A zero-strain Na-deficient NASICON-type Na2.8Mn0.4V1.0Ti0.6(PO4)3 cathode for wide-temperature rechargeable Na-ion batteries

Abstract

Na superionic conductor (NASICON) type cathode materials with high structural stability and fast Na⁺ diffusion have been considered as high-power candidates for the exploration of Na-ion batteries. However, the substitution of active elements with low cost and additional attributes remains epoch-making due to the structural flexibility and insufficient utilization of the introduced components. Herein, the Na-deficient strategy based on charge balance is employed to take full advantage of the Na⁺ ions and active transition metals within the voltage window of 2.0–4.2 V. The optimized Na_2.8Mn_0.4V_1.0Ti_0.6(PO₄)₃ cathode realizes a 2.1 e⁻ redox reaction with a 76% utilization rate of Na⁺ ions rooted in the lattice, allowing a discharge capacity of 126.2 mA h g⁻¹ and superior capacity retention of 88.1% at 20 C over 3000 cycles. Consequently, the developed cathode also achieved superior reaction reversibility and remarkable Na-storage properties, even under extreme working conditions and with full cell configurations. This work could provide new perspectives and an efficient regulation protocol for high-performance Na-ion batteries.