Carbon-Coated Flower-Like TiO₂ Nanosphere as an Ultrastable Anode Material for Potassium-Ion Batteries: Structure Design and Mechanism Study

Titanium dioxide (TiO2) is a promising anode with long-term cyclability and low cost for potassium-ion batteries (PIBs), while its potential application is limited by the low electron/ion conductivity and lack of understanding of K+ ion storage behavior. In this work, a carbon-decorated flower-like TiO2 nanosphere composed of ultrathin nanosheets (denoted as TO/C) was simply synthesized in a one-step process. The desirable structure features of hierarchical flower-like TiO2 and the conductive carbon coating make TO/C a high-performance PIB anode with high specific capacity (172.1 mAh g–1 at 0.1C) and superior durability (100 mAh g–1 at 1C even after 2300 cycles). The K+ storage behaviors were deeply analyzed by the multiple electrochemical characterizations and theoretical calculations. It is revealed that the stable SEI film and the sufficient phase transition in the first discharge process contribute greatly to the stable K+ intercalation/deintercalation within the TiO2 in the subsequent cycles, and the anatase phase is a more suitable anode material than bronze for PIBs. This work provides a structure design strategy for high-performance PIBs anode and may further push the PIBs toward practical application.