Improved high-rate performance of Na3V2(PO4)3 with an atomic layer deposition-generated Al2O3 layer as a cathode material for sodium-ion batteries

Because of its sodium superionic conductor structure, Na3V2(PO4)3 has been recognized as a promising candidate cathode material for room-temperature sodium-ion batteries. However, Na3V2(PO4)3 suffers from a severe capacity loss, especially at a high charge-discharge rate. To overcome this limitation, in this work Na3V2(PO4)3 was coated with Al2O3 films (NVP@Al) using atomic layer deposition (ALD). The electrochemical performances of the NVP@Al nanocomposites as cathodes for sodium-ion batteries were investigated NVP@Al nanocomposite exhibited a relatively flat voltage plateau at 3.4 V in a non-aqueous sodium cell. When tested as a cathode in a voltage range of 2.5 V-4.0 V, NVP@ Al exhibited initial charge and discharge capacities of 132 mAh/g and 107 mAh/g, respectively. The ALD-coated Na3V2(PO4)3 electrodes exhibited significantly increased capacities, because of transformations of the as-deposited Al2O3 into a more Na+-conductive material. These preliminary results indicate that NVP@Al is a prospective cathode material for room-temperature sodium-ion batteries.