Energy deposition of high-energy ions and the resulting electron-ion energy partition in dense plasmas are of essential importance in understanding the hot-spot ignition and burning of inertial confinement fusion. In this work, the energy deposition and electron-ion energy partition of high-energy ions are studied in a wide range of temperatures and densities based on the improved T-matrix model. Compared with the stopping power model based on the assumption of small-angle scattering, the improved T-matrix model can consistently take into account the large-angle Coulomb scattering and the resulting transversal deflection of the high-energy ions. We investigate the influence of the effect of transversal deflection on the electron-ion energy partition and propose a fitting formula for the energy partition fraction to plasma electrons. This formula is applicable to inertial confinement fusion simulations. It is found that when the effect of transversal deflection is considered, the relative energy deposited into electrons in plasma is reduced by about 27.5% at most. This conclusion suggests that the transversal deflection of energetic ions, induced by the large-angle Coulomb scattering and its cumulative effect, ought to be considered in accurately simulating the hot-spot ignition and burning of the fuel in inertial confinement fusion.