Co₃O₄ Hollow Porous Nanospheres with Oxygen Vacancies for Enhanced Li–O₂ Batteries

Abstract

Creating oxygen vacancies to tune the surface electronic structure is a feasible approach to enhance the electrocatalytic activities of noble-metal-free transition-metal oxides for Li−O 2 batteries. Herein, vacancy-rich Co 3 O 4 hollow porous nanospheres have been obtained through a facile reduction strategy from Co 3 O 4 hollow porous nanospheres, which were prepared in a self-template construction manner through a solvothermal synthesis followed by a heat treatment. The reduced Co 3 O 4 hollow porous nanospheres composed of numerous nanoparticles show a unique porous and hollow structure with abundant surface oxygen vacancies. The oxygen vacancy defects can produce more electrochemical active sites and improve the electrical conductivity as well as increase the adsorbed oxygen-containing molecules for the enhanced Li−O 2 battery performance. Therefore, the reduced Co 3 O 4 sample with oxygen vacancies shows lower overpotential, higher discharge capacity, longer cycling life, and better rate capability than the pristine one. KEYWORDS: Li−O 2 batteries, oxygen vacancies, defects, Co 3 O 4 , hollow, spheres

Unveiling Intrinsic Potassium Storage Behaviors of Hierarchical Nano Bi@N‐Doped Carbon Nanocages Framework via In Situ Characterizations

“…By contrast, the bismuth NPs in the 550‐Bi@N‐CNCs (Supporting Information, Figure S22; Movie S4) and 700‐Bi@N‐CNCs (Supporting Information, Figure S23; Movie S5) are both broken and seriously agglomerated after the depotassiation process. The comparative real‐time observations here visualize the superior structural reversibility of the 850‐Bi@N‐CNCs, which ensures the formation of a stable yet thin SEI layer on the outer robust N‐CNCs, [31–34] and a close electronic contact between the continuous carbon network and Bi NPs meantime [35–37] . While for the 550‐Bi@N‐CNCs or 700‐Bi@N‐CNCs, the repetitive rupturing and reformation of the passivating SEI film occur, and always convert the cyclable K species in electrode sur‐/interfaces to dead K in the SEI, eventually leading to the death of the batteries due to the K exhaustion.…”

“…Moreover,a fter 20 potassiation/ depotassiation cycles,t he well-defined 850-Bi@N-CNCs still can maintains its structural integrity without noticeable structure rupture (Supporting Information, Movie S3), which authenticates that the internal void space and elastic shell of N-CNCs can effectively relieve the volume expansion of Bi NPs.B yc ontrast, the bismuth NPs in the 550-Bi@N-CNCs (Supporting Information, Figure S22;M ovie S4) and 700-Bi@N-CNCs (Supporting Information, Figure S23;Movie S5) are both broken and seriously agglomerated after the depotassiation process.T he comparative real-time observations here visualize the superior structural reversibility of the 850-Bi@N-CNCs,which ensures the formation of astable yet thin Angewandte Chemie Forschungsartikel SEI layer on the outer robust N-CNCs, [31][32][33][34] and ac lose electronic contact between the continuous carbon network and Bi NPs meantime. [35][36][37] While for the 550-Bi@N-CNCs or 700-Bi@N-CNCs,the repetitive rupturing and reformation of the passivating SEI film occur, and always convert the cyclable Ks pecies in electrode sur-/interfaces to dead Ki n the SEI, eventually leading to the death of the batteries due to the Ke xhaustion.…”

Unveiling Intrinsic Potassium Storage Behaviors of Hierarchical Nano Bi@N‐Doped Carbon Nanocages Framework via In Situ Characterizations

“…Research Articles SEI layer on the outer robust N-CNCs, [31][32][33][34] and ac lose electronic contact between the continuous carbon network and Bi NPs meantime. [35][36][37] While for the 550-Bi@N-CNCs or 700-Bi@N-CNCs,the repetitive rupturing and reformation of the passivating SEI film occur, and always convert the cyclable Ks pecies in electrode sur-/interfaces to dead Ki n the SEI, eventually leading to the death of the batteries due to the Ke xhaustion.…”

Toward high‐performance lithium‐oxygen batteries with cobalt‐based transition metal oxide catalysts: Advanced strategies and mechanical insights

“…The catalytic active site could be created by defect engineering strategy, including the control of Co 2+ /Co 3+ ratio and the introduction of oxygen/cationic vacancies, which causes the activation and partial dissociation of O O bonds during the oxygen adsorption process. The main methods of manufacturing defects are summarized as follows: the use of chemical reduction, 15,18 changing the heat-treatment temperature, 44,78 incorporating metals or metal oxides, and so on. 20,23,31 In 2015, Song et al 96 found that the Co 3+ active site plays an even greater role in comparison with Co 2+ , which determines the adsorption properties of reactants, as shown in Figure 5A.…”