Lithium storage of SnP2O7 anode coated by N-doped carbon and anchored on P-doped carbon framework

Abstract

N-doped carbon-coated SnP2O7 anodes anchored on P-doped carbon framework (SPO/C-P@C-N) have been successfully synthesized via a novel and environmentally friendly method, using a green raw material of phytic acid as phosphorus and carbon sources, and dimethylimidazole as the second carbon source and nitrogen source. N-doped carbon coating and P-doped carbon framework inhibit the volume shrinkage and expansion, improve the electronic conductivity and diffusion coefficient of Li+ ions as well as capacitive contribution ratio, reduce the charge transfer resistance and the particle size, and then enhance the electrochemical performance of SPO/C-P@C-N. SPO/C-P@C-N-1.2 with the carbon content of 18.5 wt% exhibits excellent electrochemical performance. The discharge specific capacity is 416.6 mAh/g at 0.5 A/g after 200 cycles. 234.3 mAh/g is kept at 2 A/g for the 1000th cycle. In addition, the discharge specific capacity of the LiNi0.5Mn1.5O4//SPO/C-P@C-N-1.2 full cell is 206.6 mAh/g for the 200th cycle at 0.5C in 1.4–4.4 V. The full cell can power green, red, blue, and orange light-emitting diode (LED) bulbs, as well as LED small light strings and heart-shaped circuit boards. It is the first report on SnP2O7 successfully applied to full cells, demonstrating the potential application.