(707d) Nanowire Based Hybrid Materials as Anodes for Lithium Ion Batteries

Lithium ion batteries (LIBs) have considerable advantages over conventional Ni-Cd batteries in terms of energy to weight ratios and battery life. Present energy demands have increased interest to develop new class of high capacity LIBs. Constant search for a stable high capacity anode material for LIB's is underway because of the low capacity of graphite (372 mAhg-1). Sn and SnO2 have theoretical capacities three times the capacity of graphite but it has been shown that the capacity fading with cycling is a considerable problem in these materials.

Nanowires, with high surface areas and better charge transport properties have been shown to perform better than their thin film counterparts. However, pure phase SnO2 nanowires have shown severe degradation with cycling and the specific capacity fades to 170 mAhg-1 over 40 cycles. The post-lithiated samples show a distorted nanowire structure with big agglomerates. To overcome the problem of capacity loss with cycling, we present a simple and generic concept of nanowire based hybrid materials as high capacity anodes for Li-ion batteries. A hybrid system with Sn nanoclusters/ SnO2 nanowires is shown to retain high capacity over 100 charge-discharge cycles. The capacity fading is low and the structural integrity of the nanowire architecture is confirmed by scanning electron microscopy. This hybrid structure concept is being extended to other high capacity materials like silicon and germanium which can offer significant enhancements in portable electronics.