Zn-Ion Batteries: Boosting the Rate Capability and Low-temperature Performance by Combining Structure and Morphology Engineering

Electrolyte Modulation Strategies for Low-Temperature Zn Batteries

Aqueous rechargeable Zn metal batteries (ARZBs) are extensively studied recently because of their low-cost, high-safety, long lifespan, and other unique merits. However, the terrible ion conductivity and insufficient interfacial redox dynamics at low temperatures restrict their extended applications under harsh environments such as polar inspections, deep sea exploration, and daily use in cold regions. Electrolyte modulation is considered to be an effective way to achieve low-temperature operation for ARZBs. In this review, first, the fundamentals of the liquid-solid transition of water at low temperatures are revealed, and an in-depth understanding of the critical factors for inferior performance at low temperatures is given. Furthermore, the electrolyte modulation strategies are categorized into anion/concentration regulation, organic co-solvent/additive introduction, anti-freezing hydrogels construction, and eutectic mixture design strategies, and emphasize the recent progress of these strategies in low-temperature Zn batteries. Finally, promising design principles for better electrolytes are recommended and future research directions about high-performance ARZBs at low temperatures are provided.

Prussian White Cathode Materials for All-Climate Sodium-Ion Batteries

Prussian white (PW) is considered one of the most promising cathode materials for sodium-ion batteries because of its large ion diffusion channels, low lattice strain, facile preparation, nontoxicity, and low cost. At present, research on PW mainly focuses on optimizing the material's structures for the ambient environment yet less on its practical application under extreme temperatures. In this Spotlight, we intend to offer progress we have made in developing PW cathode materials working over wide temperatures in terms of intrinsic feasibility and development prospects. These findings provide a direction to promote the practical viability of PW under extreme conditions.

Zn3V4(PO4)6: A New Rocking-Chair-Type Cathode Material with High Specific Capacity Derived from Zn2+/H+ Cointercalation for Aqueous Zn-Ion Batteries

Phosphate cathode materials with a stable and open framework structure are expected to be one of the favorable cathode materials for aqueous zinc-ion batteries (AZIBs). However, the slow migration rate of Zn²⁺ and complex mechanism in aqueous electrolyte are serious problems that limit their application at the present. Here, a new rocking-chair-type cathode material Zn₃V₄(PO₄)₆@C (ZVP@C) for AZIBs is synthesized for the first time and evaluated using a composite carbon coating to improve the electronic conductivity. Benefiting from the two-electron reaction of vanadium and the cointercalation of Zn²⁺/H⁺, ZVP@C/30%BP delivers a specific capacity as high as 120 mAh·g^-1 at 0.04 A·g^-1. A good capacity retention of 80% after 400 cycles at 1 A·g^-1 is also obtained, which is attributed to the stable crystal structure and the cointercalation reaction of Zn²⁺/H⁺. The reaction mechanism is investigated by in situ X-ray diffraction (XRD), ex situ XRD, ex situ X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS). This work not only provides a new phosphate cathode material for AZIBs but also gives a new strategy for improving the specific capacity of phosphate cathode material.

Metal-Organic Framework-Based Materials for Aqueous Zinc-Ion Batteries: Energy Storage Mechanism and Function

Aqueous rechargeable zinc-ion batteries (ZIBs) featuring competitive performance, low cost and high safety hold great promise for applications in grid-scale energy storage and portable electronic devices. Metal-organic frameworks (MOFs), relying on their large framework structure and abundant active sites, have been identified as promising materials in ZIBs. This review comprehensively presents the current development of MOF-based materials including MOFs and their derivatives in ZIBs, which begins with Zn storage mechanism of MOFs, followed by introduction of various types of MOF-based cathode materials (PB and PBA, Mn-based MOF, V-based MOF, conductive MOF and their derivatives), and the regulation approaches for Zn deposition behavior. The key factors and optimization strategies of MOF-based materials that affect ZIBs performance are emphasized and discussed. Finally, the challenges and further research directions of MOF-based materials for advanced zinc-ion batteries are provided.