Carbon nanotubes as host platforms for lithium metal anodes: CNT-centric composite and surface engineering strategies

Lithium metal anodes are promising candidates for next-generation high-energy-density batteries owing to their ultra-high theoretical capacity. However, their practical application is hindered by uncontrolled dendrite growth, unstable solid electrolyte interphase (SEI) formation, and mechanical failure caused by large volume fluctuations during cycling. Carbon nanotubes (CNTs) have emerged as attractive host platforms due to their one-dimensional (1D) conductive networks, mechanical robustness, and high surface area, enabling current homogenization, stress accommodation, and suppression of localized lithium deposition. While most existing reviews broadly discuss carbon-based hosts, this review exclusively focuses on carbon nanotubes, enabling a targeted assessment of CNT-specific advantages and limitations in lithium metal anodes. We classify CNT-based host engineering strategies into three categories: CNT-centric heterogeneous architectures, CNT–carbon allotrope architectures, and intrinsic engineering of CNT hosts. CNT-centric heterogeneous architectures incorporate lithiophilic materials—such as metals, metal oxides, polymers, and MXenes—onto CNT backbones to regulate lithium nucleation, ion transport, and mechanical stability. CNT–carbon allotrope architectures construct hierarchical carbon–carbon architectures to enhance electronic connectivity and structural robustness, while surface functionalization tunes CNT surface chemistry to control lithiophilicity, interfacial reactions, and SEI stability. Finally, we discuss key challenges associated with CNT-based hosts and summarize strategies to address them. By correlating CNT modification strategies with electrochemical performance, this review provides structure–function insights and outlines future directions for CNT-enabled lithium metal anodes.