Hierarchical Mesoporous/Macroporous Co-Doped NiO Nanosheet Arrays as Free-Standing Electrode Materials for Rechargeable Li-O2 Batteries

Anchoring NiO Nanosheet on the Surface of CNT to Enhance the Performance of a Li-O2 Battery

Li₂O₂, as the cathodic discharge product of aprotic Li-O₂ batteries, is difficult to electrochemically decompose. Transition-metal oxides (TMOs) have been proven to play a critical role in promoting the formation and decomposition of Li₂O₂. Herein, a NiO/CNT catalyst was prepared by anchoring a NiO nanosheet on the surface of CNT. When using the NiO/CNT as a cathode catalyst, the Li-O₂ battery had a lower overpotential of 1.2 V and could operate 81 cycles with a limited specific capacity of 1000 mA h g⁻¹ at a current density of 100 mA g⁻¹. In comparison, with CNT as a cathodic catalyst, the battery could achieve an overpotential of 1.64 V and a cycling stability of 66 cycles. The introduction of NiO effectively accelerated the generation and decomposition rate of Li₂O₂, further improving the battery performance. SEM and XRD characterizations confirmed that a Li₂O₂ film formed during the discharge process and could be fully electrochemical decomposed in the charge process. The internal network and nanoporous structure of the NiO/CNT catalyst could provide more oxygen diffusion channels and accelerate the decomposition rate of Li₂O₂. These merits led to the Li-O₂ battery’s better performance.

Synthesis of Fe-doped NiO nanosheets on carbon cloth for improved catalytic performance in Li–O2 batteries

The substitution of Ni2+ in NiO with Fe3+ can significantly improve the cycling stability and discharge/recharge capacities of Li–O2 batteries.

A free-standing 3D porous all-ceramic cathode for high capacity, long cycle life Li-O2 batteries

The all-ceramic RuO₂@La_0.7Ca_0.3CuO₃ membrane cathode contributes to an ultra-high capacity of 21 518 mA h g^-1 over 110 cycles in Li-O₂ batteries. A simple infiltration technique is effective for obtaining a highly active supported RuO₂ catalyst, and a solvent with a high donor number should be preferentially chosen because it contributes to a much higher capacity.

Doping regulation in transition metal compounds for electrocatalysis

In electrocatalysis, doping regulation has been considered as an effective method to modulate the active sites of catalysts, providing a powerful means for creating a large variety of highly efficient catalysts for various reactions. Of particular interest, there has been growing research concerning the doping of two-dimensional transition-metal compounds (TMCs) to optimize their electrocatalytic performance. Despite the previous achievements, mechanistic insights of doping regulation in TMCs for electrocatalysis are still lacking. Herein, we provide a systematic overview of doping regulation in TMCs in terms of background, preparation, impacts on physicochemical properties, and typical applications including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, CO₂ reduction reaction, and N₂ reduction reaction. Notably, we bridge the understanding between the doping regulation of catalysts and their catalytic activities via focusing on the physicochemical properties of catalysts from the aspects of vacancy concentrations, phase transformation, surface wettability, electrical conductivity, electronic band structure, local charge distribution, tunable adsorption strength, and multiple adsorption configurations. We also discuss the existing challenges and future perspectives in this promising field.

A unique hierarchical structure: NiCo2O4 nanowire decorated NiO nanosheets as a carbon-free cathode for Li–O2 battery

The hierarchical structure of NiCo2O4 nanowire modified NiO nanosheets was successfully fabricated and showed excellent cycling stability at a current density of 200 mA g−1 as a carbon-free cathode for Li–O2 batteries.

Spinel Zinc Cobalt Oxide (ZnCo2O4) Porous Nanorods as a Cathode Material for Highly Durable Li-CO2 Batteries

Li-CO₂ batteries are of great interest among researchers due to their high energy density and utilization of the greenhouse gas CO₂ to produce energy. However, several shortcomings have been encountered in the practical applications of Li-CO₂ batteries, among which their poor cyclability and high charge overpotential necessary to decompose the highly insulating discharge product (Li₂CO₃) are the most important. Herein, the spinel zinc cobalt oxide porous nanorods with carbon nanotubes (ZnCo₂O₄@CNTs) composite is employed as a cathode material in Li-CO₂ batteries to improve the latter's cycling performance. The ZnCo₂O₄@CNT cathode-based Li-CO₂ battery exhibited a full discharge capacity of 4275 mAh g^-1 and excellent cycling performance over 200 cycles with a charge overpotential below 4.3 V when operated at a current density of 100 mA g^-1 and fixed capacity of 500 mAh g^-1. The superior performance of the ZnCo₂O₄@CNT cathode composite was attributed to the synergistic effects of ZnCo₂O₄ and CNT. The highly porous ZnCo₂O₄ nanorod structures in the ZnCo₂O₄@CNT catalyst showed enhanced catalytic activity/stability, which effectively promoted CO₂ diffusion during the discharging process and accelerated Li₂CO₃ decomposition at a low charge overpotential.