Synthesis, Properties, and Application of Small-Molecule Hole-Transporting Materials Based on Acetylene-Linked Thiophene Core.

Three small molecule organic compounds based on conjugated acetylene-linked methoxy triphenylamine terminal groups with different substituted thiophene cores were synthesized and firstly applied as hole-transporting materials (HTMs). The electron-deficient acetylene linkers can tune the energy levels of frontier molecular orbitals. The physical property measurements show that the HTMs (CJ-05, CJ-06, and CJ-07) possess good stability, hydrophobicity, and film-forming ability. Further, the HTMs were applied in the MAPbI3-based perovskite solar cells (PSCs), and the best power conversion efficiency (PCE) of 6.04%, 6.77%, and 6.48% was achieved, respectively, which implies that they exhibit great potential in photovoltaic applications.

Pilot-Scale Synthesis Sodium Iron Fluorophosphate Cathode with High Tap Density for a Sodium Pouch Cell.

Sodium-ion batteries (SIBs) have attracted wide interest for energy storage because of the sufficient sodium element reserve on the earth; however, the electrochemical performance of SIBs cannot achieve the requirements so far, especially, the limitation of cathode materials. Here, a kilogram-scale route to synthesize Na2 FePO4 F/carbon/multi-walled carbon nanotubes microspheres (NFPF@C@MCNTs) composite with a high tap density of 1.2 g cm-3 is reported. The NFPF@C@MCNTs cathode exhibits a reversible specific capacity of 118.4 mAh g-1 at 0.1 C. Even under 5 C with high mass loading (10 mg cm-2 ), the specific capacity still maintains at 56.4 mAh g-1 with a capacity retention rate of 97% after 700 cycles. In addition, a hard carbon||NFPF@C@MCNTs pouch cell is assembled and tested, which exhibits a volumetric energy density of 325 Wh L-1 and gravimetrical energy density of 210 Wh kg-1 (base on electrode massing), and it provides more than 200 cycles with a capacity retention rate of 92%. Furthermore, the pouch cell can operate in an all-climate environment ranging from -40 to 80 °C. These results demonstrate that the NFPF@C@MCNTs microspheres are a promising candidate cathode for SIBs and facilitate its practical application in sodium cells.

Towards High-Performance Aqueous Zinc Batteries via a Semi-Conductive Bipolar-Type Polymer Cathode.

Aqueous Zn-organic batteries have received considerable attention owing to their green, low-cost and high safe nature. Unfortunately, organic materials generally exhibit insulator nature (≈10-10  S cm-1 ), and most of reported promising performances of Zn-organic batteries are achieved with a low mass-loading (≈2 mg cm-2 ) in cathode, which is far away from practical application (10 mg cm-2 ). Herein, we demonstrate a semi-conductive polymer poly(1,8-diaminonaphthalene) (PDAN) cathode material for Zn batteries, which shows a moderate electronic conductivity (5.9×10-5  S cm-1 ). Theoretical calculations and in situ/ex situ analysis reveal that the cathode involves a bipolar-type charge storage mechanism. Accordingly, the Zn//PDAN cell exhibits a promising capacity (140 mAh g-1 at 0.1 A g-1 ) and a remarkable cycle stability (1000 cycles without capacity fading) at a high mass-loading (10 mg cm-2 ). These encouraging results shed light on the design of advanced organic electrode.

VPO4 F Fluorophosphates Polyanion Cathodes for High-Voltage Proton Storage.

Proton batteries are emerging in electrochemical energy storage because of the associated fast kinetics, low cost and high safety. However, their development is hindered by the relatively low energy density due to the limited choice of cathode materials. Herein, metal phosphate polyanion cathodes are proposed as the proton cathode for the first time. Combining experimental results and theoretical simulations, a universal criterion for the proton cathode was put forward. Vanadium fluorophosphate (VPO4 F) was demonstrated as a promising high-voltage proton cathode material with a specific capacity of 116 mAh g-1 at a high potential of 1.0 V (vs. SHE). The proton insertion/extraction mechanism in the VPO4 F electrode was also verified through X-ray diffraction (XRD) and photoelectron spectroscopy (XPS). Furthermore, the stability of VPO4 F was investigated in various electrolytes and the optimized electrolyte enabled the stable operation of VPO4 F for 300 cycles. This work provides new inspiration in the exploitation of new electrode materials for electrochemical proton storage devices.

Insight into the Effect of TDMs on the Tribological Behaviors of the Ionic Liquid Composite Films.

Ionic liquid (IL) combined with 2D materials has evoked considerable attention in the field of lubrication applications because of their speical structure and outstanding lubrication properties. However, the ambiguous effect of the 2D materials on the friction and anti-wear properties of the IL needs futher study. Here, we have obtained two families of IL composite films with additives of MoS 2 and graphene via a combined process of spin-coated and curing, and the distinction of the effects of two additives on the tribological performance of the IL films was studied. The friction tests showed that the friction coefficient and anti-wear life of the IL films were greatly enhanced after the addition of MoS 2 or graphene, which could be attributed to the improved load-carrying capacity and the second lubrication phase. Under a low addition content, graphene had more advantages to reduce the friction of the films, and MoS 2 was more beneficial to the tribological properties with the additional content increased. The films with low friction and good anti-wear properties may be valuable for the rational design of lubrication films for the practical engineering applications.