All-solid-state electrochromic Li-ion hybrid supercapacitors for intelligent and wide-temperature energy storage

Newly proposed electrochromic Li-ions hybrid supercapacitors (ELHSs), incorporating energy storage and electrochromic functions into one hybrid system, provide huge potential for next-generation portable and intelligent electron devices. The critical next step in the future implementation is to explore a high-rate and stable battery-type electrochromic positive electrode to match the capacitive electrochromic negative electrode even under harsher environments. Herein, spinel LiMn₂O₄ electrodes coating with LiNbO₃ thin layer (namely LMO@LNO) possess interconnected microstructures and multipores are successfully fabricated and severed as high-performance battery-type electrochromic positive electrode for ELHSs. The resulting LMO@LNO electrode exhibits remarkable electrochromic and energy storage performances, including large optical modulation (∼42.1%), high specific capacity (127.6 mAh g⁻¹) and robust long-term electrochemical stability (over 1000 cycles). The Li-ion migration kinetics and electrochromic mechanism of the positive electrode are further comprehensively analyzed through experimental characterizations and density functional theory (DFT) calculations. By pairing with a transparent WO₃ electrochromic capacitor-type negative electrode, an all-solid-state ELHS with a maximum working voltage of 2.3 V is assembled, delivering an impressive energy/power density (106.1 Wh kg⁻¹/574.7 W kg⁻¹) and admirable capacity retention of 83.5% after 3000 cycles. Significantly, the as-obtained ELHS with excellent environmental compatibility and reversible electrochromic performance even operate at progressively varying temperatures (RT ∼ 60 °C). This work provides a new opportunity to design next-generation safe and intelligent hybrid energy storage system for consumer electronics.