Systematic study and effective improvement of voltammetry for accurate electrochemical window measurement of solid electrolytes

•The mechanism of voltammetric electrochemical window measurements is explained.•The influence of testing parameters on electrochemical window measurement is analyzed.•A step voltammetry method is applied to measure the electrochemical window of Li10GeP2S12.•The electrochemical window measurement methods of liquid and solid electrolytes are suggested.