Structural and electrochemical studies of novel Na7V3Al(P2O7)4(PO4) and Na7V2Al2(P2O7)4(PO4) high-voltage cathode materials for Na-ion batteries

Operando XRD studies illustrate the reversible electrochemical process in the range of 2.7–4.2 V vs. Na⁺/Na for new Na₇V_4−xAl_x(P₂O₇)₄(PO₄) (x = 1, 2) compositions with increasing of the capacity at higher voltage.