Search

The utilization of liquid electrolytes (LEs) concerns inevitable dendrite growth and safety issues. In contrast, solid polymer electrolytes suffer from unsettled low ionic conductivity and interfacial impedance issues. The intermediary gel polymer electrolytes (GPEs) improve safety by incorporating a sturdy polymer matrix and ionic conductivity as an advantage of percolating LEs responsible for gelation. The overall stability and compatibility of GPEs with different electrode materials depend on the polymers, plasticizers, and precursors utilized. No single polymer has a wide energy gap to exhibit stability against Li metal anodes and oxidative stability against high‐voltage cathodes. Thereafter, symmetric GPEs (SGPEs) possess limitations while simultaneously satisfying the two electrode requirements, which hinders their practical applications. Asymmetric GPEs (ASGPEs) generally comprise a bilayer or gradient structure, wherein the side contacting the cathode is modified to promote oxidative stability for a stable cathode electrolyte interface (CEI). The corresponding side in contact with the anode is modified to be mechanically and chemically compatible with dendritic lithium. Overall, asymmetric structural engineering enables electrode compatibility while maintaining the physical competency of GPEs. Herein, the focus is to summarize the current transition from SGPEs to asymmetric ones, which promotes multifunctionality while overcoming specific constraints associated with the electrodes. [ABSTRACT FROM AUTHOR]

Catalysts assumed that properly designed bimetallic systems would provide superior catalytic performance due to the cooperative effects between two atoms. Dual single‐atom catalyst (DSAC) PdN4/CuN4 is synthesized using a simple, cost‐effective, and efficient electrochemical reduction method. The palladium single‐atom is prepared first by electrochemical reduction of copper phthalocyanine to create defective N4 sites. The new structural feature is characterized by copper reduction from Cu‐N4 coordination and the formation of defected N4 (▫M‐N4) sites, which react with a Pd precursor and form PdN4 on the host surface. The DSAC PdN4/CuN4 technique synergistically improves electrocatalytic performance toward the ethylene glycol oxidation reaction. It possesses excellent glycolate selectivity (above 88%) in an alkaline solution with an onset oxidation potential as low as 0.6 V versus a reversible hydrogen electrode, compared to commercial Pd/C. The DSAC electrocatalyst is characterized by its high current density of 83.92 mA cm−2 and high faradic efficiency value (>80%) for glycolate at 1.0 VRHE. The findings suggest a promising method to synthesize the DSACs in varying transition metals to achieve highly efficient, selective, and environmentally friendly catalysts for different applications. [ABSTRACT FROM AUTHOR]

Electrochemical reduction of carbon dioxide (CO2RR) into value‐added chemicals is a promising tactic to mitigate global warming. However, this process resists catalyst preparation, low faradaic efficiency (FE%) towards multi‐carbon products, and insights into mechanistic understanding. Indeed, it is demonstrated that this Fe single‐atom catalyst (Fe SAC) exists in three oxygen coordination of Fe–(O)3 configuration in Nafion coated functionalized multi‐wall carbon nanotubes (Fe‐n‐f‐CNTs), which is obtained via a simple ionic exchange method under ambient conditions. The electrochemical performance reveals that Fe SACs achieve an FE of 45% and a yield rate of 56.42 µmol cm−2 h−1 at −0.8 VRHE for ethanol. In situ X‐ray analysis reveals that the Fe SACs have variable electronic states and keeps close +3 of the oxidation state at the potential range of CO2RR. The catalytic feature reduces the reaction energy and induces the electrons transferred to the adsorbed products intermediates of *COOH and *OCHO, thus promoting CO. The carboxylic functional group on the CNTs stabilizes the Fe active sites via electrostatic interaction, verified by density functional theory calculations. The yield rate of Fe SACs indicates that the Fe single‐atom site can instantly provide a large CO to help conversion of CO2‐to‐C2 product on the CNTs. [ABSTRACT FROM AUTHOR]

Zinc metal is considered a promising anode material for aqueous zinc ion batteries. However, it suffers from dendrite growth, corrosion, and low coulombic efficiency (CE) during plating/stripping. Herein, a concentrated hybrid (4 m Zn(CF3SO3)2 + 2 m LiClO4) aqueous electrolyte (CHAE) to overcome the challenges facing the Zn anode is reported. The developed electrolyte achieves dendrite‐free Zn plating/stripping and obtains an excellent CE of ≈100%, surpassing the previously reported values. The combination of synchrotron‐based in operando transmission X‐ray microscopy, X‐ray diffraction, and ex situ X‐ray photoelectron spectroscopy analyses indicate that the denser, anion‐derived passivation layer formed using the CHAE facilitates homogeneous current distribution and better prevents freshly deposited Zn from directly contacting the electrolyte than the looser, solvent‐derived layers formed from a dilute hybrid aqueous electrolyte (DHAE). The beneficial effects of the CHAE on the compact, dense, and stable salt‐anion‐derived passivation layer can be attributed to its unique solvation structure, which suppresses the water‐related side reactions and widens the electrochemical potential window. In the hybrid Zn||LiFePO4 configuration, the CHAE‐based cell delivered a stable performance of CE >99% and capacity retention >90% after 285 cycles. In contrast, the DHAE‐based cell exhibits capacity retention of <65% after 170 cycles. [ABSTRACT FROM AUTHOR]

It is essential to decouple the interfacial reactions taking place at the anode and cathode in rechargeable batteries. However, due to the reactive nature of Li, it is challenging to use Li‐metal batteries (LMBs) protocol to decouple the interfacial reactions. The by‐products from the anode or cathode become mixed in Li/NMC111 cells, which make decoupling interfacial reactions difficult. Here, reactions at electrodes are successfully decoupled and demystified using a protocol combining anode‐free LMB (AFLMB) with online electrochemical mass spectroscopy. LiPF6 in ethylene carbonate (EC)/diethyl carbonate (DEC) and EC/ethyl methyl carbonate (1:1 v/v%) electrolytes are used to compare interfacial reactions in Li/NMC111 and Cu/NMC111 cells. In Cu/NMC111, the evolution of CO2, CO, and C2H4 gases at the initial stage of first charging is due to interfacial reactions at Cu surface due to solid–electrolyte‐interphase formation. However, the evolution of CO2 and CO gases at high voltage in the entire cycles is associated with chemical and/or electrochemical electrolyte oxidation at the cathode. This work paves a new concept to decouple interfacial reactions at electrodes for developing electrochemically stable electrolytes to improve the performance with the long‐cycling life of AFLMBs and LMBs. [ABSTRACT FROM AUTHOR]