Plate-to-Layer Bi2MoO6/MXene-Heterostructured Anode for Lithium-Ion Batteries

Abstract

Bi₂MoO₆ is a potentially promising anode material for lithium-ion batteries (LIBs) on account of its high theoretical capacity coupled with low desertion potential. Due to low conductivity and large volume expansion/contraction during charge/discharge cycling of Bi₂MoO₆, effective modification is indispensable to address these issues. In this study, a plate-to-layer Bi₂MoO₆/Ti₃C₂T_x (MXene) heterostructure is proposed by electrostatic assembling positive-charged Bi₂MoO₆ nanoplates on negative-charged MXene nanosheets. MXene nanosheets in the heterostructure act as a highly conductive substrate to load and anchor the Bi₂MoO₆ nanoplates, so as to improve electronic conductivity and structural stability. When the mass ratio of MXene is optimized to 30%, the Bi₂MoO₆/MXene heterostructure exhibits high specific capacities of 692 mAh g^-1 at 100 mA g^-1 after 200 cycles and 545.1 mAh g^-1 with 99.6% coulombic efficiency at 1 A g^-1 after 1000 cycles. The results provide not only a high-performance lithium storage material, but also an effective strategy that could address the intrinsic issues of various transition metal oxides by anchoring them on MXene nanosheets to form heterostructures and use as anode materials for LIBs.

Keywords: Bi2MoO6; Electrostatic self-assembly; Heterostructure; Lithium-ion batteries; MXene.

Fig. 1

Schematic diagram for the simple electrostatic self-assembly of positive-charged Bi₂MoO₆ nanoplates on the negative-charged MXene nanosheets

Fig. 2

SEM images of a MXene nanosheets, b Bi₂MoO₆ nanoplates, c, d Bi₂MoO₆/MXene-50%, e, f Bi₂MoO₆/MXene-30%, and g, h Bi₂MoO₆/MXene-10%

Fig. 3

TEM images of a, b Bi₂MoO₆/MXene-50%, c, d Bi₂MoO₆/MXene-30%, and e, f Bi₂MoO₆/MXene-10%. g STEM and corresponding element (Bi, Mo, Ti, and C) mapping images of the Bi₂MoO₆/MXene-30%

Fig. 4

Characterization of Bi₂MoO₆/MXene heterostructures: a, b XRD patterns, c Raman speatra of the Bi₂MoO₆/MXene heterostructures. High-resolution of d Bi 4f, e Mo 3d, f O 1s, and g Ti 2p XPS spectrum of Bi₂MoO₆/MXene-30%

Fig. 5

Electrochemical performance of the Bi₂MoO₆/MXene electrodes: a CV curves of Bi₂MoO₆/MXene-30% for the first three cycles at 0.1 mV s⁻¹. b Charge/discharge profiles of Bi₂MoO₆/MXene-30% at 100 mA g⁻¹ at different cycles. c Cycling performance of Bi₂MoO₆/MXene-50%, Bi₂MoO₆/MXene-30%, Bi₂MoO₆/MXene-10%, and pristine Bi₂MoO₆ electrodes at 100 mA g⁻¹ for 200 cycles. d Charge/discharge profiles of Bi₂MoO₆/MXene-30% at different current rates. e Comparison of rate capabilities of Bi₂MoO₆/MXene-30% at various current rates from 50 to 2000 mA g⁻¹. f Long-term cycling performance of Bi₂MoO₆/MXene-30% in 1000 cycles at 1 A g⁻¹

Fig. 6

Electrochemical kinetic analysis of Li storage behavior of Bi₂MoO₆/MXene-30%. a GITT profiles (current pulse at 100 mA g⁻¹ for 30 min followed by 1 h relaxation), b diffusion coefficients calculated from GITT profiles according to overpotential, c CV curves at various scan rates from 0.2 to 3 mV s⁻¹ in the voltage range of 0.01–3 V (vs. Li⁺/Li), d log(i)–log(v) curves, e CV profile measured at 1 mV s⁻¹ with shaded area displaying the pseudocapacitive contribution, and f normalized proportions of capacitive and diffusion-controlled contribution at various scan rates