Lithium metal anodes hold great potential for high-energy-density secondary batteries. However, the uncontrollable lithium dendrite growth causes poor cycling efficiency and severe safety concerns, hindering lithium metal anode from practical application. Electrolyte components play important roles in suppressing lithium dendrite growth and improving the electrochemical performance of long-life lithium metal anode, and it is still challenging to effectively compromise the advantages of the conventional electrolyte (1 mol·L⁻¹ salts) and high-concentration electrolyte (> 3 mol·L⁻¹ salts) for the optimizing electrochemical performance. Herein, we propose and design an interfacial high-concentration electrolyte induced by the nitrogen- and oxygen-doped carbon nanosheets (NO-CNS) for stable Li metal anodes. The NO-CNS with abundant surface negative charges not only creates an interfacial high-concentration of lithium ions near the electrode surface to promote charge-transfer kinetics but also enables a high ionic conductivity in the bulk electrolyte to improve ionic mass-transfer. Benefitting from the interfacial high-concentration electrolyte, the NO-CNS@Ni foam host presents outstanding electrochemical cycling performances over 600 cycles at 1 mA·cm⁻² and an improved cycling lifespan of 1,500 h for symmetric cells.

Practical applications of lithium-sulfur (Li-S) batteries are hindered mainly by the low sulfur utilization and severe capacity fading derived from the polysulfide shuttling. Catalysis is an effective remedy to those problems by promoting the conversion of polysulfides to reduce their accumulation in the electrolyte, which needs the catalyst to have efficient adsorption ability to soluble polysulfides and high activity for their conversion. In this work, we have proposed a bimetallic compound of NiCo₂S₄ anchored onto sulfur-doped graphene (NCS@SG) to fabricate a catalytic interlayer for Li-S batteries. Compared to CoS, the NiCo₂S₄ demonstrated much higher catalytic activity toward sulfur reduction reaction due to its multiple anchoring and catalytic active sites derived from the coordination of the bimetallic centers. As a result, the NCS@SG interlayer dramatically improved the specific capacity, rate performance, and cyclingstability of Li-S batteries. Especially, when the areal sulfur loading of the NCS@SG battery increased to 15.3 mg·cm^–2, the high-capacity retention of 93.9 % could be achieved over 50 cycles.

The practical application of lithium-sulfur batteries with a high energy density has been plagued by the poor cycling stability of the sulfur cathode, which is a result of the insulating nature of sulfur and the dissolution of polysulfides. Much work has been done to construct nanostructured or doped carbon as a porous or polar host for promising sulfur cathodes, although restricting the polysulfide shuttle effect by improving the redox reaction kinetics is more attractive. Herein, we present a well-designed strategy by introducing graphitic carbon nitride (g-C₃N₄) into a three-dimensional hierarchical porous graphene assembly to achieve a synergistic combination of confinement and catalyzation of polysulfides. The porous g-C₃N₄ nanosheets in situ formed inside the graphene network afford a highly accessible surface to catalyze the transformation of polysulfides, and the hierarchical porous graphene-assembled carbon can function as a conductive network and provide appropriate space for g-C₃N₄ catalysis in the sulfur cathode. Thus, this hybrid can effectively improve sulfur utilization and block the dissolution of polysulfides, achieving excellent cycling performance for sulfur cathodes in lithium-sulfur batteries.