Porous ZnMn2O4 nanospheres: Facile synthesis through microemulsion method and excellent performance as anode of lithium ion battery

• ZnMn2(CO3)3 nanoshpere was developed as precursor through a facile microemulsion method.
• ZnMn2O4 from the thermal decomposition of ZnMn2(CO3)3 adopts a porous nanosphere structure.
• The porous ZnMn2O4 nanoshpere exhibits excellent rate capability and cyclic stability.

Porous ZnMn2O4 nanospheres are synthesized through a facile microemulsion method. Crystal structure, morphology and electrochemical performance of the product as anode of lithium ion battery were investigated with FESEM, TEM, HRTEM, BET, XPS, XRD, CV, EIS, and charge/discharge test, with a comparison of ZnMn2O4 microparticle synthesized by sol-gel method. It is found that the microemulsion can effectively control particle size and morphology of the precursor and thus porous ZnMn2O4 nanospheres consisting of smaller primary nanoparticles can be successfully obtained, which exhibit far better rate capability and cyclic stability than ZnMn2O4 microparticles. The porous ZnMn2O4 nanospheres deliver a reversible capacity of 300 mAh g−1 at 6000 mA g−1 and yield a capacity retention of 91% after 120 cycles at 200 mA g−1, compared to the 20 mAh g−1 and 0% of ZnMn2O4 microparticles, respectively. The space in the porous structure of ZnMn2O4 nanospheres buffers the mechanical strain induced by the volume change during cycling, which causes destruction of ZnMn2O4 microparticle, resulting in the excellent cyclic stability. Moreover, the primary nanoparticles in ZnMn2O4 nanospheres reduce the path of lithium ion transportation and increase reaction sites for lithium intercalation/deintercalation, leading to the better rate capability of porous ZnMn2O4 nanospheres than ZnMn2O4 microparticles.