Synergistic Heteroatom Doping in Hard Carbon Anodes: Unlocking High Performance in Potassium-Ion Batteries

The increasing demand for energy storage systems that deliver both high performance and environmental sustainability has driven significant interest in potassium-ion batteries (PIBs) as viable substitutes for lithium-ion batteries (LIBs). However, their large-scale application remains constrained by inherent drawbacks, such as limited energy density, poor cycling stability, and suboptimal electrochemical performance. Among various anode candidates, hard carbon (HC) has attracted considerable attention owing to its structural robustness and large specific surface area (SSA). Recent research indicates that heteroatom doping is an effective strategy to enhance the electrochemical properties of HC, leading to improved potassium (K) storage capacity, superior rate performance, and extended cycle life. This review summarizes recent progress in doped HC anodes, with a particular focus on the transition from single-element doping to multi-element doping approaches. The synergistic interactions within multi-dopant systems are systematically discussed, highlighting their potential to overcome the shortcomings of single-doped materials and achieve comprehensive performance improvements. Finally, current challenges and future perspectives for the development of advanced doped HC anodes in PIBs are outlined.