A High Rate and Stable Hybrid Li/Na-Ion Battery Based on a Hydrated Molten Inorganic Salt Electrolyte

Redox Electrolytes-Assisting Aqueous Zn-Based Batteries by Pseudocapacitive Multiple Perovskite Fluorides Cathode and Charge Storage Mechanisms

Aqueous Zn-based batteries (AZBs) have attracted intensive attention. However, to explore advanced cathode materials with in-depth elucidation of their charge storage mechanisms, improve energy storage capacity, and construct novel cell systems remain a great challenge. Herein, a new pseudocapacitive multiple perovskite fluorides (ABF3 ) cathode is designed, represented by KMF-(IV, V, and VI; M = NiCoMnZn/-Mg/-MgFe), and constructed Zn//KMF-(IV, V, and VI) AZBs and their flexible devices. Ex situ tests have revealed a typical bulk phase conversion mechanism of KMF-VI electrode for charge storage in alkaline media dominated by redox-active Ni/Co/Mn species, with transformation of ABF3 nanocrystals into amorphous metal oxide/(oxy)hydroxide nanosheets. By employing single or bipolar redox electrolyte strategies of 20 mm [Fe(CN)6 ]3- or/and 10 mm SO3 2- /Cu[(NH3 )4 ]2+ acting on KMF-(IV, V, and VI) cathode and Zn anode, the AZBs show an improved energy storage owing to additional capacity contribution of redox electrolytes. The as-designed Zn//polyvinyl alcohol (PVA)-KOH-K3 [Fe(CN)6 ]//KMF-(IV, V, and VI) redox gel electrolytes-assisting flexible AZBs (RGE-FAZBs) exhibit remarkable performance under different bending angles because of slight dissolution corrosion of zinc anode compared with liquid electrolytes. Overall, the work demonstrates the novel idea of conversion-type multiple ABF3 cathode for redox electrolytes-assisting AZBs (RE-AZBs) and their flexible systems, showing great significance on electrochemical energy storage.

Modulation of Solvation Structure and Electrode Work Function by an Ultrathin Layer of Polymer of Intrinsic Microporosity in Zinc Ion Batteries

Zinc ion batteries are promising candidates for large-scale energy storage systems. However, they suffer from the critical problems of insufficient cycling stability due to internal short-circuiting by zinc dendrites and zinc metal orphaning. In this work, a polymer of intrinsic microporosity (PIM-1) is reported as an ion regulating layer and an interface modulator, which promotes a uniform Zn plating and stripping process. According to spectroscopic analyses and computational calculations, PIM-1 enhances the reaction kinetics of a Zn metal electrode by altering the solvation structure of Zn²⁺ ions and increasing the work function of the Zn surface. As a result, the PIM-1 coating significantly improves the cyclability (1700 h at 0.5 mA cm^-2 ) and Coulombic efficiency (99.6% at 3 mA cm^-2 ) of the Zn/Zn²⁺ redox reaction. Moreover, the PIM-1 coated Zn operates for more than 200 h at 70% Zn utilization even under 10 mA cm^-2 and 110 h at 95% Zn utilization of the Zn metal electrode. A Zn||V₂ O₅ full cell employing the PIM-1 layer exhibits seven times longer cycle life compared to the cell using bare Zn. The findings in this report demonstrate the potential of microporous materials as a key ingredient in the design of reversible Zn electrodes.

Eutectic Electrolytes Chemistry for Rechargeable Zn Batteries

Rechargeable zinc batteries (RZBs) have proved to be promising candidates as an alternative to lithium-ion batteries due to their low cost, inherent safety, and environmentally benign features. While designing cost-effective electrolyte systems with excellent compatibility with electrode materials, high energy/power density as well as long life-span challenge their further application as grid-scale energy storage devices. Eutectic electrolytes as a novel class of electrolytes have been extensively reported and explored taking advantage of their feasible preparation and high tunability. Recently, some perspectives have summarized the development and application of eutectic electrolytes in metal-based batteries, but their infancy requires further attention and discussion. This review systematically presents the fundamentals and definitions of eutectic electrolytes. Besides, a specific classification of eutectic electrolytes and their recent progress and performance on RZB fields are introduced as well. Significantly, the impacts of various composing eutectic systems are disserted for critical RZB chemistries including attractive features at electrolyte/electrode interfaces and ions/charges transport kinetics. The remaining challenges and proposed perspectives are ultimately induced, which deliver opportunities and offer practical guidance for the novel design of advanced eutectic electrolytes for superior RZB scenarios.

Inorganic Electrolyte for Low-Temperature Aqueous Sodium Ion Batteries

Aqueous sodium ion batteries have received widespread attention due to their great application potential and high safety. However, the serious capacity fading under low temperature dramatically restricts their practical application. Compared to flammable and toxic organic antifreezing additives, addition of common cheap inorganic inert additives to improve low-temperature performance is of interest scientifically. Herein, low-cost calcium chloride is served as antifreezing additive in 1 m NaClO₄ aqueous electrolyte due to its strong interaction with water molecules. The freezing point of the optimized electrolyte is significantly reduced to below -50 °C with an ultrahigh ionic conductivity (7.13 mS cm^-1 ) at -50 °C. All pure inorganic composition of the full battery delivers a high capacity of 74.5 mAh g^-1 under 1 C (1 C = 150 mA g^-1 ) at -30 °C. More importantly, when tested under 10 C at -30 °C, the battery can achieve an ultralong cycling stability of 6000 cycles with no obvious capacity decay, indicating fast Na⁺ transport under low temperature. Significantly, this work provides an easy-to-operate strategy by adding cheap inorganic salt to develop high-performance low-temperature aqueous batteries.

Growth Mechanism of Micro/Nano Metal Dendrites and Cumulative Strategies for Countering Its Impacts in Metal Ion Batteries: A Review

Metal-ion batteries are capable of delivering high energy density with a longer lifespan. However, they are subject to several issues limiting their utilization. One critical impediment is the budding and extension of solid protuberances on the anodic surface, which hinders the cell functionalities. These protuberances expand continuously during the cyclic processes, extending through the separator sheath and leading to electrical shorting. The progression of a protrusion relies on a number of in situ and ex situ factors that can be evaluated theoretically through modeling or via laboratory experimentation. However, it is essential to identify the dynamics and mechanism of protrusion outgrowth. This review article explores recent advances in alleviating metal dendrites in battery systems, specifically alkali metals. In detail, we address the challenges associated with battery breakdown, including the underlying mechanism of dendrite generation and swelling. We discuss the feasible solutions to mitigate the dendrites, as well as their pros and cons, highlighting future research directions. It is of great importance to analyze dendrite suppression within a pragmatic framework with synergy in order to discover a unique solution to ensure the viability of present (Li) and future-generation batteries (Na and K) for commercial use.