Abstract
The current status of lithium-ion battery technology has approached its theoretical capacity ceiling, necessitating a reevaluation of the cathode material design strategy. Over the past several decades, intercalation and conversion reactions have been recognized as the predominant chemistries governing lithium-ion battery cathode materials. While each of these charge storage mechanisms individually enables the development of high-energy-density cathode materials, integrating both mechanisms within a single-phase material presents significant challenges. Intercalation hosts demand facile lithium-ion diffusion kinetics facilitated by a well-defined crystal structure, whereas the repeated conversion reactions, accompanied by structural reorganization, can compromise intercalation capabilities. Recently, our research group demonstrated the reversible operation of intercalation-conversion combined chemistry within a single-phase material, specifically amorphous LiFeSO4F. To elucidate the underlying factors enabling the reversible utilization of intercalation and conversion reactions, we established a model system using the tavorite phase LiFeSO4F and systematically manipulated its degree of amorphization. The investigation of electrochemical properties across varying degrees of amorphization, along with first-principle computational simulations, elucidated the role of the amorphous structure in facilitating intercalation-conversion combined chemistry. The amorphous structure was found to promote an increase in conversion redox voltage and facilitate conversion kinetics, thereby enabling the reversible utilization of intercalation-conversion chemistry. Furthermore, our studies revealed that certain intercalation host materials can reversibly utilize conversion reactions through amorphization. These findings suggest a new paradigm for cathode design that integrates intercalation and conversion reactions, thereby expanding the possibilities within cathode chemistry.
Published Version
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