Nanograined pure and SnO_2 mixed Li4Ti_5O_(12) structures as high performance anodes for lithium ion batteries

摘要

1.Introduction Batteries for high energy and high power applications such as in electric vehicles (EVs), hybrid electric vehicles (HEVs) and plugin electric vehicles (PEVs) requires electrode materials which can offer high energy density and high rate capability~([1][2]). Nano-structuring of electrode materials has enabled to acquire smaller diffusion length, high surface area and porosity in electrodes that enabled to overcome the practical difficulties. Lithium titanate (LTO) (theoretical capacity 175 mAh/g) is one among the high voltage (1.5V vs Li/Li~+) anode materials which has excellent rate capability due to its high lithium diffusion co-efficient and zero-crystal strain during lithium ion interaction and de-intercalation reactions~([3][4][5]). We have recently demonstrated that nanostructured donut shaped LTO exhibit high performance due to above said advantages~([6][7]). Similarly, Sn and SnO_2 are high capacity anode materials involving Li-alloying de-alloying mechanism, however, huge volume change (300%) during charge discharge results in mechanical disintegration and capacity fading~([8]). The present challenge is under research by minimising the volume expansion of the material by nanostructuring these high capacity materials and processing them with carbon, graphene, CNT in the form of composites~([9][10]). In the present article we are focussing on enhancing the cycling stability and rate capability of SnO_2 material by fabricating SnO_2/LTO composite as hollow fibers. A simple sol-gel electrospinning route was chosen for fabricating the composite hollow fibers of SnO_2 and LTO. A comparative electrochemical study of the sol-gel synthesised LTO submicron rods and SnO_2/LTO composite hollow fibers are depicted in this article.