Article pubs.acs.org/est
Upcycling of Packing-Peanuts into Carbon Microsheet Anodes for Lithium-Ion Batteries Vinodkumar Etacheri, Chulgi Nathan Hong, and Vilas G. Pol* School of Chemical Engineering, Purdue University, 480 Stadium Mall Drive, West Lafayette, Indiana 47907-2100, United States
Downloaded by UNIV OF NEBRASKA-LINCOLN on August 24, 2015 | http://pubs.acs.org Publication Date (Web): July 2, 2015 | doi: 10.1021/acs.est.5b01896
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ABSTRACT: Porous carbon microsheet anodes with Li-ion storage capacity exceeding the theoretical limit are for the first time derived from waste packing-peanuts. Crystallinity, surface area, and porosity of these 1 μm thick carbon sheets were tuned by varying the processing temperature. Anodes composed of the carbon sheets outperformed the electrochemical properties of commercial graphitic anode in Li-ion batteries. At a current density of 0.1 C, carbon microsheet anodes exhibited a specific capacity of 420 mAh/g, which is slightly higher than the theoretical capacity of graphite (372 mAh/g) in Li-ion half-cell configurations. At a higher rate of 1 C, carbon sheets retained 4-fold higher specific capacity (220 mAh/g) compared to those of commercial graphitic anode. After 100 charge−discharge cycles at current densities of 0.1 and 0.2 C, optimized carbon sheet anodes retained stable specific capacities of 460 and 370 mAh/g, respectively. Spectroscopic and microscopic investigations proved the structural integrity of these high-performance carbon anodes during numerous charge−discharge cycles. Considerably higher electrochemical performance of the porous carbon microsheets are endorsed to their disorderness that facilitate to store more Li-ions than the theoretical limit, and porous 2-D microstructure enabling fast solid-state Li-ion diffusion and superior interfacial kinetics. The work demonstrated here illustrates an inexpensive and environmentally benign method for the upcycling of packaging materials into functional carbon materials for electrochemical energy storage. graphene, and fullerenes were also used for Li-ion storage.16−21 Improved electrochemical performances of these 1-D and 2-D nanostructures resulted from the superior electronic and Li-ion diffusion due to their unique microstructure, high surface area, and porosity. However, these high surface area carbons experienced severe capacity fading upon prolonged cycling due to increased reactivity with electrolyte. State of the art synthesis of these carbonaceous materials often involve the use of hydrocarbon precursors such as acetylene or coal.22,23 Intricate synthetic methods including chemical vapor deposition (CVD), electric arc discharge, and laser deposition are usually employed for the fabrication of carbon nanotubes and graphene.24−26 These complex methods rely on hydrocarbon precursors, which are commercially nonviable and expensive. It is therefore necessary to explore a simple scalable and inexpensive synthetic method for high capacity carbon electrodes for Li-ion batteries. We addressed the above-mentioned issues by fabricating high-performance porous microsheet anodes from waste starch based packing peanuts (Figure 1). Although previous attempts
1. INTRODUCTION Rechargeable Li-ion batteries are integral part of modern portable electronic devices, medical implants, and electric vehicles.1−5 Their acceptability for a wide range of applications resulted from the increased energy density and high rate capabilities compared to other secondary batteries.6−9 Graphite is mostly used as the anode material for these rechargeable Liion batteries due to only 10% volume change during lithium intercalation into ordered graphitic planes, and improved electronic conductivity over alternative metal-oxide electrodes.3 Despite these advantages, the specific capacity of graphite is limited to 372 mAh/g, and high rate performances are not promising. These drawbacks of conventional graphite anodes seriously limit the energy and power density of Li-ion batteries.10−12 Moreover, lithiation occurs at lower potentials (
