Atomically dispersed metal sites anchored in N-doped carbon nanosheets with enhanced Li storage performance

Abstract

The topological structure of carbon materials for lithium storage performance is an active issue in energy resources. However, the low specific capacity of carbon materials limits their application in the rapidly developing market, although they have the highest marginal value. Herein, we develop a facile method for scaled-up production of materials with atomically dispersed metal sites anchored on nitrogen-enriched carbon nanosheets (M–N–C), including nickel, iron and manganese metal sites. This is the first time that low-cost atomically dispersed M–N–C has been used to enhance Li storage performance. The anchoring of the atomically dispersed metal sites effectively improves the extent of carbonization and optimizes the electronic structure, which enhances the conductivity and accelerates the adsorption kinetics for Li⁺; this results in high capacity and superior rate performance. In the case of Mn–N–C, it presents an ultrahigh specific capacity of 500 mA h g⁻¹ at 1 A g⁻¹ after 1000 cycles. The atomically dispersed materials also demonstrate satisfactory rate performance, with an extremely high specific capacity of 328 mA h g⁻¹ at 10 A g⁻¹; this is greatly superior to that of N-doped carbon nanosheets (<200 mA h g⁻¹). Similarly, the Ni–N–C and Fe–N–C nanosheet materials display excellent performance in Li storage. These results suggest that this strategy will open a new path for the design of alkali ion storage materials and provide new insight into the relationship between the topological structures of carbon materials and their alkali ion storage performance.