Ning Wan

Improved Li storage performance in SnO2 nanocrystals by a synergetic doping

Tin dioxide (SnO2) is a widely investigated lithium (Li) storage material because of its easy preparation, two-step storage mechanism and high specific capacity for lithium-ion batteries (LIBs). In this contribution, a phase-pure cobalt-doped SnO2 (Co/SnO2) and a cobalt and nitrogen co-doped SnO2 (Co-N/SnO2) nanocrystals are prepared to explore their Li storage behaviors. It is found that the morphology, specific surface area, and electrochemical properties could be largely modulated in the doped and co-doped SnO2 nanocrystals. Gavalnostatic cycling results indicate that the Co-N/SnO2 electrode delivers a specific capacity as high as 716 mAh g−1 after 50 cycles, and the same outstanding rate performance can be observed in subsequent cycles due to the ionic/electronic conductivity enhancement by co-doping effect. Further, microstructure observation indicates the existence of intermediate phase of Li3N with high ionic conductivity upon cycling, which probably accounts for the improvements of Co-N/SnO2 electrodes. The method of synergetic doping into SnO2 with Co and N, with which the electrochemical performances is enhanced remarkably, undoubtedly, will have an important influence on the material itself and community of LIBs as well.

AlF3 Surface‐Coated Li[Li0.2Ni0.17Co0.07Mn0.56]O2 Nanoparticles with Superior Electrochemical Performance for Lithium‐Ion Batteries

Li-rich layered cathode materials have already drawn considerable attention owing to their high capacity performance for Li-ion batteries (LIBs). In this work, layered Li-rich Li[Li0.2 Ni0.17 Co0.07 Mn0.56 ]O2 nanoparticles are surface-modified with AlF3 through a facile chemical deposition method. The AlF3 surface layers have little impact on the structure of the material and act as buffers to prevent the direct contact of the electrode with the electrolyte; thus, they enhance the electrochemical performance significantly. The 3 wt % AlF3 -coated Li-rich electrode exhibits the best cycling capability and has a considerably enhanced capacity retention of 83.1 % after 50 cycles. Moreover, the rate performance and thermal stability of the 3 wt % AlF3 -coated electrode are also clearly improved. Surface analysis indicates that the AlF3 coating layer can largely suppress the undesirable growth of solid electrolyte interphase (SEI) film and, therefore, stabilizes the structure upon cycling.

Enhanced Structural and Electrochemical Stability of Self-Similar Rice-Shaped SnO2 Nanoparticles

A facile one-pot hydrothermal strategy is applied to prepare Co and F codoped SnO2 (Co-F/SnO2) nanoparticles, which exhibit a unique rice-shaped self-similar structure. Compared with the pristine and Co-doped counterparts (SnO2 and Co/SnO2), the Co-F/SnO2 electrode demonstrates higher capacity, better cyclability, and rate capability as anode material for lithium ion batteries (LIBs). A high charge capacity of 800 mAh g-1 can be successfully delivered after 50 cycles at 0.1 C, and a high reversible capacity of 700 mAh g-1 could be retained after 100 cycles at 5 C. The excellent lithium storage performances of the Co-F/SnO2 nanoparticles could be attributed to the synergetic effects of the doped Co and F, as well as the unique hierarchical self-similar structure with moderate oxygen defect and inactive pillars, which not only facilitates the fast diffusion of Li ions, but also stabilizes the structure during the electrochemical cycling.