Carbon nanoparticle-entrapped macroporous Mn₃O₄ microsphere anodes with improved cycling stability for Li-ion...

Manganese oxide (Mn₃O₄) has garnered substantial attention as a low-cost, environment-friendly anode material. It undergoes a conversion reaction involving the formation of Li₂O 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 Mn₃O₄ microspheres with a unique maze-like porous interior. We fabricate the Mn₃O₄/C composites using a scalable two-step process involving the thermal decomposition of MnCO₃ in water vapor and mixing in a carbon-dispersed solution. The fabricated Mn₃O₄/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 Mn₃O₄. 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.