Dual-Carbon Confined SnP2O7 with Enhanced Pseudocapacitances for Improved Li/Na-Ion Batteries

Tin-based materials have obtained much attention in lithium-ion batteries (LIBs) due to high specific capacity. However, the large volume change and poor electroconductivity hinder their further practical application. Herein, a C18N12 (CN)-wired amorphous carbon coated pyrophosphate tin (SnP2O7@C) ultrafine nanoparticles composite (SnP2O7@C/CN) is prepared by solvothermal-calcination with phytic acid (PA) as phosphorus and carbon sources simultaneously. Ultrafine-nanocrystallization and dual-carbon doping enhances the pseudocapacitance of SnP2O7@C/CN and thus, exhibit good electrochemical performance and high lithium/sodium storage efficiency. As anode of LIBs, the SnP2O7@C/CN exhibits a superior reversible capacity of 557.3 mAh/g after 100 cycles at a current density of 0.2 A/g and a conspicuous cyclability of 352.3 mAh/g after 800 cycles at 1 A/g. For sodium-ion batteries (SIBs), the stable discharge capacity of SnP2O7@C/CN electrode is 91.5 mAh/g after 800 cycles at a high current density of 2 A/g. This strategy can increase active sites, provide large electrolyte/electrode contact area, and improve electroconductivity. Moreover, SnP2O7@C/CN electrode provides a buffer space for structural strains caused by volume changes during charging and discharging.