context: The cycle stability in terms of the charge capacity for the two kinds of films in the Li/Al-ion electrolyte was also evaluated as shown in Fig. 3a and b (details for the in situ measurement of both the charge capacity and the transmittance are provided in the ESI†). After 1000 cycles, the capacity retention was about 78% for the Ti-V2O5 film and 72% for the WO3 film. The cycle stability in terms of the electrochromic performance is obtained by monitoring the optical contrast between the colored and the bleached state of the films. As shown in Fig. 3c and d, after 1000 cycles, the Ti-V2O5 film still delivered a transmittance contrast of up to 24.8% at 400 nm, and for the WO3 film, a contrast up to 47.4% was delivered at 780 nm. These values show that 69.5% of the optical modulation can be retained for Ti-V2O5 and 65.4% can be retained for the WO3 film after 1000 cycles. As a comparison, the Al-ion electrolyte, which is commonly used in Al-based EES devices, was applied to replace the Li/Al-ion electrolyte. As shown in Fig. S6,† for both the Ti-V2O5 and the WO3 films, the optical contrast in the transmittance spectra drops rapidly within 100 cycles, indicating that the mixed ion electrolyte effectively promotes the cycle stability of the electrochromic films.
answer:  Li/Al-ion