A Membrane-Free Rechargeable Seawater Battery Unlocked by Lattice Engineering

Seawater batteries that directly utilize natural seawater as electrolytes are ideal sustainable aqueous devices with high safety, exceedingly low cost, and environmental friendliness. However, the present seawater batteries are either primary batteries or rechargeable half-seawater/half-nonaqueous batteries because of the lack of suitable anode working in seawater. Here, a unique lattice engineering to unlock the electrochemically inert anatase TiO2 anode to be highly active for the reversible uptake of multiple cations (Na+, Mg2+, and Ca2+) in aqueous electrolytes is demonstrated. Density functional theory calculations further reveal the origin of the unprecedented charge storage behaviors, which can be attributed to the significant reduction of the cations diffusion barrier within the lattice, i.e., from 1.5 to 0.4 eV. As a result, the capacities of anatase TiO2 with 2.4% lattice expansion are ≈100 times higher than the routine one in natural seawater, and ≈200 times higher in aqueous Na+ electrolyte. The finding will significantly advance aqueous seawater energy storage devices closer to practical applications.

Recent Advances in Structural Optimization and Surface Modification on Current Collectors for High-Performance Zinc Anode: Principles, Strategies, and Challenges

The last several years have witnessed the prosperous development of zinc-ion batteries (ZIBs), which are considered as a promising competitor of energy storage systems thanks to their low cost and high safety. However, the reversibility and availability of this system are blighted by problems such as uncontrollable dendritic growth, hydrogen evolution, and corrosion passivation on anode side. A functionally and structurally well-designed anode current collectors (CCs) is believed as a viable solution for those problems, with a lack of summarization according to its working mechanisms. Herein, this review focuses on the challenges of zinc anode and the mechanisms of modified anode CCs, which can be divided into zincophilic modification, structural design, and steering the preferred crystal facet orientation. The possible prospects and directions on zinc anode research and design are proposed at the end to hopefully promote the practical application of ZIBs.

2D Materials Boost Advanced Zn Anodes: Principles, Advances, and Challenges

Aqueous zinc-ion battery (ZIB) featuring with high safety, low cost, environmentally friendly, and high energy density is one of the most promising systems for large-scale energy storage application. Despite extensive research progress made in developing high-performance cathodes, the Zn anode issues, such as Zn dendrites, corrosion, and hydrogen evolution, have been observed to shorten ZIB's lifespan seriously, thus restricting their practical application. Engineering advanced Zn anodes based on two-dimensional (2D) materials are widely investigated to address these issues. With atomic thickness, 2D materials possess ultrahigh specific surface area, much exposed active sites, superior mechanical strength and flexibility, and unique electrical properties, which confirm to be a promising alternative anode material for ZIBs. This review aims to boost rational design strategies of 2D materials for practical application of ZIB by combining the fundamental principle and research progress. Firstly, the fundamental principles of 2D materials against the drawbacks of Zn anode are introduced. Then, the designed strategies of several typical 2D materials for stable Zn anodes are comprehensively summarized. Finally, perspectives on the future development of advanced Zn anodes by taking advantage of these unique properties of 2D materials are proposed.

Towards the practical application of Zn metal anodes for mild aqueous rechargeable Zn batteries

Rechargeable aqueous Zn batteries have been widely investigated in recent years due to the merits of high safety and low cost. However inevitable dendrite growth, corrosion and hydrogen evolution of Zn anodes severely compromise the practical lifespan of rechargeable Zn batteries. Despite the encouraging improvements for Zn anodes reported in the literature, the comprehensive understanding of Zn anodes under practical conditions is still often neglected. In this article, we focus on the “less-discussed” but critically important points for rechargeable aqueous Zn batteries, including revisit of the relationship between the coulombic efficiency and lifespan of Zn anodes, the rational control of the pH environment in the vicinity of Zn anodes, the design of appropriate aqueous separators and the relevant estimation of practical energy density for aqueous Zn batteries. It concludes that energy density of 60–80 W h kg⁻¹ for aqueous Zn batteries should be realistic in practice with appropriate cell design. We also propose practical technical recommendations for the rational development of aqueous Zn batteries based on research experience from the community and our group. We hope this article offers readers more practical insights into the future development of aqueous Zn batteries as competitive technology for practical use.

This perspective article focuses on discussing several “less-developed” but important topics for Zn anodes and try to present readers a practical angle to look at the development of aqueous Zn batteries.

Unraveling H+/Zn2+ Sequential Conversion Reactions in Tellurium Cathodes for Rechargeable Aqueous Zinc Batteries

Progress toward practical rechargeable aqueous zinc (Zn) batteries is impeded by the low energy density. The use of tellurium (Te) cathodes featuring multielectron redox reactions offers one possible approach to mitigating this dilemma. However, the corresponding energy-storage mechanisms in aqueous electrolytes are not established yet. Here, we uncover a H⁺/Zn²⁺-involved sequential conversion reaction with 6e^- transfer for Te-based cathodes, which accounts for the outstanding capacity (over 460 mAh g^-1 at 50 mA g^-1). Two distinct redox processes, corresponding to TeO₂ ↔ Te and Te ↔ ZnTe, are explicitly revealed within the electrochemical window of routine aqueous Zn electrolytes. The mechanism elucidated here complements the understanding of energy-dense Te centers and propels the exploration of high-capacity electrodes for multivalent battery chemistries.