In‐Plane Assembled Single‐Crystalline T‐Nb₂O₅ Nanorods Derived from Few‐Layered Nb₂CT_x MXene Nanosheets for Advanced Li‐Ion Capacitors

Abstract

physisorption/shallow Faradaic reaction on the electrode surfaces/interfaces, display higher power density and longer lifespan but relatively lower energy density. [4-8] As a consequence, one point worth noting is that neither single LIBs nor ECs could fully meet the increasingly harsh demands currently, if they were just applied alone. [6-8] Recently, lithium-ion capacitors (LICs), as a competitive device incorporating both merits of LIBs and ECs in one, emerge and become a research hotspot in the field of energy storage. [9-13] Nevertheless, the kinetics of the battery-type anode materials fundamentally originating from electrochemical intercalation of lithium ions are much slower than the capacitive cathodes relying mainly on fast surface ion adsorption and desorption. [14,15] It becomes a critical yet challenging issue for advanced LICs how to effectively conquer the innate imbalance in electrochemical dynamics of the involved electrodes. Commonly, the cathodes for LICs are mainly porous carbonaceous materials with electric double layer capacitances, such as activated carbon (AC) [16] and graphene, [17] and so on. With the aim to well match the advanced cathodes, the anode materials themselves are required to possess high rate characteristics. Since the fast pseudocapacitance properties of RuO 2 were investigated by Trasatti and Buzzanca, various pseudocapacitive materials such as TiO 2 , [18] Li 4 Ti 5 O 12 , [19] MnO 2 , [20] and Nb 2 O 5 [12] have been widely investigated in LICs. They are ideal candidates to bridge the huge gap between the diffusion-limited Li-insertion process and the surface-controlled physical adsorption/desorption. [11,21,22] Particularly, niobium pentoxides (Nb 2 O 5) stands out from others, benefiting from its high safety, large theoretical capacity (≈200 mAh g −1), and extremely small volume expansion rate (≈5%) over electrochemical lithiation/delithiation. [23,24] So far, the hybridization with hetero-phase carbon materials and/or nanodimensional strategies have been intensively developed to purposefully enhance electronic/ionic transport of the Nb 2 O 5 itself toward efficient charge storage. [10,16,17,25,26] Moreover, specific crystal structures of Nb 2 O 5 , i.e., pseudohexagonal (TT-phase) and orthorhombic (T-phase) phases, hold a great influence upon their electrochemical properties. [27-29] Compared to the TT-Nb 2 O 5 , T-Nb 2 O 5 Lithium-ion capacitors (LICs) have attracted enormous interest thanks to their competitive power/energy densities and long-duration lifespan. However, the sluggish insertion kinetics of battery-type anodes seriously limits comprehensive performance of LICs. It is therefore imperative yet significant to develop advanced anodes with high-rate Li + intercalation. Herein, first the in-plane assembled single-crystalline orthorhombic Nb 2 O 5 nanorods (T-Nb 2 O 5 NRs) are designed and constructed via efficient hydrothermal and subsequent annealing treatment by employing few-layered Nb 2 CT x nanosheets as a niobium-based precursor. The inherent formation...

Tetrabutylammonium‐Intercalated 1T‐MoS2 Nanosheets with Expanded Interlayer Spacing Vertically Coupled on 2D Delaminated MXene for High‐Performance Lithium‐Ion Capacitors

“…Ti 3 C 2 T x is a typical one of different‐type MXenes for energy storage material owing to the metallic conductivity, mechanical stability, large lateral size, and unique layered structure. [ 32–36 ] Although the intrinsic lower capacity characteristic of Ti 3 C 2 T x limits its further applications, Ti 3 C 2 T x is often used as a 2D substrate to construct heterostructure with transition‐metal oxides (TMOs), transition‐metal sulfides (TMSs), and carbonaceous materials. [ 37–39 ] Compared with other conductive 2D materials, Ti 3 C 2 T x etched by hydrofluoric acid (HF) has rich terminations (such as O, OH, F) on the surface, which can bond other components to improve the stability of the heterostructure, as well as the stable monolayer and fewer‐layer Ti 3 C 2 T x can be obtained by ion intercalation and delamination, which can provide an excellent interlayer space and more sites to increase the loading of active material.…”

Shear-structured MoNb6O18 as a new anode for lithium-ion batteries

“…0 voltage ranges, the electrode exhibits the highest charge capacity of 137.6 mAh/g and retention rate of 93 % after 60 cycles between 1.0~3.0 V. The lithium storage properties of MNO also are compared with reported Nb-based and other anode electrodes (Table S1). [5,20,24,33,34] The Li-ion diffusion behavior of in MoNb 6 O 18 electrode was investigated CV measurement at the different voltage ranges at various scan speeds increased from 0.2 to 1.0 mV/s. As shown in Fig.…”

“…[17] Recently, niobium-based oxides have been extensively investigated as high-rate anode materials for LIBs, due to their high theoretical capacities based-on multielectron reactions, fast lithium ion transport, most importantly, secure operating voltage (above 1.0 V vs Li + /Li) for safety features. [18][19][20] Therefore, niobium-based oxides anodes are promising candidates for high-powder LIBs anodes, specific in EV. [21] Most of niobiumbased oxides adopt Wadsley-Roth crystallographic shear structure with blocks consisting of distorted MO 6 octahedra sharing corners, and built of n × m × ∞ ReO 3 -type units (n and m are the numbers of MO 6 octahedra along the length and width of the blocks).…”

Lithium Storage in Carbon Cloth–Supported KNb3O8 Nanorods Toward a High‐Performance Lithium‐Ion Capacitor

“…Thereby, novel anodes with high capacity and fast charge/discharge properties are highly required for developing high‐performance LICs. [ 10–12 ]…”