Al substituted Mn position on Li[Ni0.5Co0.2Mn0.3]O2 for high rates performance of cathode material

Abstract Li[Ni0.5Co0.2Mn0.3-xAlx]O2 cathode materials were successfully synthesized via a facile ball milling method. XRD refinement analysis proves that Al element is favourably substituted the position of Mn in the transition metal layer and solidly restrains the cationic mixing. After 150 cycles at 10 C, compared with NCM whose discharge capacity loss is 56.3 mAhg−1, Li[Ni0.5Co0.2Mn0.275Al0.025]O2 (NCM-25) loses only 32.9 mAhg−1. Even at higher 15 C, NCM-25 still delivers the highest initial discharge capacity of 97.8 mAhg−1, and exhibits prominent capacity retention than NCM after 300 cycles. EIS measurement suggests NCM-25 has 3.24 × 10−8 cm2 s−1 of the coefficient lithium ion and 0.32395 mA cm−2 of the exchange current density after cycling, which indicates that Rct is validly restrained and alleviates the degree of polarization. After cycling, XRD and XPS results indicate Al-doped furnishes surface protection avoiding the electrolyte corrosion and restrains the formation of oxygen species in the process of lithiation/delithiation. Electrochemical tests suggest Al-doped samples have appealing improvements in cycling at high rates.