In conventional tungsten oxide-based electrochromic batteries (ECBs), tungsten oxide acts as the cathode and Zn foil as the anode, but low redox potential leads to a limited discharge plateau, low areal capacitance, and power density, restricting practical applications. In this study, a novel WO₃||acid-modified graphite foil (WO₃||AGF) ECB was developed using AGF as the cathode, WO₃ as the anode, and a hybrid Zn²⁺/Al³⁺ electrolyte. The AGF offers advantages, such as high ion storage capacity, fast kinetics, and a high electrode potential, ensuring a high discharge voltage and capacity for the WO₃||AGF ECB. The prepared WO₃||AGF ECB not only exhibits excellent electrochromic performance but also demonstrates superior energy storage capabilities. At a charge/discharge current density of 0.5 mA·cm⁻², the WO₃||AGF ECB achieves a stable discharge capacity of 315.6 mAh·m⁻², which is 7.8 times higher than that of the traditional Zn||WO₃ ECB. Moreover, the rapid ion diffusion kinetics of the AGF ensure the cycling stability of the device at high voltages, maintaining 94.4% optical modulation after 8000 coloring/bleaching cycles. This work provides a novel approach by designing more compatible electrode material systems to achieve ECBs with high energy and power densities.

Buildings account for over 30% of global energy consumption, about half of which is used for heating, cooling and ventilation to regulate indoor temperatures. With the energy crisis looming, saving energy from thermal regulation in buildings will make a significant contribution to sustainable development. Windows and walls are major enveloping parts of buildings, responsible for regulating light and heat indoors from the sun. However, compared to the well-studied smart windows, research on smart building envelopes is still lacking. Herein, we demonstrate a reflective-type dual-function electrochromic (DFEC) device for building envelopes, capable of producing rich color variations in the visible (VIS) and achieving large average reflectivity modulation of over 80% in the near infrared (NIR). Due to the inherent energy recyclability of EC batteries, the DFEC devices reveal ultra-low energy consumption of 30.7 mWh/m² and power consumption of 0.4 mW/cm² in single EC cycle. As a demonstration, the DFEC device exhibits a remarkable performance in solar thermal management with a temperature difference of 5 °C between its colored (heating) and bleached (cooling) states, indicating an extensive potential for application in energy-efficient building envelopes.