To realize the large-scale application of energy storage batteries by reducing costs, it is very important and necessary to find an ideal cathode for alkali metal ion batteries (MIBs). Iron is a common, low-cost, and resource-rich element in nature. The development of iron-based fluorides and phosphates as battery cathode materials has attracted more and more researchers’ great interest due to their high theoretical specific capacity, high working potential, low costs, and environmental friendliness. In this paper, the application of FeF3·0.33H2O@C and FePO4 as cathodes for Li-ion and Na-ion batteries is investigated in detail.First part, the demand for energy storage applications in today's world is increasing, and obtaining charge storage devices with both energy and power advantages is the focus of energy materials research. Recently, compared with the research on pseudocapacitive anode materials, the research on pseudocapacitive cathode materials is rare. Herein, FeF3·0.33H2O@CNS (carbon nanosheets) composites were successfully prepared by solid-phase fluorination, in which nitrogen-doped carbon nanosheets tightly encapsulated ultrafine FeF3·0.33H2O particles. The pseudocapacitive properties of as-prepared FeF3·0.33H2O@CNS cathode are verified by the analysis of the Li+ storage kinetics of the electrode material, and the results show that the FeF3·0.33H2O@CNS cathode has a higher capacitance distribution than bare FeF3·0.33H2O cathode, resulting in higher rate capability and excellent cycling performance (capacity retention at 1C after 200 cycles of 97.2%). The excellent performance of FeF3·0.33H2O@CNS//LCNS full cells also shows its excellent application feasibility. In short, improving the electrochemical performance of cathode materials by tuning their pseudocapacitive contributions is an effective means to modify electrode materials, and this strategy will obtain ideal electrode materials with high energy and high power density.Second part, compared with the intercalation-reaction cathode materials, iron fluoride based on the conversion reaction is an excellent cathode material with high working voltage and ultra-high specific discharge capacity in alkali- MIBs. However, the iron fluoride material has the disadvantages of poor electrical conductivity, sluggish electrochemical kinetics and electrode pulverization and dissolution. A pomegranate-structured FeF3·0.33H2O@carbon nanocomposite (FeF3·0.33H2O@C) was successfully synthesized by hydrothermal synthesis and in situ solid-phase synthesis. Pomegranate-structured FeF3·0.33H2O@C cathodes can effectively reduce electrode polarization due to the unique hierarchical carbon coating structure, plus other structural advantages (coordinated volume expansion, reduced Fe dissolution, inhibited nanoparticle coarsening), the composite can obtain good reversibility and excellent battery rate performance. The FeF3·0.33H2O@C electrode achieved a capacity retention rate of 93% after 200 cycles in Li-ion battery tests. And the FeF3·0.33H2O@C electrode in SIBs achieved an ultra-high energy density of 1015 Wh kg-1. Third part, uniform amorphous FePO4 nanospheres were successfully synthesized by a simple one-step hydrothermal synthesis method. The SEM pictures show that the samples are uniform nanospheres with a diameter of 255 nm. X-ray diffraction (XRD) data confirmed the sample to be an amorphous structure. The data of XRD, energy spectrum analysis, and XPS analysis after the amorphous material annealing confirmed the nature of the sample as FePO4. The necessity of amorphous FePO4 cathodes as a replacement for olivine NaFePO4 cathodes was analyzed by the crystal phase structure diagram. The ex-situ XRD results at different charge-discharge potentials confirmed the transition between amorphous FePO4 and microcrystalline structures. The amorphous FePO4 cathodes achieves a reversible capacity of 152.5 mAh g-1 close to the theoretical specific capacity at low current density. Furthermore, the amorphous FePO4 cathodes exhibited excellent stable cycling performance after 200 cycles at a current density of 20 mA g-1. Therefore, amorphous FePO4 may be an ideal cathode material for a feasible and low-cost high-performance Na-ion battery.In summary, low-cost and environmentally friendly iron-based fluoride and iron-based phosphate cathode materials were successfully synthesized and studied, they both obtained excellent electrochemical performance in battery tests and showed good application feasibility. These studies will open up new avenues for large-scale commercial applications of energy storage batteries