Optimized few-layer MoS2 confined in carbon bowls via pore filling and chemical bond enabling fast kinetics for high-rate potassium storage

Abstract

Molybdenum sulfide (MoS₂) is a prospective anode material for potassium-ion batteries, owing to its large interlayer spacing and superior theoretical capacity. Nevertheless, its practical application is hindered by sluggish kinetics and inferior structural stability, which limit its potassium storage performance. Herein, we employ hollow hard-soft carbon bowls (HSCB), consisting of soft carbon uniformly coated on hard carbon bowls, as nanoreactors to confine few-layered MoS₂ nanosheets. The mesoporous carbon shells of HSCB enhance electrolyte penetration and enable rapid charge transfer and robust structural protection, while the mechanical coupling induced by pore filling, alongside the exist of CSMo chemical bonds, further reinforces the structural integrity of MoS₂. Additionally, the creation of few-layered MoS₂ structures and MoS₂/carbon heterostructures promotes efficient K-ion adsorption and diffusion. Notably, there is a strong linear relationship between MoS₂ content and electrochemical performance, including initial Coulomb efficiency, rate performance, and reaction kinetics. Consequently, the optimized MoS₂/HSCB anode demonstrating a superior reversible capacity of 630 mAh g⁻¹ at 0.1 A g⁻¹, an exceptional rate capacity of 251 mAh g⁻¹ at 10 A g⁻¹, and excellent cycling stability, retaining 369 mAh g⁻¹ at 0.5 A g⁻¹ after 700 cycles. Remarkably, a potassium-ion hybrid capacitor assembled with MoS₂/HSCB anode achieves superior energy/power densities of 122 Wh kg⁻¹/11266 W kg⁻¹, along with splendid capacity retention of 89.5 % after 5000 cycles. This work not only offers an innovative approach for the structural engineering of high-performance sulfide-based composite materials but also elucidates the impact of sulfide content on electrochemical performance.