Unlocking Ion Transport Limitation in KTi₂(PO₄)₃ Anode for Aqueous Potassium-Ion Batteries

Aqueous potassium-ion batteries (APIBs) are considered as promising candidates for large-scale energy storage applications, due to their eco-friendliness, high-safety, and low-cost. However, the stagnation of exploring anode materials severely impedes the further development of APIBs. KTi₂(PO₄)₃ (KTP) is an ideal anode for APIBs due to its stable structural framework, high theoretical capacity, and low operating voltage. Nevertheless, KTP has poor intrinsic electronic conductivity, and the synthesized KTP powders are usually agglomerated particles with large-size. In this work, KTP is engineered via the strategy of solvent-controlled morphology. The uniform thin carbon-coated KTP nanoparticles enable low agglomeration and small size. Meanwhile, a low-cost hybrid aqueous/nonaqueous electrolyte with high ionic conductivity and wide electrochemical window is elaborately designed to match the KTP anode. The KTP using this electrolyte exhibits a specific capacity of 127 mAh g^-1 at 1 C (128 mA g^-1) and a cycle lifespan of 65 000 cycles (more than 150 days) at 50 C with negligible capacity loss. The assembled full cell exhibits an ultralong cycle life (capacity retention of 85% at 50 C after 4000 cycles), superior rate capability, and long-term operation under -20 °C. In summary, this work may have an important influence on the development of APIBs.