Metal organophosphates: electronic structure tuning from inert materials to universal alkali-metal-ion battery cathodes

Organic cathodes for alkali-metal-ion batteries attract great attentions in recent years, but the ion storage sites are limited to some finite functional groups. This is because an organic cathode must have proper lowest unoccupied molecular orbitals (LUMO) to accept electrons at high potential. Herein, a novel type of organophosphate-based cathode has successfully been explored by tuning the LUMO energy level of organophosphates through metal ions with an inert electron pair. For the first time, the P=O of phytate (PA), N,N,N′,N′-ethylenediaminetetrakis(methylene phytate) (EDTMP), and diethylenetriaminepentakis(methyl phytate) (DTPMP) is activated by lead/bismuth (with 6s2 electron pair) to storage Li/Na/K ions reversibly. Typically, density functional theory calculations indicate that the LUMO energy of Bi-PA is greatly reduced from − 0.99 (PA) to − 4.61 eV, which shows the first discharge capacity of 173, 182 and 206 mAh·g−1 and the reversibly capacity of 102, 102 and 101 mAh·g−1 with the discharge platform of 2.4, 2.1 and 2.4 V for Li/Na/K-ion battery cathodes, respectively. Similarly, with proper LUMO energy level, Pb-PA (− 4.63 eV), Pb-EDTMP (− 3.71 eV), and Pb-DTPMP (− 4.45 eV) all exhibit admirable performance. This unique strategy of organic materials to alkali-metal-ion battery cathodes offers a new avenue for future energy storage systems.Graphical abstract