Thursday, 23 June 2016
Riverside Center (Hyatt Regency)
Li-rich cathode materials with the general formula Li1+xM1-xO2 (M = Mn, Ni, Co; x <= 0.2) are very promising cathode materials for lithium ion batteries, particularly due to their significantly higher specific capacity (>200 mAh g-1) compared to state of the art cathode materials.[1] Popular members of the Li‑rich family, like Li1.2Mn0.56Ni0.16Co0.08O2 [2] and the Co-free compound Li1.2Mn0.6Ni0.2O2 have already been structurally and electrochemically investigated, but mostly on laboratory scale. Thus, in order to obtain larger amounts of high-quality Li-rich cathode materials, the upscaling effects of the established co-precipitation synthesis route were thoroughly investigated in this work, specifically for the above mentioned stoichiometries. With regard to the upscaling process, the impact of the synthesis parameters (e.g. stirring speed and type, pH value, reaction time) on the resulting morphology of the precursor as well as that of the final oxide and consequently, its electrochemical performance was analyzed. For each material three differently sized batches were synthesized, one in a laboratory scale of 4 g and two larger batches up to 75 g.
For the Co-free materials a significant upscaling effect was observed (see Fig. 1): The faster stirring of the larger batches lead to larger, spherically shaped precursor particles. However, these large precursor particles form more inhomogeneous target materials upon calcination, which consequently resulted in an inferior electrochemical performance. The more homogeneous cathode particles of the small batches show very promising electrochemical properties with regard to both rate capability and capacity retention.
For the Co-free materials a significant upscaling effect was observed (see Fig. 1): The faster stirring of the larger batches lead to larger, spherically shaped precursor particles. However, these large precursor particles form more inhomogeneous target materials upon calcination, which consequently resulted in an inferior electrochemical performance. The more homogeneous cathode particles of the small batches show very promising electrochemical properties with regard to both rate capability and capacity retention.
References:
[1] M.M.Thackeray, S.-H. Kang, C.S. Johnson, J.T. Vaughey, R. Benedek, S.A. Hackney, Journal of Materials Chemistry, 17 (2007) 3112-3125.
[2] J. Li, R. Klöpsch, S. Nowak, M. Kunze, M. Winter, S. Passerini, Journal of Power Sources, 196 (2011) 4821-4825.