The development of PIBs is challenged by the availability of suitable cathode materials capable of stably hosting the large-sized K⁺, whose continuous intercalation/deintercalation in the crystalline framework will cause serious phase deformation and irreversible structure degradation. Here, we demonstrated the possibility of achieving a highly reversible potassiation/depotassiation process in a layered metal oxide of K_5/9Mn_7/9Ti_2/9O₂. We confirmed that the existence of Ti can effectively combat the transition metal slab gliding of the P2-type structure during the electrochemical reaction. The destructive P2–O2 phase transition was efficiently diminished even when charged to a high voltage of 4.2 ​V, instead forming a stable OP4 phase which was able to switch back to its pristine P2-type structure upon discharge, accordingly providing an improved electrochemical performance of PIBs. We expect that the discovery and fundamental understanding of such a reversible P2-OP4 phase transition provide insights in the structural design of PIBs cathodes.

PIB的发展受到能否稳定容纳大型K ⁺的合适阴极材料的挑战，后者在晶体框架中的连续嵌入/脱嵌将导致严重的相变形和不可逆的结构退化。在这里，我们证明了在K _5/9 Mn _7/9 Ti _2/9 O ₂的层状金属氧化物中实现高度可逆的钾化/去钾化工艺的可能性。。我们证实，Ti的存在可以有效地抵抗电化学反应过程中P2型结构的过渡金属平板滑动。即使将其充电至4.2V的高电压，破坏性的P2-O2相变也能有效减少，而是形成稳定的OP4相，放电后能够切换回其原始P2型结构，从而提供改善的电化学性能PIB。我们期望这种可逆的P2-OP4相变的发现和基本理解将为PIB阴极的结构设计提供深刻见解。