NiO Nickel oxide (NiO) normally functions in alkaline electrolyte, which conflicts with WO₃’s acidic or organic operating environments. Most WO₃-NiO complementary devices use Li⁺-containing organic solutions as the electrolytes, which lead to low NiO electrochromic activity and safety hazards. Herein, Li-doped NiO (Li_xNiO_y) nanosheet arrays were hydrothermally grown on FTO glass, and their electrochromic and pseudocapacitive behaviors were investigated in Zn²⁺/K⁺ aqueous electrolyte (Figures a–c.). Li_xNiO_y delivers optical modulations of 39.01% at 600 nm and 21.62% at 1200 nm, outperforming pure NiO. It reversibly switches between colouring and bleaching states, with preferential visible-light absorption and partial near-infrared transmittance, offering spectral complementarity to WO₃. After 500 coloration/bleaching cycles, Li_xNiO_y retains 68.39% optical modulation, far exceeding the 33.82% retention of pure NiO. The material exhibits areal specific capacitance of 5.16 mF/cm² at 0.01 mA/cm². In addition, the material showed a high coulombic efficiency (>95%) and good stability (62.0% capacitance retention after 1000 cycles) (Figures d–i.). Despite inferior optical modulation compared with alkaline/organic systems originating from the large hydrated radius and strong electrostatic interaction of Zn²⁺, the warm-mode spectral regulation and WO₃-compatible characteristics enable a promising strategy for all-aqueous, low-cost, safe dual-band smart windows.
 

Li-doped NiO；electrochromism；aqueous electrolyte；WO3；nanosheet arrays；dual-band smart window；pseudocapacitance