Reappraisal of hard carbon anodes for practical lithium/sodium-ion batteries from the perspective of full-cell matters

Hard carbon (HC) has the potential to be a viable commercial anode material in both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). However, current battery performance evaluation methods based on half-cells are insufficient for accurately assessing the performance of HC anodes due to their ultra-low discharge voltage windows. To develop the next-generation of large-scale rechargeable batteries, it is necessary to examine reported HC materials from a full-cell perspective. This review emphasizes the importance of full-cell validation and provides a comprehensive overview of HC anodes - including their history, fundamentals, carbon chemistry induced by temperature, microstructure correlation with electrochemical performance, and debates surrounding lithium/sodium-ion storage mechanisms. Additionally, this review highlights various optimization strategies and suggests potential areas for future application of HC-based lithium-ion batteries (HC-LIBs) and HC-based sodium-ion batteries (HC-SIBs). Furthermore, different challenges and strategies that need to be addressed are presented in the hope of providing inspiration and guidance for the commercialization of HC anodes.