RESUMEN
Lithium-oxygen (Li-O2 ) batteries are attracting more attention owing to their superior theoretical energy density compared to conventional Li-ion battery systems. With regards to the catalytically electrochemical reaction on a cathode, the electrocatalyst plays a key role in determining the performance of Li-O2 batteries. Herein, a new 3D hollow α-MnO2 framework (3D α-MnO2 ) with porous wall assembled by hierarchical α-MnO2 nanowires is prepared by a template-induced hydrothermal reaction and subsequent annealing treatment. Such a distinctive structure provides some essential properties for Li-O2 batteries including the intrinsic high catalytic activity of α-MnO2 , more catalytic active sites of hierarchical α-MnO2 nanowires on 3D framework, continuous hollow network and rich porosity for the storage of discharge product aggregations, and oxygen diffusion. As a consequence, 3D α-MnO2 achieves a high specific capacity of 8583 mA h g-1 at a current density of 100 mA g-1 , a superior rate capacity of 6311 mA h g-1 at 300 mA g-1 , and a very good cycling stability of 170 cycles at a current density of 200 mA g-1 with a fixed capacity of 1000 mA h g-1 . Importantly, the presented design strategy of 3D hollow framework in this work could be extended to other catalytic cathode design for Li-O2 batteries.
RESUMEN
A freestanding SnO2@N-CNF film prepared by electrospinning exhibits excellent flexibility and a high surface area of 506 m(2) g(-1). When used as an anode for lithium-ion batteries, a high reversible capacity of 754 mAh g(-1) is maintained after the 300(th) cycle at 1 A g(-1) . Even when the current density increases to 5 A g(-1), the SnO2@N-CNF still delivers 245.9 mAh g(-1).
RESUMEN
Yolk-shell NiS2/carbon spheres (yolk-shell NiS2/C) have been synthesized by one-step annealing of yolk-shell Ni-metal-organic framework spheres. In particular, both the inner yolk sphere and the outer shell of yolk-shell NiS2/C can provide catalytically active sites for the redox of polysulfide confined in the yolk-shell structure, providing enhanced redox kinetics. A yolk-shell NiS2/C-sulfur cathode exhibits a high rate capacity of 569 mA h g-1 at 2C and shows excellent cycling stability, demonstrating the superiority of the yolk-shell structure.
RESUMEN
Potassium-ion batteries (PIBs) are attracting intensive interest for large-scale applications due to the high natural abundance of potassium sources. However, the large radius of K+ makes it difficult for electrode materials to accommodate the repeated K+ insertion and extraction. Thus, developing high-performance electrode materials for PIBs remains a great challenge. Herein, we present the rational design and fabrication of hierarchical carbon-coated MoSe2/MXene hybrid nanosheets (MoSe2/MXene@C) as a superior anode material for PIBs. Specifically, the highly conductive MXene substrate can effectively relieve the aggregation of MoSe2 nanosheets and improve the electronic conductivity. Moreover, the carbon layer enables us to reinforce the composite structure and further enhance the overall conductivity of the hybrid nanosheets. Meanwhile, strong chemical interactions are found at the interface of MoSe2 nanosheets and MXene flakes, contributing to promoting the charge-transfer kinetics and improving the structural durability. Consequently, as an anode material for PIBs, the resulting MoSe2/MXene@C achieves a high reversible capacity of 355 mA h g-1 at 200 mA g-1 after 100 cycles and an outstanding rate performance with 183 mA h g-1 at 10.0 A g-1. The presented design strategy holds great promise for developing more-efficient electrode materials for PIBs.
RESUMEN
Molybdenum disulfide (MoS2) has attracted extensive research interest as a fascinating anode for sodium-ion batteries (SIBs) because of its high specific capacity of 670 mA h g-1. However, unsatisfied cycling durability and poor rate performance are two barriers that hinder MoS2 for practical application in SIBs. Herein, 3D interconnected MoS2 with enlarged interlayer spacing epitaxially grown on 1D electrospinning carbon nanofibers (denoted as MoS2@CNFs) was prepared as a flexible anode for SIBs via l-cysteine-assisted hydrothermal method. Benefitting from the C-O-Mo bonding between the CNFs and MoS2 as well as the rational design with novel structure, including the well-retained 3D interconnected and conductive MoS2@CNFs networks and expanded (002) plane interlayer space, the flexible MoS2@CNFs electrode achieves a remarkable specific capacity (528 mA h g-1 at 100 mA g-1), superior rate performance (412 mA h g-1 at 1 A g-1), and ultralong cycle life (over 600 cycles at 1 A g-1 with excellent Coulombic efficiencies exceeding 99%). The elaborate strategy developed in this work opens a new avenue to prepare highly improved energy storage materials, especially suitable for flexible electronics.
RESUMEN
Freestanding and highly compressible nitrogen-doped carbon foam (NCF) with excellent hydrophilicity and good electrochemical properties is prepared. Based on NCF electrodes, a high-performance all solid-state symmetric supercapacitor device is fabricated with native, full compressibility, and excellent mechanical stability, addressing two major problems in the current technology.
RESUMEN
Perovskites show excellent specific catalytic activity toward both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline solutions; however, small surface areas of the perovskites synthesized by traditional sol-gel methods lead to low utilization of catalytic sites, which gives rise to poor Li-O2 batteries performance and restricts their application. Herein, a hierarchical mesporous/macroporous perovskite La0.5Sr0.5CoO3-x (HPN-LSC) nanotube is developed to promote its application in Li-O2 batteries. The HPN-LSC nanotubes were synthesized via electrospinning technique followed by postannealing. The as-prepared HPN-LSC catalyst exhibits outstanding intrinsic ORR and OER catalytic activity. The HPN-LSC/KB electrode displays excellent performance toward both discharge and charge processes for Li-O2 batteries, which enhances the reversibility, the round-trip efficiency, and the capacity of resultant batteries. The synergy of high catalytic activity and hierarchical mesoporous/macroporous nanotubular structure results in the Li-O2 batteries with good rate capability and excellent cycle stability of sustaining 50 cycles at a current density of 0.1 mA cm(-2) with an upper-limit capacity of 500 mAh g(-1). The results will benefit for the future development of high-performance Li-O2 batteries using hierarchical mesoporous/macroporous nanostructured perovskite-type catalysts.