Stabilizing plasma-induced highly nitrogen-deficient g-C3N4 by heteroatom-refilling for excellent lithium-ion battery anodes

The modulation of vacancies is an attractive strategy to improve the conductivities of semiconductor materials for high-performance electrodes in lithium-ion batteries. However, it is a dilemma that the defective structure with high content vacancies is instable and also hard to preserve during long-term cycling. Herein, a heteroatom-refilling strategy has been proposed with the example of refilling oxygen in nitrogen-deficient g-C3N4. With the support of theoretic prediction, we produced the g-C3N4 with high nitrogen vacancies (C/N ≈ 2.52) by high-energy hydrogen plasma bombardment, and then filled oxygen by exposure to air. The obtained oxygen refilled g-C3N4 shows not only improved conductivity but also superior electrochemical performance (high capacity of 647 mAh·g−1 after 400 cycles at 0.1 A·g−1 and ultra-stable cycle of 232.8 mAh·g−1 after 5000 cycles at 1 A·g−1). It is found that such enhancement is contributed by the reduced band gap, enhanced lithium absorption energy and different charge density due to the vacancy modulation as well as the increased specific surface and active sites caused by the plasma bombardment. Our work proves the vacancy modulation strategy with heteroatom-refilling and the technical approach of the plasma-based method are effective and have abroad applications in energy and other fields.