High specific capacity and excellent stability of interface-controlled MWCNT based anodes in lithium ion battery
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High specific capacity and excellent stability of interface-controlled MWCNT based anodes in lithium ion battery Indranil Lahiri1, Sung-Woo Oh2, Yang-Kook Sun2 and Wonbong Choi1 1 Department of Mechanical and Materials Engineering, Florida International University, Miami, FL 33174, U.S.A. 2 Department of Energy Engineering, Hanyang University, Seoul 133791, Korea ABSTRACT Rechargeable batteries are in high demand for future hybrid vehicles and electronic devices markets. Among various kinds of rechargeable batteries, Li-ion batteries are most popular for their obvious advantages of high energy and power density, ability to offer higher operating voltage, absence of memory effect, operation over a wider temperature range and showing a low self-discharge rate. Researchers have shown great deal of interest in developing new, improved electrode materials for Li-ion batteries leading to higher specific capacity, longer cycle life and extra safety. In the present study, we have shown that an anode prepared from interface-controlled multiwall carbon nanotubes (MWCNT), directly grown on copper current collectors, may be the best suitable anode for a Li-ion battery. The newly developed anode structure has shown very high specific capacity (almost 2.5 times as that of graphite), excellent rate capability, nil capacity degradation in long-cycle operation and introduced a higher level of safety by avoiding organic binders. Enhanced properties of the anode were well supported by the structural characterization and can be related to very high Li-ion intercalation on the walls of CNTs, as observed in HRTEM. This newly developed CNT-based anode structure is expected to offer appreciable advancement in performance of future Li-ion batteries. INTRODUCTION In recent years, appreciable research efforts were taken for development of next generation Li-ion batteries offering higher capacity and better stability [1]. In spite of showing low capacity, graphite (theoretical specific capacity 372 mAhg-1) [2] is widely used as the anode material for most commercial Li-ion batteries owing to its excellent stability. Many researches are, thus, aimed at developing new anode materials with higher capacities. Higher surface area of nanomaterials, as compared to their bulk counterparts, is expected to offer more sites for lithium ion intercalation and a better performance. One of the various nanomaterials, used as anode material for Li-ion batteries, is carbon nanotube (CNT) [3] which has attracted researchers’ attention since 2001. However, the initial efforts [4-6] failed to show any appreciable performance. In spite of offering low capacity, CNTs, like graphite, showed good stability in long term operation [7]. Other allotropes of carbon, i.e., graphene and fullerene and their composites have shown a highest capacity of 784 mAhg-1, at a current rate of 0.13C and with capacity fading [8]. Si and SnO2 are very promising materials as anodic replacements, due to their high theoretical specific capacity, 4200 and 782 mAhg-1, respectively [9, 10]. How
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