The Versatility of Layered Two-Dimensional Heterostructures for Energy Storage: Bridging Scientific Insights and Practical Applications.

Nanoscale manipulation of electronic and ionic charge interactions within electrode materials is the cornerstone for advancing electrochemical energy storage. Compared to bulk materials, 2D confined anodes provide lamellar channels to mobile ions for electrochemical interactions. However, individual 2D layers are often inefficient in delivering desired properties for stable and rapid kinetics in battery operations. To address this, 2D-2D heterostructures (2D HRs) that integrate the properties of two or more layers via van der Waals or covalent bonds can give optimized interfacial features. These structures modulate electronic properties, such as band positions, activation energies, diffusion barriers, and binding energies for intercalating ions, thereby regulating the electrochemical characteristics of batteries to meet practical challenges. In this context, this review includes the latest experimental and theoretical investigations to explore the multifunctional roles of 2D HRs in monovalent ion (Li, Na, and K) batteries (MIBs). First, it elucidates the fundamentals concerning the impacts of HRs in charge storage mechanisms and outlines pathways for synthesizing their novel designs. Then, it summarizes the different configurations of 2D HRs utilized in designing MIBs. Finally, it underscores the current challenges and future perspectives for implementing 2D HRs as advanced anode materials in batteries.