Insights into Li(+) Migration Pathways in α-Li3VF6: A First-Principles Investigation

Molybdenum Disulfide-Coated Lithium Vanadium Fluorophosphate Anode: Experiments and First-Principles Calculations

To develop a new anode material to meet the increasing demands of lithium-ion battery, MoS2 is used for the first time to modify the C/LiVPO4 F anode to improve its lithium-storage performance between 3 and 0.01 V. Morphological observations reveal that the MoS2 -modified C/LiVPO4 F particles (M-LVPF) are wrapped by an amorphous carbon as interlayer and layered MoS2 as external surface. Charge-discharge tests show that M-LVPF delivers a high reversible capacity of 308 mAh g(-1) at 50 mA g(-1) . After 300 cycles at 1.0 A g(-1) , a capacity retention of 98.7 % is observed. Moreover, it exhibits high rate capability with a specific capacity of 199 mAh g(-1) at 1.6 A g(-1) . Electrochemical impedance spectroscopy tests indicate that the lithium-ion diffusion and charge-exchange reaction at the surface of M-LVPF are greatly enhanced. First-principles calculations for the MoS2 (001)/C/LiVPO4 F (010) system demonstrate that the absorption of MoS2 on C/LiVPO4 F is exothermic and spontaneous and that the electron transfer at the MoS2 -absorbed C/LiVPO4 F surface is enhanced.

Interstitial lithium diffusion pathways in γ-LiAlO2: a computational study

Although the Li diffusion in single crystalline γ-LiAlO2 was studied with temperature-dependent Li-7 NMR spectroscopy and conductivity measurements recently, the exact diffusion pathways are not yet clearly identified. Therefore, the present study aims at elucidating the diffusion pathways in γ-LiAlO2 theoretically from first principles. Competing pathways for Li diffusion are investigated using the climbing-image nudged-elastic-band approach with periodic quantum-chemical density functional theory (DFT) method. Li can migrate between two regular LiO4 tetrahedral sites via Li point defect (VLi) and via a Li Frenkel defect (VLi + Lii). On the basis of calculated activation energies for Li diffusion pathways, it is concluded that Li conductivity is strongly dependent on the distribution of Li vacancies and interstitial Li in the lattice. For Frenkel defects where Lii is far away from the migrating Li atom, the calculated activation energies for jumps to nearest-neighbor vacant sites agree with experimental values.