title: Storage and Effective Migration of Li-Ion for Defected β-LiFePO4 Phase Nanocrystals.
abstract: Lithium iron phosphate, a widely used cathode material, crystallizes typically in olivine-type phase, α-LiFePO4 (αLFP). However, the new phase β-LiFePO4 (βLFP), which can be transformed from αLFP under high temperature and pressure, is originally almost electrochemically inactive with no capacity for Li-ion battery, because the Li-ions are stored in the tetrahedral [LiO4] with very high activation barrier for migration and the one-dimensional (1D) migration channels for Li-ion diffusion in αLFP disappear, while the Fe ions in the β-phase are oriented similar to the 1D arrangement instead. In this work, using experimental studies combined with density functional theory calculations, we demonstrate that βLFP can be activated with creation of effective paths of Li-ion migration by optimized disordering. Thus, the new phase of βLFP cathode achieved a capacity of 128 mAh g(-1) at a rate of 0.1 C (1C = 170 mA g(-1)) with extraordinary cycling performance that 94.5% of the initial capacity retains after 1000 cycles at 1 C. The activation mechanism can be attributed to that the induced disorder (such as FeLiLiFe antisite defects, crystal distortion, and amorphous domains) creates new lithium migration passages, which free the captive stored lithium atoms and facilitate their intercalation/deintercalation from the cathode. Such materials activated by disorder are promising candidate cathodes for lithium batteries, and the related mechanism of storage and effective migration of Li-ions also provides new clues for future design of disordered-electrode materials with high capacity and high energy density.
authors.affiliation: School of Advanced Materials, Peking University , Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.
authors.forename: Hua
authors.initials: H
authors.lastname: Guo
authors.affiliation: School of Advanced Materials, Peking University , Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.
authors.forename: Xiaohe
authors.initials: X
authors.lastname: Song
authors.affiliation: School of Advanced Materials, Peking University , Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.|Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Zengqing
authors.initials: Z
authors.lastname: Zhuo
authors.affiliation: School of Advanced Materials, Peking University , Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.
authors.forename: Jiangtao
authors.initials: J
authors.lastname: Hu
authors.affiliation: School of Advanced Materials, Peking University , Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.
authors.forename: Tongchao
authors.initials: T
authors.lastname: Liu
authors.affiliation: School of Advanced Materials, Peking University , Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.
authors.forename: Yandong
authors.initials: Y
authors.lastname: Duan
authors.affiliation: School of Advanced Materials, Peking University , Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Electrochemical Technology Program, Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Zonghai
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Wanli
authors.initials: W
authors.lastname: Yang
authors.affiliation: School of Advanced Materials, Peking University , Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.|Electrochemical Technology Program, Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States.
authors.forename: Khalil
authors.initials: K
authors.lastname: Amine
authors.affiliation: School of Advanced Materials, Peking University , Shenzhen Graduate School, Shenzhen 518055, People's Republic of China.
authors.forename: Feng
authors.initials: F
authors.lastname: Pan
keywords: activation; density functional theory; disorder; lithium migration passages; β-LiFePO4