Mn-based aqueous zinc-ion batteries (ZIBs) are promising candidate for large-scale rechargeable energy storage because of easy fabrication, low cost, and high safety. Nevertheless, the commercial application of Mn-based cathode is hindered by the challenging issues of low rate capability and poor cyclability. Herein, a manganese-vanadium hybrid, K-V2C@MnO2 cathode, featured with MnO2 nanosheets uniformly formed on a V2CTX MXene surface, is elaborately designed and synthesized by metal-cation intercalation and following in situ growth strategy. Benefiting from the hybrid structure with high conductivity, abundant active sites, and the synergistic reaction of Mn2+ electrodeposition and inhibited structural damage of MnO2, K-V2C@MnO2 shows excellent electrochemical performance for aqueous ZIBs. Specifically, it presents the high specific capacity of 408.1 mAh g-1 at 0.3 A g-1 and maintains the specific capacity of 119.2 mAh g-1 at a high current density of 10 A g-1 in a long-term cycle of up to 10000 cycles. It is superior to almost all reported Mn-based cathodes for ZIBs in the aqueous electrolyte. The superior electrochemical performance suggests that the Mn-based cathode materials designed in this work can be a rational approach to be applied for high-performance ZIBs cathodes.

Superior-Performance Aqueous Zinc-Ion Batteries Based on the In Situ Growth of MnO2 Nanosheets on V2CTX MXene.

Tuning Zn2+ coordination tunnel by hierarchical gel electrolyte for dendrite-free zinc anode.

The rapid advance of mild aqueous zinc-ion batteries (ZIBs) is driving the development of the energy storage system market. But the thorny issues of Zn anodes, mainly including dendrite growth, hydrogen evolution, and corrosion, severely reduce the performance of ZIBs. To commercialize ZIBs, researchers must overcome formidable challenges. Research about mild aqueous ZIBs is still developing. Various technical and scientific obstacles to designing Zn anodes with high stripping efficiency and long cycling life have not been resolved. Moreover, the performance of Zn anodes is a complex scientific issue determined by various parameters, most of which are often ignored, failing to achieve the maximum performance of the cell. This review proposes a comprehensive overview of existing Zn anode issues and the corresponding strategies, frontiers, and development trends to deeply comprehend the essence and inner connection of degradation mechanism and performance. First, the formation mechanism of dendrite growth, hydrogen evolution, corrosion, and their influence on the anode are analyzed. Furthermore, various strategies for constructing stable Zn anodes are summarized and discussed in detail from multiple perspectives. These strategies are mainly divided into interface modification, structural anode, alloying anode, intercalation anode, liquid electrolyte, non-liquid electrolyte, separator design, and other strategies. Finally, research directions and prospects are put forward for Zn anodes. This contribution highlights the latest developments and provides new insights into the advanced Zn anode for future research. 

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Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives

Engineering interfacial layers to enable Zn metal anodes for aqueous zinc-ion batteries

Aqueous Zn-ion batteries own great potential on next generation wearable batteries due to the high safety and low cost. However, the uncontrollable dendrites growth and the negligible subzero temperature performance impede the batteries practical applications. Herein, it is demonstrated that dimethyl sulfoxide (DMSO) is an effective additive in ZnSO4 electrolyte for side reactions and dendrites suppression by regulating the Zn-ion solvation structure and inducing the Zn2+ to form the more electrochemical stable (002) basal plane, via the higher absorption energy of DMSO with Zn2+ and (002) plane. Moreover, the stable reconstructed hydrogen bonds between DMSO and H2 O dramatically lower the freezing point of the electrolyte, which significantly increases the ionic conductivity and cycling performance of the aqueous batteries at subzero temperatures. As a consequence, the symmetrical Zn/Zn cell can be kept stable for more than 2100 h at 20 °C and 1200 h at -20 °C without dendrite and by-products formation. The Zn/MnO2 batteries can perform steadily for more than 3000 cycles at 20 °C and 300 cycles at -20 °C. This work provides a facile and feasible strategy on designing high performance and dendrite free aqueous Zn-ion batteries for various temperatures.

Immunizing Aqueous Zn Batteries against Dendrite Formation and Side Reactions at Various Temperatures via Electrolyte Additives.

Aqueous zinc-ion batteries (ZIBs) have emerged as the most promising alternative energy storage system, but the development of a suitable cathode and the issues of Zn anodes have remained challenging. Herein, an effective strategy of high-capacity layered Mg0.1V2O5·H2O (MgVO) nanobelts together with a concentrated 3 M Zn(CF3SO3)2 polyacrylamide gel electrolyte was proposed to achieve a durable and practical ZIB system. By adopting the designed concentrated gel electrolyte which not only inherits the high-voltage window and wide operating temperature of the concentrated electrolyte but also addresses the Zn dendrite formation problem, the prepared cathode exhibits an ultrahigh capacity of 470 mAh g-1 and a high rate capability of 345 mAh g-1 at 5.0 A g-1, and the assembled quasi-solid-state ZIBs achieve 95% capacity retention over 3000 cycles as well as a wide operating temperature from -30 to 80 °C, demonstrating a promising prospect for large-scale energy storage. In situ X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis (TGA) investigations also demonstrate a complex reaction mechanism for this cathode involving the (de)insertion of Zn2+, H+, and water molecules during cycling. The water molecules will reinsert into the interlayer and act as "pillars" to stabilize the host structure when Zn2+ is fully extracted.

High-Capacity Layered Magnesium Vanadate with Concentrated Gel Electrolyte toward High-Performance and Wide-Temperature Zinc-Ion Battery.

Zn2+ Induced Phase Transformation of K2MnFe(CN)6 Boosts Highly Stable Zinc-Ion Storage

Aqueous zinc hybrid capacitors are receiving intensive scientific interest due to them having the merits of both capacitors and batteries in achieving safety, high power and energy density, as well as long cycle life. Nonetheless, the dendrite growth and side reactions at the Zn/electrolyte interface are the biggest obstacles preventing them from large-scale applications. Here, we show that a non-conductive polyacrylamide (PAM)/polyvinylpyrrolidone (PVP) binary blend layer coated on a Zn anode can effectively suppress Zn dendrites and side reactions. The precise combination of ultra-high molecular weight PAM and low molecular weight PVP provides an excellent artificial anode/electrolyte interfacial layer with balanced adhesion, mechanical strength and hydrophilicity. The binary polymer interphase fundamentally uniformizes the localized electric field to regulate the ion migration in Zn plating/stripping, giving rise to superior electrochemical performance for the aqueous zinc hybrid capacitors. This study represents a promising approach for mitigating the long-lasting Zn dendrite growth issue.

Uniformizing the electric field distribution and ion migration during zinc plating/stripping via a binary polymer blend artificial interphase

Aqueous full K-ion batteries (AFKIBs) featuring high safety, low cost, and environmental friendliness represent the future of advanced energy storage technologies. However, current AFKIB systems are still in need of suitable electrolytes and electrode materials, not to mention durability. Here, we report a “rocking-chair” type aqueous full K-ion system with KTi2(PO4)3/C crystalline nanoparticles as the anode material with near zero-strain, iron hexacyanoferrate as the cathode, and 21 m KCF3SO3 as a water-in-salt electrolyte. Benefitting from the fast reaction kinetics and high structural stability of KTi2(PO4)3/C, the full battery achieves a high capacity retention of 96.7% over 30 000 cycles, excellent rate performance with full charge and discharge in 1 minute, and a high energy density of 47.3 W h kg−1. Demonstration of the performance of this AFKIB system expands the avenues of exploration for large-scale energy storage.

Zhuqing Zhou

Papers

High-Capacity Layered Magnesium Vanadate with Concentrated Gel Electrolyte toward High-Performance and Wide-Temperature Zinc-Ion Battery.

Zn2+ Induced Phase Transformation of K2MnFe(CN)6 Boosts Highly Stable Zinc-Ion Storage

Uniformizing the electric field distribution and ion migration during zinc plating/stripping via a binary polymer blend artificial interphase

An ultra-long life aqueous full K-ion battery

A hybrid superconcentrated electrolyte enables 2.5 V carbon-based supercapacitors