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Optimal geometrical configuration and oxidation state of cobalt cations in spinel oxides to promote the performance of Li-O2 battery
Nano Research 2024, 17 (1): 221-227
Published: 15 March 2023
Downloads:59

Co3O4 is considered as one of promising cathode catalysts for lithium oxygen (Li-O2) batteries, which contains both tetrahedral Co2+ sites (Co2+Td) and octahedral Co3+ sites (Co3+Oh). It is important to reveal the effect of optimal geometric configuration and oxidation state of cobalt ion in Co3O4 to improve the performance of Li-O2 batteries. Herein, through regulating the synthesis process, Co2+ and Co3+ sites in Co3O4 were replaced with Zn and Al atoms to form materials with a unique Co site. The Li-O2 batteries based on ZnCo2O4 showed longer cycle life than that of CoAl2O4, suggesting that in Co3O4, the Co3+Oh site is a relatively better geometric configuration than Co2+Td site for Li-O2 batteries. Theoretical calculations revealed that Co3+Oh sites provide higher catalysis activity, regulating the adsorption energy of the intermediate LiO2 and accelerating the kinetics of the reaction in batteries, which further leads to the change of the morphology of the discharge product and ultimately improves the electrochemical performance of the batteries.

Research Article Issue
Hollow catalysts through different etching treatments to improve active sites and oxygen vacancies for high-performance Li-O2 battery
Nano Research 2023, 16 (5): 6798-6804
Published: 22 February 2023
Downloads:51

Li-O2 batteries are regarded as one of the most promising next-generation battery systems due to their high theoretical energy density, and finding effective cathode catalysts with fine-tuned structure is a key way to improve the performance. Herein, based on the structure of cubic zeolitic imidazolate framework-67 (ZIF-67), a series of hollow catalysts were synthesized by different chemical etching treatments. Firstly, from the perspective of metal, nickel nitrate is used for etching, and hollow Ni ZIF is obtained through Kirkendall effect. Secondly, hollow TA-ZIF is obtained by adding tannic acid to replace the methylimidazole ligand. Hollow structures have larger surface areas, and materials can expose more active sites, which can lead to better performance of Li-O2 batteries. On this basis, having more oxygen vacancies can also improve the battery performance. At the same time, further loading noble metal ruthenium on the synthesized cobalt-based catalyst can effectively reduce the overpotential of Li-O2 battery and improve the battery performance. For TA-ZIF with more stable hollow structure and more oxygen vacancies, the cycle performance reaches 330 cycles after loading Ru. Compared with the 64 cycles of solid Co3O4, it has a great improvement.

Research Article Issue
Ordered two-dimensional porous Co3O4 nanosheets as electrocatalysts for rechargeable Li-O2 batteries
Nano Research 2019, 12 (2): 299-302
Published: 10 October 2018
Downloads:32

Lithium-oxygen batteries have attracted considerable interest in the past a few years, because they have higher theoretical specific energy than Li-ion batteries. However, the available energy densities of the Li-O2 batteries are much less than expected. It is particularly urgent to find catalyst with high activity. Herein, a series of Co3O4 with different morphologies (ordered two-dimensional porous nanosheets, flowerlike and cuboidlike) were successfully prepared through facile hydrothermal and calcination methods. Ordered two-dimensional Co3O4 nanosheets show the best cycling stability. Detailed experimental results reveal that the superiority of the unique two-dimensional uniform porous structures is vital for Li-O2 batteries cathode catalysts. Due to the ordered structures with high surface areas and active sites, the catalysts indicate a high specific discharge capacity of about 10, 417 mAh/g at a current density of 200 mA/g, and steadily cycle for more than 50 times with a limited capacity of 1, 000 mAh/g.

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