A water-in-salt electrolyte (WiSE) offers an electrochemical stability window much wider than typical aqueous electrolytes but still falls short in accommodating high-energy anode materials, mainly because of the enrichment of water molecules in the primary solvation sheath of Li + . Herein, we report a new strategy in which a non-Li cosalt was introduced to alter the Li + -solvation sheath structure. The presence of an asymmetric ammonium salt (Me 3 EtN•TFSI) in water increases the solubility of LiTFSI by two times, pushes the salt/water molar ratio from 0.37 in WiSE to an unprecedented value of 1.13, and significantly suppresses the water activity in both bulk electrolyte and the Li + -solvation sheath. This new 63 m (mol kg solvent −1 ) aqueous electrolyte (42 m LiTFSI + 21 m Me 3 EtN•TFSI) offers a wide potential window of 3.25 V and supports a 2.5 V aqueous Li-ion battery (LiMn 2 O 4 //Li 4 Ti 5 O 12 ) to deliver a high energy density of 145 Wh kg −1 stably over 150 cycles.

Engineering a stable solid electrolyte interphase (SEI) is critical for suppression of lithium dendrites. However, the formation of a desired SEI by formulating electrolyte composition is very difficult due to complex electrochemical reduction reactions. Here, instead of trial-anderror of electrolyte composition, we design a Li-11 wt % Sr alloy anode to form a SrF 2 -rich SEI in fluorinated electrolytes. Density functional theory (DFT) calculation and experimental characterization demonstrate that a SrF 2 -rich SEI has a large interfacial energy with Li metal and a high mechanical strength, which can effectively suppress the Li dendrite growth by simultaneously promoting the lateral growth of deposited Li metal and the SEI stability. The Li−Sr/Cu cells in 2 M LiFSI-DME show an outstanding Li plating/stripping Coulombic efficiency of 99.42% at 1 mA cm −2 with a capacity of 1 mAh cm −2 and 98.95% at 3 mA cm −2 with a capacity of 2 mAh cm −2 , respectively. The symmetric Li−Sr/Li−Sr cells also achieve a stable electrochemical performance of 180 cycles at an extremely high current density of 30 mA cm −2 with a capacity of 1 mAh cm −2 . When paired with LiFePO 4 (LFP) and LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes, Li−Sr/LFP cells in 2 M LiFSI-DME electrolytes and Li−Sr/NMC811 cells in 1 M LiPF 6 in FEC:FEMC:HFE electrolytes also maintain excellent capacity retention. Designing SEIs by regulating Li-metal anode composition opens up a new and rational avenue to suppress Li dendrites.

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In electrochemical energy storage and conversion systems, the anodic oxygen evolution reaction (OER) accounts for a large proportion of the energy consumption. The electrocatalytic urea oxidation reaction (UOR) is one of the promising alternatives to OER, owing to its low thermodynamic potential. However, owing to the sluggish UOR kinetics, its potential in practical use has not been unlocked. Herein, we developed a tungsten‐doped nickel catalyst (Ni‐WOx) with superior activity towards UOR. The Ni‐WOx catalyst exhibited record fast reaction kinetics (440 mA cm−2 at 1.6 V versus reversible hydrogen electrode) and a high turnover frequency of 0.11 s−1, which is 4.8 times higher than that without W dopants. In further experiments, we found that the W dopant regulated the local charge distribution of Ni atoms, leading to the formation of Ni3+ sites with superior activity and thus accelerating the interfacial catalytic reaction. Moreover, when we integrated Ni‐WOx into a CO2 flow electrolyzer, the cell voltage is reduced to 2.16 V accompanying with ≈98 % Faradaic efficiency towards carbon monoxide.

The lack of high-power and stable cathodes prohibits the development of rechargeable metal (Na, Mg, Al) batteries.Herein, poly(hexaazatrinaphthalene)(PHATN), an environmentally benign, abundant and sustainable polymer, is employed as auniversal cathode material for these batteries. In Na-ion batteries (NIBs), PHATN delivers ar eversible capacity of 220 mAh g À1 at 50 mA g À1 ,c orresponding to the energy density of 440 Wh kg À1 ,and still retains 100 mAh g À1 at 10 Ag À1 after 50 000 cycles,w hich is among the best performances in NIBs.S uch an exceptional performance is also observed in more challenging Mg and Al batteries.P HATN retains reversible capacities of 110 mAh g À1 after 200 cycles in Mg batteries and 92 mAh g À1 after 100 cycles in Al batteries. DFT calculations,X -ray photoelectron spectroscopy, Raman, and FTIR showt hat the electron-deficient pyrazine sites in PHATN are the redoxc enters to reversibly react with metal ions.