Layered superconductor Cu${}_{0.11}$TiSe${}_2$ as a high-stable K-cathode

The cathode material is one of the main restricting factors for the development of potassium-ion batteries (PIBs). The poor conductivity, sluggish reaction kinetics, and unstable crystal structure of cathode materials have impeded their electrochemical performance. Here, controlled intercalation of TiSe${}_2$ with Cu is used to yield a layered superconductor Cu${}_{0.11}$TiSe${}_2$, which exhibits increased electrons and ions transfer rates and improved crystal structure stability. The insertion of Cu not only improves the electronic conductivity and reduces the diffusion barrier but also plays a role in crystal structure support, which further leads to a highly reversible charge and discharge process of Cu${}_{0.11}$TiSe${}_2$. The layered superconductor Cu${}_{0.11}$TiSe${}_2$ exhibits an excellent cycling performance with a capacity retention of 80% after 300 cycles at a current density of 20 mA g${}^{-1}$ and a superior rate capability with a capacity of 45 mAh g${}^{-1}$ at 1000 mA g${}^{-1}$ ($\approx$8C). Furthermore, a full battery assembled with the Cu${}_{0.11}$TiSe${}_2$ cathode and graphite anode exhibits a high reversible capacity of 74 mAh g${}^{-1}$ at a current density of 20 mA g${}^{-1}$. This study provides a new path for developing the high-performance cathode material of PIBs and other alkali metal-ion batteries. (© 2021 Wiley‐VCH GmbH)