Nanostructured electrodes for next generation rechargeable electrochemical devices

Nanostructured intercalating electrodes offer immense potential for significantly enhancing the performance of rechargeable rocking chair (e.g. Li+ and Mg2+) and asymmetric hybrid batteries. The objective of this work has been to develop a variety of cathode (e.g. V2O5, LiMnO2 and LiFePO4) and anode (e.g. Li4Ti5O12) materials with unique particle characteristics and controlled composition to reap the maximum benefits of nanophase electrodes for rechargeable Li-based batteries. Different processing routes, which were chosen on the basis of the final composition and the desired particle characteristics of electrode materials, were developed to synthesize a variety of electrode materials. Vapor phase processes were used to synthesize nanopowders of V2O5 and TiO2. TiO2 was the precursor used for producing ultrafine particles of Li4Ti5O12. Liquid phase processes were used to synthesize nanostructured LiMnxM1−xO2 and LiFePO4 powders. It was found that (i) nanostructured V2O5 powders with a metastable structure have 30% higher retention capacity than their coarse-grained counterparts, for the same number of cycles; (ii) the specific capacity of nanostructured LiFePO4 cathodes can be significantly improved by intimately mixing nanoparticles with carbon particles and that cathodes made of LiFePO4/C composite powder exhibited a specific capacity of not, vert, similar145 mAh/g (85% of the theoretical capacity); (iii) nanostructured, layered LiMnxM1−xO2 cathodes demonstrated a discharge capacity of not, vert, similar245 mAh/g (86% of the theoretical capacity) at a slow discharge rate; however, the composition and structure of nanoparticles need to be optimized to improve their rate capabilities and (iv) unlike micron-sized (1–10 μm) powders, ultrafine Li4Ti5O12 showed exceptional retention capacity at a discharge rate as high as 10 C in Li-test cells.