Utilization of 2D materials in aqueous zinc ion batteries for safe energy storage devices.

Aqueous rechargeable battery has been an intense topic of research recently due to the significant safety issues of conventional Li-ion batteries (LIBs). Amongst the various candidates of aqueous batteries, aqueous zinc ion batteries (AZIBs) hold great promise as a next generation safe energy storage device due to its low cost, abundance in nature, low toxicity, environmental friendliness, low redox potential, and high theoretical capacity. Yet, the promise has not been realized due to their limitations, such as lower capacity compared to traditional LIB, dendrite growth, detrimental degradation of electrode materials structure as ions intercalate/de-intercalate, and gas evolution/corrosion at the electrodes, which remains a significant challenge. To address the challenges, various 2D materials with different physiochemical characteristics have been utilized. This review explores fundamental physiochemical characteristics of widely used 2D materials in AZIBs, including graphene, MoS2, MXenes, 2D metal organic framework, 2D covalent organic framework, and 2D transition metal oxides, and how their characteristics have been utilized or modified to address the challenges in AZIBs. The review also provides insights and perspectives on how 2D materials can help to realize the full potential of AZIBs for next-generation safe and reliable energy storage devices.

Advances in high-voltage supercapacitors for energy storage systems: materials and electrolyte tailoring to implementation.

To achieve a zero-carbon-emission society, it is essential to increase the use of clean and renewable energy. Yet, renewable energy resources present constraints in terms of geographical locations and limited time intervals for energy generation. Therefore, there is a surging demand for developing high-performance energy storage systems (ESSs) to effectively store the energy during the peak time and use the energy during the trough period. To this end, supercapacitors hold great promise as short-term ESSs for rapid power recovery or frequency regulation to improve the quality and reliability of power supply. In particular, the electrical double layer capacitor (EDLC) which offers long and stable cycle retention, high power densities, and fast charge/discharge characteristics with a moderate operating voltage window, is a suitable candidate. Yet, for implementation of the EDLC in ESSs, further research effort is required in terms of increasing the operating voltage and energy densities while maintaining the long-term cycle stability and power densities which are desirable aspects for ESS operation. Here, we examine the advances in EDLC research to achieve a high operating voltage window along with high energy densities, covering from materials and electrolytes to long-term device perspectives for next-generation supercapacitor-based ESSs.