Multiple Active Sites Carbonaceous Anodes for Na⁺ Storage: Synthesis, Electrochemical Properties and Reaction Mechanism Analysis

Owing to the earth-abundant resources, cost effective materials and stable electrochemical properties, sodium-ions batteries (SIBs) show long-term potential in responding to the rapid consumption of lithium resources and the ever-increasing development of new energy storage devices. Nevertheless, the intrinsic properties of the large ion radius (Na⁺ 1.02 Å vs Li⁺ 0.76 Å) and positive reduction potential (Na/Na⁺ −2.71 V vs Li/Li⁺ −3.04 V) may impede ion diffusion, thus causing serious volume expansion, resulting in poor cycling stability. To address these issues, the incorporation of active sites into carbonaceous anode is considered as an efficient strategy to enhance interfacial compatibility, enlarge interlayer distance, and supply reversible Faradic pseudo-capacitance. Herein, the multiple active sites carbonaceous anodes for SIBs anode are comprehensively reviewed. Typically, carbonaceous materials are categorized into diffusion and surface controlled based on Na storage mechanism, and the concepts of intrinsic/extrinsic active sites are proposed according to the types of active sites. Furthermore, to reveal the reaction kinetics and guide the rational design of high performance anodes, the (spectro) electrochemical analysis methods and corresponding key parameters are introduced. Additionally, primary superiorities, essential issues, and supposed solutions of multiple active sites carbonaceous Na anodes are discussed and the future development directions are also proposed. This review may provide new design thoughts for high performance carbonaceous Na storage anodes.