Nickel-zinc microbatteries have been constructed for use in wireless microsensors and similar microsystems. A high power density is required for the batteries to meet the size and power requirements of these systems. A mathematical model of the side-by-side nickel-zinc cell was developed and used to increase the power density cell geometry by optimizing. Simulations showed that energy density could be increased slightly and power density almost doubled through changes in geometry. Testing of cells fabricated with the optimized geometry showed increases in capacity and power consistent with the simulations. Power densities of 140 mW/cm(2) were observed for these cells. These power levels are sufficient to meet the projected needs of many autonomous microsystems including remote microsensors. (C) 2003 The Electrochemical Society.