https://www.cell.com/joule/pdf/S2542-4351(20)30094-5.pdf

Scientific Challenges for the Implementation of Zn-Ion Batteries

Rechargeable aqueous metal-ion batteries are very promising as alternative energy storage devices during the post-lithium-ion era because of their green and safe inherent features. Among the different aqueous metal-ion batteries, aqueous zinc-ion batteries (ZIBs) have recently been studied extensively due to their unique and outstanding benefits that hold promise for large-scale power storage systems. However, zinc anode problems in ZIBs, such as zinc dendrites and side reactions, severely shorten the ZIB's cycle lifetime, thus restricting their practical application. Here, we sum up in detail the recent progress on general strategies to suppress zinc dendrites and zinc anode side reactions based on advanced materials and structure design, including the modification of the planar zinc electrode surface layer, internal structural optimization of the zinc bulk electrode, modification of the electrolyte and construction of the multifunctional separator. The various functional materials, structures and battery efficiencies are discussed. Finally, the challenges for ZIBs are identified in the production of functional zinc anodes.

Challenges in the material and structural design of zinc anode towards high-performance aqueous zinc-ion batteries

The development of low-cost and high-safety zinc-ion batteries (ZIBs) has been extensively discussed and reviewed in recent years, but the work on the comprehensive discussion and perspectives in developing zinc-ion electrolytes is still relatively lacking. Faced with critical challenges and bottlenecks practically, the viability of ZIBs critically depends on the development of suitable electrolytes and their practical considerations. In this review, a systematic summary with regard to the basic characteristics of zinc-ion electrolytes facing different issues from optimization strategies to the fundamental science of electrolyte/electrode interfaces (EEIs), particularly in the feasible modifications and advanced characterizations of EEIs, has been put forward. Due to the lack of consideration of the practical issues in major academic studies, we have particularly highlighted aspects that mainly focus on the choice of the electrolyte system, dosage of liquid and fluid electrolytes, status of gel and all-solid electrolytes, together with other concerns related to the electrolytes. The final section proposes significant perspectives to guide and promote the development of zinc-ion electrolytes.

Fundamentals and perspectives in developing zinc-ion battery electrolytes: a comprehensive review

Despite the prevalence of lithium ion batteries in modern technology, the search for alternative electrochemical systems to complement the global battery portfolio is an ongoing effort. The search has resulted in numerous candidates, among which mildly acidic aqueous zinc ion batteries have recently garnered significant academic interest, mostly due to their inherent safety. As the anode is often fixed as zinc metal in these systems, most studies address the absence of a suitable cathode for reaction with zinc ions. This has led to aggressive research into viable intercalation cathodes, some of which have shown impressive results. However, many investigations often overlook the implications of the zinc metal anode, when in fact the anode is key to determining the energy density of the entire cell. In this regard, we aim to shed light on the importance of the zinc metal anode. This perspective offers a brief discussion of zinc electrochemistry in mildly acidic aqueous environments, along with an overview of recent efforts to improve the performance of zinc metal to extract key lessons for future research initiatives. Furthermore, we discuss the energy density ramifications of the zinc anode with respect to its weight and reversibility through simple calculations for numerous influential reports in the field. Finally, we offer some perspectives on the importance of optimizing zinc anodes as well as a future direction for developing high-performance aqueous zinc ion batteries.

/pdf/aqueous-zinc-ion-batteries-focus-on-zinc-metal-anodes-bv8c9z5p8o.pdf

Aqueous zinc ion batteries: focus on zinc metal anodes

Strategies for the Stabilization of Zn Metal Anodes for Zn‐Ion Batteries

Tuning Zn2+ coordination environment to suppress dendrite formation for high-performance Zn-ion batteries

Aqueous zinc (Zn) batteries (AZBs) are widely considered as a promising candidate for next-generation energy storage owing to their excellent safety features. However, the application of a Zn anode is hindered by severe dendrite formation and side reactions. Herein, an interfacial bridged organic-inorganic hybrid protection layer (Nafion-Zn-X) is developed by complexing inorganic Zn-X zeolite nanoparticles with Nafion, which shifts ion transport from channel transport in Nafion to a hopping mechanism in the organic-inorganic interface. This unique organic-inorganic structure is found to effectively suppress dendrite growth and side reactions of the Zn anode. Consequently, the Zn@Nafion-Zn-X composite anode delivers high coulombic efficiency (ca. 97 %), deep Zn plating/stripping (10 mAh cm-2 ), and long cycle life (over 10 000 cycles). By tackling the intrinsic chemical/electrochemical issues, the proposed strategy provides a versatile remedy for the limited cycle life of the Zn anode.

An Interface-Bridged Organic-Inorganic Layer that Suppresses Dendrite Formation and Side Reactions for Ultra-Long-Life Aqueous Zinc Metal Anodes.

Structure and Properties of Prussian Blue Analogues in Energy Storage and Conversion Applications

Aqueous Zn-MnO2 batteries using mild electrolyte show great potential in large-scale energy storage (LSES) application, due to high safety and low cost. However, structure collapse of manganese oxides upon cycling caused by the conversion mechanism (e.g., from tunnel to layer structures for α-, β-, and γ-phases) is one of the most urgent issues plaguing its practical applications. Herein, to avoid the phase conversion issue and enhance battery performance, a structurally robust novel phase of manganese oxide MnO2 H0.16 (H2 O)0.27 (MON) nanosheet with thickness of ≈2.5 nm is designed and synthesized as a promising cathode material, in which a nanosheet structure combined with a novel H+ /Zn2+ synergistic intercalation mechanism is demonstrated and evidenced. Accordingly, a high-performance Zn/MON cell is achieved, showing a high energy density of ≈228.5 Wh kg-1 , impressive cyclability with capacity retention of 96% at 0.5 C after 300 cycles, as well as exhibiting rate performance of 115.1 mAh g-1 at current rate of 10 C. To the best current knowledge, this H+ /Zn2+ synergistic intercalation mechanism is first reported in an aqueous battery system, which opens a new opportunity for development of high-performance aqueous Zn ion batteries for LSES.

Unravelling H + /Zn 2+ Synergistic Intercalation in a Novel Phase of Manganese Oxide for High-Performance Aqueous Rechargeable Battery

Manganese oxides (MnO2 ) are promising cathode materials for various kinds of battery applications, including Li-ion, Na-ion, Mg-ion, and Zn-ion batteries, etc., due to their low-cost and high-capacity. However, the practical application of MnO2 cathodes has been restricted by some critical issues including low electronic conductivity, low utilization of discharge depth, sluggish diffusion kinetics, and structural instability upon cycling. Preintercalation of ions/molecules into the crystal structure with/without structural reconstruction provides essential optimizations to alleviate these issues. Here, the intrinsic advantages and mechanisms of the preintercalation strategy in enhancing electronic conductivity, activating more active sites, promoting diffusion kinetics, and stabilizing the structural integrity of MnO2 cathode materials are summarized. The current challenges related to the preintercalation strategy, along with prospects for the future research and development regarding its implementation in the design of high-performance MnO2 cathodes for the next-generation batteries are also discussed.

Runzhi Qin

Papers

Tuning Zn2+ coordination environment to suppress dendrite formation for high-performance Zn-ion batteries

An Interface-Bridged Organic-Inorganic Layer that Suppresses Dendrite Formation and Side Reactions for Ultra-Long-Life Aqueous Zinc Metal Anodes.

Structure and Properties of Prussian Blue Analogues in Energy Storage and Conversion Applications

Unravelling H + /Zn 2+ Synergistic Intercalation in a Novel Phase of Manganese Oxide for High-Performance Aqueous Rechargeable Battery

Preintercalation Strategy in Manganese Oxides for Electrochemical Energy Storage: Review and Prospects