Carbon Coated NASICON Type Li₃V_2-xM_x(PO₄)₃(M=Mn, Fe and Al) Materials with Enhanced Cyclability for Li-Ion Batteries

We report the synthesis and optimization of metal (Mn, Fe and Al) doped NASICON type Li 3 V 2 (PO 4 ) 3 by solid-state reaction method. Among the metal doping, 0.02 mol concentration of Al is found better performing electrode while approaching the removal of three moles of lithium between 3-4.8 V vs. Li. Adipic acid with various concentrations is used to generate in-situ carbon layer over the 0.02 mol Al doped Li 3 V 2 (PO 4 ) 3 particulates (Li 3 V 1.98 Al 0.02 (PO 4 ) 3 ). Presence of carbon on the surface of particulates is confirmed by TEM and Raman analysis. Half-cell Li/C-Li 3 V 1.98 Al 0.02 (PO 4 ) 3 (0.15 mol of adipic acid) exhibited the highest reversible capacity of ∼182 mAh g −1 (2.77 moles of lithium) at a current density of 0.1 mA cm −2 compared to rest of the adipic acid concentrations. Further, the cell retained 83% of capacity after 50 galvanostatic charge-discharge cycles at ambient conditions. Li-insertion/extraction mechanism and improvement in electronic conductivity profiles are validated through cyclic voltammetry and electrochemical impedance spectroscopy, respectively.