Enhanced capacity and cycle life of nitrogen-doped activated charcoal anode for the lithium ion battery: a solvent-free approach

Abstract

Herein, we investigated the electrochemical performance of nitrogen-doped commercial activated charcoal (R-AC) for lithium-ion batteries (LIBs). With this aim, nitrogen was doped into R-AC via a solvent-free approach, which involved annealing R-AC under N₂ and NH₃ atmospheres at 800 °C, and the product was tested as an anode for LIBs. The sample annealed under an NH₃ atmosphere (NH-AC) had a nitrogen doping level of 4.7 at% with a specific surface area of 894.5 m² g⁻¹ and a reduced O/C ratio of 0.31 in comparison to the sample annealed under an N₂ atmosphere (N-AC) and R-AC. Raman spectroscopy detected disorder/defects owing to the introduction of various C–N–C terminal bonds on the surface of R-AC, which significantly improved the electrical conductivity of both N-AC and NH-AC. Therefore, endowed with these physicochemical properties, NH-AC delivered a high specific capacity of 736.4 mA h g⁻¹ at 50 mA g⁻¹ (up to 150 cycles) and 524 mA h g⁻¹ at 200 mA g⁻¹ even after 500 cycles, which indicates much better performance in comparison to those of R-AC, N-AC and commercial graphite. This remarkable electrochemical performance of NH-AC can be attributed to the synergistic effect of its large specific surface area, disordered graphitic structure, and low charge transfer resistance, which enable it to act as an anode for high-performance LIBs.