1T/2H Mixed-phase MoS2 with enlarged interlayer spacing induced via bacteria-derived carbon for long-lifespan pseudocapacitors

Pseudocapacitors (PCs) are considered prospective candidates for large-scale aqueous energy storage systems due to their high power density. However, the poor cycling stability resulting from sluggish metal ion transport kinetics and the instability of the electrode structures hinders their further applications. To address this issue, an effective strategy of 1T/2H mixed-phase MoS2 directly grown on the electrochemically activated carbon (EC) induced via bacteria-derived carbon (BC) from bacillus subtilis was proposed to achieve efficient anodes for potassium ion capacitors. The inherent nitrogen elements found in the bacteria-derived carbon, along with a trace amount of amines and their derivatives generated from amino acid decarboxylation, act as support by inserting into the MoS2 interlayer. Amines and their derivatives as intercalators could suppress the MoS2 layer stacking and mitigate structure damage, which is responsible for preventing rapid capacity fading. Thus, the mixed-phase MoS2 with an expanded interlayer spacing of 0.94 nm achieves a remarkable durability with a capacitance retention of 110.2 % after 40,000 cycles at 10 A g−1. Density Functional Theory (DFT) reveals that the mixed-phase MoS2 could improve electron transfer ability and cyclic stability, in which the rich vacancies introduced by bacteria-derived carbon could enhance the K+ adsorption. To highlight, the asymmetric capacitor device (ASC) adopting mixed-phase MoS2 anode shows a long lifespan (88 % capacitance retention over 10,000 cycles). This work will provide a green approach to boost cycling performance of MoS2 anodes and shed light on developing high-performance MoS2-based materials for electrochemical energy storage.