title: Pre-Lithiation of Li(Ni1-x-yMnxCoy)O2 Materials Enabling Enhancement of Performance for Li-Ion Battery.
abstract: Transition metal oxide materials Li(NixMnyCoz)O2 (NMCxyz) based on layered structure are potential cathode candidates for automotive Li-ion batteries because of their high specific capacities and operating potentials. However, the actual usable capacity, cycling stability, and first-cycle Coulombic efficiency remain far from practical. Previously, we reported a combined strategy consisting of depolarization with embedded carbon nanotube (CNT) and activation through pre-lithiation of the NMC host, which significantly improved the reversible capacity and cycling stability of NMC532-based material. In the present work we attempt to understand how pre-lithiation leads to these improvements on an atomic level with experimental investigation and ab initio calculations. By lithiating a series of NMC materials with varying chemical compositions prepared via a conventional approach, we identified the Ni in the NMC lattice as the component responsible for accommodating a double-layered Li structure. Specifically, much better improvements in the cycling stability and capacity can be achieved with the NMC lattices populated with Ni(3+) than those populated with only Ni(2+). Using the XRD we also found that the emergence of a double-layer Li structure is not only reversible during the pre-lithiation and the following delithiation, but also stable against elevated temperatures up to 320 °C. These new findings regarding the mechanism of pre-lithiation as well as how it affects the reversibility and stability of NMC-based cathode materials prepared by the conventional slurry approach will promote the possibility of their application in the future battery industry.
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: Zongxiang
authors.initials: Z
authors.lastname: Hu
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: Shu
authors.initials: S
authors.lastname: Xiao
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: U.S. Army Research Laboratory , Adelphi, Maryland 20783, United States.
authors.forename: Kang
authors.initials: K
authors.lastname: Xu
authors.affiliation: 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(NixMnyCoz)O2 (NMCxyz); ab initio calculations; cycling stability and capacity; double-layered Li structure; pre-lithiation