RESUMEN
Flexible magnesium (Mg)-air batteries provide an ideal platform for developing efficient energy-storage devices toward wearable electronics and bio-integrated power sources. However, high-capacity bio-adaptable Mg-air batteries still face the challenges in low discharge potential and inefficient oxygen electrodes, with poor kinetics property toward oxygen reduction reaction (ORR). Herein, spinel nickel cobalt oxides (NiCo2 O4 ) nanowires immobilized on nitrogen-doped Ti3 C2 Tx (NiCo2 O4 /N-Ti3 C2 Tx ) are reported via surface chemical-bonded effect as oxygen electrodes, wherein surface-doped pyridinic-N-C and Co-pyridinic-N moieties accounted for efficient ORR owing to increased interlayer spacing and changed surrounding environment around Co metals in NiCo2 O4 . Importantly, in polyethylene glycol (PVA)-NaCl neutral gel electrolytes, the NiCo2 O4 /N-Ti3 C2 Tx -assembled quasi-solid wearable Mg-air batteries delivered high open-circuit potential of 1.5 V, good flexibility under various bent angles, high power density of 9.8 mW cm-2 , and stable discharge duration to 12 h without obvious voltage drop at 5 mA cm-2 , which can power a blue flexible light-emitting diode (LED) array and red smart rollable wearable device. The present study stimulates studies to investigate Mg-air batteries involving human-body adaptable neutral electrolytes, which will facilitate the application of Mg-air batteries in portable, flexible, and wearable power sources for electronic devices.
RESUMEN
Pseudocapacitive asymmetric supercapacitors are promising candidates for achieving high energy density in flexible energy storage devices. However, seeking suitable positive electrode materials that are compatible with negative electrode materials remains a considerable challenge. In the current study, a pseudocapacitive Ti3C2Tx MXene used as negative electrodes is rationally compatible with redox-type V2O5 as positive electrodes, resulting in the assembly of an all-pseudocapacitive Ti3C2Tx MXene//V2O5 asymmetric flexible energy storage device. The solid-state asymmetric device can deliver an energy density of 8.33 mW h cm-3 at a current density of 0.5 A g-1. Moreover, it can operate in an expanded voltage window of 1.5 V, with dominant surface-capacitive charge-storage mechanisms. Additionally, the device can power a yellow light-emitting diode for up to 7 s, indicating the potential of the device for use in practical applications. This study demonstrates the possibility of using other two-dimensional transition-metal carbide nanosheets for high-energy density flexible energy storage devices.
