and exhibited the best cycling performance for a KIB cathode material to date. A combination of electrochemical profiles, ex situ X-ray diffraction, and first-principles calculations was used to understand the overall potassium storage mechanism of P3-K 0.69 CrO 2 . Based on a reversible phase transition, P3-K 0.69 CrO 2 delivers a high discharge capacity of 100 mA h g À1 and exhibits extremely high cycling stability with B65% retention over 1000 cycles at a 1C rate. Moreover, the K-ion hopping into the P3-K 0.69 CrO 2 structure was extremely rapid, resulting in great power capability of up to a 10C rate with a capacity retention of B65% (vs. the capacity at 0.1C).
C/NVMP allowed high electrochemical performance supported by the replace V by the Mn promoted the easier electron transfer through lower band gap energy than Mn-free NVP and carbon coating increase the electric conductivity up to 2 × 10−3 s cm−1, which led to superior electrode performance.
Because of their distinct energy potentials, Li air‐breathing batteries have been highlighted as promising energy storage systems; however, the sluggish oxygen reduction and evolution reactions (ORR and OER) disturb the reversible cell operation during cycling. Therefore, catalyst materials should be tailored to mitigate the low efficiencies of air‐breathing batteries. A porphyrin‐derived catalyst is optimized by introducing different metal‐centered organometallic phthalocyanine (MPc) complexes and their potential application as redox mediators (RMs) for fabricating efficient Li–O2 cells is investigated. The feasibility of each MPc is determined as a potential RM by calculating its orbital levels. The electrochemical properties of the Li–O2 cells employing the diverse MPc‐RMs are compared. The MPc‐containing Li–O2 cells exhibit improved cell performance, reduced polarization, and stable cyclability with auto‐oxygenated properties as revealed by directly injecting superoxide species into the MPc‐containing electrolytes. The synergistic effects of blended MPcs—a mixture consisting of the two most effective MPcs—in both the OER and ORR regions in ambient air atmosphere are also elucidated. The reaction mechanism of the MPc‐containing cells is proposed based on first‐principles calculations and experimental results. The introduction of natural functional catalysts provides a basis for developing effective eco‐friendly catalysts for application to sustainable air‐breathing batteries.
Na0.97KFe(SO4)2 was successfully prepared via slow evaporation and a low-temperature process, and its outstanding electrochemical performance was demonstrated.
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