A comprehensive review on the role of lithium in biodegradable metals

With the advancement of biomedical materials, biodegradable metals have demonstrated broad application prospects in fields such as orthopedic fixation and cardiovascular stents due to their appropriate mechanical properties, controllable degradation rates, and favorable biocompatibility. Metals like magnesium (Mg) and zinc (Zn) can gradually degrade and be absorbed by the body after fulfilling their intended functions, eliminating the need for secondary surgical removal. However, existing materials still face challenges such as insufficient mechanical strength, mismatched degradation rates, and limited biological functionality. Lithium (Li), as a lightweight and active element, can significantly modulate the microstructure, degradation behavior, and biological effects of biodegradable metals, yet systematic reviews on this topic remain scarce. Therefore, a thorough investigation into the role of Li in biodegradable metals holds significant scientific and practical value for the development of high-performance biomedical materials. This paper systematically reviews the role of Li in biodegradable metals, focusing on its effects on mechanical properties, degradation behavior, and biocompatibility. STATEMENT OF SIGNIFICANCE: This paper systematically elucidates the research progress on the multiscale regulation mechanisms and synergistic effects of Li in biodegradable metallic materials. As the lightest metallic element, Li exhibits unique structure-function integration characteristics in biodegradable alloy systems. From a multidimensional "structure-performance-degradation-bioeffect" perspective, this review clarifies the synergistic mechanisms of Li, providing theoretical foundations and design principles for developing novel medical alloys with high mechanical properties, matched degradation rates, and active biological functionalities.