Vacant Manganese-Based Perovskite Fluorides@Reduced Graphene Oxides for Na-ion Storage with Pseudocapacitive Conversion/Insertion Dual Mechanisms.

Na-ion capacitors (NICs) and Na-ion-based dual-ion batteries (Na-DIBs) have been considered to be promising alternatives to traditional lithium-ion batteries (LIBs) because of Na-ion abundance and low cost, but their energy density, power density and cycle life are limited. Herein, d ual vacancies (including K + and F - vacancies) perovskite fluoride K 0.86 MnF 2.69 @ reduced graphene oxide (rGO) (recorded as Mn-G) as anode for NICs and Na-DIBs have been developed. The special conversion/intercalation dual Na-ion energy storage mechanism and pseudocapacitive dynamics are analyzed in detail. The Mn-G//AC NICs and Mn-G//KS6 Na-DIBs delivered a maximum energy density of 92.7 Wh kg -1 and 187.6 Wh kg -1 , maximum power density of 20.2 kW kg -1 and 21.12 kW kg -1 , and long cycle performance of 61.3% and 68.4% after 1000 cycles at 5 A g -1 , respectively. Moreover, Mn-G//AC NICs and Mn-G//KS6 Na-DIBs can work well in a wide range of temperatures (-20-40 °C). This result makes it competitive in Na-ion storage applications with high energy/power density in a wide temperature range.