title: Prelithiation Activates Li(Ni0.5Mn0.3Co0.2)O2 for High Capacity and Excellent Cycling Stability.
abstract: Transition metal oxide materials Li(NixMnyCoz)O2 (NMC) based on layered structures are expected to replace LiFePO4 in automotive Li-ion batteries because of their higher specific capacity and operating potential. However, the actual usable capacity is much lower than the promised theoretical value [Uchaker, E.; Cao, G. Nano Today 2014, 9, 499-524; Tarascon, J.-M.; Armand, M. Nature 2001, 414, 359-367], in addition to the often poor cycling performance and the first-cycle Coulombic efficiency, for which Mn(II)-dissolution, its immobilization in solid electrolyte interface (SEI), oxidation of electrolytes by Ni, and other parasitic process thereat have been held responsible [Zhan, C., et al. Nat. Commun. 2013, 4, 2437; Wang, L., et al. J. Solid State Electrochem. 2009, 13, 1157-1164; Lin, F., et al. Nat. Commun. 2014, 5, 4529]. Previously, we reported a composite Li(Ni0.5Mn0.3Co0.2)O2 (NMC532) depolarized by the embedded carbon nanotube (CNT) and achieved capacity close to the theoretical limit [Wu, Z., et al. Nano. Lett. 2014, 14, 4700-4706]; unfortunately, this high capacity failed to be maintained in long-term cycling due to the degrading contacts between the active ingredient and CNT network. On the basis of that NMC532/CNT composite, the present work proposes a unique "prelithiation process", which brought the cathode to low potentials before regular cycling and led to an interphase that is normally formed only on anode surfaces. The complete coverage of cathode surface by this ∼40 nm thick interphase effectively prevented Mn(II) dissolution and minimized the side reactions of Ni, Co, and Mn at the NMC interface during the subsequent cycling process. More importantly, such a "prelithiation" process activated a structure containing two Li layers near the surface of NMC532 particles, as verified by XRD and first principle calculation. Hence, a new cathode material of both high capacity with depolarized structure and excellent cycling performance was generated. This new structure can be incorporated in essentially all the NMC-based layered cathode materials, providing us with an effective tool to tailor-design future new cathode materials for lithium batteries.
authors.affiliation: †School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
authors.forename: Zhongzhen
authors.initials: Z
authors.lastname: Wu
authors.affiliation: †School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
authors.forename: Shunping
authors.initials: S
authors.lastname: Ji
authors.affiliation: †School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
authors.forename: Jiaxin
authors.initials: J
authors.lastname: Zheng
authors.affiliation: †School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
authors.forename: Zongxiang
authors.initials: Z
authors.lastname: Hu
authors.affiliation: †School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
authors.forename: Shu
authors.initials: S
authors.lastname: Xiao
authors.affiliation: †School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wei
authors.affiliation: †School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, 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, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Lin
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: §U.S. Army Research Laboratory, Adelphi, Maryland20783, United States.
authors.forename: Kang
authors.initials: K
authors.lastname: Xu
authors.affiliation: †School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen 518055, 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, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Pan
keywords: Li(Ni0.5Mn0.3Co0.2)O2; carbon nanotube (CNT); prelithiation; solid electrolyte interface (SEI); two-layer Li