Electrochemical Performance and Safety of Lithium Ion Battery Anodes Incorporating Single Wall Carbon Nanotubes
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Electrochemical Performance and Safety of Lithium Ion Battery Anodes Incorporating Single Wall Carbon Nanotubes Matthew J. Ganter1, Roberta A. DiLeo1, Amanda Doucett1,2 Christopher M. Schauerman1, Reginald E. Rogers1,2, Gabrielle Gaustad1, and Brian J. Landi1,2 1 Golisano Institute for Sustainability, NanoPower Research Laboratories, 111 Lomb Memorial Drive,Rochester, NY 14623-5608, U.S.A 2 Chemical and Biomedical Engineering, 77 Lomb Memorial Drive, Rochester, NY 14623-5608, U.S.A ABSTRACT Single wall carbon nanotubes (SWCNTs) were incorporated into lithium ion battery anodes as conductive additives in mesocarbon microbead (MCMB) composites and as a freestanding support for silicon active materials. In the traditional MCMB composite, 0.5% w/w SWCNTs were used to replace 0.5% w/w SuperP conductive additives. The composite with 0.5% SWCNTs had nearly three times the conductivity which leads to improved electrochemical performance at higher discharge rates with a 20% increase in capacity at greater than a C/2 rate. The thermal stability and safety was measured using differential scanning calorimetry (DSC), and a 35% reduction in exothermic energy released was measured using the highly thermally conductive SWCNTs as an additive. Alternatively, free-standing SWCNT papers were coated with increasing amounts of silicon using a low pressure chemical vapor deposition technique and a silane precursor. Increasing the amount of silicon deposited led to a significant increase in specific capacity (>2000 mAh/g) and coulombic efficiency (>90%). At the highest silicon loading, the surface area of the electrode was reduced by over an order of magnitude which leads to lower solid electrolyte interface formation and improved safety as measured by DSC. INTRODUCTION The higher energy and power density of lithium-ion batteries over other rechargeable battery chemistries have made them the preferred approach to energy storage for portable devices, and the prevalent technology to enable electrification of vehicles. However, improvement in key metrics such as energy and power density, safety, and cycle life are needed to fully utilize lithium ion batteries in large scale applications. The use of nanomaterials in lithium ion batteries has led to significant gains in the electrochemical performance of battery materials by enabling faster ionic conduction and stability of active materials with cycling. While much of the focus is on decreasing the size of active cathode and anode particles to the nanoscale, improved rate capability, cycling, and energy density has been realized through the use of highly conductive and lightweight nanomaterials as conductive additives or free-standing electrode supports. Single wall carbon nanotubes (SWCNTs) are a promising candidate for use in lithium ion batteries due to their high aspect ratio and 1-D nanostructure which results in high electronic and thermal conductivity[1, 2]. SWCNTs can be used in lithium-ion electrodes as a conductive additive in traditional composites, a free-standing active anode, and
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