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In recent years, thermal imaging and sensing technologies have seen dramatic increases in usage for a range of applications. However, the material cost and manufacturing complexity of infrared optics remain a major barrier toward their democratization. Here, a solution‐processed plasmonic reflective filter (PRF) is presented as a scalable, disordered, and low‐cost thermal infrared (TIR) optic. The PRF selectively absorbs sunlight and specularly reflects TIR wavelengths, with a performance comparable to state‐of‐the‐art infrared optics made of materials like Germanium. Unlike the latter, however, the PRF is fabricated using low‐cost materials and a “dip‐and‐dry” chemical synthesis technique, which enables orders of magnitude lower manufacturing costs. The PRF's optical functionality and integration into infrared imaging systems are experimentally demonstrated. The chemical synthesis technique also affords exceptional spectral tuneability and material compatibility compared to traditional fabrication methods. The PRF's tuneable and broadband TIR yield can be augmented by inexpensive dielectric or polymeric filters to yield novel capabilities such as wide‐area ambient temperature surveys. Practically, the PRF represents a significant advance toward democratizing the benefits of thermal imaging and sensing. Scientifically, it represents a previously unexplored optical functionality of disordered materials, and a new direction for versatile chemical synthesis in designing optical components. 

Li-ion diffusion and lithiation kinetics in MnO/C nanocomposites were systematically investigated by monitoring the change in the charge transfer resistance and the ion diffusion coefficient, and the kinetically predominant process at various charge/discharge states. Crystal field analysis and density functional theory (DFT) calculations were introduced to reveal the relationship between the electronic structure of the phase compositions, the displayed electrochemical potential and its profile. The split 3d orbitals in the Mn ion determine the ordering of the electron migration and energy difference, leading to the different potential profiles in the lithiated/delithiated process. The phase compositions strongly affect the intrinsic properties of the MnO/C nanocomposites, increasing the ion diffusion coefficient from ∼10 −15 to 10 −11 cm 2 s −1 when the electrode progressed from the fully charged to fully discharged state, while both the surface redox reaction and the solid-state diffusion could be the limiting process depending on the lithiation/delithiation states. In addition, the MnO/C anode delivers an energy efficiency of 90% in a Li-ion hybrid capacitor, suggesting a promising and competitive application in the future.