Beibei Li

Honeycomb-like carbon nanoflakes as a host for SnO2 nanoparticles allowing enhanced lithium storage performance

While possessing potential advantages as electrodes for lithium-ion batteries, SnO2@carbon composites have been suffering from one common drawback – aggregation of Sn particles during the repeated alloying–dealloying cycles and the resulting pulverization issue. We combat this issue through the fabrication of honeycomb-like SnO2@carbon nanoflakes (SnO2@CNFs) that are able to confine SnO2 nanoparticles within well-separated carbon cavities, so that the Li–Sn alloying–dealloying reaction occurs in the independent microreactors thus avoiding aggregation of Sn metal particles formed. The SnO2 particle size, loading amount and the coverage density are controlled by adjusting the weight ratio between the tin precursor and the CNF. Transmission electron microscopy confirms that the highly graphitic honeycomb-like CNF matrix efficiently buffers and accommodates volume changes of the Li–Sn alloy. Used as anode materials for lithium-ion batteries, the SnO2@CNFs with 66.0 wt% SnO2 display the highest lithium storage capacity, delivering a discharge capacity of 940 mA h g−1 after 150 cycles at 200 mA g−1. For the long-term and high-rate applications, the SnO2@CNFs with 41.5 wt% SnO2 show the best electrochemical performance, delivering a discharge capacity of 400 mA h g−1 at 1 A g−1 after 500 cycles.

A Hierarchical Phosphorus Nanobarbed Nanowire Hybrid: Its Structure and Electrochemical Properties

Nanostructured phosphorus-carbon composites are promising materials for Li-ion and Na-ion battery anodes. A hierarchical phosphorus hybrid, SiC@graphene@P, has been synthesized by the chemical vapor deposition of phosphorus on the surfaces of barbed nanowires, where the barbs are vertically grown graphene nanosheets and the cores are SiC nanowires. A temperature-gradient vaporization-condensation method has been used to remove the unhybridized phosphorus particles formed by homogeneous nucleation. The vertically grown barb shaped graphene nanosheets and a high concentration of edge carbon atoms induced a fibrous red phosphorus (f-RP) growth with its {001} planes in parallel to {002} planes of nanographene sheets and led to a strong interpenetrated interface interaction between phosphorus and the surfaces of graphene nanosheets. This hybridization has been demonstrated to significantly enhance the electrochemical performances of phosphorus.

Hydrothermal synthesis and electrochemical properties of tin titanate nanowires coupled with SnO2 nanoparticles for Li-ion batteries

Tin titanate nanowires coupled with SnO2 nanoparticles have been prepared by combining hydrolysis of the Sn(II) precursor with tin-to-hydrogen ion exchange using layered hydrogen titanate nanowires as conformal templates under hydrothermal conditions. This synthetic strategy allows for incorporation of electrochemically active Sn into the layered titanate and simultaneous deposition of SnO2 nanoparticles on the as-prepared tin titanate nanowires. When used as anode materials in lithium ion batteries, the tin titanate nanowires coupled with SnO2 nanoparticles showed improved cycle performance and increased lithium storage capacity as compared with mesoporous SnO2 nanoparticle aggregates and hydrogen titanate nanowires. Electrochemical study indicated that introduction of SnO2 nanoparticles supported on tin titanate can buffer the large volume changes during the Li–Sn alloying and dealloying process in flexible layered titanate nanostructures with large interlayer distance. Besides, these composite structures exhibited remarkably low (<0.5 V) voltage for the Li insertion electrode in lithium ion batteries.

Binding SnO2 nanoparticles onto carbon nanotubes with assistance of amorphous MoO3 towards enhanced lithium storage performance

We report the synthesis of a novel SnO2/MoO3/carbon nanotubes (CNTs) hybrid (denote as SMC) via hydrothermally treating aqueous SnCl4-Na2MoO4-CNTs suspension. The hydrolysis of SnCl4 promotes the precipitation of Na2MoO4, resulting in the simultaneous coprecipitation of the amorphous MoO3 and SnO2 nanoparticles which attach onto the CNTs (Note that no MoOx is produced in the absence of SnCl4). When used as anode materials for lithium ion batteries (LIBs), the as-prepared SMC hybrid delivers a high reversible capacities of 1032 and 887mAh/g after 50 cycles at current densities of 200 and 500mA/g, respectively, and still retains a reversible capacity of 496mAh/g even after 200 cycles at a higher rate of 2A/g, which shows much better lithium storage performance than that of the counterpart hybrid of SnO2/CNTs (denote as SC, with only 569mAh/g after 50 cycles at 200mA/g). The enhanced electrochemical performance of SMC can be attributed to a synergistic effect, namely, MoO3 not only confines SnO2 nanoparticles onto the CNTs but also brings additional lithium storage capacity, while the flexible conductive CNT networks facilitate the charge transfer and electrolyte diffusion.