Nitrogen-rich Graphite Flake from Hemp as Anode Material for High Performance Lithium-ion Batteries

Biomass-derived carbon (BC) has attracted extensive attention as anode material for lithium ion batteries (LiBs) due to its natural hierarchical porous structure and rich heteroatoms that can adsorb Li+. However, the specific surface area of pure biomass carbon is generally small, so we can help NH3 and inorganic acid produced by urea decomposition to strip biomass, improve its specific surface area and enrich nitrogen elements. The nitrogen-rich graphite flake obtained by the above treatment of hemp is named NGF. The product that has a high nitrogen content of 10.12% has a high specific surface area of 1151.1 m(2) g(-1). In the lithium ion battery test, the capacity of NGF is 806.6 mAh g(-1) at 30 mA g(-1), which is twice than that of BC. NGF also showed excellent performance that is 429.2 mAh g(-1) under high current testing at 2000 mA g(-1). The reaction process kinetics is analyzed and we found that the outstanding rate performance is attributed to the large-scale capacitance control. In addition, the results of the constant current intermittent titration test indicate that the diffusion coefficient of NGF is greater than that of BC. This work proposes a simple method of nitrogen-rich activated carbon, which has a significantly commercial prospect.

Automated summary

Biomass-derived carbon (BC) is a promising anode material for lithium ion batteries (LiBs) due to its natural hierarchical porous structure. However, the specific surface area of pure biomass carbon is small. To address this issue, we introduced NH3 and inorganic acid produced by urea decomposition to strip biomass, thereby improving its specific surface area and nitrogen content. The resulting nitrogen-rich graphite flake (NGF) exhibited a high specific surface area of 1151.1 m(2) g(-1) and a nitrogen content of 10.12%. In lithium ion battery tests, NGF showed a capacity of 806.6 mAh g(-1) at 30 mA g(-1), which was twice that of BC. It also demonstrated excellent performance with a capacity of 429.2 mAh g(-1) at 2000 mA g(-1). The exceptional rate performance was attributed to large-scale capacitance control and the diffusion coefficient of NGF was found to be higher than that of BC.