Improving the Electrochemical Performance of Lithium Metal Batteries with Hollow Shell Microspheres and Polypyrrole Vapor Phase-Coated LiV₃O₈ Cathodes

Abstract

New hollow shell structured lithium trivanadate (LiV 3 O 8 ) microspheres were synthesized by a spray drying method, and the effect of a vapor-phase-polypyrrole coating on the surface of this active material was studied. A thin and uniform coating layer could form by a simple vapor-phase-polymerization (VPP) method. The polypyrrole coating layer not only compensates for the low conductivity of the active material but also prevents its direct contact with the electrolyte and reduces vanadium dissolution. The LiV 3 O 8 morphology and presence of the coating layer were confirmed using Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The electrochemical performance was analyzed using a battery testing system and impedance spectroscopy. The cycle performance of the Li-powder/polypyrrole-VPPcoated hollow shell LiV 3 O 8 cell showed a higher capacity and greater capacity retention (LiV 3 O 8 : 160.80 mA h g −1 , 62.31%; coated LiV 3 O 8 : 206.55 mA h g −1 , 82.02%) in the range of 1.8-4.0 V at a 0.2 C-rate, even after 200 cycles. The rate capability at various current densities was also high. Further, it had a low charge transfer resistance, which remained low even after many cycles. Thus, the combined effect of hollow-shell-structure and polypyrrole-VPP coating, led LiV 3 O 8 to its improved electrochemical performance.

CNTs/LiV3O8/Y2O3 Composites with Enhanced Electrochemical Performances as Cathode Materials for Rechargeable Solid-State Lithium Metal Batteries

“…For solving these issues, a wide variety of strategies have been performed for maintaining the structural integrity and improving the electrical conductivity of LiV 3 O 8 . For example, the coatings of conductive polymers, graphene oxide, or metal oxides have been proved to be an efficient strategy for improving the Li-ion storage performance of LiV 3 O 8 . − The elemental substitution for V is another effective approach accomplished by introducing Mo, Ni, or Si, which can form a mix-valence state of V 4+ /V 5+ and provide abundant oxygen vacancies in LiV 3 O 8 . − In addition, it has been demonstrated that controlling the morphology of the LiV 3 O 8 cathode material has an aggressive impact on its electrochemical performance. ,, …”