Enhancing the rate capability of Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) by partial co-substitution of V 3+ and Al 3+ for Fe 2+

Partial co-substitution of V 3+ and Al 3+ for Fe 2+ in NFPP lowers the band gap and Na + diffusion energy barrier of NFPP, thus effectively improving its rate capability.