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.

Sc2C as a Promising Anode Material with High Mobility and Capacity: A First‐Principles Study

“…For Na atoms, the formation energy increased with the increase in x , and a negative enough formation energy of −0.23 eV persisted at x= 2. These values are much larger than those for other typical electrode materials, such as the formation energy of Li on Nb 2 C (−0.02 eV atom −1 ) and Mo 2 C (−0.01 eV atom −1 ), and also Na on Ca 2 N (−0.003 eV atom −1 ) and GeS (−0.02 eV atom −1 ) . Therefore, these values practically ensure the good stability of Li 2 Sc 2 C and Na 2 Sc 2 C. Here, x= 2 means that there is one Li/Na adlayer on each side of the Sc 2 C layer, and the chemical stoichiometry for the fully adsorbed systems can be written as Li 2 Sc 2 C and Na 2 Sc 2 C. Given that multilayer adsorption means high storage capacity, we next explored the average adsorption energy as the Li/Na atom number was increased.…”

“…We assumed that the charge–discharge processes follow the common half‐cell reaction in aqueous solution [Eqns. ] …”

Recent Advances in Layered Ti3C2Tx MXene for Electrochemical Energy Storage

“…For a 2D structural material, a larger interlayer distance means smaller volume changes and a lower intercalation barrier . Inspired by the facts that the interlayer spacing of Ti 3 C 2 T x can be artificially tuned and that its surface can be modified, researchers have made numerous efforts in using Ti 3 C 2 T x and Ti 3 C 2 T x ‐based composites for LIBs, SIBs, LSBs, and other kinds of batteries . Chemical modification, structural design, and combination with other materials are the three most popular strategies to improve the performance of rechargeable batteries.…”

“…[186,191,192] Inspired by the facts that the interlayer spacing of Ti 3 C 2 T x can be artificially tuned and that its surface can be modified, researchers have made numerous efforts in using Ti 3 C 2 T x and Ti 3 C 2 T x -based composites for LIBs, SIBs, LSBs, and other kinds of batteries. [74,137,138,193,194] Chemical modification, structural design, and combination with other materials are the three most popular strategies to improve the performance of rechargeable batteries. In this Review, we mainly discuss the applications of Ti 3 C 2 T x in LIBs, SIBs, and LSBs.…”

Two dimensional superconductors in electrides

“…The special physical properties all bring a great application prospect and have attracted extensive attention. The high specific capacity and suitable migration energy barrier suggest that 2D electride is a promising anode material for sodium ion batteries [26][27][28]. In addition, utilizing the powerful predictive ability of the first-principles calculations, many works [29][30][31][32] suggest abundant compounds to be 2D electride.…”