Synthesis and characterization of lithium aluminum-doped spinel (LiAlxMn2−xO4) for lithium secondary battery

LiAlxMn2−xO4 has been synthesized using various aluminum starting materials, such as Al(NO3)3, Al(OH)3, AlF3 and Al2O3 at 600–800°C for 20 h in air or oxygen atmosphere. A melt-impregnation method was used to synthesize Al-doped spinel with good battery performance in this research. The Al-doped content and the intensity ratio of (3 1 1)/(4 0 0) peaks can be important parameters in synthesizing Al-doped spinel which satisfies the requirements of high discharge capacity and good cycleability at the same time. The decrease in Mn3+ ion by Al substitution induces a high average oxidation state of Mn ion in the LiAlxMn2−xO4 material. The electrochemical behavior of all samples was studied in Li/LiPF6-EC/DMC (1:2 by volume)/LiAlxMn2−xO4 cells. Especially, the initial and last discharge capacity of LiAl0.09Mn1.97O4 using LiOH, Mn3O4 and Al(OH)3 complex were 128.7 and 115.5 mAh/g after 100 cycles. The Al substitution in LiMn2O4 was an excellent method of enhancing the cycleability of stoichiometric spinel during electrochemical cycling.