Designing a pseudocapacitive binary Zn/Mn perovskite fluoride anode with a conversion/alloying/insertion hybrid mechanism for advanced Na-ion capacitors and Na-based dual ion batteries

Abstract

Na-ion capacitors (NICs) and Na-based dual ion batteries (Na-DIBs) have received intensive attention due to their high energy density, high power density, and long cycle life and the low cost of sodium. Hence, a novel perovskite KZMF(3-1)@rGO nanocrystal used as the sodium-storage anode is coupled with an activated carbon (AC) cathode and a graphite (KS6) cathode to construct NICs and Na-DIBs, respectively. The KZMF(3-1)@rGO electrode with a superconducting carbon black (SP) conductive agent and 0.85 M NaPF₆/EC : DEC : EMC(1 : 1 : 1)/5% FEC electrolyte delivers high capacity (114 mAh g⁻¹/0.05 A g⁻¹) and ultralong cycling performance (75%/500/0.3 A g⁻¹). The constructed KZMF(3-1)@rGO//AC NICs and KZMF(3-1)@rGO//KS6 Na-DIBs even demonstrated excellent energy/power densities (73.2–33.4 Wh kg⁻¹/0.54–17.2 kW kg⁻¹, 200.2–22.9 Wh kg⁻¹/0.98–23.5 kW kg⁻¹) and cycle life (68%/1000/5 A g⁻¹, 61%/1000/5 A g⁻¹). Furthermore, this paper verifies the hybrid conversion/alloying/insertion reaction mechanism of the KZMF(3-1)@rGO anode by electrochemical analysis and ex situ characterization, which provides new insights and ideas for the future development of new anode materials.