However, the further development of LIBs is restricted by the limited energy density, especially given the emerging large-scale energy storage applications. [2] Lithium metal is a competitive anode candidate with the merits of high theoretical capacity (3860 mAh g −1 ) and very low reduction potential (−3.04 V vs a standard hydrogen electrode). [3] Nonetheless, the problem of lithium dendrites and the stability of the electrolyte-electrode interphase still hinder its commercialization. [4] Furthermore, conventional carbonate electrolytes are flammable and can induce lithium dendrites, resulting in the production of "dead Li," which reduces the battery performance and raises safety concerns. [5] To address the severe dendrite issues in lithium metal batteries (LMBs), the formula design of the electrolyte has been proven to be an effective strategy. [6] As an additive, Lithium nitrate (LiNO 3 ) is generally recognized as an enhancer that forms robust solid electrolyte interphase (SEI) layers. [7] The NO 3 − derived reduction products, such as Li x N and LiN x O y , are good Li + conductors, thus accelerating the plating/ stripping behavior of Li + . [8] In addition, LiNO 3 binds to solvents or active substances in the electrolyte to strengthen the SEI layers and inhibit dendritic growth. [9] However, the strong interaction between Li + and NO 3 − cannot be broken in the conventional carbonate electrolyte, resulting in the extremely low solubility of LiNO 3 and hindering its application. [10] Although the ether electrolyte can dissolve a certain amount of LiNO 3 , its low operating voltage makes it difficult to meet the requirement of the LMB. Hence, it is essential to develop a safe and stable electrolyte with high LiNO 3 solubility to achieve better LMB. To date, various strategies have been reported to promote LiNO 3 dissolution in carbonate electrolytes such as using co-solvents, [11] slow release, [12] polymer-mediation, [13] and introducing solvent promoters. [14] However, these methods are characterized by complex processes and high costs. Therefore, there is an urgent need for a method that can facilitate LiNO 3 dissolution. Deep eutectic solvents (DESs), eutectic liquid mixtures of two or more solids formed by strong intermolecular forces, are new green solvents that have been widely utilized in extraction, organic synthesis, and electrochemistry. [15] DESs exist as liquids over a wide range of temperatures and offer excellent thermal stability. Moreover, Lithium nitrate is widely used as an additive in electrolytes to regulate the solid electrolyte interphase (SEI). However, the application of LiNO 3 in lithium metal batteries (LMBs) is limited by its extremely low solubility in conventional carbonate-based electrolytes. In this study, a non-flammable deep eutectic solvent (DES) with lithium bis(trifluoromethanesulfonyl)imide and N-methylacetamide (NMAC) as the main components is chosen as the LMB electrolyte. Using theoretical calculations and experiments, the strong interaction between NMAC and LiNO ...

The development of graphene conductive inks with a high conductivity and dispersion stability in water poses considerable challenges. Herein, a highly conductive Ag/carbon quantum dots (CQDs)/graphene (G) composite with good dispersity and stability in water was prepared for the first time through the in situ photoreduction of AgNO3 and deposition of Ag onto graphene nanosheets obtained via CQD-assisted liquid-phase exfoliation. Ag nanoparticles with an average size of ∼1.88 nm were uniformly dispersed on graphene nanosheets. The Ag/CQDs/G composite exhibited good dispersity and stability in water for 30 days. The formation mechanism of the Ag/CQDs/G composites was also discussed. CQDs played a vital role in coordinating with Ag+ and reducing it under visible light conditions. The addition of only 1.58 wt % of Ag NPs to the CQDs/G film resulted in a significant decrease in the electrical resistivity by approximately 89.5%, reaching a value of 0.054 Ω cm for a 40 μm thick Ag/CQDs/G film. A low resistivity of 2.15 × 10–3 Ω cm for the Ag/CQDs/G film was achieved after rolling compression with a compression ratio of 78%. The Ag/CQDs/G film exhibited good conductivity and durability when bent, rolled, or twisted. Moreover, the resistivity of the film displayed a slight deviation after 5000 bending cycles, indicating its outstanding stability. This study provides an efficient strategy for preparing graphene-based conductive composites with good dispersibility and stability in water as well as novel high-performance conductive inks for application in flexible printed electronics.

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The co-engineering of defects and N doping is highly important for the development of advanced metal-free carbon-based electrocatalysts for the oxygen reduction reaction (ORR). It remains a great challenge to efficiently tune the doped nitrogen species, and the role of oxygen species is often overlooked. Here, a facile strategy is developed for fabricating three-dimensional oxygen and nitrogen codoped porous carbon (ONPC) via air pre-oxidation, followed by carbonization. The optimal catalyst, i.e., ONPC-300, mainly contains pyridinic N and graphitic N species with oxygen-rich functional (ketone CO) groups and has an enhanced specific surface area, superhydrophilic surface structure, and abundant defect sites for ORR, which endows it with excellent ORR performance, as evidenced by a half-wave potential of 0.862 V and high long-term stability over 100 h in an alkaline medium. Density functional theory (DFT) calculations reveal that ketone CO groups can optimize the adsorption energy of intermediates and decrease the energy barrier for the rate-determining steps, thus promoting the ORR activity. A flow Zn–air battery using ONPC-300 as the cathode shows outstanding performance, including a remarkable peak power density of 258.5 mW cm–2, high discharge stability over 180 h, and an ultralong cycle life exceeding 800 h.