SiO_2@C hollow sphere anodes for lithium-ion batteries

As anode materials for lithium-ion batteries, SiO2 is of great interest because of its high capacity, low cost and environmental affinity. A facile approach has been developed to fabricate SiO2@C hollow spheres by hydrolysis of tetraethyl orthosilicate（TEOS） to form SiO2 shells on organic sphere templates followed by calcinations in air to remove the templates, and then the SiO2 shells are covered by carbon layers.Electron microscopy investigations confirm hollow structure of the SiO2@C. The SiO2@C hollow spheres with different SiO2 contents display gradual increase in specific capacity with discharge/charge cycling,among which the SiO2@C with SiO2 content of 67 wt% exhibits discharge/charge capacities of 653.4/649.6 mAh g^（-1） over 160 cycles at current density of 0.11 mA cm^（-2）. The impedance fitting of the electrochemical impedance spectroscopy shows that the SiO2@C with SiO2 content of 67 wt% has the lowest charge transfer resistance, which indicates that the SiO2@C hollow spheres is promising anode candidate for lithium-ion batteries.

Rational synthesis of SnS_2@C hollow microspheres with superior stability for lithium-ion batteries

Tin-based nanomaterials have been extensively explored as high-capacity anode materials for lithium ion batteries（LIBs）. However,the large volume changes upon repeated cycling always cause the pulverization of the electrode materials. Herein,we report the fabrication of uniform SnS_2@C hollow microspheres from hydrothermally prepared SnO_2@C hollow microspheres by a solid-state sulfurization process. The as-prepared hollow SnS_2@C microspheres with unique carbon shell,as electrodes in LIBs,exhibit high reversible capacity of 814 mA h g^（-1） at a current density of 100 mA g^（-1）,good cycling performance（783 mA h g^（-1） for 200 cycles maintained with an average degradation rate of 0.02% per cycle） and remarkable rate capability（reversible capabilities of 433 mA h g^（-1）at 2C）. The hollow space could serve as extra space for volume expansion during the charge-discharge cycling,while the carbon shell can ensure the structural integrity of the microspheres. The preeminent electrochemical performances of the SnS_2@C electrodes demonstrate their promising application as anode materials in the next-generation LIBs.

Carbon shell coated hollow NiCoSe_(x)composite as high-performance anode for lithium storage

Hollow NiCoSe_(x)(H-NiCoSe_(x)) nanospheres encapsulated with carbon shell were prepared via one-step easy solvothermal method followed by the carbon coating process.H-NiCoSe_(x)@C has large interior void with the uniform dimension around 350 nm and the thickness of carbon shell around 20-30 nm.Coupling with the large interior void as well as robust protective carbon shell,H-NiCoSe_(x)@C can retain the reversible capacity of 805.6 mAh·g^(-1) after 100 cycles at 200 mA·g^(-1).In particular,H-NiCoSe_(x)@C delivers large reversible capacity of 1532.2 mAh·g^(-1) upon cycling for 1000 loops at 1000 mA·g^(-1)with the capacity retention as high as 128.2% upon long period of activation.Even at the high rate of 3000 mA·g^(-1),its specific capacity still retains up to 659.3 mAh·g^(-1).The superior lithium storage performances for H-NiCoSe_(x)@C profit from its robust hollow core-shell structure as well as enhanced electrical conductivity and ion transport.