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/SnO 2 ) nanoparticles (NPs)/N‐doped carbon shell (SWCNTB@SnO 2 @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 SnO 2 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 SnO 2 and the conductive network. The LIB/SIB with the self‐adaptive SWCNTB@SnO 2 @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.