Self-templating preparation and electrochemical performance of LiMnPO4 hollow microspheres

Abstract

Hollow microspheres fabricated from nanoparticles are considered as one of the most attractive architectures for energy storage devices owing to their high tap density, short Li+ diffusion length, and good cycling stability. It is, however, difficult to fully assess the effectiveness of controlling the parameters of hollow microspheres, such as their structure and size. This is due to the adverse effects of the applied treatments, especially in the case of lithium-based microspheres used for energy storage. In the present study, LiMnPO4 hollow microspheres with evolvable structures (hollow, urchin-like, and yolk-shell architectures) and tuneable sizes (600 nm, 1.5 μm, and 3 μm) were synthesised via a facile solvothermal process using precipitated Li3PO4 hollow microspheres as the sacrificial templates. A possible formation mechanism is proposed in this paper based on observations from time-dependent experiments. The process parameters such as the additive ((NH4)2SO4), diethylene glycol (DEG)-to-H2O volume ratio of the solvent, and Li3PO4 template size were found to distinctly impact the final phase, structure, and size of the products. Compared with the 3-μm urchin-like and 600-nm hollow microspheres, the 3-μm hollow microspheres exhibited excellent electrochemical properties including a high rate capability and good cycling stability, which can be attributed to the synergy between the nano-size of the subunits and the stable structure of the microspheres.