We study prethermal discrete time-crystalline (PDTC) phases in one-dimensional spin-1/2 chains with power-law–modulated nearest-neighbor interactions under periodic Floquet driving. This system supports robust period-doubled dynamics across a wide range of grading exponents, stabilized by the interplay between coherent driving and spatially varying coupling. This work proposes the PDTC phases as an excellent platform for engineering robust quantum batteries. Within the PDTC phase, the energy stored in the system, interpreted as a quantum battery, increases superlinearly with system size, although no super-liner scaling advantage persists in the normalized stored energy. The main advantage of the PDTC phase in quantum batteries arises from emergent stable subharmonic responses by suppression of heating. These responses remain stable even in the presence of imperfections in initial state preparation or deviations from ideal driving. As a result, the PDTC-based approach is inherently offers robust platform for realizing quantum battery. In contrast, standard time-dependent protocols require careful parameter fine-tuning or precise synchronization of measurements with the optimal time for extracting maximal power during transient dynamics. Beyond energy storage, we demonstrate that the PDTC phase supports enhanced quantum sensing in a wide range of the gradient exponent. The quantum Fisher information associated with estimating timing deviations in the drive scales superextensively with system size, indicating quantum enhanced sensitivity. Particularly, the degree of quantum advantage can be tuned by varying the interaction exponent, though PDTC behavior remains robust throughout. Our results position power-law–graded interacting Floquet systems as robust platforms for storing quantum energy and achieving metrological enhancement.