High performance LiV0.96Mn0.04PO4F/C cathodes for lithium-ion batteries

Abstract

The LiV 0.96 Mn 0.04 PO 4 F/C composite was prepared by partial substitution of vanadium with manganese and in situ carbon coating of LiVPO 4 F via a modified carbothermal reduction route. Rietveld refinement of X-ray diffraction (XRD) patterns shows that the crystalline lattice is smaller than the value reported in the literature. While electron energy loss spectroscopy (EELS) on a selected area of high resolution transmission electron microscopy (HRTEM) demonstrates that Mn is successfully doped into LiVPO 4 F, X-ray photoelectron spectroscopy (XPS) indicates the co-existence of Mn 3+ and Mn 4+ . With $6.29 wt% residual carbon (estimated by thermogravimetric analysis, TGA) included, the specific discharge capacity of LiV 0.96 Mn 0.04 PO 4 F/C at 0.1 C and 6 C could reach 138 mA h g À1 and 98 mA h g À1 , respectively. The capacity retention after 1000 cycles at 1 C is about 90%, corresponding to only 0.01% loss per cycle. Electrochemical impedance spectroscopy (EIS) shows that the charge transfer resistance (R ct ) is significantly reduced by Mn substitution, and the lithium diffusion coefficient was calculated to be 1.34 Â 10 À13 cm 2 s À1 , which is an order of magnitude higher than that of pristine LiVPO 4 F/C. Moreover, LiV 0.96 Mn 0.04 PO 4 F/C retains 74% of its initial capacity after 500 cycles at 1 C at 65 C, indicating its potential application at high temperatures.

Improving the Electrochemical Performances of LiVPO4F/C Cathode by Doping AlF3 with Dual Functions for Lithium Ion Batteries

“…Oxalic acid and PVDF are pyrolyzed to generate the amorphous pyrolytic carbon. The lattice parameters of LiV 1‐x Al x PO 4 F/C are similar to literatures ,. With the increasing of Al 3+ doping ratio, the lattice parameters ( a , b , c and V ) decrease gradually and lattice shrinks because the ionic radius of Al 3+ (53.5 pm) is smaller than that of V 3+ (64 pm).…”

“…It can be found that the charge transfer resistance ( R ct ) drops gradually with the increasing of doping ratio, which decreases from 278.8 Ω (undoped sample) to 180.6 Ω, 132.5 Ω, 76.5 Ω and 67.1 Ω when the doping ratio x is 0.01, 0.02, 0.03 and 0.04. The R ct value of LiV 0.97 Al 0.03 PO 4 F/C is lower than literatures ,,. It presents an inverse relationship between conductivity and resistivity.…”

“…S. Zhong has also conducted the doping of Al 3+ through the separately synthesis of AlPO 4 at 900 °C . Y. Xu has doped LiVPO 4 F by MnO 2 and TiO 2 , in which the intermediate V 0.96 PO 4 and V 0.95 PO 4 instead of VPO 4 are synthesized. The Y‐doped LiVPO 4 F is also researched .…”

Polyanion Compounds as Cathode Materials for Li-Ion Batteries

“…By optimizing preparation conditions, the reversible capacity can be as high as 155 mAh/g with a small voltage polarization, which is very close to the theoretical capacity of 156 mAh/g [43]. Additionally, long-term cycling stability was achieved for LiV 0.96 Mn 0.04 PO 4 F, with a capacity retention of 90 % after 1000 cycles [44]. LiVPO 4 F exhibits high ionic conductivity but poor electronic conductivity [45].…”

Graphene‐Containing Nanomaterials for Lithium‐Ion Batteries

“…LiVPO 4 F has been widely investigated as a potential cathode material for LIBs operating at 4.2 V vs. Li/Li + . [ 61,383 ] Cyclability of a nanosized LiVPO 4 F/graphene composite (LVPF/G) synthesized via a facile mechano-chemical approach exhibited an initial charge capacity of 287 mAh g −1 at rate of 0.1 C (1 C = 310 mA g −1 ) with no capacity fading after 100 cycles and a good rate capability of 168 mAh g −1 at 10 C under 0.01-3 V vs. Li/Li + . [ 384 ] Roh et al [ 385 ] developed a LiTi 2 (PO 4 ) 3 /rGO nanocomposite with a NASICON-type structure that delivered a reversible …”