Development of Transition Metal Oxides as Next Generation Anode Materials for Potassium-Ion Batteries

Rechargeable ion batteries are a vital technology of the modern world, with batteries using lithium ions (LIBs) as the charge carriers being of particular importance. However, lithium has a relatively low crustal abundance and limited global distribution, so the development of alternative rechargeable ion batteries is imperative. One promising ion battery chemistry is potassium based, with the K+ ion as the charge carrier. For the negative electrode, transition oxide-based materials are very promising in high-performance applications, where rapid charge and discharge are essential. Below is a short overview of the three projects included in this thesis. KTiNbO5 (KTNO) has been demonstrated as a promising negative electrode material for lithium and sodium-ion batteries (LIBs and NIBs) but has not been reported in detail for KIBs. By synthesizing solvothermally in the presence of rGO, a KTNO/rGO nanocomposite was created that showed enhanced performance compared to pristine KTNO. The charge storage mechanism of the materials was investigated, indicating that the material was a low-strain, intrinsic pseudocapacitive material. While KTNO exhibits promising performance, it remains far behind graphite, particularly at low rates. By replacing the K+ in the interlayer spacing with Ni2+ through a facile ion-exchange, the performance could be boosted by 240 %. The source of the increased electrochemical performance could be attributed to the increase in the interlayer spacing, as well as the additional redox activity of the nickel. Lastly, to demonstrate the potential of potassium-ion batteries as alternatives to LIBs in low-cost uses, a full cell will be optimized with the positive electrode incorporating K2Mn[Fe(CN)6] and the negative electrode comprising of graphite. The full cell was then optimized in terms of N/P ratio and formation protocols. This confirms the feasibility and promise of potassium-ion full cells.