Aluminum‐Ion Batteries and the Promise of TiO 2 Electrode

Aqueous aluminum‐ion batteries have emerged as a viable substitute to lithium‐ion systems because of the natural presence of aluminum, low cost, high theoretical capacity, and the natural safety of aqueous electrolytes. Despite their advantages, aluminum‐ion batteries are associated with a known poor growth capability due to the slow kinetics of multivalent ion exchange, interfacial transport, and the unavailability of high‐efficiency electrode materials that may be utilized within the narrow electrochemical stability window of aqueous electrolytes. This perspective is a critical review of recent developments in aqueous aluminum‐ion batteries with particular focus on titanium dioxide‐based negative electrodes. It centers on the science of Al 3+ storage, interfacial charge transfers, and how electrode architecture can be used to control rate capability, cycling stability, and reversibility. Titanium dioxide is contrasted with typical carbonaceous materials using normalized performance metrics and radar chart analyses, and is used to illustrate the material's equilibrium, kinetics, and scalability. In addition, there are unresolved problems associated with the electrode II, current collector II, and electrolyte triad, which are described within the framework of transport theory, interfacial kinetics, and the trade‐offs of practical design. In this work, one can find valuable lessons and principles that limit performance and explain why some results in the literature appear inconsistent, thereby helping guide the practical design of reliable and scalable aqueous aluminum‐ion battery electrodes. In this context, titanium dioxide stands out as an attractive platform for safe and sustainable stationary energy storage.