Dual modification of Ti3C2Tx MXene hybridization and cut-off voltage adjustment for MoS2 to achieve stable sodium storage performance

Abstract

Molybdenum disulfide (MoS₂), a typical layered transition metal sulfide with a large interlayer distance, narrow band gap structure, and high theoretical capacity for sodium storage, shows tremendous promise for sodium-ion batteries (SIBs). Unfortunately, the inadequate cycling stability due to the mechanical failure caused by the deep conversion reaction upon cycling at low voltage, combined with its intrinsic poor electical conductivity, results in degraded electrochemical performance. In this work, a novel Ti₃C₂T_x MXene was introduced to fabricate a MoS₂/Ti₃C₂T_x hybrid through a facile hydrothermal approach, dramatically increasing the reaction kinetics of the hybrid electrode. Additionally, further increasing the discharge cut-off voltage to 0.2 V, the target MoS₂/Ti₃C₂T_x exhibits remarkable sodium storage performance in terms of specific capacity, cyclability, and rate capability. Strikingly, the capacity hardly ever decays after 1000 cycles at 1.0 A g⁻¹. Noteworthily, the impressive sodium storage performance of MoS₂/Ti₃C₂T_x within 0.2–3.0 V originates from the effective avoidance of deep conversion reations below 0.2 V and improved electronic kinetics from the combination with Ti₃C₂T_x flakes. Moreover, ex situ phase characteriztion, kinetic study, and pseudocapacitive effect for charge storage were also investigated to reveal the origin of the improved electrochemical performance. Importantly, the modifications of both electrode structure and cut-off voltage provide an effective way to optimize the electrochemical redox of the target electrode.