Enhancement of Electrochemical Properties of SIBs by Generating a New Phase in Potassium-Doped NaV6O15 Film Electrodes

Potassium-doped NaV6O15thinfilms have beengrown onfluorine-doped tin oxide (FTO) conductive glass using asimple low-temperature liquid-phase deposition method andthrough the annealing process. X-ray photoelectron spectroscopyrevealed that potassium ions were successfully doped in NaV6O15thinfilms. The kinetics analysis based on cyclic voltammetrymeasurements showed that the doped potassium ions enhancedthe Na+intercalation behavior and induced the formation of a newphase. Moreover, high-resolution transmission electron microscopyfurther verified the formation of the new phase. The annealeddopedfilms exhibited excellent structural stability during cycling.With these benefits, the capacities of thefilm electrodes annealedat 400 and 450 degrees C were maintained to be 83.24 and 188.16% after 100 cycles, respectively. The surprising capacity growth of thedopedfilm annealed at 450 degrees C can be attributed to the phase transition from NaV6O15to NaV3O8. The discharge-charges profilesfurther showed that the capacityfirst increased and then decreased during the charging/discharging process. Also, thechronoamperometry curve test revealed that the Na+transference number of the NaClO4/PC electrolyte was 0.077. Due to thesynergistic effect of NaV3O8and NaV6O15, thefilm showed capacity growth instead of capacity fading. It is the doped potassium ionsthat prevent the structural collapse, ensuring that the phase transition can be smoothly carried out during the cycles. Our researchpresents an effective way for improving electrode materials with a long cycle life.

Automated summary

Potassium-doped NaV6O15 thin films were grown on fluorine-doped tin oxide (FTO) conductive glass using a simple low-temperature liquid-phase deposition method and annealing process. The doped potassium ions enhanced the Na+ intercalation behavior and induced the formation of a new phase, resulting in improved structural stability and capacity growth of the films.