Research advances in magnesium and magnesium alloys worldwide in 2020

Herein, a novel dual single-atom catalyst comprising adjacent Fe-N4 and Mn-N4 sites on 2D ultrathin N-doped carbon nanosheets with porous structure (FeMn-DSAC) was constructed as the cathode for a flexible low-temperature Zn-air battery (ZAB). FeMn-DSAC exhibits remarkable bifunctional activities for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Control experiments and density functional theory calculations reveal that the catalytic activity arises from the cooperative effect of the Fe/Mn dual-sites aiding *OOH dissociation as well as the porous 2D nanosheet structure promoting active sits exposure and mass transfer during the reaction process. The excellent bifunctional activity of FeMn-DSAC enables the ZAB to operate efficiently at ultra-low temperature of -40 °C, delivering 30 mW cm-2 peak power density and retaining up to 86 % specific capacity from the room temperature counterpart. 

Engineering Dual Single‐Atom Sites on 2D Ultrathin N‐doped Carbon Nanosheets Attaining Ultra‐Low Temperature Zn‐Air Battery

The new‐generation flexible aqueous zinc‐ion batteries require enhanced mechanical properties and ionic conductivities at low temperature for practical applications. This fundamentally means that it is desired that the hydrogel electrolyte possesses antifreezing merits to resist flexibility loss and performance decrease at subzero temperatures. Herein, a highly flexible polysaccharide hydrogel is realized in situ and is regulated in zinc‐ion batteries through the Hofmeister effect with low‐concentration Zn(ClO4)2 salts to satisfy the abovementioned requirements. The chaotropic ClO4− anions, water, and polymer chains can form ternary and weak hydrogen bonding (HB), which enables the polymer chains to have improved mechanical properties, breaks the HB of water to remarkably decrease the electrolyte freezing point, and reduces the amounts of free water for effective side reactions and dendrite inhibition. Consequently, even at −30 °C, the Zn(ClO4)2 in situ optimized hydrogel electrolyte features a high ionic conductivity of 7.8 mS cm−1 and excellent flexibility, which enables a Zn/polyaniline (PANI) battery with a reversible capacity of 70 mA h g−1 under 5 A g−1 for 2500 cycles, and renderd the flexible full battery with excellent cycling performances under different bending angles. This work provides a new pathway for designing high‐performance antifreezing flexible batteries via the Hofmeister effect.

Antifreezing Hydrogel Electrolyte with Ternary Hydrogen Bonding for High‐Performance Zinc‐Ion Batteries

Multi-Functional Hydrogels for Flexible Zinc-Based Batteries Working under Extreme Conditions

The practical application of the Zn‐metal anode for aqueous batteries is greatly restricted by catastrophic dendrite growth, intricate hydrogen evolution, and parasitic surface passivation. Herein, a polyanionic hydrogel film is introduced as a protective layer on the Zn anode with the assistance of a silane coupling agent (denoted as Zn–SHn). The hydrogel framework with zincophilic –SO3− functional groups uniformizes the zinc ions flux and transport. Furthermore, such a hydrogel layer chemically bonded on the Zn surface possesses an anti‐catalysis effect, which effectively suppresses both the hydrogen evolution reaction and formation of Zn dendrites. As a result, stable and reversible Zn stripping/plating at various currents and capacities is achieved. A full cell by pairing the Zn–SHn anode with a NaV3O8·1.5 H2O cathode shows a capacity of around 176 mAh g−1 with a retention around 67% over 4000 cycles at 10 A g−1. This polyanionic hydrogel film protection strategy paves a new way for future Zn‐anode design and safe aqueous batteries construction.

Stable Zinc Anodes Enabled by a Zincophilic Polyanionic Hydrogel Layer

Scientometric review of proton-conducting solid oxide fuel cells

A New Solid‐State Zinc–Air Battery for Fast Charge

Flexible solid-state zinc-air batteries (ZABs) generally suffer from poor electrolyte/electrode contact and mechanical degradation in practical applications. In addition, CO2 corrosion is also a common issue for ZABs with alkaline electrolyte. Herein, we report a thermoreversible alkaline hydrogel electrolyte that can simultaneously solve the aforementioned problems. Through a simple cooling process, the hydrogel electrolyte transforms from solid state to liquid state that can not only restore the deformed electrolyte layer to its original state but also rebuild intimate contact between electrode and electrolyte. Moreover, the ZAB based on this hydrogel electrolyte exhibits an unprecedented anti-CO2 property. As a result, such a battery shows almost 2.5 times discharge duration than that of ZAB based on liquid electrolyte.

/pdf/self-healing-and-anti-co2-hydrogels-for-flexible-solid-state-3hg4bvs0hr.pdf

Siyuan Zhao

Papers

Multi-Functional Hydrogels for Flexible Zinc-Based Batteries Working under Extreme Conditions

Scientometric review of proton-conducting solid oxide fuel cells

A New Solid‐State Zinc–Air Battery for Fast Charge

Self-Healing and Anti-CO2 Hydrogels for Flexible Solid-State Zinc-Air Batteries.

All-in-one and bipolar-membrane-free acid-alkaline hydrogel electrolytes for flexible high-voltage Zn-air batteries