Li resources, together with its growing depletion, has seriously hindered the sustainable development of LIBs. [6] In recent years, enormous effort has been devoted to developing alternative EES technologies, especially sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs), owing to the similar chemical properties of Na, K, and Li, [6] and the high abundance and accessibility of Na and K. Figure 1a shows the physical properties and economic indicators of Li, Na, and K carrier ions for rechargeable batteries. The ranking of Li, Na, and K according to their natural abundance in the crust is 27th (0.0017 wt%), 6th (2.36 wt%), and 7th (2.09 wt%), [7] respectively. In particular, PIBs are more attractive because the redox potential versus the standard hydrogen electrode of K + /K (−2.93 V) is lower than that of Na + /Na (−2.71 V) and closer to that of Li + /Li (−3.04 V) in aqueous electrolytes. [8,9] Moreover, both theoretical and experimental studies have revealed that the K/K + couple exhibits a low reduction potential compared with Na/Na + and even Li/Li + in nonaqueous electrolytes (e.g., KPF 6 -ethylene carbonate [EC]/propylene carbonate [PC]). [10,11] The weaker Lewis acidity of K + relative to Li + or Na + favors a smaller Stokes radius of solvated ions, [12] which facilitates faster ion mobility and higher ion conductivity, thereby improving the rate performance of PIBs. [13] As illustrated in Figure 1b, potassium plating takes place at a lower potential for PIBs compared with LIBs and SIBs, thus providing a greater possibility to achieve a wider electrochemical voltage window. [14] These findings, in principle, give rise to a higher energy density for PIBs. [15] More strikingly, PIBs benefit from the fact that K + can be electrochemically inserted into graphite (like Li + ) to form graphite intercalation compounds (KC 8 ) with a theoretical capacity of ≈279 mAh g −1 ; [16][17][18] thus, PIBs have great potential for commercial applications. These characteristics make PIBs an exciting alternative or complementary energy storage candidate to the present LIBs.Nevertheless, although the pioneering study on the K-intercalation reaction can be traced back to 2004, [19] the development of PIBs is less satisfactory owing to the difficulty in finding suitable host materials with acceptable electrochemical performance. This difficulty arises mostly from the large atomic radius (1.38 Å) of K + , [8] which considerably reduces With increasing demand for grid-scale energy storage, potassium-ion batteries (PIBs) have emerged as promising complements or alternatives to commercial lithium-ion batteries owing to the low cost, natural abundance of potassium resources, the low standard reduction potential of potassium, and fascinating K + transport kinetics in the electrolyte. However, the low energy density and unstable cycle life of cathode materials hamper their practical application. Therefore, cathode materials with high capacities, high redox potentials, and good structural stability are required with the advance...

Aqueous zinc‐ion batteries (AZIBs) have attracted considerable attention as promising next‐generation power sources because of the abundance, low cost, eco‐friendliness, and high security of Zn resources. Recently, vanadium‐based materials as cathodes in AZIBs have gained interest owing to their rich electrochemical interaction with Zn2+ and high theoretical capacity. However, existing AZIBs are still far from meeting commercial requirements. This article summarizes recent advances in the rational design of vanadium‐based materials toward AZIBs. In particular, it highlights various tactics that have been reported to increase the intercalation space, structural stability, and the diffusion ability of the guest Zn2+, as well as explores the structure‐dependent electrochemical performance and the corresponding energy storage mechanism. Furthermore, this article summarizes recent achievements in the optimization of aqueous electrolytes and Zn anodes to resolve the issues that remain with Zn anodes, including dendrite formation, passivation, corrosion, and the low coulombic efficiency of plating/stripping. The rationalization of these research findings can guide further investigations in the design of cathode/anode materials and electrolytes for next‐generation AZIBs.

No abstract

Battery-type materials for supercapacitors have attracted increasing research interest owing to their high energy density. However, their poor electrode kinetics severely limit the utilization of redox-active sites on the electrode surface, resulting in subpar electrochemical performance. Herein, we incorporate both Cu dopants and O vacancies into Co 3 O 4 nanocrystals confined in a carbon matrix (O v -Cu-Co 3 O 4 @C) which are assembled into nanowires. This heterostructured architecture with multifunctional nanogeometries provides a high intercomponent synergy, enabling high accessibility to active species. Moreover, the Cu dopants and O vacancies in O v -Cu-Co 3 O 4 @C synergistically manipulate the electronic states and provide more accessible active sites, resulting in enhanced electrical conductivity and enriched redox chemistry. The O v -Cu-Co 3 O 4 @C achieves a significantly improved specific capacity and rate performance, exceeding those of Co 3 O 4 @C. The asymmetric supercapacitors with O v -Cu-Co 3 O 4 @C deliver a high energy density of 64.1 W h kg −1 at 800 W kg −1 , exhibiting good flexibility without significant performance degradation under different bending states.