All-in-one electrochromic gel consist of benzylboronic acid viologen with superior long-term stability and self-healing property

The viologen-based gel is typical kind of electrochromic materials, there are currently two main limited problems for application in electrochromic devices (ECD). The electrochromic layer may be damaged due to aging, film stress, etc., or viologen dimerization occurs after repeated service cycles, which have a significant impact on the reliability of ECD. To address these limitations, we synthesized benzyl boronic acid viologen (BBV) and mixed it with an electrolyte containing polyvinyl alcohol (PVA). The boronic acid group in BBV can form boronic ester linkages with the hydroxyl group in PVA, resulting in a self-healing all-in-one electrochromic gel. The immobilized viologen with boronic ester linkages would slow down its diffusion rate and effectively mitigate its poor cycling stability caused by dimerization. Meanwhile, the reversibility of the dynamically cross-linked boronic ester linkages leads to self-healing ability of the electrochromic gel. The all-in-one electrochromic gel demonstrated excellent mechanical properties, with a tensile strength of 33 kPa, and significant self-healing performance within 30 min at room temperature, with a healing efficiency of 96.57%. The ECD prepared using this gel exhibited excellent properties, with a response time of 3.9 s for coloring and 7.4 s for bleaching at a driving voltage of 0 to 1.3 V, as well as good optical contrast (71.33%) and high cycling stability (10,000 cycles/82.66%). Benzylboronic acid viologen was synthesized and an all-in-one electrochromic gel with self-healing function was prepared, which has good long-term stability and high contrast for electrochromic devices. [Display omitted] •SynThesized BBV formed an all-in-one electrochromic gel after mixing with PVA.•Reversibility of the boronic ester linkages leads to the self-healing ability of gel.•The healing efficiency of the gel was 96.57% at room temperature for 30 min.•BBV is immobilized on the polymer grid, effectively inhibiting viologen aggregation.•The cycling stability of this gel-prepared ECD was excellent (10,000 cycles/82.66%).