Litao Yu

In the current research project, we have prepared a novel Sb@C nanosphere anode with biomimetic yolk–shell structure for Li/Na-ion batteries via a nanoconfined galvanic replacement route. The yolk–shell microstructure consists of Sb hollow yolk completely protected by a well-conductive carbon thin shell. The substantial void space in the these hollow Sb@C yolk–shell particles allows for the full volume expansion of inner Sb while maintaining the framework of the Sb@C anode and developing a stable SEI film on the outside carbon shell. As for Li-ion battery anode, they displayed a large specific capacity (634 mAh g–1), high rate capability (specific capabilities of 622, 557, 496, 439, and 384 mAh g–1 at 100, 200, 500, 1000, and 2000 mA g–1, respectively) and stable cycling performance (a specific capacity of 405 mAh g–1 after long 300 cycles at 1000 mA g–1). As for Na-ion storage, these yolk–shell Sb@C particles also maintained a reversible capacity of approximate 280 mAh g–1 at 1000 mA g–1 after 200 cycles.

A harmonized three-component composite system which preserves the characteristics of individual components is of interest in the field of energy storage. Here, we present a graphene-encapsulated MXene Ti2CTx@polyaniline composite (GMP) material realized in a systematically stable configuration with different ternary nanomaterials for supercapacitor electrodes. Due to the different ζ-potentials in a high-pH solution, chemically converted graphene (negatively charged) is thoroughly unfolded to allow full encapsulation, but the MXene Ti2CTx@polyaniline composite with a low positive ζ-potential is easily attracted toward a counter-charged substance. The obtained GMP electrode exhibits improved cycling stability and better electrochemical performance owing to the use of mechanically robust and chemically inert graphene and the densely intercalated conductive polyaniline between the multilayer MXenes. The GMP electrode has a high gravimetric capacitance of 635 F g–1 (volumetric capacitance of 1143 F cm–3) at a current density of 1 A g–1 with excellent cycling stability of 97.54% after 10 000 cycles. Furthermore, the asymmetric pouch-type supercapacitor assembled using the GMP as a positive electrode and graphene as a negative electrode yields a high energy density of 42.3 Wh kg–1 at a power density of 950 W kg–1 and remarkable cycling stability (94.25% after 10 000 cycles at 10 A g–1).

The MOFs (metal–organic frameworks) have been extensively used for electrode materials due to their high surface area, permanent porosity, and hollow structure, but the role of antimony on the MOFs is unclear. In this work, we design the hollow spheres Ni-MOFs with SbCl3 to synthesize NiSb⊂CHSs (NiSb-embedded carbon hollow spheres) via simple annealing and galvanic replacement reactions. The NiSb⊂CHSs inherited the advantages of Ni-MOFs with hollow structure, high surface area, and permanent porosity, and the NiSb nanoparticles are coated by the formed carbon particles which could effectively solve the problem of vigorous volume changes during the Li+ insertion/extraction process. The porous and network structure could well provide an extremely reduced pathway for fast Li+ diffusion and electron transport and provide extra free space for alleviating the structural strain. The NiSb⊂CHSs with these features were used as Li-ion batteries for the first time and exhibited excellent cycling performance, high specific capacity, and great rate capability. When coupled with a nanostructure LiMn2O4 cathode, the NiSb⊂CHSs//LiMn2O4 full cell also characterized a high voltage operation of ≈3.5 V, high rate capability (210 mA h g–1 at a current density of 2000 mA g–1), and high Coulombic efficiency of approximate 99%, meeting the requirement for the increasing demand for improved energy devices.

To solve the problem of large volume change and low electronic conductivity of earth-abundant ilmenite used in rechargeable Na-ion batteries (SIBs), an anode of tiny ilmenite FeTiO3 nanoparticle embedded carbon nanotubes (FTO⊂CNTs) has been successfully proposed. By introducing a TiO2 shell on metal–organic framework (Fe-MOF) nanorods by sol–gel deposition and subsequent solid-state annealing treatment of these core–shell Fe-MOF@TiO2, such well-defined FTO⊂CNTs are obtained. The achieved FTO⊂CNT electrode has several distinct advantages including a hollow interior in the hybrid nanostructure, fully encapsulated ultrasmall electroactive units, flexible conductive carbon matrix, and stable solid electrolyte interface (SEI) of FTO in cycles. FTO⊂CNT electrodes present an excellent cycle stability (358.8 mA h g–1 after 200 cycles at 100 mA g–1) and remarkable rate capability (201.8 mA h g–1 at 5000 mA g–1) with a high Coulombic efficiency of approximately 99%. In addition, combined with the typical Na3V2(PO4)3 cathode to constitute full SIBs, the assembled FTO⊂CNT//Na3V2(PO4)3 batteries are also demonstrated with superior rate capability and a long cycle life.

A cathode of FeF₃/C nanocomposites has been fabricated by a simple vapor-solid fluoridation route which shows superior Na-ion storage performance.