Boosting the performances of 100 cm2 laminated WO3–NiO electrochromic device using WO3 covered NiO as counter electrode

The polymer electrolyte (PE) is the key component for a typical laminated WO 3 –NiO electrochromic device (ECD). However, the electrochemical fragility usually makes it be easily damaged by the parasitic side oxidation reaction from the Ni 4+ at nickel oxide to generate gas bubbles within a short term running. Herein, we disclose a viable strategy through adopting WO 3 covered NiO as counter electrode to address this problem. In this investigated case, to render the ECD with neutral color, our previously-developed Nb doped WO 3 , Li and Si co-doped NiO, and PVB based electrolyte are employed as the basic constituents. The results demonstrate that the sputtered WO 3 cover layer offers multiple advantages, involving forming an ultra-thin blocking layer to avoid a direct contact between nickel oxide and electrolyte, improving the film quality by removing the defects and achieving an effective W doping in nickel oxide matrix to ensure a highly cyclic stability, decreasing the Li + transport impedance to realize a rapid response, enhancing the device critical current density to 0.45 mA cm −2 to conduct a trade-off between response rate and lifetime, and constructing a homogeneous electric field to realize an uniform coloring or bleaching over a larger 100 cm 2 sized ECD.