Porous LiMn2O4 microspheres as durable high power cathode materials for lithium ion batteries

Abstract

Porous LiMn₂O₄ microspheres, which are constructed with nanometer-sized primary particles, have been synthesized by a facile method using porous MnCO₃ microspheres as a self-supporting template. The LiMn₂O₄ microspheres were characterized by XRD, SEM and HR-TEM. The as-synthesized porous LiMn₂O₄ microspheres exhibit high rate capability and long-term cyclability as cathode materials for lithium ion batteries, with the specific discharge capacity of 119, 107 and 98 mA h g⁻¹ and the corresponding capacity retention of 82, 91 and 80% for up to 500 cycles at 2, 10 and 20 C, respectively. The high rate performance and good cyclability are believed to result from the porous structure, reasonable primary particle size and high crystallinity of the obtained material, which favor fast Li intercalation/deintercalation kinetics by allowing electrolyte insertion through the nanoparticles and high structural stability during the reversible electrochemical process. The high level of Mn⁴⁺ concentration on the surface of the sample can alleviate the Jahn–Teller transition, which was triggered normally by the equal amounts of Mn⁴⁺/Mn³⁺ concentration on the surface of the LiMn₂O₄ cathode material. This good example offering extended cycle life at 20 C rate for the LiMn₂O₄ microspheres indicates their promising application as cathode materials for high performance LIBs.