La-based perovskites for capacity enhancement of Li-O2 batteries

Li-O2 batteries are a promising technology for the upcoming energy storage requirements because of their high theoretical specific energy density of 11,680 Wh kg-1. Currently, the actual capacity of Li-O2 batteries is much lower than this theoretical value. In many studies, perovskites have been applied as catalysts to improve the air electrode reactions in Li-O2 batteries. The effects of structure and doping on the catalytic activity of perovskites are still unclear. La1-xSrxCoO3-δ (x = 0.1, 0.3, and 0.5) and La0.9Sr0.1YbO3-δ mixed with carbon black (Vulcan XC500 or Super P) were used as air electrode catalysts. Electrochemical characterizations were conducted using a Swagelok-type cell. The charge-discharge capacity and cyclic voltammetry (CV) performance were investigated in this study. The La1-xSrxCoO3-δ (x = 0.1, 0.3, and 0.5) is a suitable cathode catalyst for Li-O2 batteries. In this study, the La0.5Sr0.5CoO3-δ/Super P cathode demonstrated the highest discharge capacity (6,032 mAh g-1). This excellent performance was attributed to the large reaction area and enhanced Li2CO3 generation.

First Application of Nitrogen-Doped Carbon Nanosheets Derived from Lotus Leaves as the Electrode Catalyst for Li-CO2/O2 Battery

The development of Li-CO2/O2 battery with high energy density and long-term stability is urgently needed to fulfill the carbon neutralization and pollution-free environment targets. The biomass-derived heteroatom-doped carbon catalyst with the combination of high-efficiency catalytic activity and sustainable supply is a promising cathode catalyst in Li-CO2/O2 battery. Specifically, the unique morphology and mesopore structure can promote the transfer of CO2, O2, and Li+. Abundant channel pores can provide discharge products accommodation to the largest extent. Nitrogen dopant, the commonly recognized active sites in carbon, can improve the electron conductivity and accelerate the sluggish kinetic reaction. Therefore, utilizing the louts leaves as the precursor, we successfully prepare the cellular-like nitrogen-doped activated carbon nanosheets (N-CNs) through the appropriate pyrolysis carbonization method. The as-synthesized carbon nanosheets display a three-dimensional interconnecting pore structure and abundant N-dopant actives, which dramatically improve the electrochemical catalytic activity of N-CNs. The Li-CO2/O2 battery with the N-CNs cathode delivers a high discharge capacity of 9825 mAh g−1, low overpotential of 1.21 V, and stable cycling performance of 95 cycles. Thus, we carry out a facile method for N-doped carbon nanosheets preparation derived from the cheap natural biomass, which can be the effective cathode catalyst for environmental-friendly Li-CO2/O2 battery.

Mechanisms for self-templating design of micro/nanostructures toward efficient energy storage

The ever-growing demand in modern power systems calls for the innovation in electrochemical energy storage devices so as to achieve both supercapacitor-like high power density and battery-like high energy density. Rational design of the micro/nanostructures of energy storage materials offers a pathway to finely tailor their electrochemical properties thereby enabling significant improvements in device performances and enormous strategies have been developed for synthesizing hierarchically structured active materials. Among all strategies, the direct conversion of precursor templates into target micro/nanostructures through physical and/or chemical processes is facile, controllable, and scalable. Yet the mechanistic understanding of the self-templating method is lacking and the synthetic versatility for constructing complex architectures is inadequately demonstrated. This review starts with the introduction of five main self-templating synthetic mechanisms and the corresponding constructed hierarchical micro/nanostructures. Subsequently, the structural merits provided by the well-defined architectures for energy storage are elaborately discussed. At last, a summary of current challenges and future development of the self-templating method for synthesizing high-performance electrode materials is also presented.

Composite NiCo2 O4 @CeO2 Microsphere as Cathode Catalyst for High-Performance Lithium-Oxygen Battery

The large overpotential and poor cycle stability caused by inactive redox reactions are tough challenges for lithium-oxygen batteries (LOBs). Here, a composite microsphere material comprising NiCo₂ O₄ @CeO₂ is synthesized via a hydrothermal approach followed by an annealing processing, which is acted as a high performance electrocatalyst for LOBs. The unique microstructured catalyst can provide enough catalytic surface to facilitate the barrier-free transport of oxygen as well as lithium ions. In addition, the special microsphere and porous nanoneedles structure can effectively accelerate electrolyte penetration and the reversible formation and decomposition process of Li₂ O₂ , while the introduction of CeO₂ can increase oxygen vacancies and optimize the electronic structure of NiCo₂ O₄ , thereby enhancing the electron transport of the whole electrode. This kind of catalytic cathode material can effectively reduce the overpotential to only 1.07 V with remarkable cycling stability of 400 loops under 500 mA g^-1 . Based on the density functional theory calculations, the origin of the enhanced electrochemical performance of NiCo₂ O₄ @CeO₂ is clarified from the perspective of electronic structure and reaction kinetics. This work demonstrates the high efficiency of NiCo₂ O₄ @CeO₂ as an electrocatalyst and confirms the contribution of the current design concept to the development of LOBs cathode materials.

Versatile design of metal-organic framework cathode for Li-O2 and Li-O2/CO2 batteries

In this study, we propose a versatile design for metal-organic framework cathodes with the aim of improving the reversibility of Li-O₂ and Li-O₂/CO₂ batteries. The porous nanoarchitecture of Co₃O₄-incorporated carbon wrapped with carbon nanotubes is beneficial for facilitating the reversible electrochemical reactions with O₂ and CO₂, ensuring long-term cycling performance.

Curtailing the Overpotential of Li-CO2 Batteries with Shape-Controlled Cu2 O as Cathode: Effect of Illuminating the Cathode

Li-air batteries are limited to lab-scale research owing to the uninterrupted formation of discharge products. In the case of Li-CO₂ batteries, the increase in overpotential caused by Li₂ CO₃ formation results in cell death. In this study, Cu₂ O crystals having three different types of shapes (i.e., cubic, octahedral, and rhombic) were synthesized to compare their catalytic activity toward CO₂ reactions. The full-cycle and long-term stability test revealed that rhombohedral Cu₂ O facilitates Li₂ CO₃ decomposition more efficiently than that of cubic and octahedral Cu₂ O. The cycle was extended to investigate the photocatalytic activity of the rhombic Cu₂ O by illuminating the cell. The repeated cycles to 1 h showed a maximum overpotential of 1.5 V, which is 0.5 V lower than that of the cell without illumination. A postmortem analysis of the cell after dividing the cycles into segments demonstrated interesting results concerning the role of light and Cu₂ O during the cell cycle.

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.