Trace Nb-doped Na_(0.7)Ni_(0.3)Co_(0.1)Mn_(0.6)O_(2) with suppressed voltage decay and enhanced low temperature performance

摘要

The P2-type manganese-based Na_(0.7)MnO_(2) cathode materials attract great interest due to their high theoretical capacity.However,these materials suffer from rapid capacity fading,poor rate performance and severe voltage decay resulting from phase transition and sluggish reaction kinetics.In this work we report a novel Nb-doped Na_(0.7)[Ni_(0.3)Co_(0.1)Mn_(0.6)]_(1-x)Nb_(x)O_(2) with significantly suppre ssed voltage decay and enhanced cycling stability.The strong Nb-O bond can efficiently stabilize the TMO fra mework,and the as prepared material demonstrates much lower discharge midpoint voltage decay(0.132 V) than that of pristine one(0.319 V) after 200 cycles.Consequently,a remarkably improved cycling perfo rmance with a capacity retention of 87.9% after 200 cycle at 0.5 C is achieved,showing a 2.4 fold improvement as compared to the control sample Na_(0.7)Ni_(0.3)Co_(0.1)Mn_(0.6)O_(2)(~37% rotation).Even at 2 C,a capacity retention of 68.4% is retained after 500 cycles.Remarkably,the as prepared material can be applied at low temperature of-20℃,showing a capacity retention of 81% as compared to that at room temperature.