Low self-discharge all-solid-state electrochromic asymmetric supercapacitors at wide temperature toward efficient energy storage

Electrochromic asymmetric supercapacitors (EASs) have attracted tremendous attention in recent years because of their potential for next-generation civilian portable and intelligent electronics. However, obtaining all -solid-state EASs with low self-discharge rates and outstanding environmental compatibility remains a crucial chal-lenge. Herein, a high-performance all-solid-state EAS was fabricated based on MnO2 positive electrochromic electrode and WO3 negative electrochromic electrode. The obtained EAS exhibits high power/energy density (991.2 W kg -1/117 Wh kg- 1 and 15840 W kg -1/44.3 Wh kg -1), superior electrochemical cycle-life (remains 98.4% of its initial capacity after 2000 continuous cycles even at 60 degrees C). Significantly, the fabricated EAS can still maintain a stable and reversible color change even in harsh environments where operating temperatures are constantly changing from-20 degrees C to 60 degrees C. In addition, the underlying self-discharge process and mechanisms of EASs were comprehensively demonstrated at various temperatures. The diffusion-controlled mechanism domi-nates in the initial discharging process at high working temperatures (such as 60 degrees C), while both charge redis-tribution and diffusion-controlled mechanism contribute equally at lower operating temperatures (such as-20 degrees C). Impressively, the EAS presents a small voltage loss (all below 18%) within 10 h when operated at extreme temperatures. This work can enlighten and promote the development of low self-discharge electro-chromic devices at widely operating temperatures for efficient energy storage.