Influence of nano-fibrous and nano-particulate morphology on the rate capability of Li3V2(PO4)3/C Li-ion battery cathode

Abstract

We demonstrate contrasting differences in the electrochemical performances of Li3V2(PO4)3 with thin-carbon coating (LVP/C) in the nanoparticulate (LVP/C-np) and nanofibrous (LVP/C-nf) morphologies synthesized by a sol-gel and electrospinning processes, respectively. LVP/C-nf exhibits a highly-interconnected pearl-like microstructure, and LVP/C-np has discontinuous aggregates of nanoparticles, as evidenced by high-resolution scanning and transmission electron microscopy. Electrochemical studies show that the nanoparticle cathodes exhibit higher capacity fading than nanofibrous cathodes with increasing C-rate. LVP/C-np and LVP/C-nf cathodes exhibit a discharge capacity of 137 mA h g−1 and 124 mA h g−1 at 0.1 C rate. Large carbon content in LVP/C-nf (∼23.3%) unlike the LVP/C-np (∼2.5%) underestimates the actual capacity. The high C-rate performance is better for LVP/C-nf (58.74 mA h g−1 at 10C-rate and 28.75 mA h g−1 at 30 C-rate) compared to LVP/C-np (37.23 mA h g−1 at 10C-rate) as tested in the voltage range 3 V-4.8 V. The most prominent observation is that LVP/C-np cathodes show lower capacity retention of only 48.6%. In contrast, the cathodes with nanofibrous morphology retain nearly 77.2% of their initial discharge capacities after 500 cycles at 1C-rate. Present study highlights the importance of the well-connected microstructure of the cathode as an essential criterion to achieve the high-rate capability and long cycling stability of high voltage cathodes for quick charge battery applications.