Superconducting-diode effect induced by inversion-symmetry breaking in a stepped <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mi>NbSe</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> nanof

The nonreciprocal supercurrent phenomenon, known as the superconducting-diode effect (SDE), has garnered great attention because of its immense potential for future nondissipative quantum devices. Here, we demonstrate lateral inversion-symmetry breaking generated by the asymmetric thickness for the realization of the SDE in a stepped ${\mathrm{NbSe}}_{2}$ nanoflake, which eliminates the need for complex conventional heterostructures or epitaxial structures. The electrical measurements and theoretical calculations reveal a robust SDE efficiency of up to 22.6%, primarily attributed to the presence of lateral inversion-symmetry-breaking-induced asymmetric vortex entry. Our findings emphasize the universality and effective control of vortices in achieving SDEs, and open alternative avenues for advancing the application of SDEs in van der Waals superconductors.