Practical strategies for enhanced performance of anode materials in Na⁺/K⁺-ion batteries

To build a new green energy society, energy storage technology is becoming increasingly important and infiltrating into almost every aspect of our daily life. Lithium-ion batteries have been widely used because they have no memory effect and a high energy density. However, it is not clear whether the limited lithium resources can support such an energy system during its march towards our goal of sustainable development. To address this issue, sodium-ion and potassium-ion batteries are considered to be suitable alternative power sources because of their much more abundant reserves on our planet. The successful application of these two new battery systems requires the development of advanced electrode materials. Although many materials with promising performance have been reported, further improvements are still needed to achieve a high energy density and a long cycle life to meet the requirement for commercialization. Instead of categorizing different candidate anode materials according to their nanostructures or compositions, in this review, we aim to provide a comprehensive understanding of different effective strategies to address the specific drawbacks in these materials, including the construction of heterojunctions, the introduction of diffusion channels and heteroatom doping to enhance the ionic and electronic conductivity, and the strategic design of an unique structure or chemical composition to improve the stability of the electrode. We also summarize some challenges associated with these strategies, which need to be addressed in order to achieve a more intensive application of sodium-ion and potassium-ion batteries.