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

Abstract LiAl x Mn 2− x O 4 has been synthesized using various aluminum starting materials, such as Al(NO 3 ) 3 , Al(OH) 3 , AlF 3 and Al 2 O 3 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 Mn 3+ ion by Al substitution induces a high average oxidation state of Mn ion in the LiAl x Mn 2− x O 4 material. The electrochemical behavior of all samples was studied in Li/LiPF 6 -EC/DMC (1:2 by volume)/LiAl x Mn 2− x O 4 cells. Especially, the initial and last discharge capacity of LiAl 0.09 Mn 1.97 O 4 using LiOH, Mn 3 O 4 and Al(OH) 3 complex were 128.7 and 115.5 mAh/g after 100 cycles. The Al substitution in LiMn 2 O 4 was an excellent method of enhancing the cycleability of stoichiometric spinel during electrochemical cycling.