Sodium additive to improve rate performance of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 material for Li-ion batteries

•Sodium additive induced a dispersed secondary phase with structure of Na0.7MnO2.05.•The two-phase composite showed improved rate performance.•Sodium additive enhanced electrical conductivity and lithium ionic conductivity.•The sodium in the Na0.7MO2.05 can be activated for the transportation of Li+.

The effects of sodium additive on the microstructure and electrochemical properties of Li[Li0.2Mn0.54Ni0.13Co0.13]O2-based material have been investigated. XRD patterns show that the sodium additive doesn't incorporate into the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 lattice, but induces a dispersed secondary phase with the structure of Na0.7MnO2.05. The two-phase composite shows an improved rate performance in comparison with the single phase of Li[Li0.2Mn0.54Ni0.13Co0.13]O2, which can be attributed to the enhanced electrical conductivity and lithium ion diffusion. The interfaces between Li[Li0.2Mn0.54Ni0.13Co0.13]O2 and the secondary phase provide fast diffusion paths for Li+. DC electrical conductivity and EIS are used to elucidate the phenomenon.