Enhanced cyclic stability and performance of electrochromic energy storage devices with in-situ solid electrolyte interphase

Electrochromic energy storage devices (EESDs) that integrate optical modulation with energy storage capabilities are emerging as promising candidates for next-generation smart windows, particularly in automotive panoramic sunroofs. Currently, challenges remain in enhancing the long-term stability and performance required for practical use. This study reports the in-situ formation of an optimized organic–inorganic hybrid solid-electrolyte interphase (SEI) layer facilitated by the use of a Zn²⁺/K⁺ dual-ion electrolyte system, which effectively stabilizes the electrode–electrolyte interface. The SEI consists of an organic-rich outer layer and an inorganic-rich inner layer, composed of ZnCO₃, Zn₃(PO₄)₂, ZnF₂, and ZnS. Such hybrid organic–inorganic configuration plays a crucial role in facilitating zinc ion transfer and deposition, as well as enhancing the reversibility of the electrodes. Enhanced cyclic stability and exceptional electrochromic performance of the PB||Zn EESD are achieved via SEI, including high optical modulation (ΔT = 69.98 %), rapid switching dynamics (t_c = 13.8 s, t_b = 12.8 s), excellent coloration efficiency (131.48 cm² C⁻¹) and outstanding long-term stability (90.8 % retention of optical modulation after 6000 cycles). Essentially, the integrated dual function reflects the efficient energy management strategy since users typically utilize the EESDs to advance solar thermo-optic modulation performance in smart windows while the zero power consumption integrating photovoltaic solar cells is more dominant. This work provides a promising and sustainable solution for applications requiring long-term stability and energy efficiency.