title: 2D Electrides as Promising Anode Materials for Na-Ion Batteries from First-Principles Study.
abstract: Searching for suitable anodes with good performance is a key challenge for rechargeable Na-ion batteries (NIBs). Using the first-principles method, we predict that 2D nitrogen electride materials can be served as anode materials for NIBs. Particularly, we show that Ca2N meets almost all the requirements of a good NIB anode. Each formula unit of a monolayer Ca2N sheet can absorb up to four Na atoms, corresponding to a theoretical specific capacity of 1138 mAh·g(-1). The metallic character for both pristine Ca2N and its Na intercalated state NaxCa2N ensures good electronic conduction. Na diffusion along the 2D monolayer plane can be very fast even at room temperature, with a Na migration energy barrier as small as 0.084 eV. These properties are key to the excellent rate performance of an anode material. The average open-circuit voltage is calculated to be 0.18 V vs Na/Na(+) for the chemical stoichiometry of Na2Ca2N and 0.09 V for Na4Ca2N. The relatively low average open-circuit voltage is beneficial to the overall voltage of the cell. In addition, the 2D monolayers have very small lattice change upon Na intercalation, which ensures a good cycling stability. All these results demonstrate that the Ca2N monolayer could be an excellent anode material for NIBs.
authors.affiliation: School of Physics, Beijing Institute of Technology , Beijing 100081, China.|Research Laboratory for Quantum Materials and EPD Pillar, Singapore University of Technology and Design , Singapore 487372, Singapore.
authors.forename: Junping
authors.initials: J
authors.lastname: Hu
authors.affiliation: Department of Physics, Jiangxi Normal University , Nanchang 330022, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Xu
authors.affiliation: Research Laboratory for Quantum Materials and EPD Pillar, Singapore University of Technology and Design , Singapore 487372, Singapore.
authors.forename: Shengyuan A
authors.initials: SA
authors.lastname: Yang
authors.affiliation: School of Physics, Beijing Institute of Technology , Beijing 100081, China.|Research Laboratory for Quantum Materials and EPD Pillar, Singapore University of Technology and Design , Singapore 487372, Singapore.
authors.forename: Shan
authors.initials: S
authors.lastname: Guan
authors.affiliation: Department of Physics, Jiangxi Normal University , Nanchang 330022, China.
authors.forename: Chuying
authors.initials: C
authors.lastname: Ouyang
authors.affiliation: School of Physics, Beijing Institute of Technology , Beijing 100081, China.
authors.forename: Yugui
authors.initials: Y
authors.lastname: Yao
keywords: 2D electride; Na-ion batteries; anode material; diffusion barrier; open-circuit voltage