Due to the increased need for flexible electronic goods in recent years, energy storage technologies with high energy densities and flexibility have been quickly developed. Among various energy storage systems, flexible lithium-ion batteries (LIBs) have high energy density, elasticity to mechanical deformation, and stable electrochemical performance, making them the most promising battery technology for wearable electronic products. As one of the components of flexible lithium-ion batteries, flexible electrode materials play an important role. Carbon nanomaterials, represented by carbon nanotubes, graphene, and others, have excellent mechanical flexibility, large specific surface area, and high conductivity, making them a research hotspot in the field of electrode materials. As a result, this research describes the function of various carbon nanomaterials in flexible lithium-ion batteries and analyzes the difficulties they encounter. Finally, the path of electrode material development in the future is anticipated. It can provide a reference for the research of related electrode materials in future lithium batteries.