2D VS2 @MXene Based Zinc Ion Batteries with SPANI-Contained Electrolyte Enables Dendrite-Free Anode for Stable Cycling.

Regarded as one of the popular cathode materials in aqueous zinc ion batteries (ZIBs), VS2 has unsatisfied cycling stability and relatively low capacity owing to its poor conductivity and low mechanical properties. To this regard, compositing VS2 with high-conductive 2D transition metal carbide (MXene) has been an effective method recently. However, the Zn dendrite on the anode electrode derived from the uncontrollable sluggish migration of solvated Zn2+ /H2 O ions seriously threatens the application safety of ZIB batteries. To effectively regulate the diffusion of zinc ions, in this work a conductive polymeric electrolyte of sulfonated polyaniline (SPANI) is added in the electrolyte solution. Under the Zn2+ /SPANI interactions confirmed by X-ray diffraction, Raman, and zeta potential experiments, the Zn2+ /H2 O combination is weakened, and the deposition rate of Zn2+ is increased evaluated by the galvanostatic intermittent titration technique. Theoretical simulation shows that the electrostatic shielding by SPANI combining Zn2- at the zinc/electrolyte interface has important contribution to the significant suppression of Zn dendrite. Accordingly, the fabricated VS2 @MXene||ZnSO4 +SPANI||Zn battery shows high capacity (368.0 mAh g-1 at 0.1 A g-1 ), which remains 96% after 5000 cyclic charge-discharge operations. This work develops an available strategic idea for suppressing growth of metallic dendrites to improve the ZIB performances.

Enhanced Electrochemical Performance by Strongly Anchoring Highly Crystalline Polyaniline on Multiwalled Carbon Nanotubes.

Highly crystalline polyaniline (PANI) was strongly anchored on a multiwalled carbon nanotube (MWNT) surface, slowly grown from a controlled isothermal crystallization method utilizing π-π interactions. The crystalline PANI particles are approximately 10-38 nm thick, and the space between them varies from near 0 to 55 nm as reaction conditions vary. The highly crystalline nanohybrid (CNH) showed electrochemical performance enhancement compared with that of neat MWNTs, PANI, and the reference hybrid synthesized from chemical polymerization. The specific capacitance (SC) of CNHs was 726 F g-1 coupled with an excellent rate capability. Moreover, the strong combination between PANI and MWNTs as well as the crystalline structure in PANI improved the bulk conductivity, the interfacial charge transportation, and the cycling stability of the CNHs. The SC value of the CNHs remained almost unchanged upon 1000 charge-discharge cycles, followed by just a slight decline of 2.6% after 10 000 cycle tests. X-ray diffraction data shows the SC decline mainly resulted from the structural variation of crystalline PANI. Furthermore, the resulting CNHs showed significant electrocatalytic behavior toward H2O2 and exhibited a low detection limit of 4.4 µM due to the enhanced electron transportation between MWNTs and PANI. The reported method opens a gateway to design high-performance MWNT/PANI hybrids for use in electrochemical sensors, fuel cells, and energy-storage related devices.

Enhanced Electronic Communication and Electrochemical Sensitivity Benefiting from the Cooperation of Quadruple Hydrogen Bonding and π-π Interactions in Graphene/Multi-Walled Carbon Nanotube Hybrids.

By designing a molecule labeled as UPPY with both ureidopyrimidinone (UP) and pyrene (PY) units, the supramolecular self-assembly of multiwalled carbon nanotube (MWNT) and reduced graphene oxide (rGO) was driven by the UP quadruple hydrogen-bonding and PY-based π-π interactions to form a novel hybrid of rGO-UPPY-MWNT in which the morphology of rGO-wrapped MWNT was found. Bridged by the two kinds of noncovalent bonding, enhanced electronic communication occurred in rGO-UPPY-MWNT. Also, under the cooperation of UP quadruple hydrogen-bonding and PY-based π-π interactions, higher electrical conductivity and better charge transfer were observed for rGO-UPPY-MWNT, compared with the rGO-MWNT composite without such noncovalent bonds, and that with just single PY-based π-π interaction (rGO-PY-MWNT) or UP quadruple hydrogen bond (rGO-UP-MWNT). Specifically, the electrical conductivity of rGO-PY-MWNT hybrids was increased approximately sevenfold, and the interfacial charge transfer resistance was nearly decreased by 1 order of magnitude compared with rGO-MWNT, rGO-UP-MWNT, and rGO-PY-MWNT. Resulting from its excellent electrical conductivity and charge transfer properties, the rGO-UPPY-MWNT modified electrode exhibited enhanced electrochemical activity toward dopamine with detection limit as low as 20 nM.