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Prototyping of nanoporous carbon membranes with three-dimensional microscale patterns is significant for integration of such multifunctional materials into various miniaturized systems. Incorporating nano material synthesis into microelectronics technology, we present a novel approach to direct prototyping of carbon membranes with highly nanoporous structures inside. Membranes with significant thicknesses (1 ~ 40 μm) are rapidly prototyped at wafer level by combining nano templating method with readily available microfabrication techniques, which include photolithography, high-temperature annealing and etching. In particular, the high-surface-area membranes are specified as three-dimensional electrodes for micro supercapacitors and show high performance compared to reported ones. Improvements in scalability, compatibility and cost make the general strategy promising for batch fabrication of operational on-chip devices or full integration of three-dimensional nanoporous membranes with existing micro systems.

Graphical abstract Highlights • The interlayer distance of hard carbon crystallites is tunable. • The defect sites of hard carbon for Na-ion storage can be tunable. • The designed carbon anode exhibits an excellent electrochemistry property. • Na-ion full-cell delivers a high energy density of 247 Wh kg−1 (vs. anode). Abstract Hard carbon materials hold the most promising application among all anode materials for sodium-ion batteries because of the high storage capacity and good cycling stability. However, the low initial Coulombic efficiency limits their further commercialization. Herein, a new carbonization strategy is presented to prepare a cost-effective hard carbon material as anodes for sodium-ion batteries by pyrolyzing the interpenetrating polymer networks (IPNs) made from the mixture of biomass-derivative lignin and epoxy resin. By adjusting heat-treatment temperatures and the lignin/epoxy resin mass ratios, we can adjust the interlayer distance of carbon crystallites and defect sites for Sodium-ion storage, and thus obtain a hard carbon with a high capacity of 316 mAh g−1, a high ICE of 82%, and good rate capability (e.g. , 161 mAh g−1 at 300 mA g−1), all of which are superior to or comparable to those state-of-the-art carbons reported in literatures, by the help of a large interlayer distance of 3.95 Å. Besides, a full cell with the configuration of as-prepared hard carbon anode versus air-stable O3-Na 0.9 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 cathode is further demonstrated, while it presents a high ICE of 80% and an energy density of 247 Wh kg anode −1 (vs. hard carbon) with good cycle performance. These excellent properties verify that our synthetic strategy is feasible, scalable and can be extended into the fabrication of various carbon anode materials with anticipative microstructures for the economical SIBs. [ABSTRACT FROM AUTHOR]

A novel strategy for the synthesis of hierarchical porous carbons (HPCs) from resol by potassium acetate activation for advanced supercapacitor electrodes was reported. The resultant HPCs with a high specific surface area up to 1201 m 2 g −1 as a supercapacitor electrode exhibits a high specific capacitance of 226 F g −1 at 0.05 A g −1 . Besides, the electrode shows high rate capability with 62.4% retention from 0.05 to 20 A g −1 . Moreover, it demonstrates good cyclic stability, showing a high capacitance retention of 97.1% over 5000 charge-discharge cycles at 2.0 A g −1 . The facile, efficient and template-free synthesis strategy for novel 3D-HPCs may promote commercial application of HPCs in the fields of supercapacitors. [ABSTRACT FROM AUTHOR]

Graphene inducing graphitization of hard carbon can be realized via assemble of PF and GO with hydrogen bonding, and sequential inducing tendency during carbonization process. [Display omitted] • A hard carbon with less defects and lower specific surface area is synthesized. • The unique structure is realized via graphene induced graphitization of hard carbon. • The hard carbon exhibits ultrahigh initial coulombic efficiency (90.4%). • A Na-ion full cell with great stability and superior rate capability is demonstrated. Hard carbons exhibit great potential as anode materials for Sodium-ion batteries (SIBs). However, the large initial irreversible capacity is still a major obstacle in their practical application. It is widely known that lower surface area and fewer defects may increase the initial Coulombic efficiency (ICE) for carbon anode in SIBs. In this study, a graphene-induced graphitization strategy is proposed for synthesizing less defective hard carbon. This strategy is realized through the assembly of phenolic resin (PF) and graphene oxide (GO) taking advantage of their hydrogen bonding interaction. Thus, aromatic ring near graphene has a strong tendency to be arranged along the graphene layer during pyrolysis process, a significant transition from sp 3 to sp 2 hybridization carbon occurs, endowing hard carbon with fewer defects and lower surface area. The structural advantages of the hard carbon contribute to the superior ICE (90.4%), the highest ever reported, and excellent reversible specific capacity of 343 mA h g−1 at 30 mA g−1 even after 100 cycles. [ABSTRACT FROM AUTHOR]