Pre-heat treatment of carbonate precursor firstly in nitrogen and then oxygen atmospheres: A new procedure to improve tap density of high-performance cathode material Li1.167(Ni0.139Co0.139Mn0.556)O2 for lithium ion batteries

In order to increase the tap density of Li-rich layered materials, a new pre-heat treatment procedure of (Ni1/6Co1/6Mn4/6)CO3 precursors firstly using N-2 and then O-2 is adopted to separate processes of CO2 emission and O-2 absorption, which presumably can reduce porosity of materials and then result in an improved tap density. In contrast to one-step pre-heat treatment procedure only in O-2, two-steps procedure causes differences in morphology, tap density, particle distribution as well as structure for resultant metal oxides. A remarkably improved tap density of metal oxide with dense particles is observed with two-steps procedure. Consequently, Li-1.167(Ni0.139Co0.139Mn0.556)O-2 obtained through two-steps procedure (LM-N) presents dense particle, much improved tap density, small BET specific surface area and additional existence of Ni3+ in comparison with that obtained through one-step procedure (LM-O), although both samples exhibit similar well-defined layered structure. However, the results of cyclic voltammograms and charge discharge test demonstrate the inferior electrochemical performances of LM-N with a discharge capacity of 76.7 mAh g(-1) for LM-N, which is in stark contrast with 267.9 mAh g(-1) of LM-O. This is possibly associated with the dense morphology, lattice defect as well as large R-ct for LM-N. (C) 2015 Elsevier B.V. All rights reserved.