Carbon nanoparticle-entrapped macroporous MnO microsphere anodes with improved cycling stability for Li-ion batteries.

Manganese oxide (MnO) has garnered substantial attention as a low-cost, environment-friendly anode material. It undergoes a conversion reaction involving the formation of LiO and metallic Mn to provide high-energy Li-ion batteries. However, its low electrical conductivity and significant volume change reduce its capacity during the initial lithiation/delithiation, hindering its practical application. To improve the cycle performance, we propose a new composite structure wherein we entrap carbon nanoparticles in macroporous MnO microspheres with a unique maze-like porous interior. We fabricate the MnO/C composites using a scalable two-step process involving the thermal decomposition of MnCO in water vapor and mixing in a carbon-dispersed solution. The fabricated MnO/C composites with varying carbon contents exhibit a high maximum discharge capacity retention of 86% after 50 cycles, compared to the 18% given by bare MnO. The entrapped carbon nanoparticles improve the cycle performance both electrochemically and physically. The microstructure of the composite particles and the fabrication process developed in this study will help improve the performance of other conversion-type anode materials that suffer from cycle degradation, including inexpensive transition metal oxides and sulfides.