Trace Nb-doped Na0.7Ni0.3Co0.1Mn0.6O2 with suppressed voltage decay and enhanced low temperature performance

The P2-type manganese-based Na0.7MnO2 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 Na0.7[Ni0.3Co0.1Mn0.6]1-xNbxO2 with significantly suppressed voltage decay and enhanced cycling stability. The strong Nb-O bond can efficiently stabilize the TMO framework, 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 performance 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 Na0.7Ni0.3Co0.1Mn0.6O2 (∼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 °C, showing a capacity retention of 81% as compared to that at room temperature.