ICE optimization strategies of hard carbon anode for sodium-ion batteries: from the perspective of material synthesis

With the continuous exploration of researchers in the field of sodium-ion batteries, the performance of these batteries has been greatly improved, and they have a wide range of application prospects in large-scale energy storage, traffic power and other fields. Hard carbon is the most important anode material for sodium-ion batteries. Although it has the advantages of low cost, stable structure and performance, it still has the problems of low initial Coulombic efficiency (ICE) and poor rate performance in application. In order to solve the problem of low ICE of hard carbon anode in sodium-ion batteries, in recent years the literature about hard carbon anode in sodium-ion batteries has been comprehensively reviewed. Based on the microstructure of hard carbon material, the causes of low ICE of hard carbon are analyzed. At the same time, from the point of view of material structure design and regulation, the current optimization strategies of hard carbon anode ICE are summarized, including the following aspects: optimization and improvement of the carbonization process, precursor screening and design, surface coating strategy, micro-pore structure control, catalytic carbonization strategy. We hope that this review will provide reference for further optimization of hard carbon properties and its large-scale application in sodium-ion batteries.