Liquid lens offers a simple solution to achieve tunable optical powers. This approach, however, suffers from deteriorated resolution at high diopters. In this study, a plano-convex liquid lens with aspherical cross-section is developed. Such configuration allows for the lens profiles at high diopters to be close to spherical shapes by alleviating the edge-clamping effects. Resolution tests of a 6mm lens with optimized asphericity exhibit improved resolutions in both center and peripheral regions at 40 and 100 diopters than the lenses with planar membranes. It shows that aspherical membranes can improve the resolving power of liquid lenses at high diopters, thus providing a new route of optimizing the imaging performance of adaptive liquid lenses for various applications.