On-chip electrochemical energy storage devices have attracted growing attention due to the decreasing size of electronic devices. Various approaches have been applied for constructing the microsupercapacitors. However, the microfabrication of high-performance microsupercapacitors by conventional and fully compatible semiconductor microfabrication technologies is still a critical challenge. Herein, unique three-dimensional (3D) Co3O4 nanonetwork microelectrodes formed by the interconnection of Co3O4 nanosheets are constructed by controllable physical vapor deposition combined with rapid thermal annealing. This construction process is an all dry and rapid (≤5 minutes) procedure. Afterward, by sputtering highly electrically conductive Pt nanoparticles on the microelectrodes, the 3D Co3O4/Pt nanonetworks based microsupercapacitor is fabricated, showing a high volume capacitance (35.7 F cm−3) at a scan rate of 20 mV s−1 due to the unique interconnected structures, high electrical conductivity and high surface area of the microelectrodes. This microfabrication process is also used to construct high-performance flexible microsupercapacitors, and it can be applied in the construction of wearable devices. The proposed strategy is completely compatible with the current semiconductor microfabrication and shows great potential in the applications of the large-scale integration of micro/nano and wearable devices.

Silicon oxide (SiOx) shows great potential for lithium ion battery (LIB) anodes due to its high capacity, environmental friendliness, low cost and high abundance. Herein, we used low-cost mesoporous silica spheres to synthesize core–shell structured porous carbon-coated SiOx nanowires (pC–SiOx NWs) as a new LIB anode through a novel self-sacrificed method. The one-dimensional structure can accommodate large volume expansion without breaking. The porous carbon coating hinders the penetration of the electrolyte into pC–SiOx NWs and formation of a stable solid-electrolyte interphase (SEI) film on the external surface of pC–SiOx NWs. As a result, the composite shows excellent cycling stability with high reversible specific capacities of 1060 mA h g−1 (100 cycles) and 623 mA h g−1 (150 cycles) at current densities of 100 mA g−1 and 500 mA g−1, respectively. The proposed facile and scalable synthesis is highly competitive for large-scale applications in lithium storage devices/systems.

Exploring non-noble and high-efficiency electrocatalysts is critical to large-scale industrial applications of electrochemical water splitting. Currently, nickel-based selenide materials are promising candidates for oxygen evolution reaction due to their low cost and excellent performance. In this work, we report the porous nickel–iron bimetallic selenide nanosheets ((Ni0.75Fe0.25)Se2) on carbon fiber cloth (CFC) by selenization of the ultrathin NiFe-based nanosheet precursor. The as-prepared three-dimensional oxygen evolution electrode exhibits a small overpotential of 255 mV at 35 mA cm–2 and a low Tafel slope of 47.2 mV dec–1 and keeps high stability during a 28 h measurement in alkaline solution. The outstanding catalytic performance and strong durability, in comparison to the advanced non-noble metal catalysts, are derived from the porous nanostructure fabrication, Fe incorporation, and selenization, which result in fast charge transportation and large electrochemically active surface area and enhance the release of oxygen bubbles from the electrode surface.Keywords: carbon fiber cloth (CFC); electrochemical catalyst; nickel−iron bimetallic selenide; oxygen evolution; porous nanosheets

Photoresist, a frequently used material in existing microfabrication processes, can be utilized in carbon micro electro mechanical system (C-MEMS) since the patterned carbon micro/nano structures can be formed by pyrolysis of a patterned photoresist. These pyrolyzed carbon microstructures have been used as functional and structural units in carbon-MEMS. Compositing and integration with high performance nanostructures is one important strategy for carbon microstructures with applications in microdevices. Herein, we report a patterned microelectrode of pyrolyzed carbon with embedded NiO/Ni nanospheres (carbon/NiO/Ni) fabricated by a novel microfabrication process combing optimized photolithography with pyrolysis. The microsupercapacitors with interdigital carbon/NiO/Ni (C/NiO/Ni) microelectrodes show a high capacitance of 2.75 mF cm−2. In this microsupercapacitor, the C/NiO/Ni is utilized as the active electrode material and current collector, which makes the microfabrication facile and compatible with micromachining technologies. In addition, the C/NiO/Ni microelectrode pyrolyzed at 900 °C shows a higher capacitance than that of pyrolyzed carbon microelectrodes. The optimized microfabrication process with effectiveness and repeatability shows great potential for fine micropatterning of carbon and electrochemically active materials on a large scale, especially for the microstructuring of a carbon-based composite.

Transition metal oxides have attracted much interest for their high energy density in lithium batteries. However, the fast capacity fading and the low power density still limit their practical implementation. In order to overcome these challenges, one-dimensional yolk–shell nanorods have been successfully constructed using manganese oxide as an example through a facile two-step sol–gel coating method. Dopamine and tetraethoxysilane are used as precursors to obtain uniform polymer coating and silica layer followed by converting into carbon shell and hollow space, respectively. As anode material for lithium batteries, the manganese oxide/carbon yolk–shell nanorod electrode has a reversible capacity of 660 mAh/g for initial cycle at 100 mA/g and exhibits excellent cyclability with a capacity of 634 mAh/g after 900 cycles at a current density of 500 mA/g. An enhanced capacity is observed during the long-term cycling process, which may be attributed to the structural integrity, the stability of solid electrolyte interphase layer, and the electrochemical actuation of the yolk–shell nanorod structure. The results demonstrate that the manganese oxide is well utilized with the one-dimensional yolk–shell structure, which represents an efficient way to realize excellent performance for practical applications.

Sodium ion batteries (SIBs), as potential candidates for large-scale energy storage systems, have attracted great attention from researchers. Herein, a V2O5·nH2O xerogel composed of thin acicular interconnected nanowire networks has been synthesized via a facile freeze-drying process. The interlayer spacing of V2O5·nH2O is larger than that of orthorhombic V2O5 due to the intercalation of water molecules into the layer structure. As the cathode of a SIB, V2O5·nH2O exhibits a high initial capacity of 338 mA h g−1 at 0.05 A g−1 and a high-rate capacity of 96 mA h g−1 at 1.0 A g−1. On the basis of combining ex-situ XRD and FTIR spectroscopy, the Na+ ion intercalation storage reactions are discussed in detail. By modeling calculations, the pseudocapacitive behavior makes a great contribution to the high capacities. Our work demonstrates that V2O5·nH2O with large interlayer spacing is a promising candidate for high capacity sodium-based energy storage.

Conversion/alloying reactions, in which more lithium ions are involved, are severely handicapped by the dramatic volume changes. A facile and versatile strategy has been developed for integrating the SnO2 nanorod array in the PPy nanofilm for providing a flexible confinement for anchoring each nanorod and maintaining the entire structural integrity and providing sustainable contact; therefore, exhibiting much more stable cycling stability (701 mA h g−1 after 300 cycles) and better high-rate capability (512 mA h g−1 at 3 A g−1) when compared with the core–shell SnO2–PPy NA.

Three-dimensional porous V2O5 hierarchical microplates have been fabricated by a one-step top-down strategy, and display an excellent rate capability and stable capacity of 110 mA h g−1 at 2000 mA g−1 after 100 cycles. We have demonstrated that the facile approach of a solid-phase conversion is promising for large-scale fabrication of highly porous micro/nano materials.

To combine the merits of the one-dimensional structure and the porous structure, mesoporous VO2 nanowires have been designed and reported for the first time. Excellent cycling stability and enhanced rate performance are obtained and may be attributed to the mesoporous nanowires, realizing both high surface area for more active sites and facile stress relaxation resulting in excellent structure stability. Our results demonstrate that the mesoporous nanowires are favourable for high-rate and long-life lithium batteries.

•Heterogeneous branched core–shell SnO2–PANI nanorod arrays have been developed.•The PANI shell releases the stress of volume expansion during cycling.•The SnO2 nanorod arrays maintain mechanical integrity due to the PANI shell.•The PANI shell and the nickel foam realize three dimensional electron transports.•Cycling stability and rate capability are greatly enhanced.SnO2 with high theoretical capacity has long suffered from its instinct large volume variation and low electrical transport linked to poor cycling stability and rate performance. Here we present the heterogeneous branched core–shell SnO2–PANI nanorod arrays which have been successfully designed and fabricated by an efficient and facile hydrothermal treatment followed by electrodeposition. The heterogeneous core–shell SnO2–PANI nanorod arrays exhibit a high reversible capacity of 506 mAh/g after 100 cycles, resulting the capacity fading of 0.579% per cycle between 20 and 100 cycles, much lower than that of nanosheet-assembled hierarchal SnO2–PANI nanorod arrays (1.150%) and bare SnO2 nanorod arrays (1.151%). At high current density of 3000 mA/g, heterogeneous core–shell SnO2–PANI nanorod arrays maintain a capacity of 660 mAh/g after the current density returns to 100 mA/g, 3 times as high as that of nanosheet-assembled hierarchal SnO2–PANI nanorod arrays (206 mAh/g) and 6 times as high as that of bare SnO2 nanorod (124 mAh/g). The enhanced electrochemical performance can be attributed to the branched conductive PANI shells, which not only release the stress of volume expansion and maintain mechanical integrity during cycling, but also realize three dimensional transport for electrons. Our work demonstrates a great potential for the application of heterogeneous branched core–shell PANI–SnO2 nanorod arrays for lithium batteries.

Silicon oxide (SiOx) shows great potential for lithium ion battery (LIB) anodes due to its high capacity, environmental friendliness, low cost and high abundance. Herein, we used low-cost mesoporous silica spheres to synthesize core–shell structured porous carbon-coated SiOx nanowires (pC–SiOx NWs) as a new LIB anode through a novel self-sacrificed method. The one-dimensional structure can accommodate large volume expansion without breaking. The porous carbon coating hinders the penetration of the electrolyte into pC–SiOx NWs and formation of a stable solid-electrolyte interphase (SEI) film on the external surface of pC–SiOx NWs. As a result, the composite shows excellent cycling stability with high reversible specific capacities of 1060 mA h g−1 (100 cycles) and 623 mA h g−1 (150 cycles) at current densities of 100 mA g−1 and 500 mA g−1, respectively. The proposed facile and scalable synthesis is highly competitive for large-scale applications in lithium storage devices/systems.

Conversion/alloying reactions, in which more lithium ions are involved, are severely handicapped by the dramatic volume changes. A facile and versatile strategy has been developed for integrating the SnO2 nanorod array in the PPy nanofilm for providing a flexible confinement for anchoring each nanorod and maintaining the entire structural integrity and providing sustainable contact; therefore, exhibiting much more stable cycling stability (701 mA h g−1 after 300 cycles) and better high-rate capability (512 mA h g−1 at 3 A g−1) when compared with the core–shell SnO2–PPy NA.

Sodium ion batteries (SIBs), as potential candidates for large-scale energy storage systems, have attracted great attention from researchers. Herein, a V2O5·nH2O xerogel composed of thin acicular interconnected nanowire networks has been synthesized via a facile freeze-drying process. The interlayer spacing of V2O5·nH2O is larger than that of orthorhombic V2O5 due to the intercalation of water molecules into the layer structure. As the cathode of a SIB, V2O5·nH2O exhibits a high initial capacity of 338 mA h g−1 at 0.05 A g−1 and a high-rate capacity of 96 mA h g−1 at 1.0 A g−1. On the basis of combining ex-situ XRD and FTIR spectroscopy, the Na+ ion intercalation storage reactions are discussed in detail. By modeling calculations, the pseudocapacitive behavior makes a great contribution to the high capacities. Our work demonstrates that V2O5·nH2O with large interlayer spacing is a promising candidate for high capacity sodium-based energy storage.

Three-dimensional porous V2O5 hierarchical microplates have been fabricated by a one-step top-down strategy, and display an excellent rate capability and stable capacity of 110 mA h g−1 at 2000 mA g−1 after 100 cycles. We have demonstrated that the facile approach of a solid-phase conversion is promising for large-scale fabrication of highly porous micro/nano materials.