Fig. 4: Crystal structure evolution of NVOPF/8%KB cathode.

a The charge–discharge curves of NVOPF/8%KB at a current rate of 0.1C in in situ XRD experiment. b The in situ XRD patterns. c The variation of cell parameters during the charging process. d High-resolution 23Na SSNMR spectra of NVOPF/8%KB electrode under various states. e Ex situ UV-vis spectra of the NVOPF/8%KB electrode.