Tetragonal aluminum phosphide monolayer as a promising anode material for alkali metal-ion battery applications

Two-dimensional (2-D) materials with excellent stability and large specific area are often regarded as electrode candidates for alkali metal-ion batteries (AIBs). Here, we have systematically investigated the feasibility of a newly 2-D tetragonal aluminum phosphide material, t-AlP monolayer, as an anode material for AIBs via firstprinciples calculations. Our results indicate that all considered alkali metal ions (Li/Na/K) are tightly bound to t-AlP monolayer and that t-AlP monolayer shows good metallicity after adsorption of Li/Na/K. Moreover, the low ion diffusion barriers are calculated as small as 0.04 eV for Li, 0.22 eV for Na, and 0.26 eV for K, suggesting that fast charging/discharging rates for t-AlP monolayer. Most impressively, except for Li, t-AlP monolayer exhibits a fairly high theoretical storage capacity, especially for K, which is up to 1850 mA h g(-1), surpassing most 2-D electrode materials. Additionally, t-AlP monolayer presents low average open circuit voltage values (0.225 V for Na, 0.266 V for K) as well as good cycling stability. To sum up, all of the above features indicate that t-AlP monolayer is a promising potential anode material for AIBs, especially for potassium-ion batteries (PIBs).