Ultra-capacity and low-cost P3-type K0.5Mn0.96Fe0.04O2 cathode materials for K-ion batteries

The exploration of low-cost K-ion batteries (KIBs) to alleviate lithium resource depletion and energy supply issues has reached a consensus worldwide. However, the most fatal drawback of KIBs is that the K+ radius is too large and the lack of positive electrode materials can be adapted to it. In this present study, the resource abundant transition metal elements Mn and Fe are used to construct the layered KIBs cathode material with super capacity. The P3-K0.5Mn0.96Fe0.04O2 cathode material synthesized by high-temperature solid-state method can obtain an initial discharge capacity of 168.1 mAh·g−1, which is much higher than the theoretical capacity (125.9 mAh·g−1). Based on the results of ex-situ XRD and electrochemical characterization, it can be determined that the K0.5Mn0.96Fe0.04O2 cathode material can better adapt to the deintercalation process of K+ and the introduction of Fe3+ can effectively improve the diffusion kinetics and reaction kinetics of K+. Furthermore, through the X-ray absorption near edge structure (XANES) of the Mn element, it is verified that the reversible redox process of Mn3+ and Mn4+ in K0.5Mn0.96Fe0.04O2 compound. The Fe4+ signal detected by 57Fe-Mössbauer spectroscopy confirmed the reversible redox process of iron ions. This work provides an experimental basis for the construction of low-cost, high-performance KIBs cathode materials, and helps to promote the development of new KIBs energy storage systems. © 2024 Elsevier B.V.