FeF3·0.33H2O@carbon nanosheets with honeycomb architectures for high-capacity lithium-ion cathode storage by enhanced pseudocapacitance

Abstract

There is an increasing demand for current and future applications to obtain charge storage devices with both energy and power superiority. Recently, several high-rate pseudocapacitive anode materials for Li-ion batteries have been reported; however, the research on the pseudocapacitive properties of cathode materials is much less common. Herein, an FeF₃·0.33H₂O@CNS (carbon nanosheet) composite, where ultrafine FeF₃·0.33H₂O particles are intimately embedded into nitrogen-doped carbon nanosheets, was successfully designed and fabricated. The pseudocapacitive effect of the composite cathode was demonstrated and explored by its Li⁺ storage kinetic analysis. The results demonstrated that the FeF₃·0.33H₂O@CNS cathode with a higher capacitance distribution rate than bare FeF₃·0.33H₂O provides higher rate performance with discharge capacities of 235, 175, and 143 mA h g⁻¹ at 0.1C, 1C, and 5C, respectively. It also displayed an excellent cycle performance (capacity retention of 97.2% at 1C after 200 cycles). FeF₃·0.33H₂O@CNS//LCNS full cells combined with pre-lithiated carbon nanosheets (LCNSs) also exhibit excellent electrochemical performance. Therefore, the electrochemical performance of cathode materials can be improved by adjusting their pseudocapacitive contribution, which represents a promising and effective strategy for obtaining electrode materials with high energy and high-power densities.