Polyethylene glycol-assisted synthesis of hierarchically porous layered lithium-rich oxide as cathode of lithium ion battery

A hierarchically porous layered lithium-rich oxide, 0.5Li(2)MnO(3)center dot 0.5LiMn(1/3)Ni(1/3)Co(1/3)O(2), is synthesized by co-precipitation of metal oxalates with an assistance of a moderate polyethylene glycol (PEG2000). The morphology and crystal structure of the product are characterized by scanning electron microscope, transmission electron microscopy and X-ray diffraction, and its performance as cathode of lithium ion battery is evaluated with charge/discharge tests. It is found that the as-synthesized oxide exhibits excellent rate capability and cyclic stability: delivering an initial discharge capacity of 262 mAh g(-1) at 0.1C (1C = 250 mA g(-1)) and 135 mAh g(-1) at 4C, and possessing a capacity retention of 83% after 200 cycles at 4C. These performances can be attributed to the unique structure of the as-synthesized oxide: uniform secondary microspheres of about 10 mu m, which is composed of uniform primary microparticles of about 2 mu m, and hierarchically porous structure with pores distributed among primary and secondary particles. The hierarchically porous structure provides large reaction sites for lithium ion insertion/extraction and large space to buffer the volume change during cycling, leading to the excellent rate capability and cyclic stability of the as-synthesized oxide. (C) 2015 Elsevier B.V. All rights reserved.