Design of Nb5+-doped high-nickel layered ternary cathode material and its structure stability.

LiNi0.8Co0.1Mn0.1O2(NCM811) is one of the most promising cathode materials for high-energy lithium-ion batteries, but there are still problems such as rapid capacity decay during charge and discharge and poor cycle performance. Elemental doping can significantly improve the electrochemical performance of high nickel ternary cathode materials. In this work, Nb5+-doped NCM811 cathode material was successfully synthesized. The results show that Nb5+doping helps to increase the interlayer spacing of the lithium layer, electron transport, and structural stability, thereby significantly improving the conductivity of Li+. At a high voltage of 4.6 V, the initial discharge specific capacity of 1% Nb5+-doped NCM811 cathode material at 0.1 C is 222.3 mAh·g-1, and the capacity retention rate after 100 cycles at 1 C is 92.03%, which is far more than the capacity retention rate of NCM811 under the same conditions (74.30%). First-principles calculations prove that 1% Nb5+-doped NCM811 cathode material shows the highest electronic conductivity and Nb5+doping will not change the lattice structure, demonstrating the effectiveness of the proposed strategy.

Na and Cl co-doping modified LiNi0.5Co0.2Mn0.3O2as cathode for lithium-ion battery.

In recent years, ternary nickel-rich layered oxides have gradually replaced traditional binary cathode materials in the lithium-ion battery market due to their advantages of high energy density and environmental protection. However, their structural instability of cathode materials has seriously affected the cycle performance of the battery. In order to optimize the internal structure of LiNi0.5Co0.2Mn0.3O2(NCM523), the modified LiNi0.5Co0.2Mn0.3O2was prepared byin situdoping Na and Cl wet grinding solid phase method. After 80 cycles at 1 C, the capacity retention rate was 80.91%, which was higher than that of LiNi0.5Co0.2Mn0.3O2by 70.00%. Scanning electron microscopy showed that the surface corrosion of LiNi0.5Co0.2Mn0.3O2was effectively alleviated by Na and Cl co-doping. In addition, the band structure, state density and volume changes were obtained by simulation. The results show that the impedance, capacity and capacity retention data are very compatible with the simulation results. Therefore, Na and Cl doping can effectively optimize the internal structure of LiNi0.5Co0.2Mn0.3O2and improve its electrochemical performance. The combination of simulation and experiment provides a new approach for the modification of ternary cathode materials.

Aerobic oxidative acylation of nitroarenes with arylacetic esters under mild conditions: facile access to diarylketones.

A facile and regioselective base-mediated aerobic oxidative acylation of nitroarenes to access diarylketones under mild conditions has been developed. It features the use of bench-stable and readily available arylacetates as acyl surrogates, and the absence of transition-metals and synthetic oxidants. This protocol involves a cascade CDC/oxidative decarboxylation process.

Synthesis of carboxylate-functionalized graphene nanosheets for high dispersion of platinum nanoparticles based on the reduction of graphene oxide via 1-pyrenecarboxaldehyde.

A one-step reduction/functionalization strategy for the synthesis of carboxylate-functionalized graphene nanosheets is reported in this paper. 1-pyrenecarboxaldehyde (PCA) is introduced as a new reductant for the chemical reduction of graphene oxide (GO), serving three roles: reducing GO to graphene nanosheets (GNs), stabilizing the as-prepared GNs due to the electrostatic repulsion of the oxidation products of PCA (1-pyrenecarboxylate, PC⁻) on the surface of the GNs and anchoring Pt nanoparticles (Pt NPs) with high dispersion and small particle size. Transmission electron microscopy shows that Pt NPs with an average diameter of 1.3 ± 0.2 nm are uniformly dispersed on the surface of the PC⁻-functionalized GNs (PC⁻-GNs). The obtained Pt NPs/PC⁻-GNs nanohybrids have higher electrocatalytic activity and stability towards methanol oxidation in comparison with Pt NPs supported on GNs obtained by the chemical reduction of GO with the typical reductant, hydrazine.

A strategy for the high dispersion of PtRu nanoparticles onto carbon nanotubes and their electrocatalytic oxidation of methanol.

Carbon nanotubes (CNTs) were non-covalently functionalized by 1-pyrenecarboxaldehyde (PCA) via π-π stacking interactions. PCA not only acts as the reductant for the deposition of PtRu nanoparticles, but the oxidation product of PCA can also effectively anchor and stabilize the in-situ-produced PtRu NPs on the surface of CNTs. Transmission electron microscopy demonstrates that PtRu NPs are uniformly dispersed on the surface of CNTs with small particles sizes of about 1.7 nm. The obtained PtRu-NP/CNT composites have higher electrochemical surface areas, electrocatalytic activities, and better stability towards methanol oxidation compared to PtRu NPs supported on pristine CNTs.

Chitosan-functionalized carbon nanotubes as support for the high dispersion of PtRu nanoparticles and their electrocatalytic oxidation of methanol.

Carbon nanotubes (CNTs) were non-covalently functionalized with chitosan (Chit) and then employed as the support for PtRu nanoparticles. The functionalization was carried out at room temperature without the use of corrosive acids, thereby preserving the integrity and the electronic conductivity of the CNTs. Transmission electron microscopy reveals that PtRu nanoparticles were highly dispersed on the surface of Chit-functionalized CNTs (CNT-Chit) with small particle-size. Cyclic voltammetry studies indicated that the PtRu nanoparticle/CNT-Chit nanohybrids have a higher electrochemical surface area, electrocatalytic performance, and stability towards methanol oxidation compared to PtRu nanoparticles supported on the pristine CNTs.

High dispersion of platinum-ruthenium nanoparticles on the 3,4,9,10-perylene tetracarboxylic acid-functionalized carbon nanotubes for methanol electro-oxidation.

Due to lots of carboxyl groups introduced uniformly on the carbon nanotube (CNT) surface, platinum-ruthenium nanoparticles were highly dispersed on the 3,4,9,10-perylene tetracarboxylic acid-functionalized CNT surface and showed improved electrochemical properties for methanol electrooxidation.

Stabilization of platinum nanoparticles dispersed on carbon nanotubes by ionic liquid polymer.

Due to the protection of ionic liquid polymer thin film, the long-term operation stability of carbon nanotube-supported platinum nanoparticles for methanol electrooxidation has been improved.

Functionalization of carbon nanotubes by an ionic-liquid polymer: dispersion of Pt and PtRu nanoparticles on carbon nanotubes and their electrocatalytic oxidation of methanol.

Small beginnings: Metal nanoparticle/CNT nanohybrids are synthesized from carbon nanotubes (CNTs) functionalized with an ionic-liquid polymer. The Pt and PtRu nanoparticles with narrow size distribution (average diameter: (1.3+/-0.4) nm for PtRu, (1.9+/-0.5) nm for Pt) are dispersed uniformly on the CNTs (see images) and show good performance in methanol electrooxidation.