Tin Oxide Nanowires As High Energy Density Anodes for Lithium-Ion Batteries

Recently, tin oxide has attracted great attention as an anode for lithium ion batteries due to their high theoretical capacity of 782 mAhg^-1  which is two times higher than that of current commercial graphite anode.  However, the main challenges for employing tin oxide as anode are the huge volume expansion during cycling leading to electrode pulverization and irreversible capacity loss due to SEI formation. In this presentation, we report two kinds of tin oxide nanowire structures: (1) tin nanocluster covered tin oxide nanowires, (2) titania coated tin oxide nanowires. Both structures showed high capacity retention and much less morphological degradation. In addition, we also demonstrated a new method called "Solvo-plasma" for large scale production of tin oxide nanowire powders. Even at lab scale, we demonstrated production rates of 8 grams per hour [1] (See Figure 1a).

The tin nanocluster covered tin oxide nanowires show an exceptional capacity of 814 mAhg^-1 even after 100 cycles at a high current density of 100 mA/g [2]. Recently, thin protective coatings are of great interest for enhancing the durability. Here, we demonstrate that such a thin layer of protective coating of titania or alumina using atomic layer deposition technique could stabilize and improve cyclability. Figure 1b shows a 5 nm titania layer coated on tin oxide nanowires. Without coating, tin oxide nanowires exhibited a very low capacity of 300 mAhg^-1. With a 5 nm titania layer, the capacity retention increased to 767 and 664 mAhg^-1(Figure 1c) at the current density of 700 and 1500 mA/g after 30 cycles, respectively [3]. The protective coatings also reduced the irreversible capacity losses associated with SEI formation.

Figure 1: a) SEM image of SnO₂ NWs using Solvo-plasma synthesis, b) TEM image showing a thin layer of titania on tin oxide nanowires, c) the capacity retention at different current densities compared with non-coating tin oxide nanowires

References

[1] Nguyen et al., manuscript in preparation

[2] P. Meduri, C. Pendyala, V. Kumar, G. U. Sumanasekera, M. K. Sunkara,  Nano lett. 2009, 9, 612.

[3] T. Q. Nguyen, A. K. Thapa, V. K. Vendra, J. B. Jasinski, G. U. Sumanasekera and M. K. Sunkara. RSC Advances (accepted 2013)