Petal cell-derived MnO nanoparticle-incorporated biocarbon composite and its enhanced lithium storage performance

Manganese monoxide (MnO) has attracted much attention as anode materials in lithium ion (Li+) batteries (LIBs) due to its high theoretical capacity and being environmentally friendly. However, the low electrical conductivity, as well as structural collapse during the lithiation/delithiation process, limits its application. In this study, a novel MnO/C composite was feasibly synthesized by employing renewable petal cells as bioscaffolds. Mn(II) ions were firstly infiltrated into the confined space in the cellular walls of camellia petals, then transformed into MnO nanoparticles (average size of 22 nm) after calcination under nitrogen. At the same time, the camellia petal biotemplate was changed to the biocarbon in the composite, forming a C/MnO/C layer-particle-layer sandwich-like structure. Composition of the composite and chemical environment for the elements was further characterized by TG, FT-IR, Raman and XPS. When the composite is used as anode material in a half-cell LIB, the carbon layer can improve the conductivity of the electrode, and the unique sandwich-like structure can alleviate the volume expansion of MnO during the electrochemical cycling. As a result, the special MnO/C composite achieves a good specific capacity (445 mAh g(-1) at 100 mA g(-1) for more than 300 cycles) with excellent cycle stability. Quantitative analysis reveals that capacitance and diffusion mechanisms both account for Li+ storage.