DFT investigations of KTiOPO4Mx (M = K, Na, and Li) anodes for alkali-ion battery.

The properties of KTiOPO4Mx (M = K, Na, and Li; x = 0.000-1.000) as an anode for potassium-ion batteries (PIBs), sodium-ion batteries (SIBs), and lithium-ion batteries (LIBs) are investigated by density functional theory calculations. Our work reveals that the electrochemical performance of KTiOPO4 as an anode for PIBs is superior to that for SIBs and LIBs, in terms of average voltage and ion diffusion kinetics. The ab initio molecular dynamics simulations indicate that the KTiOPO4Mx anode exhibits high structural stability, and alkali ion intercalation contributes to accelerating ion diffusion during the charging process. Particularly, the low activation energy of 0.406 eV of K migration on surface KTP(210), obtained by the climbing-image nudged elastic band method, suggests a high-rate capability. The systematical comparison of the performance of KTiOPO4 as an anode for PIBs, SIBs, and LIBs on the theoretical perspective clarifies that a large channel is not always promising for small radius ion intercalation and diffusion.