High energy density lithium-ion batteries with carbon nanotube anodes
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Cory D. Cressb) United States Naval Research Laboratory, Washington, District of Columbia 20375
Ryne P. Raffaelle NanoPower Research Labs, Rochester Institute of Technology, Rochester, New York 14623 (Received 5 December 2009; accepted 7 May 2010)
Recent advancements using carbon nanotube electrodes show the ability for multifunctionality as a lithium-ion storage material and as an electrically conductive support for other high capacity materials like silicon or germanium. Experimental data show that replacement of conventional anode designs, which use graphite composites coated on copper foil, with a freestanding silicon-[single-walled carbon nanotube (SWCNT)] anode, can increase the usable anode capacity by up to 20 times. In this work, a series of calculations were performed to elucidate the relative improvement in battery energy density for such anodes paired with conventional LiCoO2, LiFePO4, and LiNiCoAlO2 cathodes. Results for theoretical flat plate prismatic batteries comprising freestanding silicon-SWCNT anodes with conventional cathodes show energy densities of 275 Wh/kg and 600 Wh/L to be theoretically achievable; this is a 50% improvement over today’s commercial cells.
I. INTRODUCTION
There is an ever growing demand for electrical energy storage to support mobile electronics, hybrid-electric/full electric vehicles, and utility-scale grid management.1 Lithium-ion technology has recently emerged as the premier rechargeable battery chemistry due to the increased energy density over other technologies.2 However, ongoing technology demands necessitate higher energy densities to reduce battery mass and volume characteristics. For today’s technology, the cathode is typically the limiting electrode based on the active material capacity, so considerable effort is underway to improve this property as well as attempt to increase the nominal cathode voltage versus Li/Liþ.3,4 In parallel, a transformative development would be the fabrication of a freestanding anode that has both high lithium-ion capacity and sufficient electron transport to remove the inactive copper current collector. Recent work has shown where carbon nanotube (CNT) electrodes are suitable structures to develop into freestanding anodes for electrochemical devices like batteries.5 The implication of using a freestanding electrode is that the entire mass contributes to the usable electrode a)
Address all correspondence to this author. e-mail: [email protected] b) Both authors contributed equally to this publication. DOI: 10.1557/JMR.2010.0209 1636
http://journals.cambridge.org
J. Mater. Res., Vol. 25, No. 8, Aug 2010 Downloaded: 21 Mar 2015
capacity (Ah/mass of electrode). This is in contrast to a conventional electrode where the usable electrode capacity is a derated value that includes mass averaging of the active material composite layer and a metal current collector substrate. Removal of the current collector (typically copper) from the anode yields the largest impact on battery specific capacity given that the mass density is 4 highe
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