Hollow catalysts through different etching treatments to improve active sites and oxygen vacancies for high-performance Li-O₂ battery

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.