Supporting Information Large-Scale Multifunctional Electrochromic-Energy Storage Device Based on Tungsten Trioxide Monohydrate Nanosheets and Prussian White Zhijie Bi, a,b Xiaomin Li,* a Yongbo Chen, a,b Xiaoli He, a,b Xiaoke Xu, a,c and Xiangdong Gao a a State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, No. 1295 Dingxi Road, Shanghai, 200050, P.R. China b University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing, 100049, P.R. China c School of Materials Science and Engineering, Shanghai Institute of Technology, No. 100 Haiquan Road, Shanghai, 201418, P.R. China * Corresponding Author: E-mail: lixm@mail.sic.ac.cn S-1
Calculation of areal capacitance The areal capacitance can be calculated from the galvanostatic charge/discharge (GCD) profiles by the following Equation S1: 1 = (S1) where C a is the areal capacitance (mf cm 2 ), I is the discharge current (ma), t is the discharge time (s), V is the potential window (V), and A is the electrode area (cm 2 ). Material selection rules To fabricate a multifunctional device which can be served as a complementary electrochromic device and an asymmetric supercapacitor, choosing two appropriate materials for the positive and negative electrodes is an important task. Two general criteria must be considered: (1) Both materials must simultaneously possess capacitive and electrochromic functions. Various transition metal compounds (WO 3, V 2 O 5, TiO 2, NiO, etc.), conducting polymers (polyaniline, etc.) and metallo-organic chelates (metal phthalocyanines, etc.), which are able to undergo reversible redox reactions in electrolyte accompanied by the color changes, can be selected as the electrode materials for the multifunctional devices. (2) The two materials should operate in matched potential windows in the same electrolyte to cooperate for complementary color change and synergetic energy storage. For example, in this paper, we choose PB and WO 3 H 2 O as positive and negative electrodes, respectively. Both materials possess capacitive and electrochromic functions in Li + electrolyte. The PB electrode exhibits a potential window of 0 to 0.6 V, while WO 3 H 2 O electrode possesses a potential window of 0.6 to 0 V. Therefore, the cooperation of the two materials enables the device to work in a widened potential window of 1.2 V, higher than those of the previously reported symmetric devices. 2 5 WO 3 H 2 O, a typical cathodic electrochromic material, takes on blue color (Li α WO 3 H 2 O) in reduction state via the intercalation of Li + and electrons, and S-2
transparent (WO 3 H 2 O) in oxidation state due to the de-intercalation of Li + and electrons. PB exhibits blue color in oxidation state by the de-intercalation of Li + and electrons, and transparent in reduction state owing to the intercalation of Li + and electrons. Thus, when PB and WO 3 H 2 O are adopted as the two electrodes of the complementary electrochromic device, they are simultaneously colored or de-colored for enlarged optical modulation. It is well known that the charge balance between the two electrodes should follow the relationship q + = q, so as to obtain a good electrochemical performance. The related equations are given as follows: = = = (S2) (S3) (S4) = (S5) where q is the charge stored in the electrode, C a is the areal capacitance, A is the electrode area, V is the potential window, and the superscripts + and indicate the positive and negative electrodes, respectively. Hence, as for WO 3 H 2 O and PB in this paper, they should possess the same areal capacitance as shown in Figure S2. In other words, as the two electrodes possess the same electrode areas, the thicknesses of WO 3 H 2 O and PB should be matched. However, if the thicknesses of both WO 3 H 2 O and PB are small, it would not only decrease the areal capacitance of the EESD, but also reduce the optical modulation of the EESD as the transmittance of the colored state would be limited. Conversely, if the thicknesses of both WO 3 H 2 O and PB are large, the optical modulation of the EESD would also be limited due to the decreasing transmittance of the bleached state. After multiple attempts, the EESD comprised of the optimal WO 3 H 2 O of 450 nm and PB of 165 nm exhibits a suitable optical modulation while the charge balance is kept. S-3
Figure S1. FTIR spectrum of the as-prepared PB film. S-4
Figure S2. (a) Transmittance spectra of the WO 3 H 2 O nanosheets at colored ( 0.6 V) and bleached (+0.4 V) states, and the transmittance spectra of the Prussian blue film at colored (+0.6 V) and bleached ( 0.2 V) states, respectively. (b) In situ transmittance responses at 650 nm for the WO 3 H 2 O nanosheets and PB film, respectively. (c) Galvanostatic charge/discharge curves of the WO 3 H 2 O nanosheets and PB film collected at different current densities of 1.12, 0.56, 0.42, 0.28 and 0.14 ma cm -2, respectively. (d) Areal capacitance of the WO 3 H 2 O nanosheets and PB film as functions of the discharge current density. S-5
Table S1. The summarized comparison of electrochromic properties of our EESD with the previously reported works. Device structure Electrolyte T /% t c /t b /s CE /cm 2 C 1 Cyclic number Ref. WO 3 //WO 3 1M H 2 SO 4 63.7 2 PANI//PANI H 2 SO 4 /PVA ~15 1000 3 WO 3 -PEDOT: PSS//CeO 2 -Ti O 2 WO 3 //NiO 0.5M H 2 SO 4 73.3 12.7/15.8 108.9 200 6 ACN/PC/ LiClO 4 /PMMA 64.2 10/13.1 136.7 100 7 V 2 O 5 //V 2 O 5 1M LiClO 4 /PC ~45 100 8 WO 3 //NiO LiClO 4 /PVA ~43 2.5/2.6 135.5 9 PB//PBV 0.1M KTFSI/SiO 2 /SN 62.5 ~10/10 157 1000 10 WO 3 H 2 O//PB 1M LiClO 4 /PC 61.7 1.84/1.95 139.4 2500 This work S-6
Figure S3. Cyclic voltammetry (CV) curves of the EESD at various scan rates ranging from 10 to 100 mv s 1. S-7
Figure S4. Areal capacitances of the large-scale EESD at different current densities. S-8
Figure S5. Galvanostatic charge/discharge profiles at different current densities of (a) 0.05, (b) 0.1, (c) 0.25 and (d) 0.5 ma cm 2 in the voltage range of 0 1.2 V and the corresponding in situ transmittance responses measured at 650 nm for the EESD. S-9
References (1) Liu, W.-W.; Feng, Y.-Q.; Yan, X.-B.; Chen, J.-T.; Xue, Q.-J. Superior Micro-Supercapacitors Based on Graphene Quantum Dots. Adv. Funct. Mater. 2013, 23, 4111-4122. (2) Yang, P.; Sun, P.; Chai, Z.; Huang, L.; Cai, X.; Tan, S.; Song, J.; Mai, W. Large-Scale Fabrication of Pseudocapacitive Glass Windows that Combine Electrochromism and Energy Storage. Angew. Chem., Int. Ed. Engl. 2014, 53, 11935-11939. (3) Wang, K.; Wu, H.; Meng, Y.; Zhang, Y.; Wei, Z. Integrated Energy Storage and Electrochromic Function in One Flexible Device: An Energy Storage Smart Window. Energy Environ. Sci. 2012, 5, 8384-8389. (4) Chen, X.; Lin, H.; Chen, P.; Guan, G.; Deng, J.; Peng, H. Smart, Stretchable Supercapacitors. Adv. Mater. 2014, 26, 4444-4449. (5) Zhu, M.; Huang, Y.; Huang, Y.; Meng, W.; Gong, Q.; Li, G.; Zhi, C. An Electrochromic Supercapacitor and Its Hybrid Derivatives: Quantifiably Determining Their Electrical Energy Storage by An Optical Measurement. J. Mater. Chem. A 2015, 3, 21321-21327. (6) Cai, G.; Darmawan, P.; Cheng, X.; Lee, P. S. Inkjet Printed Large Area Multifunctional Smart Windows. Adv. Energy Mater. 2017, 1602598. (7) Cai, G.; Darmawan, P.; Cui, M.; Chen, J.; Wang, X.; Eh, A. L.; Magdassi, S.; Lee, P. S. Inkjet-Printed All Solid-State Electrochromic Devices Based On NiO/WO 3 Nanoparticle Complementary Electrodes. Nanoscale 2016, 8, 348-357. (8) Wei, D.; Scherer, M. R.; Bower, C.; Andrew, P.; Ryhanen, T.; Steiner, U. A Nanostructured Electrochromic Supercapacitor. Nano Lett. 2012, 12, 1857-1862. (9) Xia, X.; Ku, Z.; Zhou, D.; Zhong, Y.; Zhang, Y.; Wang, Y.; Huang, M. J.; Tu, J.; Fan, H. J. Perovskite Solar Cell Powered Electrochromic Batteries for Smart Windows. Mater. Horiz. 2016, 3, 588-595. (10) Fan, M.-S.; Kao, S.-Y.; Chang, T.-H.; Vittal, R.; Ho, K.-C. A High Contrast Solid-State Electrochromic Device Based on Nano-Structural Prussian Blue and Poly(Butyl Viologen) Thin Films. Sol. Energy Mater. Sol. Cells 2016, 145, 35-41. S-10