In-situ embedding of ultrasmall MnO nanoparticles into pollen biomass-derived hollow porous N heteroatoms enriched carbon microspheres as high-performance anode for lithium-ion batteries

The transition manganese monoxide (MnO) is investigated as the one of the most promising candidates of anode nanomaterials for lithium-ion batteries (LIBs) due to its irreplaceable advantages of higher theoretical capacity, restricted voltage hysteresis and favorable electrochemical kinetics. Nevertheless, it still remains a big challenge to simultaneously resolve the nonideal properties of the relatively low dispersion of MnO, the structural metastability as well as the undesirable permeability of electrolyte. Herein, the ultrasmall MnO nanoparticles/sulfuric-acid-pretreated camellia pollen carbon (MnO/SCPC) composites are successfully fabricated by a facile bio-templating method of carbonization hydrolysis of camellia pollen, wet-impregnation treatment of Mn/SCPC precursor and followed by thermal annealing, which delivers hollow porous microspheres structure where the shell components are formed by orderly stacking of multiple ultrasmall-size MnO-loaded nanocarbon spheres. This advantageous nano-structures not only allow for a large volume change during the lithiation/delithiation process, a large accessible contact area with electrolyte and a short transport path for Li+ ions, but also enhance the amounts of electrochemically active sites while simultaneously endow them with a superior structural stability through robust interfacial interaction. These clever designs enable the MnO/SCPC composites to perform exceptionally well electrochemically. More specifically, the MnO/SCPC-600 anode possesses a high initial discharge capacity (1490 mAh·g−1) at a current density of 0.1 A·g−1, and still retains 60% of the initial capacity (894 mAh·g−1) after 100 cycles. Besides, it also exhibits a high discharge capacity of 612 mAh·g−1 at a current density of 2.0 A·g−1 and an ultralong cycling life of 584 mAh·g−1 at 1.0 A·g−1 for long period of 1000 cycles. This work also paves up a facile direction for the application of MnO/biomass-derived carbonaceous nanomaterials in LIBs.