Branched carbon-encapsulated MnS core/shell nanochains prepared via oriented attachment for lithium-ion storage

Novel branched carbon encapsulated MnS (MnS@C) nanochains were prepared by an in situ co-pyrolysis method. The morphology and structure of the MnS@C nanochains were mainly characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). It was found that the prepared MnS@C nanochains possess interesting branched structures, which are constructed by interconnected MnS@C nanoparticles with a diameter of ca. 200-400 nm. More interestingly, the MnS@C nanoparticles have novel pomegranate-like structures, in which inner cores are not made of whole nanoparticles but composed of many MnS nanoparticles. The formation mechanism of MnS@C should be attributed to an Oriented Attachment (OA) mechanism by investigating various intermediate products obtained by controlling the reaction conditions. The branched MnS@C nanochains after annealing (MnS@C-800) demonstrated perfect cycling stability and long cycle life when used as anode materials for lithium-ion batteries (LIBs). At a current density of 50 mA g(-1), the stable specific capacity is around 545 mA h g(-1) while the pure MnS anode experiences a drastic drop quickly to 300 mA h g(-1) at the initial few cycles. At 500 mA g(-1), the reversible specific capacity is ca. 318 mA h g(-1) at the initial cycle and is maintained at ca. 200 mA h g(-1) after 800 cycles.