Constructing electrode materials with fast ions and electrons transport channels is an effective solution to achieve high-power-density and longcycle potassium-ion batteries (PIBs). Herein, completely opening radial pores in N/O dual-doped carbon nanospheres (RPCNSs) are constructed as anode for high-power PIBs. The RPCNS with hierarchical structure (micro/ meso/macropores and radial channels) and N/O dual-doping permits speedy ions and electrons transportation within the carbon nanospheres anode, achieving a reversible capacity of 346 mAh g −1 at 50 mA g −1 after 360 cycles and long-term cycling life over 2000 cycles without obvious capacity attenuation. The in situ Raman and kinetic analysis (in situ electrochemical impedance spectroscopy and galvanostatic intermittent titration) suggest that the exquisitely designed pore structure and heterodoping enable highly reversible electrochemical reaction and fast de/ intercalation kinetics. Moreover, the full cells packaged with RPCNS anode can be fully charged in 10 s and exhibit the highest charge power density of 24 866 W kg −1 and longest cycling endurance of 5000 cycles in reported PIBs. The unique structural engineering provides a new way for high-power density potassium-ion storage devices.

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POMs) recently emerged as promising inorganic materials due to their varying structures, high electrochemical activities, and EC performances. [11,12] The most common and widely investigated POM structure is the Keggin structure, which is applied in biochemical, electrochemical, and catalytic areas. [13] However, studies on the EC properties of Keggin-structured POMs are limited, and their reported EC performances were inferior to other POM types. [14] Several attempts were made to improve the EC performance, including modifying the molecular structure or atomic composition, and optimizing the nanostructures [15-19] Notably, for POM-based EC materials, these approaches were employed by simultaneously selecting and controlling their nanostructures. Porous TiO 2 nanoparticle films (TNFs) are successful POMs' hosts displaying satisfactory EC performances due to their large specific surface area and porous morphology. [20-23] Further increases in ΔT were obtained by assisting the EC reaction by charge-balancing species between the working and counter electrodes in a full cell structure. Although some full cell type ECDs were achieved with POMs, [20,23] charge-balancing reactions were rarely examined, possibly because of the complicated EC mechanism, which makes it difficult to select CBMs for POMs. To create a CBM, a redox active material or electron reservoir was coated on the counter electrode (film type) or dissolved in the electrolyte (solution type). To simplify the ECD structure and avoid increasing its thickness, the solution type could be promising for high-performance ECDs. For example, a WO 3-based ECD showed enhanced EC performance when it was assembled with an electrolyte containing a tetramethylthiourea redox couple. [24,25] Similarly, viologen-based ECDs displayed fast switching times and high cycling stability in the presence of an I − /I 3 − redox mediator in a gelatin-electrolyte. [26,27] However, POM-based ECDs with redox couples in the electrolyte are not reported in literature. Noticeably, POM-based ECDs suffer from limited electrolyte choices and low optical contrast (ΔT), and POM-based EC films are mainly operated in aqueous media. [28] Also, the limited electrochemical window (1.23 V) of the aqueous electrolyte restricted their broader application in ECDs. [29] In general, water can be electrolyzed, but generates bubbles at the voltage range for coloration and bleaching of EC materials. In a A nonaqueous charge-balancing electrolyte with a redox couple (I − /I 3 −) is investigated to improve the electrochromic (EC) performance of polyoxometalate (POM)-based electrochromic devices (ECDs). PW 12 O 40 3− (PW 12)-coated porous TiO 2 nanoparticle films (PWTNF) with different thicknesses are used as the working electrode. The optical contrast (ΔT) of the optimized PW 12-ECDs reached 59.4% with the electrolyte containing the I − /I 3 − redox couple. PW 12-ECDs also show a fast response time for bleaching (t b,90% = 1.9 s) and coloration (t c,90% = 3.1 s). On the contrary, without the I − /I 3 − redox ...