Colloidally Assisted Synthesis to Phase Pure Na0.43Ni0.25Mn0.75O1.9 with Suppressed P2/O2 Phase Transition As High Stable Cathode for Na-Ion Batteries.

Wednesday, 31 May 2017
Grand Ballroom (Hilton New Orleans Riverside)
L. Chen, S. Monaco, S. Marras, G. Bertoni (Istituto Italiano di Tecnologia), F. Palazon (istituto italiano di tecnologia), and L. Manna (Italian Institute of Technology)
P2-Na2/3[NixMny]O2-based cathode materials are promising candidates for Na-ion batteries. The cycling performance of these cathodes was usually reported to drop at working voltages over 4.2 V, due to the P2/O2 irreversible phase transition. Here we demonstrate a colloidally assisted two-step synthesis to phase pure P2-Na0.43Ni0.25Mn0.75O1.9. The adopted synthetic route and the chosen Na:Ni:Mn ratio (0.43:0.25:0.75) leads to a cathode material that can withstand long charge/discharge cycles at working voltages up to 4.4 V. The XRD pattern recorded on the de-sodiated electrode (4.4 V) does not evidence the presence of any peak related to the O2 phase, corroborating the effective suppression of the P2/O2 phase transition upon Na+ intercalation/deintercalation. The discharge capacity delivered at relatively low current (C/10) is 109 mAh g-1, with a capacity retention exceeding the 93% in 20 cycles. At the high current of 1C the delivered discharge capacity is 94 mAh g-1.