Effect of Aluminum Substitution on the Structure, Electrochemical Performance and Thermal Stability of Li1+x(Ni0.40Mn0.40Co0.20−zAlz)1−xO2

"Li 1.04 (Ni 0.40 Mn 0.40 Co 0.20−z Al z ) 0.96 O 2 " (z = 0; 0.05 and 0.10) samples were synthesized using a coprecipitation method followed by calcinations at 500°C for 5 h and then at 950°C for 2 h. Structural and physico-chemical characterizations have shown that these materials were obtained pure with a small overlithiation ratio (Li/M = 1.01–1.03) and thus a significant exchange between the divalent nickel ions from the slabs and the lithium ions from the interslab spaces (between 4% for the non substituted material and 8% for the aluminum substituted ones). Aluminum substitution induces a decrease of the reversible capacity, but also a major improvement of the thermal stability in the deintercalated state (corresponding to the charge state of the battery). These results have thus shown that the composition Li 1.01 (Ni 0.39 Mn 0.40 Co 0.15 Al 0.06 ) 0.99 O 2 is very attractive for large scale lithium-ion batteries to be developed for EV and HEV applications.