Binary and Ternary Manganese Dioxide Composites Cathode for Aqueous Zinc-ion Battery

Electrolyte Decoupling Strategy for Metal Oxide-Based Zinc-Ion Batteries Free of Crosstalk Effect

The crosstalk of transition metal ions between the metal oxide cathode and Zn anode restricts the practical applications of aqueous zinc-ion batteries (ZIBs). Herein, we propose a decoupled electrolyte (DCE) consisting of a nonaqueous-phase (N-phase) anolyte and an aqueous-phase (A-phase) catholyte to prevent the crosstalk of Mn2+, thus extending the lifespan of MnO2-based ZIBs. Experimental measurements and theoretical modelling verify that trimethyl phosphate (TMP) not only synergistically works with NH4Cl in the N-phase anolyte to enable fast Zn2+ conduction while blocking Mn2+ diffusion toward anode, but also modifies the Zn2+ solvation structure to suppress the dendrite formation and corrosion on Zn anode. Meanwhile, the A-phase catholyte effectively accelerates the cathode reaction kinetics. The as-developed Zn|DCE|MnO2 cell delivers 80.13 % capacity retention after 900 cycles at 0.5 A g-1. This approach is applicable for other metal oxide cathode-based ZIBs, thereby opening a new avenue for developing ultrastable ZIBs.

A Feasible Strategy for High-Performance Aqueous Zinc-Ion Batteries: Introducing Conducting Polymer

Aqueous zinc ion batteries (AZIBs) offer great potential for large-scale energy storage because of their high safety, low cost and acceptable energy density. However, the cycle life of AZIBs is inevitably affected by parasitic reactions and dendritic growth caused by multiple factors such as electrode, electrolyte and separator, which pose significant obstacles to the practical application of AZIBs. To address these challenges, conducting polymer (CP) based materials have gained widespread attention in the realm of rechargeable batteries due to the adjustable band gap, controllable morphology, and excellent flexibility of CPs. In particular, CPs exhibit remarkable conductivity, low dimensionality, and doping characteristics, making them highly promising for integration into the AZIB system. In this review, the problems associated with the cathode, anode, electrolyte, and separator of AZIBs are discussed, and the application of CPs for their modification is summarized. The review provides a comprehensive analysis of the action mechanisms involved in the CP modification process and offers valuable insights for the design and development of CPs that can be effectively utilized in AZIBs. Additionally, the review presents a promising outlook of this research field, aiming to further advance the application of low-cost and high-performance CPs and their composites in AZIBs.

Proton-self-doped PANI@CC as the cathode for high-performance aqueous zinc-ion battery

Aqueous zinc-ion batteries (AZIB) have several advantages such as low cost, large theoretical capacity and good safety. However, the development of polyaniline (PANI) cathode materials has been limited by slow diffusion kinetics. Herein, proton-self-doped polyaniline@carbon cloth (CC) (PANI@CC) was prepared via in-situ polymerization, where polyaniline was deposited on an activated carbon cloth. The PANI@CC cathode exhibits a high specific capacity of 234.3 mA h g-1 at 0.5 A g-1, and excellent rate performance, delivering a capacity of 143 mA h g-1 at 10 A g-1. Furthermore, the reversible redox conversion during the charge-discharge process was studied using ex-situ X-ray photoelectron spectroscopy (XPS) and ex-situ Raman spectra. The results show that the excellent performance of the PANI@CC battery can be attributed to the formation of a conductive network between the carbon cloth and polyaniline. Also, a mixing mechanism involving insertion/extraction of Zn2+/H+ and a double-ion process is proposed. PANI@CC electrode is a novel idea for developing high-performance batteries.

Material Design and Energy Storage Mechanism of Mn-Based Cathodes for Aqueous Zinc-Ion Batteries

Mn-based cathodes have been widely explored for aqueous zinc-ion batteries (ZIBs), by virtue of their high theoretical capacity and low cost. However, Mn-based cathodes suffer from poor rate capability and cycling performance. Researchers have presented various approaches to address these issues. Therefore, these endeavors scattered in various directions (e. g., designing electrode structures, defect engineering and optimizing electrolytes) are necessary to be connected through a systematic review. Hence, we comprehensively overview Mn-based cathode materials for ZIBs from the aspects of phase compositions, electrochemical behaviors and energy storage mechanisms, and try to build internal relations between these factors. Modification strategies of Mn-based cathodes are then introduced. Furthermore, this review also provides some new perspectives on future efforts toward high-energy and long-life Mn-based cathodes for ZIBs.

Unveiling Critical Insight into the Zn Metal Anode Cyclability in Mildly Acidic Aqueous Electrolytes: Implications for Aqueous Zinc Batteries

The cost benefit and inherent safety conferred by the energy-dense metallic zinc anode and mildly acidic aqueous electrolytes are critical to aqueous zinc batteries' (AZBs) large-scale energy-storage ambition. Aggressive research efforts in the past five years have resulted in the discovery of several high-energy positive (cathode) host materials, but understanding of the Zn anode rechargeability and any influence of the electrolyte, which are critical for AZBs' practical development, remains limited. As we unravel here, under realistic test conditions, when parameters are set keeping practical applications in mind, Zn anode cycling appears vulnerable to dendritic failure in all common AZB electrolytes. While 3 M ZnSO₄ delivers the best overall performance for the Zn anode cycling, viability of the oxidatively stable "water in salt" electrolyte appears gravely restricted. Defying the general understanding of metal electrodeposition, a high current density is found to dramatically prolong the Zn cycling lifetime, achieving >8000 cycles at 20 mA cm^-2 for 1 mAh cm^-2 capacity in 3 M ZnSO₄. High current also allows prolonged cycling at capacities of 2 and 4 mAh cm^-2. Such a striking improvement in lifetime on going from low to high currents is further confirmed through Zn|Zn_0.25V₂O₅ and Zn|LiMn₂O₄ full-cell studies with practical electrode loading. Not surprisingly, all the parameters influence the cycled Zn morphology, which in turn dictates the propensity for short-circuit. These findings not only divulge previously unanticipated insight into the Zn anode cycling and electrolyte performance in AZBs but also offer a rational basis to gauge their practical development.