Utilization of renewable energy such as solar, wind, and geothermal power, appears to be the most promising solution for the development of sustainable energy systems without using fossil fuels. Energy storage, especially to store the energy from fluctuating power is quite vital for smoothing out energy demands with peak/off-peak hour fluctuations. Thermal energy is a potential candidate to serve as an energy reserve. However, currently the development of thermal energy storage (TES) by traditional physical means is restricted by the relatively low energy density, high temperature demand, and the great thermal energy loss during long-period storage. Chemical heat storage is one of the most promising alternatives for TES due to its high energy density, low energy loss, flexible temperature range, and excellent storage duration. A comprehensive review on the development of different types of Mg-based materials for chemical heat storage is presented here and the classic and state-of-the-art technologies are summarized. Some related chemical principles, as well as heat storage properties, are discussed in the context. Finally, some dominant factors of chemical heat storage materials are concluded and the perspective is proposed for the development of next-generation chemical heat storage technologies.

Enhancing the redox potential of cathode materials is vital for increasing the energy density of aqueous ammonium ion batteries (AIBs). Prussian blue analogues (PBAs), with their inherently high redox potentials and open frameworks, are promising candidates. However, further boosting their redox potential and understanding their NH₄⁺ ion storage mechanisms remain critical challenges. In this work, a novel ligand field‐induced dual active sites mechanism is introduced by incorporating Ni into the PBA framework, activating Ni as an additional redox center for NH₄⁺ ion storage. The electron transfer from Ni to Fe within the Ni─N≡C─Fe chain enhances the redox potential and electrochemical performance of nickel hexacyanoferrate (NiHCF). For the first time, the electrochemical activity of Ni is demonstrated in NiHCF during NH₄⁺ ions intercalation and de‐intercalation. NiHCF exhibits elevated redox potentials, superior rate performance, and robust cycling stability compared to iron hexacyanoferrate (FeHCF). Advanced characterization techniques and density functional theory calculations confirm the activation of Ni and the enhanced interaction between NH₄⁺ ions and the framework. These findings provide new insights into the NH₄⁺ ion storage mechanism of PBAs and offer a promising strategy for designing high‐energy‐density cathode materials for AIBs.

Mg-based materials are regarded as one of the most promising candidates for hydrogen storage. In order to clarify the relationship between the structures and properties as well as to understand the reaction and formation mechanisms, it is beneficial to obtain useful information about the size, morphology, and microstructure of the studied materials. Herein, the use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques for the representation of Mg-based hydrogen storage materials is described. The basic principles of SEM and TEM are presented and the characterizations of the size, morphology observation, phase and composition determination, and formation and reaction mechanisms clarification of Mg-based hydrogen storage materials are discussed. The applications of advanced SEM and TEM play significant roles in the research and development of the next-generation hydrogen storage materials.