Tuning a small electron polaron in FePO by P-site or O-site doping based on DFT+ and KMC simulation.

Due to the existence of a small polaron, the intrinsic electronic conductivity of olivine-structured LiFePO is quite low, limiting its performance as a cathode material for lithium-ion batteries (LIBs). Previous studies have mainly focused on improving intrinsic conductivity through Fe-site doping while P-site or O-site doping has rarely been reported. Herein, we studied the formation and dynamics of the small electron polaron in FePXO and FePOZ by employing the density functional theory with the on-site Hubbard correction terms (DFT+) and Kinetic Monte Carlo (KMC) simulation, where X and Z indicate the doping elements (X = S, Se, As, Si, V; Z = S, F, Cl), and and β indicate the light doping at the P position ( = 0.

Factors that affect volume change during electrochemical cycling in cathode materials for lithium ion batteries.

Intergranular cracks originating from volume change during charging/discharging have been observed in many cathodes of lithium ion batteries, which are considered to be closely related to capacity fading. Using first principles calculations to systematically study the volume behavior of representative intercalation cathodes during delithiation, we have elucidated how Coulombic interaction and bond length affect the volume behaviors of cathodes with different structural flexibility. Jahn-Teller distortions, dopants, ionic radii, site-exchanges, and deintercalation mechanisms have also been discussed to account for the volume change of different cathode materials.

Relationship between higher-order aberrations and myopia progression in schoolchildren: a retrospective study.

Aim: To investigate the relationship between higher-order aberration (HOA) and myopic progression in school children.

Methods: Between April 23, 2011 and August 29, 2011 in the children's myopia outpatient clinic of the West China Hospital of Sichuan University, 148 eyes of 74 schoolchildren were reviewed. HOAs for a 6-mm pupil were measured with an aberrometer.