Free-standing N-doped hollow carbon fibers as high-performance anode for potassium ion batteries
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Published online 9 October 2020 | https://doi.org/10.1007/s40843-020-1465-8
Free-standing N-doped hollow carbon fibers as highperformance anode for potassium ion batteries 1
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Suhua Chen , Yanhong Feng , Jue Wang , Erjin Zhang , Xinzhi Yu and Bingan Lu ABSTRACT A novel hierarchical architecture—N-doped hollow carbon fibers decorated with N-doped carbon clusters (NHCF@NCC)—was synthesized for high-performance anode material of potassium ion batteries (PIBs). The material is formulated with porous N-doped hollow carbon fibers as the backbone, which effectively shortens the diffusion length of potassium ion and increases the interface between the electrode and electrolyte. In addition, the N-doped carbon clusters attached on the hollow carbon fibers can provide abundant reactive sites. Specially, NHCF@NCC could form a freestanding electrode with a three dimensional interconnected conductive network owing to the ultrahigh aspect ratio. In this way, NHCF@NCC delivers an excellent electrochemical performance as free-standing anode materials of PIBs, exhibiting −1 a high reversible capacity of 310 mA h g at a current density −1 of 100 mA g , a long cycling stability of 1000 cycles with negligible degradation, and a superior rate performance of −1 −1 153 mA h g at a large current density of 2000 mA g . Keywords: potassium anode, N-doped hollow carbon fibers, Ndoped carbon cluster, free-standing
INTRODUCTION Potassium ion batteries (PIBs), as one of alternative energy storage devices, have been extensively studied due to the suitable working voltage from the standard electrode potential (−2.93 V vs. SHE) and the abundance of potassium source [1–5]. Research on anode electrode materials is one of the hotspots for PIBs [6–8]. Compared with other materials (alloy, conversion materials, and so on) [9–13], carbon materials have the merits of low price, environmental friendliness, stability and low redox potential [14–16]. Carbon materials with various structures have been researched for potassium ion storage, including carbon nanotubes [17], carbon nanofibers [18], carbon 1 2 3
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quantum dots [19], and graphite [2,20]. These materials show excellent electrochemical properties, demonstrating potential in term of enhanced reversible capacity [21]. There are two different types of potassium ion storage in carbon materials [7]. One is that potassium ions intercalate into graphitized sheet layers, forming a stage 1 graphite intercalation compound [2,22,23], while the other is surface capacitive storage relying on the doped heteroatoms, functional groups and defects to adsorb potassium ions [24,25]. However, relatively low reversible capacity and depressed kinetics impede PIBs’s further development [26–29]. Furthermore, the common slurry coating method for preparing electrode materials is tedious and mixed with binder and conducted agent, which cut down the electrical conductivity of electrode materials [30–32]. The two different forms of potassium ion storage (intercalation and adsorption) point the way of electr
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