Carbon and Binder-Free Air Electrodes Composed of Co3O 4 Nanofibers for Li-Air Batteries with Enhanced Cyclic Performance

Stoichiometrically optimized eg orbital occupancy of Ni-Co oxide catalysts for Li-air batteries

Li-air battery (LAB) technology is making continuous progress toward its theoretical capacity, which is comparable to gasoline. However, the sluggish reaction at the cathode is still a challenge. We propose a simple strategy to optimize the surface eg occupancy by adjusting the stoichiometric ratios of transition metal-based spinel structures through a controlled hydrothermal synthesis. Three distinct stoichiometries of Ni-Co oxides were used to demonstrate the direct correlation between stoichiometry and catalytic performance. The groundsel flower-like structure having a 1 : 1.4 Ni : Co atomic ratio with high surface area, high defect density, and an abundance of Ni3+ at the surface with semi-filled eg orbitals was found to benefit the structure promoting high catalytic activities in aqueous and aprotic media. The assembled LAB cells employing this cathode demonstrate an exceptional lifespan, operating for 3460 hours and completing 173 cycles while achieving the highest discharge capacity of 13 759 mA h g-1 and low charging overpotentials. The key to this prolonged performance lies in the full reversibility of the cell, attributed to its excellent OER performance. A well-surface adsorbed, amorphous LiO2/Li2O2 discharge product is found to possess high diffusivity and ease of decomposition, contributing significantly to the enhanced longevity of the cell.

Recent Developments for Aluminum–Air Batteries

Abstract

Environmental concerns such as climate change due to rapid population growth are becoming increasingly serious and require amelioration. One solution is to create large capacity batteries that can be applied in electricity-based applications to lessen dependence on petroleum. Here, aluminum–air batteries are considered to be promising for next-generation energy storage applications due to a high theoretical energy density of 8.1 kWh kg−1 that is significantly larger than that of the current lithium-ion batteries. Based on this, this review will present the fundamentals and challenges involved in the fabrication of aluminum–air batteries in terms of individual components, including aluminum anodes, electrolytes and air cathodes. In addition, this review will discuss the possibility of creating rechargeable aluminum–air batteries.

Graphic Abstract

Carbon nanotube/Co3O4 nanocomposites selectively coated by polyaniline for high performance air electrodes

We herein report the preparation of carbon nanotube (CNT)/Co₃O₄ nanocomposites selectively coated with polyaniline (PANI) via an electropolymerization method, for use as an effective electrode material for Li-air (Li-O₂) batteries. The Co₃O₄ catalyst attached to the CNTs facilitated the dissociation of reaction products and reduced the overpotential of the cells. As the carbon surface activates the side reactions, the PANI coating on the carbon surface of the electrode suppressed the side reaction at the electrode/Li₂O₂ and electrode/electrolyte interfaces, thus enhancing the cycle performance of the electrode. In addition, the catalytic activity of Co₃O₄ on the CNT/Co₃O₄ nanocomposites remained unaffected, as the Co₃O₄ surface was not covered with a PANI layer due to the nature of the electropolymerization method. Overall, the synergic effect of the PANI layer and the Co₃O₄ catalyst leads to a superior cyclic performance and a low overpotential for the electrode based on selectively PANI-coated CNT/Co₃O₄ nanocomposites.