Lulu Si

Bulk Ti2Nb10O29 as long-life and high-power Li-ion battery anodes

Ti2Nb10O29 is fabricated directly by solid-state reaction from commercial TiO2 and Nb2O5. Without further modification, the bulk Ti2Nb10O29 anode exhibits a reversible capacity of 144 mA h g−1 at 10 C after 800 cycles. More impressively, the capacity of the Ti2Nb10O29/LiFePO4 full-cell at 1 C stabilizes at 100 mA h g−1 after 1000 cycles.

Three-dimensional hard carbon matrix for sodium-ion battery anode with superior-rate performance and ultralong cycle life

Taking advantage of sodium polyacrylate, composed of interlaced carbon chains and inorganic functional groups (–COONa) uniformly grafted onto the carbon chains, a three-dimensional hard carbon matrix (3DHCM) has been obtained. The resultant material is composed of three-dimensional macroporous interconnected networks of carbon nanosheets (thickness, 5–30 nm). The 3DHCM has been studied as an anode material for sodium-ion batteries. The unique three-dimensional porous structure results in a high initial charge capacity of 341 mA h g−1, stable cycling capacity of 232.8 mA h g−1 (after 100 cycles, 50 mA g−1), superior-rate performance (stable capacities of 210, 197, 128 and 112 mA h g−1 at 200, 500, 5000, 8000 mA g−1, respectively) and ultralong cycle life (116 mA h g−1 at 4 A g−1 after 3000 cycles). At the same time, an increase in the trend of the sloping capacity percentage at total discharge is observed. More obvious “graphitic” domains with larger interplanar spacing (∼0.46 nm) were produced in the electrochemical cycles and detected using ex situ HRTEM, further confirming that the first higher-voltage region (above 0.1 V) should be attributed to the sodium insertion between the parallel graphene layers in the hard carbon. We also find that the electrolyte (1 M NaClO4 in PC) severely decomposes at the electrode/electrolyte interface during deep electrochemical cycles (6000 cycles), resulting in the deterioration of the electrode and fast capacity fading. Furthermore, a room-temperature sodium-ion full cell was constructed using 3DHCM as an anode and Na3V2(PO4)3/C as a cathode, (−) 3DHCM‖1 M NaClO4 in PC‖Na3V2(PO4)3/C (+), delivering a discharge capacity of 90 mA h g−1 at a current density of 500 mA g−1. We believe that our findings will be helpful in speeding up the development of room-temperature high-rate, long life and low cost sodium-ion batteries for large-scale energy storage systems, and even as alternatives to lithium-ion batteries.

Solid state synthesis of a new ternary nitride MgMoN2 nanosheets and micromeshes

In this study, a new ternary nitride MgMoN2 was synthesized by a solid-state reaction of Mo, Mg and NaN3 in a stainless steel autoclave at 700 °C. The crystal structure of MgMoN2 (a = 2.91081 A, c = 10.55029 A, Z = 2) was determined by Rietveld refinement based on the X-ray diffraction data (XRD), which comprises of alternating layers of MgN6 octahedral and MoN6 trigonal prisms. The field-emission scanning electron microscopy (FE-SEM) and the transmission electron microscopy (TEM) show that the obtained MgMoN2 was composed of nanosheets with a diameter of several micrometers and with a thickness of about 30 nm. As Mo was substituted by other molybdenum sources (such as MoO3, (NH4)6Mo7O24·4H2O or Na2MoO4·4H2O), the FE-SEM images, TEM images and the selected-area electron diffraction (SEAD) patterns show that the obtained MgMoN2 was composed of single-crystalline micromeshes with different pore sizes. An oriented aggregation mechanism was considered for the formation of MgMoN2 nanosheets and micromeshes. The as-obtained MgMoN2 micromesh is promising as a catalyst support in chemical filtration and in separations under severe operating conditions.

Fabrication of one-dimensional SnO2/MoO3/C nanostructure assembled of stacking SnO2 nanosheets from its heterostructure precursor and its application in lithium-ion batteries

Carbon-coated one-dimensional (1-D) SnO2/MoO3 nanostructure (SnO2/MoO3/C) composed of densely stacked SnO2 nanosheets, uniformly distributing in amorphous MoO3 matrix, is obtained from the 1-D SnO2/MoO3 heterostructure, which is prepared for the first time by a facile, one-pot hydrothermal method. The precursor 1-D SnO2/MoO3 heterostructure is composed of SnO2 nanosheets, adhering to the two edges of 1-D MoO3 nanobelt by lattice matching between the (140) plane of orthorhombic MoO3 and (110) plane of rutile SnO2. By prolonging the hydrothermal reaction time, the as-obtained 1-D SnO2/MoO3 heterostructure is converted to a novel 1-D nanostructure, amorphous MoO3 that deposits uniformly on the surface of the SnO2 nanosheets with the preservation of the front SnO2 1-D architecture. For optimizing performance, 1-D SnO2/MoO3/C nanostructure is obtained by carbon coating on the surface of the novel 1-D nanostructure MoO3/SnO2via the pyrolysis of acetylene. Because of the 1-D nanostructure composed of nanosheets and the carbon matrix, the SnO2/MoO3/C nanocomposites exhibit an outstanding high-rate cycling performance, delivering a reversible discharge capacity of more than 560 mA h g−1 after 120 cycles at a high current density of 200 mA g−1.

Reversible lithium-ion insertion in triclinic hydrated molybdenum oxide nanobelts

Up to the present, little success has been achieved using hydrated metal oxides as high-performance LIB anodes, which is impeding their extensive study and their wide applicability. Herein, we for the first time study the electrochemical Li storage properties of the little-studied triclinic hydrated molybdenum oxide MoO3·xH2O. Without any special efforts, such as nanosizing or carbon coating, the triclinic system MoO3·xH2O nanobelts deliver very high initial Coulombic efficiency (e.g., 98.3%) and high durable reversible Li storage capacities (e.g., 1176 mA h g−1). In light of the urgent demand for energy-storage, we hope our endeavor could blaze a new path, using hydrated metal oxides as anodes, in developing novel high-performance LIBs anodes.