Potassium‐ion hybrid capacitors (PIHCs), elaborately integrate the advantages of high output power as well as long lifespan of supercapacitors and the high energy density of batteries, and exhibit great possibilities for the future generations of energy storage devices. The critical next step for future implementation lies in exploring a high‐rate battery‐type anode with an ultra‐stable structure to match the capacitor‐type cathode. Herein, a “dual‐carbon” is constructed, in which a three‐dimensional nitrogen‐doped microporous carbon polyhedron (NMCP) derived from metal‐organic frameworks is tightly wrapped by two‐dimensional reduced graphene oxide (NMCP@rGO). Benefiting from the synergistic effect of the inner NMCP and outer rGO, the NMCP@rGO exhibits a superior K‐ion storage capability with a high reversible capacity of 386 mAh g−1 at 0.05 A g−1 and ultra‐long cycle stability with a capacity of 151.4 mAh g−1 after 6000 cycles at 5.0 A g−1. As expected, the as‐assembled PIHCs with a working voltage as high as 4.2 V present a high energy/power density (63.6 Wh kg−1 at 19 091 W kg−1) and excellent capacity retention of 84.7% after 12 000 cycles. This rational construction of advanced PIHCs with excellent performance opens a new avenue for further application and development.

Room-temperature sodium−sulfur (RT Na−S) batteries are widely considered as one of the alternative energystorage systems with low cost and high energy density. However, the both poor cycle stability and capacity are two critical issues arising from low conversion kinetics and sodium polysulfides (NaPSs) dissolution for sulfur cathodes during the charge/discharge process. Herein, we report a highly stable RT Na−S battery cathode via building heterostructures in multichannel carbon fibers. The TiN-TiO 2 @MCCFs, fabricated by electrospinning and nitriding techniques, are loaded with the active material S, forming S/TiN-TiO 2 @MCCFs as the cathode in a RT Na−S battery. At 0.1 A g −1 , the cathode produces the capacity of more than 640 mAh g −1 within 100 cycles with a high Coulombic efficiency of nearly 100%. Even at 5 A g −1 , the battery still exhibites a capacity of 257.1 mAh g −1 after 1000 cycles. Combining structural and electrochemical analyses with the first-principles calculations reveals that the incorporation of the highly electrocatalytic activity of TiN with the powerful chemisorption of TiO 2 well stabilizes S and also alleviates the shuttle effects of polysulfides. This work with simple processes and low cost is expected to promote the further development and application of metal−S batteries.

All‐solid‐state lithium metal batteries (ASSLMBs) stand out for the next generation of energy storage system. However, the further realization is severely hampered by the lithium dendrite formation in solid state electrolytes (SSEs), by mechanisms that remain controversial. Herein, with the aid of experimental and theoretical approaches, the origin of dendrite formation in representative LiBH4 SSE, which is thermodynamically stable with the Li metal, suppressing the side reaction between Li and SSE is elucidated. It is demonstrated that upon diffusion, Li+ encounters an electron, and is subsequently reduced to Li0 within the grain boundary/pore of SSE, eventually leading to short circuit. Thus, introducing LiF with the ability of interstitial filling and low electronic conductivity into SSE is the effective countermeasure, and as expected, with the addition of LiF, the critical current density (CCD) increases by 235% compared to the value of pure LiBH4. The TiS2|LiBH4–LiF|Li ASSLMBs manifest a reversible capacity of 137 mAh g−1 at 0.4 C upon 60 cycles. These findings not only unravel critical issues in Li dendrite formation in SSE, but also propose the countermeasure.

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