Anti-self-discharge ultrathin all-inorganic electrochromic asymmetric supercapacitors enabling intelligent and effective energy storage

Electrochromic asymmetric supercapacitors (EASs), incorporating electrochromic and energy storage into one platform, are extremely desirable for next-generation civilian portable and smart electronic devices. However, the crucial challenge of their fast self-discharge rate is often overlooked, although it plays an important role in practical application. Unfortunately, very limited research on EAS has focused on this critical problem. Here, an ultrathin all-inorganic EAS with excellent anti-self-discharge performance and superior electrochromic behavior is designed and manufactured by introducing a thin nano-functional layer at the electrode/electrolyte interface. The prototype all-inorganic EAS exhibited a wide working voltage of 2.2 V, a high energy/power density (81.2 mWh·cm⁻³/0.688 W·cm⁻³ and 30.6 mWh·cm⁻³/11.02 W·cm⁻³), along with outstanding electrochemical and electrochromic performance even at high temperatures. Remarkably, the introduced Ta₂O₅ layer can efficiently prohibit the redistribution and diffusion of the movable ions at the fully charged state, endowing the all-inorganic EAS with a tardy self-discharge rate of 12.6 mV·g⁻¹, which is an extremely low value when compared with previous reported research. Significantly, the ultrathin all-inorganic EASs could also well maintain a slow self-discharge rate and their original electrochemical characteristics under various environmental temperatures. We envision that the novel strategy of electrode/electrolyte interface engineering can effectively deal with the severe self-discharge challenge of EAS, and provide more opportunities for their practical applications. Graphical abstract: [Figure not available: see fulltext.]