As one of the most efficient electrochemical energy storage devices, the energy density of lithium-ion batteries (LIBs) has been extensively improved in the past several decades. However, with increased energy density, the safety risk of LIBs becomes higher too. The frequently occurred battery accidents worldwide remind us that safeness is a crucial requirement for LIBs, especially in environments with high safety concerns like airplanes and military platforms. It is generally recognized that the catastrophic thermal runaway (TR) event is the major cause of LIBs related accidents. Tremendous efforts have been devoted to coping with the TR concerns in LIBs, and thus enhance battery safety. This review first gives an introduction to the fundamentals of LIBs and the origins of safety issues. Then, the authors summarize the recent advances to improve the safety of LIBs with a unique focus on thermal-responsive and fire-resistant materials. Finally, a perspective is proposed to guide future research directions in this field. It is anticipated this review will stimulate inspiration and arouse extensive studies on further improvement in battery safety.