Polymer-chelation synthesis of compositionally homogeneous LiNi1/3Co1/3Mn1/3O2 crystals for lithium-ion cathode

Submicrometer-sized LiNi1/3Co1/3Mn1/3O2 (NCM111) crystals with homogeneous composition are prepared via a polymer-chelation chemical solution process. The complexed chelate agents of ethylenediaminetetraacetic acid (EDTA) and polyethyleneimine (PEI) could chelate all metal ions in one step, with intimate mixing at the atomic level, ensuring a homogeneous ion distribution in the product. The as-prepared NCM111 crystals have a narrow particle size distribution with an average size of 250 nm, which can effectively shorten the lithium ion diffusion path. In addition, the NCM111 crystals majorly consist of electrochemically active {010} facets and low Li+/Ni2+ cation mixing, thus delivering a high reversible discharge capacity of 156.1 mAh g−1 after 100th cycles and good rate capability of 102.7 mAh g−1 at 10 C. Furthermore, it is found that the induction of excess Li could deteriorate the rate capability and increase the Li+ solid-state diffusion resistance. However, Al3+ doping could effectively improve the cycling performance, while Nb5+ doping could increase significantly the discharge capacity as well as rate capability. Owing to the flexibility of the chelating chemistry, the synthesis should be extended to prepare other multicomponent single-crystal cathodes with homogeneous composition and desired substation.