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.

https://www.onlinelibrary.wiley.com/doi/epdf/10.1002/adma.201906652

3D-Printed Structure Boosts the Kinetics and Intrinsic Capacitance of Pseudocapacitive Graphene Aerogels.

The article reviews the recent progress of electrochemical techniques on synthesizing nano-/microstructures as supercapacitor electrodes. With a history of more than a century, electrochemical techniques have evolved from metal plating since their inception to versatile synthesis tools for electrochemically active materials of diverse morphologies, compositions, and functions. The review begins with tutorials on the operating mechanisms of five commonly used electrochemical techniques, including cyclic voltammetry, potentiostatic deposition, galvanostatic deposition, pulse deposition, and electrophoretic deposition, followed by thorough surveys of the nano-/microstructured materials synthesized electrochemically. Specifically, representative synthesis mechanisms and the state-of-the-art electrochemical performances of exfoliated graphene, conducting polymers, metal oxides, metal sulfides, and their composites are surveyed. The article concludes with summaries of the unique merits, potential challenges, and associated opportunities of electrochemical synthesis techniques for electrode materials in supercapacitors.

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A Review on Nano-/Microstructured Materials Constructed by Electrochemical Technologies for Supercapacitors

Pseudocapacitors harness unique charge-storage mechanisms to enable high-capacity, rapidly cycling devices Here we describe an organic system composed of perylene diimide and hexaazatrinaphthylene exhibiting a specific capacitance of 689 F g−1 at a rate of 05 A g−1, stability over 50,000 cycles, and unprecedented performance at rates as high as 75 A g−1 We incorporate the material into two-electrode devices for a practical demonstration of its potential in next-generation energy-storage systems We identify the source of this exceptionally high rate charge storage as surface-mediated pseudocapacitance, through a combination of spectroscopic, computational and electrochemical measurements By underscoring the importance of molecular contortion and complementary electronic attributes in the selection of molecular components, these results provide a general strategy for the creation of organic high-performance energy-storage materials Pseudocapacitors exhibit charge-storage mechanisms leading to high-capacity and rapidly cycling devices An organic system designed via molecular contortion is now shown to exhibit unprecedented electrochemical performance and stability

High-performance organic pseudocapacitors via molecular contortion

Aqueous Supercapacitor with Ultrahigh Voltage Window Beyond 2.0 Volt

Advances in graphene-based supercapacitor electrodes

A polyanionic molybdenophosphate anode for a 2.7 V aqueous pseudocapacitor

Redox Poly-Counterion Doped Conducting Polymers for Pseudocapacitive Energy Storage

A Manganese Phosphate Cathode for Long-Life Aqueous Energy Storage

Molybdenum oxide provides high theoretical capacity, but the moderate charge transfer kinetics and cycle life have limited the applications for capacitive energy storage. Herein, the electrochemica...

Xiao-Xia Liu

Papers

A polyanionic molybdenophosphate anode for a 2.7 V aqueous pseudocapacitor

Redox Poly-Counterion Doped Conducting Polymers for Pseudocapacitive Energy Storage

A Manganese Phosphate Cathode for Long-Life Aqueous Energy Storage

Activating the Highly Reversible Mo4+/Mo5+ Redox Couple in Amorphous Molybdenum Oxide for High-Performance Supercapacitors.

The energy storage behavior of a phosphate-based cathode material in rechargeable zinc batteries