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Hierarchical porous microflowers composed of porous Fe 2 O 3 /NiO nanoplates were synthesized via a facile cyanometallic framework-templated strategy. The synthesized Fe 2 O 3 /NiO microflowers were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer Emmet Teller adsorption-desorption analysis. As anode materials for lithium ion batteries, the Fe 2 O 3 /NiO microflowers exhibit excellent electrochemical performance in terms of great lithium storage capacity (1652.6 mAh g −1 at 100 mA g −1 ) and good cycling stability (1210.4 mAh g −1 capacity retention at 50th cycle). This result can be attributed to the hierarchical porous structure of the Fe 2 O 3 /NiO microflowers, which could increase active sites for lithium ions storage, accommodate the volume expansion/contraction during charge-discharge cycles, and the synergistic effect between Fe 2 O 3 and NiO. [ABSTRACT FROM AUTHOR]

• Porous MoO 3 -Fe 2 O 3 hybrid micro-octahedrons were firstly synthesized. • MoO 3 -Fe 2 O 3 anode shows enhanced initial coulombic efficiency for lithium storage. • It gives an efficient strategy to fabricate MoO 3 -based anodes for advanced LIBs. A new porous MoO 3 -Fe 2 O 3 hybrid micro-octahedrons were successfully fabricated via a simple thermolysis of cyanide-metal framework precursor of Fe 2 [Mo(CN) 8 ]· x H 2 O. The uniform MoO 3 -Fe 2 O 3 micro-octahedrons (ca.1 µm) are assembled by numerous secondary nanoparticles, and the average size is about 60 nm. When used as anodes for lithium-ion batteries, the MoO 3 -Fe 2 O 3 micro-octahedrons exhibit superior electrochemical performances in terms of high initial coulombic efficiency of 81.9%, excellent cycle performance with capacity of 1218 mAh g−1 for 350 cycles at 0.2 A g−1 and rate capability. The outstanding electrochemical performance is attributed to the strong synergy between the two components and the unique porous microstructure, which not only provide high conductivity and rich Li+ diffusion pathway for electrochemical reaction, but also reduce agglomeration and fragmentation of the electrode during charge–discharge cycle. This work provides a new direction for the design and synthesis of Mo-based electrode materials with novel structures for high performance LIBs. [ABSTRACT FROM AUTHOR]

Porous carbon is one of the most promising electrode materials for energy conversion and storage devices due to its high specific surface area, low cost, sustainability, appropriate charging/discharging voltage platform and high interlayer spacing. However, the disadvantage of insufficient energy storage capacity frustrates its wide applications. Herein, a novel N, P co-doped porous carbon derived from sugarcane bagasse (SBNP k) was prepared by hydrothermal method combined with KOH activation and carbonization, and was applied to supercapacitors (SCs) and sodium-ion batteries (SIBs). The SBNP K possesses a special hierarchical porous structure, improved surface area, larger interlayer spacing, and moderate N, P doping level. Specifically, the SBNP k carbonization at 600 °C (SBNP k -600) exhibits the highest specific capacitance (356.4 F g−1 at 1 A g−1), good rate capability and excellent cycle stability (5% loss over 10,000 cycles) in a three-electrode system. Further assembled in a symmetrical two-electrode system, the SBNP K -600//SBNP K -600 can still provide a higher energy density of 6.5 Wh kg−1 at 251.9 W kg−1 and superior cycle performance (96.5% of capacitance retention at 2 A g−1 after 20,000 cycles). Surprisingly, the SBNP K -600 as an anode for SIBs also delivers a high reversible capacity of 304.1 mAh g−1 at 25 mA g−1 and excellent cycle performance (225.7 mAh g−1 after 1000 cycles at 500 mA g−1), indicating its superior sodium storage capability. This work provides a simple and new way to enhance the electrochemical performance of biomass waste-derived carbon by heteroatom doping, which is helpful to further boost its application in the field of energy storage. [Display omitted] • Biomass sugarcane bagasse (SB) is a low cost and eco-friendly precursor. • A surface area of 2803.2 m2 g-1 and layer spacing of 0.382 nm of carbon from SB can be obtained. • 356.4 F g−1 at 1.0 A g-1 and 6.5 Wh kg-1 at 251.9 W kg-1 applied in supercapacitors. • 365.2 mAh g-1 at 25 mA g-1 and 225.7 mAh g-1 after 1000 cycles at 500 mA g-1 applied in batteries. • The electrochemical properties depend on the synergistic effect of N, P -doped nature and structures. [ABSTRACT FROM AUTHOR]

Co 3 O 4 , as a promising anode material for the next generation lithium ion batteries to replace graphite, displays high theoretical capacity (890 mAh g −1 ) and excellent electrochemical properties. However, the drawbacks of its poor cycle performance caused by large volume changes during charge-discharge process and low initial coulombic efficiency due to large irreversible reaction impede its practical application. Herein, we have developed a porous hollow Co 3 O 4 microfiber with 500 nm diameter and 60 nm wall thickness synthesized via a facile chemical precipitation method with subsequent thermal decomposition. As an advanced anode for lithium ion batteries, the porous hollow Co 3 O 4 microfibers deliver an obviously enhanced electrochemical property in terms of lithium storage capacity (1177.4 mA h g −1 at 100 mA g −1 ), initial coulombic efficiency (82.9%) and cycle performance (76.6% capacity retention at 200th cycle). This enhancement could be attributed to the well-designed microstructure of porous hollow Co 3 O 4 microfibers, which could increase the contact surface area between electrolyte and active materials and accommodate the volume variations via additional void space during cycling. [ABSTRACT FROM AUTHOR]

Hard carbon is one of the most promising anodic materials for sodium ion batteries (SIBs) because of its low charge/discharge voltage platform, high specific surface area and higher layer spacing. However, the disadvantages of its unsatisfied sodium storage capacity and high cost owing to low carbonization yield of precursors frustrate its practical use. In this paper, we have developed a hierarchical porous hard carbon derived from rice husks (HCRH) synthesized via NaOH solution impregnation method combined with reflux and carbonization at different temperature. This kind of hard carbon kept the natural porous structure of rice husk, and the rich porous structure increased the active site of Na+, shortened the diffusion distance of Na+, and promoted the transport of electrolyte. As an anode for SIBs, the HCRH carbonization at 1200 °C (HCRH-1200) with a suitable graphite layer spacing (0.382 nm)delivered the highest capacity of 328.4 mAh g−1 after 100 cycles at 25 mA g−1. This study could provide a simple method to prepare high performance anode materials for sodium ion batteries using biomass rice husk as carbon source, and this design strategy could be extended to other biomass-based carbon materials. [Display omitted] • A hierarchical porous hard carbon derived from rice husks (HCRH) was synthesized. • The HCRH could increase the active site of Na+, shorten the diffusion distance of Na+, and promote the transport of electrolyte. • The HCRH contains mesoporous structures with larger BET surface areas. • The HCRH-1200 behaves with a suitable graphite layer spacing (0.382 nm). • The HCRH-1200 delivered the highest capacity of 328.4 mAh g−1 after 100 cycles at 25 mA g−1. [ABSTRACT FROM AUTHOR]