Partic. vol. 24 pp. 87-95 (February 2016)
doi: 10.1016/j.partic.2015.03.003

Effects of multi-dopants (Zn and Ho) in stabilizing spinel structure for cathode materials in lithium rechargeable batteries—Novel chelated sol–gel synthesis

R. Thirunakaran^a,*, Taewhan Kim^b, Won-Sub Yoon^b,*

rthirunakaran@yahoo.comwsyoon@skku.edu

Abstract

Multi-doped spinels, namely LiMn₂O₄ and LiZn_xHo_yMn_2-x-yO₄ (x = 0.10–0.18; x = 0.02–0.10), for use as cathode materials for lithium-ion rechargeable batteries were synthesized via sol–gel method, using lauric acid as the chelating agent, to obtain micron-sized particles. The physical properties of the synthesized samples were investigated using differential thermal analysis, Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, energy-dispersive X-ray analysis, and electrochemical methods. XRD showed that LiMn₂O₄ and LiZn_xHo_yMn_2-x-yO₄ have high degrees of crystallinity and good phase purities. The SEM images of LiMn₂O₄ showed an ice-cube morphology with particles of size 1 μm. Charge–discharge studies showed that undoped LiMn₂O₄ delivered the discharge capacity of 124 mA h/g with coulombic efficiency of 95% during the first cycle, whereas doped spinels delivered discharge capacities of 125, 120, and 127 mA h/g in the first cycle with coulombic efficiencies of 96%, 91%, and 91%, respectively.

Graphical abstract

Keywords

Holmium; Zinc; Lauric acid; Sol–gel; Spinel cathode; Lithium-ion battery