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.