Self-Assembled Layer of Organic Phosphonic Acid Enables Highly Stable MnO2 Cathode for Aqueous Znic Batteries.

Manganese dioxide (MnO2 ) is an attractive cathode material for aqueous zinc batteries (AZBs) owing to its environmental benignity, low cost, high operating voltage, and high theoretical capacity. However, the severe dissolution of Mn2+ leads to rapid capacity decay. Herein, a self-assembled layer of amino-propyl phosphonic acid (AEPA) on the MnO2 surface, which significantly improves its cycle performance is successfully modified. Specifically, AEPA can be firmly attached to MnO2 through a strong chemical bond, forming a hydrophobic, and uniform organic coating layer with a few nanometers thickness. This coating layer can significantly inhibit the dissolution of Mn2+ by avoiding the direct contact between the electrolyte and cathode, thus enhancing the structural integrity and redox reversibility of MnO2 . As a result, the MnO2 @AEPA cathode achieves a high reversible capacity of 223 mAh g-1 at 0.5 A g-1 and a high capacity retention of 97% after 1700 cycles at 1 A g-1 . This work provides new insights in developing stable Mn-based cathodes for aqueous batteries.

Rationally Designed ZnTe@C Nanowires with Superior Zinc Storage Performance for Aqueous Zn Batteries.

Te-based materials with excellent electrical conductivity and ultra-high volume specific capacity have attracted much attention for the cost-efficient aqueous Zn batteries. However, the construction of functional structures with mild volume expansion and suppressed shuttle effects, enabling an expanded lifespan, is still a challenge for conversion-type materials. Herein, the carbon-coated zinc telluride nanowires (ZnTe@C NWs) are rationally designed as a high-performance cathode material for aqueous Zn batteries. The carbon-coated1D nanostructure could not only provide optimized transmission path for electrons and ions, but also help to maintain structure integrity upon volume variation and suppress intermediates dissolution, endowing the ZnTe@C NWs with improved cycling stability and reaction kinetics. Consequently, a reversible six-electron reaction mechanism of ZnTe@C NWs based on Te2- /Te4+ conversion with excellent output capacity (586 mAh g-1 at 0.1 A g-1 ) and lifespan (>250 mAh g-1 retained for 400 cycles at 1 A g-1 ) is eventually achieved.

Boosting Cathode Activity and Anode Stability of Zn-S Batteries in Aqueous Media Through Cosolvent-Catalyst Synergy.

Aqueous Zn-S battery with high energy density represents a promising large-scale energy storage technology, but its application is severely hindered by the poor reversibility of both S cathode and Zn anode. Herein, we develop a "cocktail optimized" electrolyte containing tetraglyme (G4) and water as co-solvents and I2 as additive. The G4-I2 synergy could activate efficient polar I3 - /I- catalyst couple and shield the cathode from water, thus facilitating the conversion kinetics of S and suppressing the interfacial side reactions. Simultaneously, it could stabilize Zn anode by forming an organic-inorganic interphase upon cycling. With boosted electrodes reversibility, the Zn-S cell delivers a high capacity of 775 mAh g-1 at 2 A g-1 , and retains over 70 % capacity after 600 cycles at 4 A g-1 . The advances can also be readily generalized to other ethers/water hybrid electrolytes, showing the universality of the "cocktail optimized" electrolyte design strategy.