Magnetic-atom strategy enables unilamellar MoS2-C interoverlapped superstructure with ultrahigh capacity and ultrafast ion transfer capability in Li/Na/K-ion batteries

Constructing a unilamellar MoS2-C interoverlapped superstructure (UIS) is the most promising way to improve electrical conductivity and alleviate volume expansion of MoS2 electrodes during Li+/Na+/K+ storage due to the maximized atomic interface contact. However, the interlayer distance of similar to 0.48 nm between MoS2 and C (lower than 0.62 nm of pristine MoS2), the unconspicuous enhancement of intrinsic conductivity of MoS2, and the inevitable decrease in capacity due to the introduced low-capacity C undoubtedly hamper ion transport and storage, thus resulting in limited enhancement of capacity and fast-charging performances of UIS. Herein, we propose a magnetic-atom strategy for UIS via a one-step high-pressure vapor-phase synthesis method, during which the interlayer electrostatic repulsion is in-situ constructed by magnetic-atom Fe and/or Co doping to adjust the interlayer distance from 0.48 to 0.64 nm. In addition, the doped magnetic atom can regulate the electronic structure of UIS to obtain the bandgap of 0 eV to enhance electron transfer. Importantly, the doped magnetic atom can be reduced to superparamagnetic metallic nanoparticles during conversion reactions, which can store abundant spin-polarized electrons to induce strong surface-capacitance effects, thus boosting ion transport and storage. Consequently, the magnetic-atom strategy endows the UIS with ultrahigh reversible capacities of 1572.1/738.5/542.3 mAh/g at 0.1C, 971.2/383.5/209.8 mAh/g at 5C after 3000 cycles, and 761.5/340.8/204.5 mAh/g at 20C as Li/Na/K-ion-battery anodes, respectively. This work verifies the efficiency of magnetic-atom strategy and paves a way for the design of other transition metal dichalcogenides for electrochemical energy storage.