3D Grid of Carbon Tubes with Mn3O4-NPs/CNTs Filled in their Inner Cavity as Ultrahigh-Rate and Stable Lithium Anode

Transition metal oxides are regarded as promising candidates of anode for next-generation lithium-ion batteries(LIBs)due to their ultrahigh theoretical capacity and low cost,but are restricted by their low conductivity and large volume expansion during Li^(+)intercalation.Herein,we designed and constructed a structurally integrated 3D carbon tube(3D-CT)grid film with Mn_(3)O_(4)nanoparticles(Mn_(3)O_(4)-NPs)and carbon nanotubes(CNTs)filled in the inner cavity of CTs(denoted as Mn_(3)O_(4)-NPs/CNTs@3D-CT)as high-performance free-standing anode for LIBs.The Mn_(3)O_(4)-NPs/CNTs@3D-CT grid with Mn_(3)O_(4)-NPs filled in the inner cavity of 3D-CT not only afford sufficient space to overcome the damage caused by the volume expansion of Mn_(3)O_(4)-NPs during charge and discharge processes,but also achieves highly efficient channels for the fast transport of both electrons and Li+during cycling,thus offering outstanding electrochemical performance(865 mAh g^(-1)at 1 A g^(-1)after 300 cycles)and excellent rate capability(418 mAh g^(-1)at 4 A g^(-1))based on the total mass of electrode.The unique 3D-CT framework structure would open up a new route to the highly stable,high-capacity,and excellent cycle and high-rate performance free-standing electrodes for highperformance Li-ion storage.

Circumventing chemo-mechanical failure of Sn foil battery anode by grain refinement and elaborate porosity design

Tin (Sn) metal foil is a promising anode for next-generation high-energy–density lithium-ion batteries (LIBs) due to its high capacity and easy processibility. However, the pristine Sn foil anode suffers nonuniform alloying/dealloying reaction with lithium (Li) and huge volume variation, leading to electrode pulverization and inferior electrochemical performance. Herein, we proposed that reduced grain size and elaborate porosity design of Sn foil can circumvent the nonuniform alloy reaction and buffer the volume change during the lithiation/delithiation cycling. Experimentally, we designed a three-dimensional interconnected porous Sn (3DIP-Sn) foil by a facile chemical alloying/dealloying approach, which showed improved electrochemical performance. The enhanced structure stability of the as-fabricated 3DIP-Sn foil was verified by chemo-mechanical simulations and experimental investigation. As expected, the 3DIP-Sn foil anode revealed a long cycle lifespan of 4400 h at 0.5 mA cm^(−2) and 1 mAh cm^(−2) in Sn||Li half cells. A 3DIP-Sn||LiFePO_(4) full cell with LiFePO_(4) loading of 7.1 mg cm^(−2) exhibited stable cycling for 500 cycles with 80% capacity retention at 70 mA g^(−1). Pairing with high-loading commercial LiNi0.6Co0.2Mn0.2O_(2) (NCM622, 18.4 mg cm^(−2)) cathode, a 3DIP-Sn||NCM622 full cell delivered a high reversible capacity of 3.2 mAh cm^(−2). These results demonstrated the important role of regulating the uniform alloying/dealloying reaction and circumventing the localized strain/stress in improving the electrochemical performance of Sn foil anodes for advanced LIBs.

Three-dimensional （3D） interconnected networks fabricated via in-situ growth of N-doped graphene/ carbon nanotubes on Co-containing carbon nanofibers for enhanced oxygen reduction

The strategy of combining highly conductive frameworks with abundant active sites is desirable in the preparation of alternative catalysts to commercial Pt/C for the oxygen reduction reaction （ORR）. In this study, N-doped graphene （NG） and carbon nanotubes （CNT） were grown in-situ on Co-containing carbon nanofibers （CNF） to form three-dimensional （3D） interconnected networks. The NG and CNT bound the interlaced CNF together, facilitating electron transfer and providing additional active sites. The 3D interconnected fiber networks exhibited excellent ORR catalytic behavior with an onset potential of 0.924 V （vs. reversible hydrogen electrode） and a higher current density than Pt/C beyond 0.720 V. In addition, the hybrid system exhibited superior stability and methanol tolerance to Pt/C in alkaline media. This method can be extended to the design of other 3D interconnected network architectures for energy storage and conversion applications.

MoS2 embedded in 3D interconnected carbon nanofiber film as a free-standing anode for sodium-ion batteries

As a typical two-dimensional transition metal dichalcogenide, molybdenum disulfide （MoS2） is considered a potential anode material for sodium-ion batteries （NIBs）, due to its relatively high theoretical capacity （~ 670 mAh·g--1）. However, the low electrical conductivity of MoS2 and its dramatic volume change during charge/discharge lead to severe capacity degradation and poor cycling stability. In this work, we developed a facile, scalable, and effective synthesis method to embed nanosized MoS2 into a thin film of three-dimensional （3D）-interconnected carbon nanofibers （CNFs）, producing a MoS2/CNFs film. The free-standing MoS2/CNFs thin film can be used as anode for NIBs without additional binders or carbon black. The MoS2/CNFs electrode exhibits a high reversible capacity of 260 mAh·g^-1, with an extremely low capacity loss of 0.05 mAh·g^-1 per cycle after 2,600 cycles at a current density of 1 A·g^-1. This enhanced sodium storage performance is attributed to the synergistic effect and structural advantages achieved by embedding MoS2 in the 3D-interconnected carbon matrix.

3D interconnected nanoporous TaN films for photoelectrochemical water splitting: thickness-controlled synthesis and insights into stability

Solar-driven photoelectrochemical(PEC) water splitting is a promising technology for sustainable hydrogen production, which relies on the development of efficient and stable photoanodes for water oxidation reaction. The thickness and microstructure of semiconductor films are generally crucial to their PEC properties. Herein, three-dimensional(3D) interconnected nanoporous Ta3N5 film photoanodes with controlled thickness were successfully fabricated via galvanostatic anodization and NH3 nitridation. The porous Ta3N5 nanoarchitectures(NAs) of 900 nm in thickness showed the highest PEC performance due to the optimal lightharvesting and charge separation. Compared with the holeinduced photocorrosion, the electrochemical oxidation at high anodic potentials resulted in severer performance degradation of Ta3N5. Although the surface oxide layer on deteriorated Ta3N5 photoanodes could be removed by NH3 re-treatment,the PEC performance was only partially recovered. As an alternative, anchoring a dual-layer Co(OH)x/Co OOH co-catalyst shell on the porous Ta3N5 NAs demonstrated substantially enhanced PEC performance and stability. Overall, this work provides reference to controllably fabricate 3D nanoporous Ta3N5-based photoanodes for efficient and stable PEC water splitting via optimizing the light absorption, hole extraction,charge separation and utilization.

Facile fabrication of three-dimensional interconnected nanoporous N-TiO_2 for efficient photoelectrochemical water splitting

Three-dimensional （3D） interconnected porous architectures are expected to perform well in photoelectrochemical （PEC） water splitting due to their high specific surface area as well as favourable porous properties and interconnections. In this work, we demonstrated the facile fabrication of 3D interconnected nanoporous N-doped TiO2 （N-TiO2 network） by annealing the anodized 3D interconnected nanoporous TiO2 （TiO2 network） in ammonia atmosphere. The obtained N-TiO2 network exhibited broadened light absorption, and abundant, interconnected pores for improving charge separation, which was supported by the reduced charge transfer resistance. With these merits, a remarkably high photocurrent density at 1.23 V vs. reversible hydrogen electrode （RHE） was realized for the N-TiO2 network without any co-catalysts or sacrificial reagents, and the photostability can be assured after long term illumination. In view of its simplicity and efficiency, this structure promises for perspective PEC applications.