Improved electrochemical performances of nanocrystalline Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode material for Li-ion batteries

Abstract

Layered Li[Li_0.2Co_0.13Ni_0.13Mn_0.54]O₂ nanoparticles were synthesized by a simple polymer-pyrolysis method and then coated with 3 wt% Al₂O₃ to form a ∼4 nm thick protective skin. The Al₂O₃-coated Li[Li_0.2Co_0.13Ni_0.13Mn_0.54]O₂ electrode demonstrates a high initial coulombic efficiency of 96.1%, a large reversible capacity of ∼311 mAh g⁻¹, and a good cyclability with 83.8% capacity retention after 70 cycles. Particularly, this material can deliver a quite high capacity of ∼239 mAh g⁻¹ at a high rate of 400 mA g⁻¹. This superior electrochemical performance results from the well-crystallized nanocores and effective surface modification of the material. The former provides a short diffusion path and fast transport channels for lithium ion insertion/extraction reactions and the latter restrains the elimination of oxide ion vacancies and metal ion rearrangement during charge–discharge cycling. Due to their simplicity and applicability, the synthetic method along with the surface modification technique is easily adopted to make high performance xLi₂MnO₃·(1 − x)LiMO₂ materials for practical battery applications.