Mingxiang Hu

Ultrasensitive Pressure Detection of Few‐Layer MoS2

Ultrasensitive pressure sensors are constructed with few-layer MoS2 films. As-designed Fabry-Perot (F-P) sensors exhibit nearly synchronous pressure-deflection responses with a very high sensitivity (89.3 nm Pa-1 ), which is three orders of magnitude higher than those of conventional diaphragm materials (e.g., silica, silver films). This kind of F-P sensor may open up new avenues for 2D materials in biomedical and environmental applications.

Ultrahigh rate sodium ion storage with nitrogen-doped expanded graphite oxide in ether-based electrolyte

Exploring anode materials with excellent rate performance and high initial coulombic efficiency (ICE) is crucial for lithium/sodium-ion batteries (LIBs/SIBs). However, it is still very challenging to achieve this goal in a cost-effective way, particularly for SIBs. Herein, graphite oxide, was treated in ammonia atmosphere for a balance between the oxygen- and nitrogen-contained functional groups and yielded nitrogen-doped expanded graphite oxide (NEGO). Electrochemical characterizations were systematically carried out in ether and ester-based electrolytes to shed light on the storage mechanism of NEGO in SIBs. The ICE of NEGO employed in ether-based electrolyte improves to 72.08% from that in ester-based electrolyte (24.73%). Moreover, the as-synthesized NEGO exhibits ∼125 mA h g−1 and ∼110 mA h g−1 capacities in ether and ester-based electrolytes, respectively, even under a record high current density (30 A g−1). Expanded surface area and nitrogen doping significantly increase the active sites and decrease the electrical resistivity from 140 Ω (EGO) to 40 Ω (NEGO) by removing excess oxygen. Moreover, small amounts of residual oxygen, particularly quinone and carboxyl, along with nitrogen occupied sites offer additional pseudocapacitance. Considering the advantages in scale-up and cost-effective production, NEGO is a promising low-cost anode material for SIBs. This study also provides strategies for the design of electrolyte for SIBs to realize practical applications in power-grid energy storage.

N, S co-doped porous carbon nanospheres with a high cycling stability for sodium ion batteries

Abstract Developing high-performance and low-cost anode materials is crucial for the practical use of sodium-ion batteries (SIBs) at room-temperature. Porous carbon nanospheres with a uniform diameter for use as SIB anode materials were synthesized by the hydrothermal treatment of glucose to obtain the spheres, and subsequent carbonization and modification with KOH activation and N, S co-doping during or after the activation using thiourea as the N and S sources. Nanospheres doped with N and S after KOH activation have a high initial specific capacity of 527 mAh g−1 at a current density of 20 mA g−1 and an excellent cycling stability with a 95.2% capacity retention after 1000 cycles at a high current density of 500 mA g−1. The capacity retention rate is higher than that of most of the state-of-the-art anode materials for SIBs. This good performance is attributed to the abundant micro-pores, the enlarged interlayer spacing produced by the co-doping, and the high conductivity of the carbon nanospheres.

High Areal Capacity Li‐Ion Storage of Binder‐Free Metal Vanadate/Carbon Hybrid Anode by Ion‐Exchange Reaction

Storing more energy in a limited device area is very challenging but crucial for the applications of flexible and wearable electronics. Metal vanadates have been regarded as a fascinating group of materials in many areas, especially in lithium-ion storage. However, there has not been a versatile strategy to synthesize flexible metal vanadate hybrid nanostructures as binder-free anodes for Li-ion batteries so far. A convenient and versatile synthesis of Mx Vy Ox+2.5y @carbon cloth (M = Mn, Co, Ni, Cu) composites is proposed here based on a two-step hydrothermal route. As-synthesized products demonstrate hierarchical proliferous structure, ranging from nanoparticles (0D), and nanobelts (1D) to a 3D interconnected network. The metal vanadate/carbon hybrid nanostructures exhibit excellent lithium storage capability, with a high areal specific capacity up to 5.9 mAh cm-2 (which equals to 1676.8 mAh g-1 ) at a current density of 200 mA g-1 . Moreover, the nature of good flexibility, mixed valence states, and ultrahigh mass loading density (over 3.5 mg cm-2 ) all guarantee their great potential in compact energy storage for future wearable devices and other related applications.

Coupled ultrasonication-milling synthesis of hierarchically porous carbon for high-performance supercapacitor

Activated carbon (AC) based supercapacitors exhibit intrinsic advantages in energy storage. Traditional two-step synthesis (carbonization and activation) of AC faces difficulties in precisely regulating its pore-size distribution and thoroughly removing residual impurities like silicon oxide. This paper reports a novel coupled ultrasonication-milling (CUM) process for the preparation of hierarchically porous carbon (HPC) using corn cobs as the carbon resource. The as-obtained HPC is of a large surface area (2288 m2 g-1) with a high mesopore ratio of ∼44.6%. When tested in a three-electrode system, the HPC exhibits a high specific capacitance of 465 F g-1 at 0.5 Ag-1, 2.7 times higher than that (170 F g-1) of the commercial AC (YP-50F). In the two-electrode test system, the HPC device exhibits a specific capacitance of 135 F g-1 at 1 A g-1, twice higher than that (68 F g-1) of YP-50F. The above excellent energy-storage properties are resulted from the CUM process which efficiently removes the impurities and modulates the mesopore/micropore structures of the AC samples derived from the agricultural resides of corn cobs. The CUM process is an efficient method to prepare high-performance biomass-derived AC materials.