Understanding of the sodium storage mechanism in hard carbon anodes

Hard carbon has been regarded as the most promising anode material for sodiumion batteries(SIBs)due to its low cost,high reversible capacity,and low working potential.However,the uncertain sodium storage mechanism hinders the rational design and synthesis of high-performance hard carbon anode materials for practical SIBs.During the past decades,tremendous efforts have been put to stimulate the development of hard carbon materials.In this review,we discuss the recent progress of the study on the sodium storage mechanism of hard carbon anodes,and the effective strategies to improve their sodium storage performance have been summarized.It is anticipated that hard carbon anodes with high electrochemical properties will be inspired and fabricated for large-scale energy storage applications.