Self‐Adaptive Electrode with SWCNT Bundles as Elastic Substrate for High‐Rate and Long‐Cycle‐Life Lithium/Sodium Ion Batteries

Massive volume change of active materials in lithium/sodium ion batteries (LIB/SIB) causes severe structural collapse of electrodes and fast capacity decay of batteries. Here, a coaxial composite of single‐wall carbon nanotube bundle (SWCNTB/SnO2) nanoparticles (NPs)/N‐doped carbon shell (SWCNTB@SnO2@C) is constructed, where SWCNTBs with exceptional elasticity are explored as a self‐adaptive substrate to supply a highly resilient conductive network. Within the confinement of hard carbon shells, SWCNTB can produce radially elastic deformation to accommodate the volume change of SnO2 during Li+/Na+ insertion/extraction. This overcomes the problem of strain fracturing of the outer carbon shell, as well as maintains close electrical contact between SnO2 and the conductive network. The LIB/SIB with the self‐adaptive SWCNTB@SnO2@C electrode presents a series of superior battery performances, for example, a high specific capacity of 608 mAh g−1 at 10 A g−1 and 600 cycles in LIB without capacity decay. An advanced self‐adaptive electrode is designed and demonstrated, which not only solves the problem of massive volume changes of active materials during charge/discharge for cyclic stability, but also supplies high conductivity throughout the electrode, for improved capacity performance. The structural investigation shows that the superelasticity of the single‐wall carbon nanotube bundle helps to protect the structural integrity while maintaining tight contact between the active materials and conductive network to ensure high capacitance upon long‐term operation.