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[Display omitted] • Carbon coated MoS 2 hierarchical microspheres are synthesized with PVP assistance. • MoS 2 @C display the capacity of 124 mAh/g over 700 cycles at 1000 mA g−1 for K ion batteries. • The capacitive contribution promises the rate ability and cycling performance of MoS 2 @C. • The K ions storage mechanism in MoS 2 @C is investigated via ex-situ XRD and TEM. Potassium ion batteries (PIBs) is becoming a capable battery technology that can be used for coming generation low-cost energy storage. Although conversion-type transition metal dichalcogenides have shown major application prospects as high-capacity anode in PIBs, the dramatic structural degradation of materials during the potassium ions (de)intercalation process leads to unsatisfied cycling performance and poor rate ability. Herein, we carry out an interfacial engineering strategy to design and synthesize carbon-coated MoS 2 hierarchical microspheres (MoS 2 @C) for PIBs. The uniform carbon coating layer maintains the structural integrity and the heterointerfaces in MoS 2 @C provide an electron transport highway. As a consequence, at 100 mA g-1, for the MoS 2 @C hierarchical microspheres, a remarkable capacity of 332 mAh g-1 can be obtained, with a remarkable cycling ability. Moreover, at 1000 mA g-1, MoS 2 @C can still provide the capacity of 124 mAh g-1 over 700 cycles. The kinetics analysis and ex-situ characterization demonstrated the fast and reversible K ions storage behavior of MoS 2 @C. This work is helpful to design other conversion-type electrode materials for metal ion storage systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen-rich biomass carbon (N-CHC) was prepared by urea etching method. • N-CHC exhibits excellent capacity and rate performance as a K+ half-cell anode. • Large specific surface area, lots of defects and heteroatoms are key advantages. • The hybrid capacitor composed of N-CHC and AC exhibits high energy and power density. Potassium ion hybrid capacitors have the advantages of high energy density, high power density, and low cost, and are expected to replace expensive lithium ion storage devices in large-scale applications. Here, an innovative nitrogen-rich biomass carbon (N-CHC) is prepared using urea as the etchant and hemp core as the raw material, which has a high specific surface area of 1185.3 m2 g−1 and nitrogen content of 8.56%. In addition, it shows a capacity of 442.4 mAh g−1 as a potassium ion half-cell anode at 30 mA g−1. Even under the high current test of 2000 mA g−1, N-CHC also shows excellent performance (175.0 mAh g−1). Further, the good rate performance is attributed to the large-scale capacitance control by analyzing reaction process kinetics. And the constant current intermittent titration technique (GITT) results show that N-CHC has a larger K+ diffusion coefficient than unetched biomass carbon. The maximum energy density of the full carbon-based hybrid capacitor composed of N-CHC anode and activated carbon cathode is 127.36 Wh kg−1, and the maximum power density is 2371 W kg−1. [ABSTRACT FROM AUTHOR]

• Carbon-coated SnS nanosheets and reduced graphene oxide composites are designed and synthesized. • Dual-carbon modification enhances the rate performance of SnS. • Potassiation stage adjustment results in stable cycling performance. Potassium ion batteries (PIBs) have attracted lots of attention due to its abundant resources. Exploring capable anode materials becomes one of the critical issues to achieve high-performance PIBs. Herein, carbon-coated SnS nanosheets and reduced graphene oxide (SnS@C/rGO) composite are designed and synthesized by a solvothermal reaction and heat treatment. The strategy of double carbon modification enhances the rate performance of SnS. Meanwhile, the cycling stability of SnS@C/rGO can be further improved by optimizing the voltage window, which can achieve the potassiation stage adjustment. K ions storage mechanism of SnS@C/rGO is investigated under different voltage windows. The deep alloying reaction occurs under low potential and is harmful to cycling performance. Moreover, the electrochemical kinetics of K ions storage is investigated by quantitative kinetics analysis. This work highlights the important effect of dual-carbon modification and adjusting the potassiation stage on the K ion storage. [ABSTRACT FROM AUTHOR]