Sp2/Sp3 hybridized carbon as an anode with extra li-ion storage capacity: Construction and origin

Abstract

Doping in carbon anodes can introduce active sites, usually leading to extra capacity in Li-ion batteries (LIBs), but the underlying reasons have not been uncovered deeply. Herein, the dodecahedral carbon framework (N-DF) with a low nitrogen content (3.06 wt %) is fabricated as the anode material for LIBs, which shows an extra value of 298 mA h g-1 during 250 cycles at 0.1 A g-1. Various characterizations and theoretical calculations demonstrate that the essence of the extra capacity mainly stems from non-coplanar sp2/sp3 hybridized orbital controlling non-Euclidean geometrical structure, which acts as new Li-ion active sites toward the excess Li+ adsorption. The electrochemical kinetics and in situ transmission electron microscope further reveal that the positive and negative curvature architectures not only provide supernumerary Li+ storage sites on the surface but also hold an enhanced (002) spacing for fast Li+ transport. The sp2/sp3 hybridized orbital design concept will help to develop advanced electrode materials.