Poly(vinylidene fluoride) (PVDF) based polymers are attracting tremendous interest because of their potential applications in advanced energy storage devices. Fundamental understanding of their crystal structure evolution has been proved elusive due to the nature of rapid crystallization rate. Fortunately, flash differential scanning calorimeter (Flash DSC) with a precise control of cooling rate helps to investigate an understanding of structure-property relationships. For the first time, a bimodal distribution of the crystallization rate of P(VDF-chlorotrifluoroethylene) (CTFE) in the whole temperature range, and a 3D profile of melting point and enthalpy dependence of annealing temperature and time, which is the corresponding crystal structure evolution and the mechanism of crystal nucleation and growth, are revealed by flash DSC. Based on the above conclusions, fast cooling or annealing at low temperature regulates the crystallization behavior, favors a tiny ferroelectric -phases, drastically reduces paraelectric spherulite sizes, and leads to greatly enhanced energy storage capacity, but reduction in discharged efficiency. For instance, compared with other processing methods, P(VDF-CTFE) quenched by liquid nitrogen achieves the highest discharged energy of 10.6 Jcm(-3) at the maximum electric field of 270 MVm(-1). (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1245-1253