The role of nanoparticle concentration and CNT coating in high-performance polymer-free micro/nanostructured carbon nanotube-nanoparticle composite electrode for Li intercalation

We investigate how Li intercalation into composite electrodes resulting from the combination of graphitic carbon felt (CF) with carbon nanotubes (CNTs) functionalized with electroactive nanoparticles (NPs) depends on NP concentration. To this end, we study CF electrodes coated or not with hydrophilic CNTs containing electrodeposited β/γ-MnO2NPs (wt% 25, 42, and 69) with hollow-nanotube structure. Galvanic coupling between the CNTs and the NPs is the reason why the electrochemical performance of CNT-NP nanocomposites varies with the NP concentration. The CNT coating on the CF electrode also avoids capacity fading of the CF/MnO2NP electrodes and prevents carbon fibers from interconnecting with SEI. More specifically, the CNTs stabilize the solid electrolyte interphase and prevent NP detachment, thereby producing electrodes with long-term cyclability. The best electrochemical performance occurs for CNT/MnO2NP mass wt% 25 (1114 mAh g−1, 1st discharge/charge Faradaic efficiency ~80% at 1 A g−1, cut-off potential = 4–0.005 V vs Li+/Li).