Hard carbon anode for lithium-, sodium-, and potassium-ion batteries: Advancement and future perspective

Due to its overall performance, hard carbon (HC) is a promising anode for rechargeable lithium-, sodium-, and potassium-ion batteries (LIBs, NIBs, KIBs). The microcrystalline structure morphology of HCs facilitates the alkali metal -ion uptake and fast ion intercalation and deintercalation throughout the pores with low-potential intercalation properties. However, the large-scale industrial application of HCs is still lagging because of the first-cycle reversible capacity, which results in low initial Coulombic efficiency (ICE) and voltage hysteresis. This review focuses on the fundamental mechanism of HCs as alkali metal-ion batteries, with the current issues being discussed. This includes the formation of solid electrolyte interphase during the first cycle with low ICE, safety concerns, and improved performances, which are vital for practical applicability. The current state-of-the-art of HC anodes is discussed here with recent literature. Furthermore, the challenges and the corresponding effective strategies to overcome the difficulties related to the commercialization of HCs as rechargeable battery anodes are discussed.