The enhancement of rate and cycle performance of LiMn2O4 at elevated temperatures by the synergistic roles of porous structure and dual-cation doping

Spinel - LiMn2O4- based cathode material has been successfully commercialized for power lithium ion batteries for largescale applications in pure electric vehicles. However, pure - LiMn2O4 suffers from poor rate performance and fast capacity fading especially at elevated temperatures derived from Mn dissolution and structural distortion. Herein, a study on the rate and cycle performance of single/double- cation doped porous - LiMn2O4 microspheres, which was prepared by an easy method using porous - MnCO3 microspheres as a self- supporting template, was performed. The as- synthesized porous - Li1.02Co0.05Mn1.90Li0.05O4 ( LMO- S4) microspheres constructed with nanometer- sized primary particles show an obvious enhancement of cyclability over other - LiMn2O4- based materials such as - Li1.02Mn2O4 ( LMO- S1), - Li1.02Mn1.95Li0.05O4 ( LMOS2) and - Li1.02Co0.05Mn1.95O4 ( LMO- S3), especially at an elevated temperature ( 55 degrees C). The obtained LMO- S4/lithium half cells deliver capacities of 113.1 and 109.0 mAh g- 1 at 1.0 and 5 C, respectively, with the corresponding capacity retentions of 88.9 and 90.2% for up to 1000 cycles. Meanwhile, it can deliver an initial capacity of 114.0 mAh g- 1 at 5 C with a capacity retention of 80.1% after 1000 cycles at 55 degrees C. Furthermore, it displays superior rate performance and cycle performance at 0 degrees C with a specific capacity of 106 mAh g- 1, and the capacity retention is 79.6% after 1000 cycles at 5 C. These results reveal that a dual- doping strategy and porous structure design play synergistic roles in the preparation of high performance - LiMn2O4- based spinel cathode material. The cation co- doped strategy can maintain the crystal structural stability and provide interfacial stability while preserving fast - Li+ diffusion during the long- time cycling at elevated temperatures. Furthermore, the porous structure favors fast - Li+ intercalation/deintercalation kinetics by allowing electrolyte insertion through the nanoparticles during the reversible electrochemical process.