Synergistically enhanced structural, thermal and interfacial stability of K0.45MnO2 via tailoring the local structure for high-energy and high-power potassium-ion batteries

• The Jahn-Teller distortion of Mn 3+ has been suppressed via microstructural engineering by Al substitution. • High bonding strength between Al and O is found to further improve structural and thermal stability. • K 0.45 Mn 0.9 Al 0.1 O 2 cathode demonstrates enhanced long-term stability and superior safety in comparison with K 0.45 MnO 2 . Mn-based layered oxides are widely considered as cost-effective cathodes for K-ion batteries (KIBs), whereas the local lattice distortion induced by the Jahn-Teller effect of Mn 3+ usually results in limited capacity and unsatisfactory cycling lives. Herein, a new P3-type K 0.45 Mn 0.9 Al 0.1 O 2 material is designed via riveting electrochemical inactive Al 3+ in the octahedral Mn 3+ sites, which is experimentally proved to play a key role in suppressing misfit dislocations at the atomic scale, enlarging the spacing of K + layers, relieving exothermic phase transition at elevated temperature and helping to form a stable and uniform cathode electrolyte interphase (CEI) layer synergistically. Thanks to these inherent merits, K 0.45 Mn 0.9 Al 0.1 O 2 delivers a high specific capacity of 152 mAh g -1 at 20 mA g -1 and excellent cyclic performance with capacity retention of 67 % over 1000 cycles, much superior to K 0.45 MnO 2 . Impressively, the full battery achieves a high energy (291 Wh kg −1 ) and power (843 W kg −1 ) densities over state-of-the-art layered cathodes for KIBs. This study not only provides a facile and effective strategy to jointly enhance the structural, thermal and interfacial stability of Mn-based layered cathodes, but also the underlying mechanism revealed here sheds light on designing novel cathodes via tailoring the local structural environments.