Fabrication of Fe nanocomplex pillared few-layered Ti 3 C 2 T x MXene with enhanced rate performance for lithium-ion bat
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BSTRACT Pillaring technologies have been considered as an effective way to improve lithium storage performance of Ti3C2Tx MXene. Nevertheless, the pillared hybrids suffer from sluggish Li+ diffusion kinetics and electronic transportation due to the compact multi-layered MXene structure, thus exhibiting inferior rate performance. Herein, the few-layered Ti3C2 MXene (f-Ti3C2 MXene) which is free from restacking can be prepared quickly based on the NH4+ ions method. Besides, Fe nanocomplex pillared few-layered Ti3C2Tx (FPTC) heterostructures are fabricated via the intercalation of Fe ions into the interlayer of f-Ti3C2 MXene. The f-Ti3C2 MXene which is immune to restacking can provide a highly conductive substrate for the rapid transport of Li+ ions and electrons and possess adequate electrolyte accessible area. Moreover, f-Ti3C2 MXene can efficiently relieve the aggregation, prevent the pulverization and buffer the large volume change of Fe nanocomplex during lithiation/delithiation process, leading to enhanced charge transfer kinetics and excellent structural stability of FPTC composites. Consequently, the FPTC hybrids exhibit a high capacity of 535 mAh·g−1 after 150 cycles at 0.5 A·g−1 and an enhanced rate performance with 310 mAh·g−1 after 850 cycles at 5 A·g−1. This strategy is facile, universal and can be extended to fabricate various few-layered MXene-derived hybrids with superior rate capability.
KEYWORDS Fe ions intercalation, few-layered MXene, pillared MXene, lithium-ion batteries
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Introduction
In recent years, the discovery of two-dimensional (2D) layered materials, including graphene [1] and dichalcogenides [2], have greatly enhanced the performance of energy storage systems (ESSs) because of their exceptional electrical conductivity, favorable chemical stability and preferable specific surface area [3]. Transition metal nitrides and carbides termed MXenes, a new member of 2D layered materials, were first synthesized by Gogotsi’ group in 2011 [4], which possess a formula of Mn+1XnTx (Where M = Ti, Nb, Sc, V, Ta, etc; X=C, N; T = –O, –OH, –F; n = 1–3). They were typically fabricated by selective etching of the A layers from their parent MAX phase (A = Al, Si, Ga, Ge, etc.) [5]. MXenes have aroused broad interests as potential electrode materials for lithium-ion batteries (LIBs) [6] and other metal-ion batteries (e.g., Na+ [7, 8], K+ [9], Zn2+ [10], and Al3+ [11]) on account of their layered structure, high metallic conductivity and unique surface chemistry. As the most extensively studied MXene, Ti3C2 delivers a moderate theoretical capacity of 320 mAh·g−1 based on density functional theory [12], which is considerably lower than that of Si (4,200 mAh·g−1) [13], Sn (994 mAh·g−1) [14], and Ge (1,624 mAh·g−1) [15] etc. Moreover, surface terminated groups (such as –F, –O and –OH) greatly limit its electrochemical performance, thus leading to a quite low specific capacity [12, 16, 17]. Continued efforts have been devoted to tackling this obstacle up to now. One feasible solution to substantially improve the
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