  There is an urgently need for the high-performance rechargeable electrical
storage devices as supplement or substitutions of lithium ion batteries due to
the shortage of lithium in nature. Herein we propose a stable 2D electrene
T'-Ca2P as anode material for Na/K ion batteries by first-principle
calculations. Our calculated results show that T'-Ca2P monolayer is an
antiferromagnetic semiconducting electrene with spin-polarized electron gas. It
exhibits suitable adsorption for both Na and K atoms, and its anisotropic
migration energy barriers are 0.050/0.101 eV and 0.037/0.091 eV in b/a
direction, respectively. The theoretical capacities for Na and K are both 482
mAh/g, while the average working voltage platforms are 0.171-0.226 V and
0.013-0.267 V, respectively. All the results reveal that the T'-Ca2P monolayer
has promised application prospects as anode materials for Na/K ion batteries.
