Robust 3.7 V-Na2/3[Cu1/3Mn2/3]O2 Cathode for Na-ion Batteries

Na-ion batteries (NIBs) have emerged as a promising technology for energy storage, yet their commercialization is hindered by the scarcity of effective and economical cathode materials. This study addresses this challenge through the re-synthesis of the P2-Na2/3[Cu1/3Mn2/3]O2 cathode material, previously underestimated in its Cu3+/Cu2+ electrochemical potential. We demonstrate that this new cathode exhibits a remarkable operating voltage of 3.7 V alongside a fully active Cu 3+/Cu2+ redox mechanism. Comprehensive testing reveals that 2.3 Ah cylindrical cells of the cathode maintain 93.1% capacity retention after 2000 cycles and achieve impressive rate capabilities with 97.2% capacity at a 10C rate. Furthermore, it maintains good performance at low temperatures (86.6% capacity at -30° C) and ensures high safety standards. Consequently, a 56 V-11.5 Ah battery pack for electric bikes was constructed, yielding stable performance with 96.5% capacity retention at the 800th cycle over a driving distance of 36 km. This research offers a viable cathode solution for economically feasible, high-voltage NIBs, significantly contributing to the advancement of the technology in both power and stationary energy storage applications.