structure that can support pseudocapacitive MnO 2 to hundreds of mg/cm 2 without sacrificing its gravimetric and volumetric performance. The electrode simultaneously achieves high gravimetric, areal, and volumetric capacitances, which is impossible for conventional bulk electrodes. Most importantly, these findings validate the new concept of ''printing'' practically feasible pseudocapacitor electrodes and devices.
Paper‐based materials are emerging as a new category of advanced electrodes for flexible energy storage devices, including supercapacitors, Li‐ion batteries, Li‐S batteries, Li‐oxygen batteries. This review summarizes recent advances in the synthesis of paper‐based electrodes, including paper‐supported electrodes and paper‐like electrodes. Their structural features, electrochemical performances and implementation as electrodes for flexible energy storage devices including supercapacitors and batteries are highlighted and compared. Finally, we also discuss the challenges and opportunity of paper‐based electrodes and energy storage devices.
Interconnected hollow carbon nanospheres (HCNSs) were prepared by pressure‐assisted reduction and graphitization of sucrose in autoclaves without template. The obtained HCNSs with a large surface area, very thin graphitic shells, and an interconnected structure exhibit excellent performances as the electrode material for lithium ion batteries.
The performance of pseudocapacitive electrodes at fast charging rates are typically limited by the slow kinetics of Faradaic reactions and sluggish ion diffusion in the bulk structure. This is particularly problematic for thick electrodes and electrodes highly loaded with active materials. Here, a surface‐functionalized 3D‐printed graphene aerogel (SF‐3D GA) is presented that achieves not only a benchmark areal capacitance of 2195 mF cm−2 at a high current density of 100 mA cm−2 but also an ultrahigh intrinsic capacitance of 309.1 µF cm−2 even at a high mass loading of 12.8 mg cm−2. Importantly, the kinetic analysis reveals that the capacitance of SF‐3D GA electrode is primarily (93.3%) contributed from fast kinetic processes. This is because the 3D‐printed electrode has an open structure that ensures excellent coverage of functional groups on carbon surface and facilitates the ion accessibility of these surface functional groups even at high current densities and large mass loading/electrode thickness. An asymmetric device assembled with SF‐3D GA as anode and 3D‐printed GA decorated with MnO2 as cathode achieves a remarkable energy density of 0.65 mWh cm−2 at an ultrahigh power density of 164.5 mW cm−2, outperforming carbon‐based supercapacitors operated at the same power density.
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