Multi-degree-of-freedom angular displacement sensors are core components in precision motion control and high-end equipment, but their measurement range and measurement accuracy are often mutually constrained. To address the problem that the existing spherical two-dimensional time-grating angular displacement sensor can only achieve a measurement range of 0°~40° in the α direction, which fails to meet the requirements of wide-range applications, this paper takes the expansion of the measurement range as the primary goal and systematically conducts optimal design and comparative performance studies on the stator pole piece shapes. Based on finite-element electric field simulations, under the condition of keeping the excitation frequency, amplitude, sensor dimensions, and other parameters consistent, three improved pole piece structures are successively proposed, and simulation comparisons of errors and harmonic characteristics over the full measurement range are performed against the initial pole piece structure. Simulation results indicate that the optimized shape, by uniformly dividing a single ring into four independent segmented arc pole pieces along orthogonal directions, effectively removes mechanical motion constraints while leveraging symmetric arrangement to achieve error averaging, and its simulation errors over the full range are significantly lower than those of the previous three structures. Experiments are conducted under conditions consistent with the simulations, and an experimental platform is built to verify the proposed structure. Results show that after optimization, the measurement range of the sensor in the α direction is substantially expanded from the initial 0°~40° to 0°~220°, while the β direction still maintains full 360° measurement capability. Before compensation, the peak-to-peak error in the α direction increases by only 0.22° compared with the initial structure, and that in the β direction increases by only 0.66°. After Fourier harmonic compensation, the peak-to-peak error in the α direction of the proposed structure within the 0°~220° range is 0.036°, indicating that under the premise of a 5.5-fold range expansion, the accuracy loss is controlled within an acceptable range. Compared with existing multi-degree-of-freedom angular displacement sensors, the four-segment ring-type pole piece structure proposed in this paper exhibits significant comprehensive advantages in balancing wide range and high precision.