Three-dimensional carbon nanotubes for high capacity lithium-ion batteries Chiwon Kang a , Mumukshu Patel a , Baskaran Rangasamy a, 1 , Kyu-Nam Jung c , Changlei Xia b , Sheldon Shi b , Wonbong Choi a, b, * a Department of Materials Science and Engineering, University of North Texas, North Texas Discovery Park 3940 North Elm St., Denton, TX 76207, USA b Department of Mechanical and Energy Engineering, University of North Texas, North Texas Discovery Park, 3940 North Elm St., Denton, TX 76207, USA c Energy Efficiency and Materials Research Division, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343, Republic of Korea highlights graphical abstract  We show a novel structure of multi- stacked 3D CNTs for a higher loading of CNTs.  The bulk density of multi-stacked 3D CNTs is twice as high as that of graphites.  The multi-stacked 3D CNTs yield a stable and high reversible volumetric capacity. article info Article history: Received 7 June 2015 Received in revised form 29 August 2015 Accepted 31 August 2015 Available online xxx Keywords: 3-Dimensional free-standing carbon nanotubes Lithium ion batteries Volumetric capacity Areal capacity Bulk density Multi-layered anode stack abstract Carbon nanotubes (CNTs) have been considered as a potential anode material for next generation Lithium-ion batteries (LIBs) due to their high conductivity, flexibility, surface area, and lithium-ion insertion ability. However, the low mass loading and bulk density of carbon nanomaterials hinder their use in large-scale energy storage because their high specific capacity may not scale up linearly with the thickness of the electrode. To address this issue, a novel three-dimensional (3D) architecture is rationally designed by stacking layers of free-standing CNTs with the increased areal density to 34.9 mg cm 2 , which is around three-times higher than that of the state-of-the-art graphitic anodes. Furthermore, a thermal compression process renders the bulk density of the multi-stacked 3D CNTs to be increased by 1.85 g cm 3 , which yields an excellent volumetric capacity of 465 mAh cm 3 at 0.5C. Our proposed strategy involving the stacking of 3D CNT based layers and post-thermal compression provides a powerful platform for the utilization of carbon nanomaterials in the advanced LIB technology. © 2015 Elsevier B.V. All rights reserved. 1. Introduction The lithium-ion battery (LIB) has been one of the most commonly used state-of-the-art energy storage systems since it was first commercialized in 1990. The commercial success of the LIB is mainly attributed to the unique features of high operating * Corresponding author. Department of Materials Science and Engineering, Uni- versityof North Texas, North Texas Discovery Park 3940 North Elm St., Denton, TX 76207, USA. E-mail address: wonbong.choi@unt.edu (W. Choi). 1 Present address: Department of Physics, School of Basic and Applied Sciences, Central University of Tamilnadu, Thiruvarur, Tamilnadu, India. Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour http://dx.doi.org/10.1016/j.jpowsour.2015.08.103 0378-7753/© 2015 Elsevier B.V. All rights reserved. Journal of Power Sources 299 (2015) 465e471