A Stoichiometric Nano-LiMn2O4 Spinel Electrode Exhibiting High Power and Stable Cycling

Abstract

Stoichiometric LiMn 2 O 4 has been synthesized using a one-pot resorcinol−formaldehyde route. The resulting material is composed of nanoparticles fused together, thus forming a porous morphology. The material when used as a cathode in a lithium battery exhibits, at 30 °C, an initial capacity of 131 mA·h g −1 retaining a capacity of 118 mA·h g −1 after 200 cycles (99.95% capacity retention per cycle) and at 50 °C an initial capacity of 132 mA·h g −1 retaining 110 mA·h g −1 after 200 cycles (99.92% capacity retention per cycle) all at a rate of C /2 (where 1 C = 148 mA g −1 ), with no evidence of structural degradation. Rate capability is demonstrated by retention of 90% of the capacity at a rate of 40 C compared with the capacity at C /5 rate. Cycling at a rate of 10 C is associated with nearly 100% power retention after 1000 cycles (initial value of 5840 W kg −1 (of LiMn 2 O 4 ) dropping to 5828 W kg −1 after 1000 cycles). Differences in the capacity retention on cycling between the material reported here and conventionally synthesized bulk LiMn 2 O 4 or nanoparticle LiMn 2 O 4 synthesized by a different sol−gel route also yielding interconnected nanoparticles are reflected in superior structural stability, lower Mn dissolution, and relatively invariant ac impedance of our nano-LiMn 2 O 4 . Such results suggest that the material prepared using the resorcinol−formaldehyde route may possess a stabilized surface that inhibits dissolution.