β-LiVP2O7 as a positive electrode material for Li-ion batteries

Abstract A novel polymorph of lithium vanadium pyrophosphate has been obtained using electrochemical Na+ for Li+ exchange in β-NaVP2O7. β-LiVP2O7 has a triclinic KAlP2O7-type structure with large tunnels along the [100] direction and demonstrates electrochemical capacity of 100 mAh g−1 within a high-voltage region of 4.0-4.2 V vs. Li/Li+ with excellent C-rate capability: increasing discharge current density from C/10 to 10C results in a capacity drop of only 7%. The (de)intercalation process is characterized by a solid solution-like behavior with the diffusion coefficient amounting to 10−12 – 10−11 cm2 s−1. A redox process at ~ 1.8 V vs. Li/Li+ leads to 200 mAh g−1 of the overall intercalation capacity within the extended voltage range that corresponds to “β-VP2O7 ↔ β-Li2VP2O7” two-electron process.