Two-step oxalate approach for the preparation of high performance LiNi_(0.5)Mn_(1.5)O_4 cathode material with high voltage

摘要

A high voltage cathode material, LiNi_(0.5)Mn_(1.5)O_4, is synthesized with a two-step approach, in which the nickel-manganese oxalate precipitate is firstly obtained by adding oxalic acid to the solution of nickel and manganese ions precursors, followed by calcining the oxalates to obtain spinel nickel-manganese oxide, incorporating lithium ions with ball milling and calcining at 900 C for 15 h. The materials are characterized with TG, XRD, SEM, BET and FTIR; it is revealed that both nickel -manganese oxide and final LiNi_(0.5)Mn_(1.5)O_4 have well defined spinel structure. The LiNi_(0.5)Mn_(1.5)O_4 spinel materials exhibit high capacities and good cyclic stability, the capacity of the materials is in the range from 126 to 136 mAh~(-1), depending on the calcining temperatures. The sample calcined at an optimal temperature of 900℃ exhibits best performance, the capacity is high up to 136 mAh g~(-1) at tenth cycle and the capacity retention after 50 cycles is 93%. For the sample prepared by mixing and milling oxalate with lithium salt, the discharge capacity is only 115 mAh g~(-1). We suggest that the spinel oxide derived from oxalate may play an important role for the high performance and high stability of the final cathode materials.