Cathode nanoarchitectonics with Na3VFe0.5Ti0.5(PO4)3: Overcoming the energy barriers of multielectron reactions for sodium-ion batteries

Abstract

High electrochemical stability and safety make Na⁺ superionic conductor (NASICON)-class cathodes highly desirable for Na-ion batteries (SIBs). However, their practical capacity is limited, leading to low specific energy. Furthermore, the low electrical conductivity combined with a decline in capacity upon prolonged cycling (>1000 cycles) related to the loss of active material-carbon conducting contact regions contributes to moderate rate performance and cycling stability. The need for high specific energy cathodes that meet practical electrochemical requirements has prompted a search for new materials. Herein, we introduce a new carbon-coated Na₃VFe_0.5Ti_0.5(PO₄)₃ (NVFTP/C) material as a promising candidate in the NASICON family of cathodes for SIBs. With a high specific energy of ∼457 Wh kg⁻¹ and a high Na⁺ insertion voltage of 3.0 V versus Na⁺/Na, this cathode can undergo a reversible single-phase solid-solution and two-phase (de)sodiation evolution at 28 C (1 C = 174.7 mAh g⁻¹) for up to 10,000 cycles. This study highlights the potential of utilizing low-cost and highly efficient cathodes made from Earth-abundant and harmless materials (Fe and Ti) with enriched Na⁺-storage properties in practical SIBs.