Enhancement of LiNi 0.5 Mn 1.5 O 4 Cathode Materials through Interfacial Modification of Amorphous Al 2 O 3 in Lithium Ion Batteries

Abstract

Metal oxide modification can improve the electrochemical stability of cathodes and the cycle-life and rate capacity of rechargeable lithium ion batteries. Spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) has been considered as a promising cathode material for its high operating potential and high energy density. In this work, amorphous nano-Al 2 O 3 with different thicknesses were applied to modify the surface of LNMO. Results of structure and surface analysis showed that the nano-Al 2 O 3 film uniformly distributed on the surface of LNMO material without changing the crystal structure of the material. The electrochemical performances revealed that the capacity decay of bare LNMO materials focused on the first 50 cycles under room and elevated temperatures. It is essential to enhance the electrochemical performances of first 50 cycles. The capacity retention of the first 50 cycles was enhanced by the man made Al 2 O 3 interface between active LNMO and electrolyte. The as-prepared surface modified LNMO material with the amount of Al 2 O 3 at 1.77% exhibited superior rate and cycling performances under the room temperature even at elevated temperature. It also showed that the interfacial effect mechanism on the enhancement of LNMO performances is significantly important during the initial charging process (0%-20% SOC). In contrast to the impedance increasing with the SOC in the bare LNMO batteries, the resistance decreased dramatically in the first 20% SOC and almost kept constant during the following charging process. Both of the interface resistance between the cathode and electrolyte and charge transfer impedance were reduced, and the diffusion rate of lithium ion were improved.