In-situ powder X-ray diffraction (XRD) is a powerful technique to study crystalline phase changes during electrochemical cycling of battery materials. However, current cell designs are bulky, expensive, and often contain beryllium. Even less expensive coin cells with Kapton windows cost more than US$20, combined with the additional cost of a special attachment within the instrument to allow for simultaneous electrochemical and XRD testing. Herein, we report the design of a low-cost electrochemical cell for in-situ XRD analysis using polymer components. The single-use cell costs less than US$1.50 and can be used in an unmodified powder X-ray diffractometer. It is tested using commercial LiFePO4 (LFP) as a well-known model system to demonstrate the ability of the cell to accurately monitor phase transitions within a cathode material during electrochemical cycling.