Li-O2 battery
attracts great interest because of the
high energy density. But the poor kinetics of the oxygen reduction
reaction (ORR) and oxygen evolution reaction (OER) have blocked the
practical application. Designing the efficient bifunctional cathode
catalysts is of great importance for the Li-O2 battery.
Tuning the electronic and surface structure of the catalysts plays
an important role. Herein, we propose to enhance the catalytic performance
of Co3O4 nanosheets for rechargable Li-O2 batteries by hydrazine hydrate-induced oxygen vacancy formation.
The hydrazine hydrate reduction not only introduces oxygen vacancies
into Co3O4 nanosheets and modulates the electronic
structure but also roughens the surface, which all contribute to the
enhancement of ORR and OER activity, especially the activity and stability
for OER. Li-O2 cells catalyzed by the oxygen defects-enriched
Co3O4 ultrathin nanosheets exhibit much better
electrochemical performances in terms of the high initial capacity
(∼11 000 mAh g–1), the lower overpotential
(∼1.1 V), and the longer cycle life (150 cycles@200
mA g–1). This can be largely attributed to the synergy
of the enriched oxygen vacancies and the roughened surface of Co3O4 nanosheets, which not only improves the electron
and Li+ conductivity but also provides more active sites
and reaction spots. The proposed facile strategy may also be applied
to modify other oxides based catalysts for Li-O2 batteries
or other fields.
As essential components in intelligent systems, printed soft electronics (PSEs) are playing crucial roles in public health, national security, and economics. Innovations in printing technologies are required to promote the broad application of high-performance PSEs at a low cost. However, current printing techniques are still facing long-lasting challenges in addressing the conflict between printing speed and performance. To overcome this challenge, we developed a new corona-enabled electrostatic printing (CEP) technique for ultra-fast (milliseconds) roll-to-roll (R2R) manufacturing of binder-free multifunctional e-skins. The printing capability and controllability of CEP were investigated through parametric studies and microstructure observation. The electric field generation, material transfer, and particle amount and size selecting mechanisms were numerically and experimentally studied. CEP printed graphene e-skins were demonstrated to possess outstanding strain sensing performance. The binder-free feature of the CEP-assembled networks enables them to provide pressure sensitivity as low as 2.5 Pa, and capability to detect acoustic signals of hundreds of hertz in frequency. Furthermore, the CEP technique was utilized to pattern different types of functional materials (e.g., graphene and thermochromic polymers) onto different substrates (e.g., tape and textile). Overall, this study demonstrated that CEP can be a novel contactless and ultrafast manufacturing platform compatible with R2R process for fabricating high-performance, scalable, and low-cost soft electronics.
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