High-lattice-adapted surface modifying Na4MnV(PO4)3 for better sodium storage

Sodium-ion batteries (SIBs) are required to possess long cycle life when used for large-scale energy storage. The polyanionic Na4MnV(PO4)3 (NMVP) reveals good cyclic stability due to its unique three-dimensional (3D) frame structure, but it still faces the challenge of interfacial degradation in practical applications. In this work, NASICON-type Na1.3Al0.7Ti1.3(PO4)3 (NATP) was deposited on the surface of NMVP to promote interface stability by surface modification and gradient doping. As a result, the optimized NMVP@2%NATP released a capacity retention of 44.8% after 1000 cycles at 5 C, much higher than that of the initial NMVP (28.9%). The enhanced electrochemical performance was mainly attributed to NATP coating acting as a fast ion transport carrier and physical barrier, significantly facilitating the Na+ diffusion and isolating side reaction at the electrode/electrolyte interface. On the other hand, Ti4+ and Al3+ cations from the NATP were partially doped inside the NMVP surface to boost the transport of Na+, and the perfect lattice matching of NVMP and NATP improved the interface and structural stability accompanying long cycling. This work demonstrated the effectiveness of surface modification with high lattice match material and provided new perspectives for high energy density solid-state SIBs.