A smart self-regenerative lithium ion supercapacitor with a real-time safety monitor

Lithium ion capacitors (LICs) show great promise for electricity storage. However, cycle degradation and unbalanced electrode kinetics of LICs are troublesome. Meanwhile, safety has become a stringent requirement for lithium devices. Finding methods to tackle these problems is rather challenging. Here, we develop a smart lithium ion supercapacitor (SLIC) by implanting a lithium electrode into a two-electrode pouch cell. The proof-of-concept SLIC has three smart functions: (1) energy boosting: it supports an on-line electrochemical charge injection protocol that boosts the energy of symmetrical all-carbon supercapacitors. A SLIC with single-wall carbon nanotubes (SWCNTs) as both electrodes has a gravimetric energy 5 times higher than conventional supercapacitors using SWCNTs and excellent durability with no measurable degradation during 10,000 cycles; (2) safety monitoring: it allows real-time diagnosis of cell decay and warns of dangers by a built-in feedback mechanism; (3) self-regeneration: it enables regeneration of a degraded SLIC by a voltage modulator. From a practical point of view, this SLIC concept offers a general solution for extending the life of sealed power sources.