Corrugated Layered Titanates as High-Voltage Cathode Materials for Potassium-Ion Batteries

Layered transition metal oxides with two-dimensional diffusion pathway and high theoretical energy density are promising cathode candidates for potassium-ion batteries (PIBs). Nevertheless, the large size of K+ increases the K+–K+ electrostatic repulsion in the layered structure, resulting in the low operating voltage in PIBs, which remains a great challenge to be solved. Herein, we develop a series of corrugated layered titanates that extend the K+–K+ distance to ∼3.9 Å, exceeding the K+–K+ distance of all reported layered oxides. By shielding the K+–K+ electrostatic repulsion, K0.8Mn0.8Ti1.2O4 and K0.8Ni0.4Ti1.6O4 as corrugated layered titanate representatives furnish high working voltages of 3.0 and 3.6 V, respectively. In addition, K0.8Mn0.8Ti1.2O4 also achieves a large reversible capacity of 77.8 mAh g–1 and a long lifetime over 300 cycles. In situ X-ray diffraction measurements indicate that K0.8Mn0.8Ti1.2O4 exhibits reversible structural evolution during de/potassiation with a lattice volume change as low as 1.4%. These findings provide new insights for the further development high-voltage layered cathodes for PIBs.