Ion Storage Materials

The ion storage layer acts in a similar active redox manner as the electro-chromic layer. During switching this layer incorporates and releases lithium ions, but in the opposite direction of the electrochromic layer. Usually this layer does not change its optical absorption during switching. Metal oxides or metal oxide combinations have been proposed as ion storage layers such as oxides based on cerium and titanium oxide as well as nickel oxides or vanadium oxides. Metal oxides suffer from their brittle nature, which limits their use in flexible devices. 

A special case are ion storage layers with complementary electrochromic activity, which may be assembled with a PEDOT layer. In a complementary electrochromic cell, both layers—dye and bleach—simultaneously increase to the overall optical contrast. Tungsten trioxide as well as Prussian Blue, iron(III) hexacyanoferrate(II/III) bleach upon reduction and were used in combination with PEDOT. Cells made from PEDOT in combination with Prussian Blue exhibited a deep blue-violet color at a potential of -2.1 V and become light blue at 0.6 V. Combination cells of alkylenedioxypyrrols or -thiophenes with ferrocene have been proposed as variable optical attenuator devices due to a large dynamic range of optical attenuation at the telecommunication wavelength of 1550 nm.  

---

Idota Y., Kubota T., Matsufuji A., Maekawa Y., Miyasaka T. Tin-Based Amorphous Oxide A High-Capacity Lithium-Ion-Storage Material. Science 1997 276 1395-97. 

Idota Y, Kubota T, Matsufuji A, Maekawa Y, Miyasaka T. Tin-based amorphous oxide a high-capacity lithium-ion-storage material. Science. 1997 276(5317) 1395—7. 

Counter Electrode Materials. The anodic electrochromic materials and ion storage materials have not been so widely studied as the cathodic electrochromic materials discussed above. In general, the main features of the impedance spectra are similar to those shown above. The impedance response of nickel oxide films with... 

Han X, Chang C, Yuan L et al (2007) Aromatie earbonyl dtaivative polymers as high-performanee Li-ion storage materials. AdvMatta-19(12) 1616-1621... 

PEDOT has been found to have useful electrochromic properties - and for a long time fed the hope of inexpensive electrochromic glazings made by simple coating techniques for architectural and automobile applications. At present it seems unlikely that PEDOT-based electrochromic glazings will appear on the market in the near future. However its potential has inspired numerous and continuing studies that intend to improve the properties of the electrochromic solid, the electrolyte, and the ion storage material and to assemble innovative electrochromic devices. 

Figure 1. The ubiquitous high- and low-molecular-weight biopol3nner PHB is a microbial storage material (carbon and reductase equivalents, cf. Figure 2) and is found as part of ion-transporting systems in procaryotic and eucaryotic organisms, respectively [2].

Fransson, L.M.L., Vaughey, J.T., Edstrom, K., and Thackeray, M.M., Structural transformations in intermetallic electrodes for lithium batteries an in situ x-ray diffraction study of lithiated MnSb and Mn2Sb, J. Electrochem. Soc., 150, A86, 2003. Yang, J., Wachtler, M., Winters, M., and Besenhard, J.O., Sub-microcrystalline Sn and Sn-SnSb powders as lithium storage materials for lithium-ion batteries, Electrochem. Solid State Lett., 2, 161, 1999. 

---