This paper investigates the design of a pixelated electrode plates for capacitive wireless charging suited for mobile phone with metal shell. The study focuses on solving the problem that the effective coupling area (ECA) is relatively small when the secondary electrode plate is shifted in X direction and/or in Y direction and the variation of ECA is kept low. For the first time, the novel concept of “vacant” pixel is introduced into the capacitive charging plate, via which the above mentioned problem of small ECA, caused by the placement offset of the secondary electrode plate, is overcome. A tristate discrete particle swarm optimization (TDPSO) scheme is applied to optimize the pixel distribution of both pixelated positive and negative electrode plates, and the vacant pixel distribution in between. Via the global search scheme TDPSO we are able to determine the shapes of positive and negative electrodes for both the primary side (charging board) and the secondary side (charged board, such as a mobile phone).