Yunchao, L., R.A. Adams, A. Arora, V.G. Pol, A.M. Levine, R.J. Lee, K. Akato, A.K. Naskar and M.P. Paranthaman, “Sustainable Potassium-Ion Battery Anodes Derived from Waste-Tire Rubber”, Journal of the Electrochemical Society, Vol. 164(6), pp. A1234-A1238, 2017. DOI: 10.1149/2.1391706jes
The recycling of waste-tire rubber is of critical importance since the discarded tires pose serious environmental and health hazards to our society. Here, we report a new application for hard-carbon materials derived from waste-tires as anodes in potassium-ion batteries. The sustainable tire-derived carbons show good reversible potassium insertion at relatively high rates. Long-term stability tests exhibit capacities of 155 and 141 mAh g−1 for carbon pyrolyzed at 1100°C and 1600°C, respectively, after 200 cycles at current rate of C/2. This study provides an alternative solution for inexpensive and environmental benign potassium-ion battery anode materials.
With the fast application of renewable energy technologies, the demand for large-scale energy storage system has increased significantly and became a growing global concern.1–3 The intermittent energy generated from solar, wind and wave requires energy storage systems to leverage the electrical grid loading. In the meantime, with the awareness of the societal costs for the extraction of fossil fuels and the gaseous emissions from combustion, the development of storage systems that can power electric vehicles attracts great attention. During the past two and half decades, great efforts have been devoted to Lithium-ion batteries (LIBs).4–10 However, the limited global availability of lithium resources, safety and high cost of extraction hinder the application of LIBs in several energy storage systems. This demands alternative energy storage devices that are based on earth-abundant elements. Recently, sodium-ion batteries (NIBs) and potassium-ion batteries (KIBs) have gradually received more attention to realize affordable rechargeable batteries for large scale systems.11–13Rapid progress has been made to advance NIB technologies. Many of the layered metal oxides and polyanionic compounds exhibited good capacity and cyclability as cathode materials in NIBs.13 On one side, developing anodes for NIBs is still a great challenge as only very limited amounts of Na can be intercalated into graphite due to the larger ionic radius of sodium (1.0 Å for Na+ vs. 0.76 Å for Li+).14 On the other hand, despite its even larger ionic size (1.40 Å), potassium ion based graphite intercalation compounds (GICs) have been demonstrated.15 The high abundance and lower cost of potassium raw materials (1000 USD t−1 for K2CO3 vs. 6500 USD t−1 for Li2CO3), mean that K-ion based electrochemical energy storage technologies can exhibit their potentials in many applications.16 Also, similar to sodium, potassium does not alloy with aluminum at lower potentials, enabling the use of aluminum as the anode current collector instead of high cost copper. Moreover, the redox potential of K/K+ (−2.94 V vs. standard hydrogen electrode, SHE) is lower than that of Na/Na+ (−2.71 V vs. SHE), indicating a higher working potential for K-ion batteries. In addition, K+ ions show higher transport numbers and mobility in non-aqueous electrolytes due to weaker Lewis acidity and smaller Stoke’s radius of solvated ions.17 A few potassium intercalation cathode materials such as Prussian blue and its analogues,11,18,19 FeSO4F,20 amorphous FePO421 and layered K0.3MnO216 have been reported. As for the anode, the use of K metal is not applicable due to its severe safety concerns. Hence, identifying the potential anode materials for KIBs is of great importance. Recently, carbon based materials (graphite, graphene and hard carbons) and tin-based composites have been studied as anodes for KIBs.15,22–26 Among these materials, hard carbons showed the most promise because graphite and tin-based composites suffered pronounced capacity fade and lower rate capability while the high cost of graphene prevents its application in the price sensitive large-energy storage field.22,25
The widespread use of vehicles results in large quantities of end-of-life tires and it was estimated on a yearly basis that approximately 1.5 billion tires are disposed globally.27 The discarded tires pose serious environmental and health threats to our society since they are non-biodegradable, flammable and could produce harmful gases. The pyrolysis of sulfonated waste-tire rubber into high value-added hard carbon provides many promising applications of waste tires in electrochemical energy storage systems.28–31 Here, we investigated the low-cost, tire-derived carbon as a potential anode material for potassium-ion batteries, presenting another important application for the waste-tire recycling products.
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