High-performance Na3V2(PO4)2F3 cathode obtained by a three-in-one strategy for self-sodium compensation, interface modification, and crosslinked carbon coatings

Sodium-ion batteries (SIBs) are encouraging substitute to lithium-ion batteries. However, the application of SIBs is limited by their sluggish kinetics and unstable cyclic stability. Here, a crosslinked carbon-covered porous Na3V2(PO4)2F3 (NVPF) composite was prepared via a carboxymethyl cellulose (CMC)-assisted sol-gel strategy. The influences of the CMC on the interface and electrochemical properties were investigated. CMC supplemented additional Na+ that compensated for the sodium loss during the generation of the solid electrolyte interface. Besides, the crosslinked carbon formed by CMC strengthened the structure. Meanwhile, the porous coating layer with a large pore provided a fast transfer path for Na+. Thus, the optimized NVPF@C@CMC delivered an outstanding discharge capacity of 125.8 mAh g-1 at 0.2C, superb rate capability of 70.4 mAh g-1 at 20C, and good high-temperature adaptability (122.8 mAh g-1 at 0.2C and 45 degrees C). Moreover, in the full battery composed of the NVPF@C@CMC and a hard carbon, a high discharge capacity of 123.3 mAh g-1 was acquired at 0.2C. These superior results can be attributed to the simultaneous realization of self-sodium compensation, interface modi-fication, and crosslinked carbon coating. Therefore, the proposed modified sol-gel method is a multi-effect synergistic approach for the advance of high-performance energy-storage materials.