Potassium-ion batteries (PIBs) have attracted tremendous attention due to their low cost, fast ionic conductivity in electrolyte, and high operating voltage. Research on PIBs is still in its infancy, however, and achieving a general understanding of the drawbacks of each component and proposing research strategies for overcoming these problems are crucial for the exploration of suitable electrode materials/electrolytes and the establishment of electrode/cell assembly technologies for further development of PIBs. In this review, we summarize our current understanding in this field, classify and highlight the design strategies for addressing the key issues in the research on PIBs, and propose possible pathways for the future development of PIBs toward practical applications. The strategies and perspectives summarized in this review aim to provide practical guidance for an increasing number of researchers to explore next-generation and high-performance PIBs, and the methodology may also be applicable to developing other energy storage systems.

Anodes equipped with limited lithium offer a way to deal with the increasing market requirement for high-energy-density rechargeable batteries and inadequate global lithium reserves. Anode-free lithium-ion batteries (AFLBs) with zero excess metal could provide high gravimetric energy density and high volumetric energy density. Moreover, the elimination of lithium with a bare current collector on the anode side can reduce metal consumption, simplify the cell technological procedure, and improve manufacturing safety. However, some great challenges, such as insufficient cycling stability, significant lithium dendrite growth, as well as unstable solid electrolyte interface, impede the commercial application of AFLBs. Fortunately, significant progress has been made for AFLBs with enhanced electrode stability and improved cycling performance. This review highlights research on the design of anode-free lithium-ion batteries over the past two decades, presents an overview of the main advantages and limitations of these designs, and provides improvement strategies including the modification of the current collectors, improvement of the liquid electrolytes, and optimization of the cycling protocols. Prospects are also given to broaden the understanding of the electrochemical process, and it is expected that the further development of these designs can be accelerated in both scientific research and practical applications.