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

Abstract Porous ZnMn 2 O 4 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 ZnMn 2 O 4 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 ZnMn 2 O 4 nanospheres consisting of smaller primary nanoparticles can be successfully obtained, which exhibit far better rate capability and cyclic stability than ZnMn 2 O 4 microparticles. The porous ZnMn 2 O 4 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 ZnMn 2 O 4 microparticles, respectively. The space in the porous structure of ZnMn 2 O 4 nanospheres buffers the mechanical strain induced by the volume change during cycling, which causes destruction of ZnMn 2 O 4 microparticle, resulting in the excellent cyclic stability. Moreover, the primary nanoparticles in ZnMn 2 O 4 nanospheres reduce the path of lithium ion transportation and increase reaction sites for lithium intercalation/deintercalation, leading to the better rate capability of porous ZnMn 2 O 4 nanospheres than ZnMn 2 O 4 microparticles.