Trumpet-Like ZnS@C Composite for High-Performance Potassium Ion Battery Anode.

ZnS has acquired increasing attention for high-performance PIBs anode because of its remarkable theoretical capacity, and redox reversibility for conversion reaction. However, the larger volume variation and delayed reaction kinetics for the ZnS in the discharge/charge processes lead to pulverization and severe capacity degradation. Herein, the trumpet-like ZnS@C composite was synthesized by template method by using sodium citrate as carbon source followed by vulcanization process. As potassium ion batteries (PIB) anode, ZnS@C composite exhibits good rate performance and long life (stable reversible capacity of 107.8 mAh/g over 2000 charge-discharge cycles at 5 A/g and high reversible capacity of 310 mAh/g at 0.1 A/g). The outstanding electrochemical performance of the ZnS@C composite is ascribed to its unique structure, which can mitigate the volume expansion of ZnS in the charge discharge process, expand the contact area between the electrode and electrolyte, and improve the conductivity of electrode materials by the introduction of carbon layer. This method of synthesizing trumpet-like ZnS@C composite provides an important strategy for obtaining potassium ion batteries anode with long cycle.

Fabrication of Nb2 O5 /Carbon Submicrostructures for Advanced Lithium-Ion Battery Anodes.

Nb2 O5 possesses superior fast Li+ storage capability for LIB anodes, benefiting from its fast pseudocapacitive behavior and low volumetric change within the cycling processes. However, the poor electric conductivity for Nb2 O5 restricts its reaction kinetics and rate property. Herein, Nb2 O5 /carbon (C) submicrostructures are fabricated by solvothermal method followed by calcination process. The Nb2 O5 /C submicrostructures exhibit outstanding rate behavior and cyclic performance (332 (194) mAh g-1 after 1000 cycles at 1 (5) A g-1 ). The superior electrochemical property is attributed to the distinctive structure for Nb2 O5 /C submicrostructures, in which Nb2 O5 nanoparticles uniformly distributed within Nb2 O5 /C composite can protect Nb2 O5 nanoparticles from agglomeration, and the porous carbon matrix can enhance electron/ion conductivity. This work furnishes a novel strategy for fabricating Nb2 O5 /C submicrostructures with superior Li+ storage performance, which can be potentially used to design other metal oxide/C submicrostructures for second battery anode.

Construction of Fe7Se8@Carbon nanotubes with enhanced sodium/potassium storage.

The Fe7Se8@Carbon (C) nanotubes are successfully synthesized using Fe3O4@C nanotubes as sacrificial templates. Fe7Se8@C nanotubes exhibit excellent rate behaviour and maintainable capacity (319 mAh g-1 at 2 A g-1 upon 720 cycles), when utilized as SIBs anode. Moreover, for PIBs anode, Fe7Se8@C nanotubes also exhibit outstanding rate behaviour and maintainable capacity 222 mAh g-1 at 2 A g-1 upon 500 cycles). The superior electrochemical performance of Fe7Se8@C nanotubes is ascribed to the unique structure, where the hierarchical hollow tubular characteristic of Fe7Se8@C composites can mitigate the volume expansion of Fe7Se8 and supply effective transmission paths for both Na+(K+) and electrons within repeated cycle processes, and additionally, N-doped carbon layer can further protect the integrality of Fe7Se8@C nanotubes from destruction within the cycle processes, and enhance electronic conductivity.

Pomegranate-like structured Nb2O5/Carbon@N-doped carbon composites as ultrastable anode for advanced sodium/potassium-ion batteries.

The distinctive pomegranate-like Nb2O5/Carbon@N-doped carbon (Nb2O5/C@NC) composites are fabricated using hydrothermal method integrated with nitrogen doped carbon coating procedure. For the SIBs anode, the Nb2O5/C@NC composites present superior rate character and sustainable capacity (117 mAh g-1 upon 1000 cycles at 5 A g-1). The in-situ X-ray diffraction (XRD) is utilized to research its sodium storage mechanism. Furthermore, for PIBs, the Nb2O5/C@NC composites present sustainable capacity (81 mAh g-1 upon 1000 cycles at 1 A g-1). The outstanding performance of Nb2O5/C@NC composites is ascribed to its unique architecture, in which Nb2O5 nanocrystals embedded in porous carbon can restrain agglomeration of Nb2O5 nanocrystals, enhance electron/ion diffusion kinetics, and ensure electrolyte accessibility, and moreover, NC shell layer can provide effective active sites and further increase ions/electrons transfer.

Fabrication of ZnSe/C Hollow Polyhedrons for Lithium Storage.

ZnSe has got extensive attention for high-performance LIBs anode due to its remarkable theoretical capacity and environmental friendliness. Nevertheless, the large volume variation for the ZnSe in the discharge/charge processes brings about rapid capacity fading and poor rate performance. Herein, ZnSe/C hollow polyhedrons are successfully synthesized by selenization of zeolitic imidazolate framework-8 (ZIF-8) with resorcinol-formaldehyde (RF) coating. The protection of C layer derived from RF coating layer and Ostwald ripening during the process of selenization play important roles in promoting formation of ZnSe/C hollow polyhedrons. The ZnSe/C hollow polyhedrons exhibit good rate performance and long-term cycle stability (345 mAh g-1 up to 1000 cycles at 1 A g-1 ) for lithium ion batteries (LIBs) anode. The improved electrochemical performance is benefit from the unique ZnSe/C hollow structure, in which the hollow structure can effectively avoid terrible volume expansion, and the thin ZnSe/C shell can not only provide adequate diffusion paths of lithium ions and but also enhance the electronic conductivity.