C.D. Ma, P. Das, J.X. Ma, Z.Z. Yuan, F. Zhou, S.-Y. Lee * and Z.-S. Wu *

Science Bulletin, 2025, accepted.

ECs offer a valuable alternative or complement to batteries in applications requiring high power output and long lifespan, particularly for systems that require rapid energy storage and release. Various types of capacitors, including EDLCs, pseudocapacitors, and hybrid capacitors, have been developed to address the performance challenges in low temperature environments. Among these efforts, the optimization of low-temperature electrolytes remains the most cost-effective and efficient approach to ensure reliable operation at ultra-low temperatures. Additionally, the development of advanced electrode materials compatible with these electrolytes plays a critical role in improving device performance. 

The microscopic structure, including ion solvation and desolvation, as well as the electrode materials' morphology structure, significantly influences low-temperature properties at the microscopic scale. Correlating microscopic structure with low temperature properties is of great significance for the in-depth analysis of the energy storage mechanism. The advancement of in-situ characterization techniques under low-temperature conditions, coupled with theoretical calculations, has provided valuable insights into how the microscopic structure influences low-temperature performance and helped to elucidate the underlying energy storage mechanism. In-situ characterization techniques allow observation of structural changes in electrode materials and electrolytes during charge and discharge cycles. Theoretical calculations, such as density -functional theory, and molecular-dynamics simulations, can simulate the intrinsic physical parameters of electrode materials and electrolytes. Additionally, emerging machine learning approaches can effectively screen potential candidates for electrode materials and electrolytes and predict the electrochemical properties of ECs, offering promising prospects for future development. Additionally, efficient and lightweight external or self-heating systems show great potential in enhancing low-temperature performance.

Overall, recent advances in the understanding of charge storage mechanisms, together with innovations in nanostructured electrode materials, low-temperature electrolytes and device architectures, have significantly improved the low-temperature performance of ECs. These advances have facilitated the transition of low-temperature EC technologies from laboratory-scale research to industrial applications, paving the way for wider implementation in extreme environments.