Li₃VO₄ (LVO) Nanosheets as a Long-life (>10,000) and High-rate Anode for its application in Sodium-ion Battery (SIBs)

Lithium-based transition metal oxides, such as LVO, are known for their exceptional capacity and intrinsic safety features, making them promising materials for lithium-ion batteries. Unfortunately, LVO's practicality is limited by its moderate lifespan under high rates [1]. The study shows that solution-processed laminar crystalline LVO (calculated bandgap: 3.95 eV), without surfactants, exhibits unparalleled high-rate performance and ultra-long cycling stability with Na⁺-ions. The X-ray diffraction analysis of LVO powder revealed that it has an orthorhombic phase with lattice constants of a=5.448 Å, b=6.327 Å, and c=4.949 Å, with the Pmn21 space group [2]. In the cyclic voltammogram (CV) test, LTO||Na showed two pairs of oxidation and reduction peaks at [1.22 & 1.43 V] and [0.254 & 0.851 V], respectively, at a lower scan rate of 0.1 mV/s. However, at 6 mV/s, the overall CV profile showed only one prominent pair of the redox couple, 1.59/0.887 V. Furthermore, LVO||Na cell delivers an initial 202 mAh/g capacity at 0.25 A/g with a capacity retention (CR) of 73.26 % after 1600 cycles during GCD cycling. Under the high current density of 5 A/g, the cell initially delivers a capacity of 51.3 mAh/g (CR: 95.5 % ) after 10,000 cycles. There is a 34.38 % decrease in the intercalation potential of the LVO||Na when we move from low to high current density. The periodic rate capability test results indicate a ~2.4% increase in the specific discharge capacity for a 0.1 C rate after repeating the cycle from 0.1 C to 10 C, with 20 cycles each. It is noted in the study that LVO||Na demonstrates an increase in overall capacity primarily due to the intercalation of larger ions compared to lithium, which is mainly due to the increased interlayer spacing between the sheets, which consequently increases the surface area for further intercalation. Furthermore, techniques such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to understand better the mechanism behind LVO||Na cell's performance.