Thiourea-based polyimide/RGO composite cathode: A comprehensive study of storage mechanism with alkali metal ions
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Published online 19 June 2020 | https://doi.org/10.1007/s40843-020-1375-2
Thiourea-based polyimide/RGO composite cathode: A comprehensive study of storage mechanism with alkali metal ions 1
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Peixun Xiong , Huiming Yin , Zifeng Chen , Chen Zhao , Jixing Yang , Shuping Huang and 1,3* Yunhua Xu ABSTRACT Although organic electrode materials have merits of abundant resources, diverse structures and environmental friendliness, their performance for electrochemical energy storage is far insufficient. In this work, a thiourea-based polyimide/reduced graphene oxide (PNTCSA/ RGO) composite was synthesized via a condensation polymerization method. As a cathode material in lithium-ion batteries, excellent performance is demonstrated with high −1 reversible capacity (144.2 mA h g ), high discharge voltage −1 (~2.5 V), and long cycling life (over 2000 cycles at 500 mA g ), which are comparable to those of other well documented inorganic electrodes. Encouraging electrochemical performance is also demonstrated for sodium-ion batteries (a cycling life of −1 800 cycles at 500 mA g ), while poor performance is delivered in potassium-ion batteries. Theoretical studies reveal that the active sites are carbonyl groups for all alkali ions but one inserted alkali metal ion is shared by two carbonyl groups from the two neighbor units. More importantly, K ions have stronger interaction with S atoms than Li/Na ions, which may lead to poor structure reversibility and account for the poor cycling performance. Our findings provide a fundamental understanding of polyimide-based polymer electrodes and help to design and develop high-performance organic electrode materials for alkali metal ion batteries. Keywords: electrochemical energy storage, polyimide, organic electrode material, lithium/sodium/potassium-ion battery
INTRODUCTION Benefiting from the high energy density and long cycle
life, lithium-ion batteries (LIBs) are widely used in various applications ranging from portable electronics to electric vehicles [1,2]. In addition, sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) are also regarded as promising candidates for large-scale electrochemical energy storage applications owing to the low cost and resource abundance of Na and K [3,4]. Over the past decades, numerous efforts have been devoted to developing potential materials for alkali metal (AM, AM=Li, Na and K) ion batteries [1,5,6]. Nevertheless, conventional AM ion batteries often use inorganic electrode materials such as transition-metal oxides, which usually show high production prices, dependence on scarce natural resources, and environmental issues due to toxicity and pollution [1,5,6]. Therefore, exploring advanced electrode materials with low-cost and ecofriendliness are highly desired for mass manufacturing and large-scale application of energy storage. Organic electrode materials possess great potential for green and sustainable AM ion storage because of their abundance in nature, potential environmental friendliness, and flexible and designab
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