An organosulfide-based energetic liquid as the catholyte in highenergy density lithium metal batteries for large-scale grid energy storage

Development of catholytes with long-cycle lifespan,high interfacial stability,and fast electrochemical kinetics is crucial for the comprehensive deployment of high-energy density lithium metal batteries(LMBs)with cost-efficiency.In this study,a lithiated 2-mercaptopyridine(2-MP-Li)organosulfide was synthesized and used as the soluble catholyte for the first time.Under the routine working mode,the LMB using this 2-MP-Li catholyte possessed high capacity retention of 55.4%with a Coulombic efficiency(CE)of near 100%after 2,000 cycles.When a cell system was fully filled with 2-MP-Li catholyte,it yielded a double capacity with 15%improvement in the capacity retention,corresponding to 0.0182%capacity decay per cycle,as well as excellent rate performance even at 6 mA·cm^(−2).These superior achievements resulted from the enhanced interfacial stability of Li anode induced by the salt-type 2-MP-Li molecule and the avoiding of using neutral catholyte as the initial active material,thereby mitigating the side reactions originating from the polysulfide shuttle effect.Furthermore,density functional theory(DFT)calculation and kinetics investigations proved the pseudocapacitive characteristic and faster ion diffusion coefficient with this design.Besides,the fabricated energy storage device showed excellent performance but with low economic cost and easy processing.Such a LMB with an alterable amount of capacity has a high potential to be applied in flow-cell type batteries for large-scale grid energy storage in the future.

New development of materials used in BFCs

Electrodes,catalysts,membranes,if present,are three main components in constructing an MFC for harvesting desired maximum power density and achieving higher coulombic efficiency (CE).Great improvements have been made,based on previous researches,in developing and diversifying materials,aside from architectures.Electrodes most familiar to us are widely used carbon materials.For anodes,carbon matrix composites(e.g.,a combination of polyaniline(PANI)with TiO2 using carbon as substrate)have gained special attention,though carbon material itself can exhibit excellent performance by diversifying molecular structures such as carbon nanotubes(CNTs).In the meanwhile,the evolution of MFC architectures,heading to the direction of improving power generation,contributes to the combination of membranes and cathodes from separate modes to diverse assemblies,on which all sorts of catalysts,such as from commonly used Pt to iron phthalocyanine (Pc),metal tetramethoxyphenylporphyrin(TMPP),MnOx,or pyrolyzed iron(Ⅱ)phthalocyanine (pyr-FePc),can be immobilized through synthesis of these catalysts with polymer such as Nafion 117 (Dupont Co.,USA)or tetrafluoroethylen(eTeflon)containing functional groups or Polypyrrol(ePPy).In addition,catholytes with aqueous cathode immersed or flowing through the surface of air-cathode are favorably proposed containing transition metal redox couples or iron chelates.

Progress and prospects of pH-neutral aqueous organic redox flow batteries:Electrolytes and membranes

Aqueous organic redox flow batteries(AORFBs),which exploit the reversible electrochemical reactions of water-soluble organic electrolytes to store electricity,have emerged as an efficient electrochemical energy storage technology for the grid-scale integration of renewable electricity.pH-neutral AORFBs that feature high safety,low corrosivity,and environmental benignity are particularly promising,and their battery performance is significantly impacted by redox-active molecules and ion-exchange membranes(IEMs).Here,representative anolytes and catholytes engineered for use in pH-neutral AORFBs are outlined and summarized,as well as their side reactions that cause irreversible battery capacity fading.In addition,the recent achievements of IEMs for pH-neutral AORFBs are discussed,with a focus on the construction and tuning of ion transport channels.Finally,the critical challenges and potential research opportunities for developing practically relevant pH-neutral AORFBs are presented.