Hierarchical donut-shaped LiMn2O4 as an advanced cathode material for lithium-ion batteries with excellent rate capability and long cycle lifeElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ta00752f

Porous micrometer-sized architecture that consists of aggregated single-crystalline nanoparticles is critical for LiMn 2 O 4 to achieve good rate capacity and cycling stability, since it can increase the contact area between the electrolyte/electrode and shorten the transport paths for electrons and lithium ions. In this paper, hierarchical porous donut-shaped LiMn 2 O 4 comprising aggregated single-crystalline nanoparticles has been successfully fabricated with MnO 2 nanosheet coated polystyrene spheres as a precursor and characterized in terms of structure and performance as the cathode for lithium ion batteries. The charge/discharge tests show that the as-obtained donut-shaped LiMn 2 O 4 exhibits excellent rate capability and high-rate cyclic stability. Surprisingly, even at a high charge/discharge rate of 10 C, the battery yields a capacity retention of over 95% after 500 cycles. The superior performance of the synthesized product can be attributed to its intrinsic structure: porous donut-shaped LiMn 2 O 4 consisting of well-connected single-crystalline nanoparticles. The interpenetrating nanoparticle reduces the path of Li ion diffusion and increases the number of reaction sites for lithium insertion/extraction; the pores provide void space to buffer the volume changes during high-rate charge/discharge. In this work, we have demonstrated a facile approach to synthesize donut-shaped LiMn 2 O 4 comprising interpenetrating nanograins, and this material demonstrates excellent high-rate cycling reversibility.