Na2.3Cu1.1Mn2O7−δ nanoflakes as enhanced cathode materials for high-energy sodium-ion batteries achieved by a rapid pyrosynthesis approach

Abstract

Sodium-ion batteries (SIBs) are among the plethora of energy storage devices (ESDs) developed by researchers in the lithium-ion battery (LIB) era of the modern electronic world. Regardless of whether SIBs can replace LIBs or not in the electric vehicle (EV) market, SIBs have undoubtedly brought about a much-needed balance to the world, where large-scale ESDs can be utilized to store electricity. Though exploitation of layered oxide cathode materials for SIBs has had a major impact, upon repeated sodium (de)intercalation, phase transition and volume expansion of these materials have been the major limitations to the realization of SIBs as mainstream ESDs. Notably, the recent development of phase transition-free, layered copper-doped sodium manganese oxide Na2.3Cu1.1Mn2O7−δ (NCuMnO) as a cathode material has helped to overcome the major limitation of sodium layered oxide materials. In the present study, we prepared NCuMnO nanoflakes by an ultrafast pyrosynthesis process and utilized them for the fabrication of SIBs. The ex situ XANES, in situ X-ray diffraction and galvanostatic intermittent titration technique results revealed the occurrence of a highly reversible electrochemical process at the NCuMnO cathode. With the novel material, superior average discharge capacities of 127 mA h g−1 and 79.24 mA h g−1 at rates of 0.2C and 20C, respectively were achieved, which were attributed to fast sodium-ion diffusion, and an exceptionally high specific energy of 457.2 W h kg−1 at a specific power of 72 W h kg−1 were achieved.