(a) Charge–discharge curves of NFVPS/rGO at 20 °C with a C/20 rate starting with a charge mode: 1st charge to 4.2 V (point 1), followed by 1st discharge to 1.5 V (point 2) and 2nd charge to 4.2 V (point 3); (b) ex situ XRD patterns of the cycled electrodes stopped at points 1, 2 and 3; (c) charge–discharge curves of NFVPS/rGO at 20 °C with C/20 rate starting with a discharge mode: 1st discharge to 1.5 V (point 1′), followed by 1st charge to 4.2 V (point 2′) and 2nd discharge to 1.5 V (point 3′); the numbers in (a) and (c) correspond to the specific capacities obtained at charged and discharged states before and after holding for 10 h. (d) Ex situ XRD patterns of the cycled electrodes stopped at points 1′, 2′ and 3′. The asterisk (*) symbol in the XRD patterns denotes the peaks due to calcite CaCO3 from plastic holder (see ESI,† Fig. S2)